My Cam Research for the Experts Eye

TXChevy

Working at The Speed of Slow
I’m hoping that the experienced folks here can help me finalize my cam selection in a mild BBC build. I’m not a pro engine builder but willing to learn as much as I can. I’ve tried to research the tons of info out there - it’s been really helpful and shows me what I don’t know, so I don’t want to guess.

Engine is a MK IV (1979) 454 bored .030 over. It’s been in my 57 Belair with a TH400/2200 Continental converter and Ford 9 in with 3.70 gears. Relatively low miles on the engine, zero issues, but it was time for a refresh on the car and the driveline. My goal on the engine is to add a slightly more aggressive cam profile and working towards a power curve of 1400-5800 rpm.

Current cam: Erson TQ20H, .050 duration Int/Exh 214, LCA 112, lift .514, 1.7 stamped steel rockers. Induction is a Holley 4150 VS on an Edelbrock RPM intake. HEI ignition. Exhaust is 1.75 tube long tube headers to 3 in exhaust with a crossover.

Heads are 427 truck “big oval”, 2.06/1.72 open chamber, with some very mild cleanup on the ports and 116cc chambers. I’d like to continue with these heads. They will be refurbished as needed by the machine shop.

Pistons are TRW L2349 with .210 dome height. Valve clearance measured with clay at .2345. Calculated compression ratio came out right at 10:1. Factory cast crank turned .010, 2 bolt mains, new scat rods, new ARP studs on the mains and of course new rings and bearings. I plan to re-use the pistons as both the pistons and the bores measured within tolerance. This will be verified by the machine shop.

I started with about 21 cams and have narrowed it down to the ones listed below. For my budget, I want to ensure all needed machining is done but I want to use a hydraulic flat tappet cam and delphi lifters, with valve springs/retainers as recommended by the cam mfg. I also plan to use 1.7 roller rockers. I looked at the info here, including data compiled by David Vizard to try to get at least a basic understanding of what would work for my goals.

One item that bubbled up to the surface was reducing the LCA much more than I thought (108/110 vs 114) but balancing it with less duration. I tried to interpret the data into a graph for each cam that helped me to visualize the cam info. I’ve talked with several cam companies but it seems a lot of the info I received is a repeat of what I can read already.

So here’s where I’ve landed in my cam homework. As mentioned, I’m trying to learn more so any additional cam suggestions/comments are appreciated, especially if I’ve gone down the rabbit hole somewhere. The info listed here is based on installation at 0 degrees. At this point I’m leaning towards the Clay Smith 012 cam. I think for the heads that I’m using, I’m not sure I would see a benefit at lifts over .542?

Thank you for your help.

Clay Smith 02-012, 1700-5700 rpm
LCA = 108, lift = Int/Exh .542,
Dur @ .050 = Int/Exh 224
ICA = 108, 8d overlap @ .050

Crower 01295 1800-5700 rpm
LCA = 110, lift = Int .525, Exh .545
Dur @ .050 = Int 229, Exh 237
ICA = 106, 13d overlap @ .050

Comp Cams Magnum 270H, 1500-5800 rpm
LCA = 110, lift = Int/Exh .533
Dur @ .050 = Int/Exh 224
ICA = 106, 4d overlap @.050

Lunati Voodoo 10110702, 1400-5800 rpm
LCA = 112, lift = Int .530/Exh .542
Dur @ .050 = Int 219/Exh 227
ICA = 108, -1d (no overlap) at .050

Summit Racing SUM 1796
LCA = 108, lift = Int/Exh .514
Dur @ .050 = Int/Exh 226
ICA =108, 10d overlap @ .050

Howards Cams 120941-11 1500-5800 rpm
LCA = 111, lift = Int/Exh .527
Dur @ .050 = Int/Exh .225
ICA = 111, 57d overlap @ .050

Clay Smith 02-013 1700-5700 rpm
LCA = 110, lift = Int/Exh .542
Dur @ .050 = Int/Exh 224
ICA = 110, 54d overlap @ .050
 

Indycars

Administrator
Staff member
Be glad to run some simulations with my Dynomation 6 if that will help you. It will take some work on your part to gather the needed info and pull it together all in one place so I don't have to search thru your thread. You have most of the camshaft info, but it is lacking the "Seat-to-Seat" duration numbers that I will need. If you have the cam cards that usually works.


Below is what I normally need.

Dynomation 6 Input Variables

Bore & Stroke:
Displacement: cubic inches
Rod Length:
Heads Make/Model with flow numbers: Flow (CFM) at several lift points.
Combustion Chamber Size in CC’s:
Dome Volume: For a domed piston use a (-) negative number.
Valve Relief Volume: For a piston with valve reliefs or dish, use a (+) positive number.
Deck Clearance:
Head Gasket Bore: [ Optional ]
Head Gasket Thickness:
Valve Sizes Intake/Exhaust:
Intake Manifold Model Type: [Single or Dual Plane]
Model #:
Carburetor Size or EFI (CFM):
Blower/Turbo Make/Model:
Belt Ratio:
SCR & DCR: Or the info to calculate SCR & DCR
[ http://garage.grumpysperformance.co...comp-ratio-cranking-pressure-calculator.4458/ ]
Header Tube Diameter: Small, Medium, Large (1-5/8", or , or)
Cam Card: Need all 8 valve timing events at seat-to-seat and at 0.050” & lobe lift or valve lift
Rocker Ratio - Intake/Exhaust:
Cam Installed per Cam Card, or Retarded or Advanced:
Fuel Used: Gasoline, Methanol, Ethanol, E85 .....

For the heads, the closest BBC I have are below or you could supply the flow numbers .....


1635345375251.png
1635345446295.png
1635345533570.png
 
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Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
great question and , certainly thinking the process through rather than making a blind stab at selection,
is the best route to take.
the clay smith you pointed out, should work ok.
and give a noticeable boost in power.

Clay Smith 02-012, 1700-5700 rpm
LCA = 108, lift = Int/Exh .542,
Dur @ .050 = Int/Exh 224
ICA = 108, 8d overlap @ .050

I think your choice of the
Lunati Voodoo 10110702, 1400-5800 rpm
LCA = 112, lift = Int .530/Exh .542
Dur @ .050 = Int 219/Exh 227
ICA = 108, -1d (no overlap) at .050

has the best chance of posting the more useable off idle to about 4500 rpm torque curve,
that youll use most of the time on the street, but the difference will be marginal,
and yes your likely to loose a few peak hp going lunati vs clay smith


why not have rick do a few simulations,
but Id pay a great deal more attention to the power/ torque curve under 4500rpm than above

compr-psi.gif


46.jpg
 
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TXChevy

Working at The Speed of Slow
Thank you! I really appreciate the help.

I tried to research some additional data and revised the cam info (I replaced the Summit cam too), it's all at the bottom of my post. I also corrected all cam data, including the Lunati that was initially listed.

It makes sense to me to focus on p/t up to 4500 which is where the engine will be running most of the time. From what I understand, getting peak p/t at 6k isn't going to make for a great Sunday drive.

I had a bit of second thought reservation (from ignorance) on the CS smith LCA of 108 so I also looked at its next version at 110 LCA, included below. I had read how tightening of the LCA moves the torque and cyl pressure downward, and can possibly increase detonation? I got to thinking - again maintaining a realistic goal of enjoying the car - that perhaps 110-112 may be an effective compromise? Maybe overthinking it.

Info that I can provide is below, thank you again for your input and advice.

Some additional info:
- I sadly just don't have the flow numbers on the heads. I think that for my purposes and to not waste your time, using the 3rd simulation of stock BBC heads with some cleanup may be a good compromise.
Bore & Stroke: 4.28 x 4.00 (engine is bored .030 over)
Displacement: cubic inches 460
Rod Length: 6.135 (std)
Heads Make/Model with flow numbers: Flow (CFM) at several lift points. GM 427 truck large oval port 3935401
Combustion Chamber Size in CC’s: 116 (measured w burrett)
Dome Volume: For a domed piston use a (-) negative number. (-)28.00cc
Valve Relief Volume: For a piston with valve reliefs or dish, use a (+) positive number.
Deck Clearance: .014
Head Gasket Bore: [ Optional ] 4.5 Per Felpro
Head Gasket Thickness: .0385
Valve Sizes Intake/Exhaust:
Intake Manifold Model Type: [Single or Dual Plane] Edelbrock dual plane RPM
Model #:
Carburetor Size or EFI (CFM): Holley 750 vac sec
Blower/Turbo Make/Model:
Belt Ratio:
SCR & DCR: Or the info to calculate SCR & DCR SCR = 10.29 DCR = 8.72 (per the calculator) These may be a bit high as I didn't have complete data on every item. My initial calculation using the V1-V5 method came out to SCR of 10:1
[ http://garage.grumpysperformance.co...comp-ratio-cranking-pressure-calculator.4458/ ] very helpful, I'll be spending considerable time on this calculator. I unprotected the sheet and used it to take a swing at the SCR/DCR.
Header Tube Diameter: Small, Medium, Large (1-5/8", or , or) 1.75
Cam Card: Need all 8 valve timing events at seat-to-seat and at 0.050” & lobe lift or valve lift plz see info at bottom
Rocker Ratio - Intake/Exhaust: 1.7
Cam Installed per Cam Card, or Retarded or Advanced:
Fuel Used: Gasoline, Methanol, Ethanol, E85 .....


Updated Cam Info:
Clay Smith 02-012, 1700-5700 rpm
LCA = 108, lift = Int/Exh .542,
Adv dur = Int/Exh 274, ICA = 108
Dur @ .050 = Int/Exh 224
8d overlap @ .050, 58d overlap @ .006
.006 EBBDC = 65, EATDC = 29
.006 IBTDC = 29, IABDC = 65
.050 EBBDC = 40, EATDC = 4
.050 IBTDC = 4, IABDC = 40

Crower 01295 1800-5700 rpm
LCA = 110, lift = Int .525, Exh .545
Adv Dur = Int 289/Exh 301, ICA = 106
Dur @ .050 = Int 229/Exh 237
13d overlap @ .050, 75d overlap @ .006
.006 EBBDC = 80.5, EATDC = 40.5
.006 IBTDC = 34.5, IABDC = 74.5
.050 EBBDC = 48.5, EATDC = 8.5
.050 IBTDC = 4.5, IABDC = 44.5

Comp Cams Magnum 270H, 1500-5800 rpm
LCA = 110, lift = Int/Exh .533
Adv dur = Int/Exh 270, ICA = 106
Dur @ .050 = Int/Exh 224
4d overlap @.050, 50d overlap @ .006
.006 EBBDC = 65, EATDC = 25
.006 IBTDC = 25, IABDC = 65
.050 EBBDC = 42, EATDC = 2
.050 IBTDC = 2, IABDC = 42

Lunati Voodoo 10110702, 1400-5800 rpm
LCA = 112, lift = Int .542/Exh .554
Adv dur = Int 262/Exh 268, ICA = 110
Dur @ .050 = Int 227/Exh 233
6d overlap at .050, 41d overlap @ .006
.006 EBBDC = 66, EATDC = 22
.006 IBTDC = 19, IABDC = 63
.050 EBBDC = 48.5, EATDC = 4.5
.050 IBTDC = 1.5, IABDC = 45.5

Lunati Voodoo 10110703 1800-6200 rpm
LCA = 110, lift = Int .554/Exh .542
Adv dur = Int 269/Exh 276, ICA = 108
Dur @ .050 = Int 219/Exh 227
10d overlap at .050, 52d overlap @ .006
.006 EBBDC = 68, EATDC = 28
.006 IBTDC = 24, IABDC = 64
.050 EBBDC = 46.5, EATDC = 6.5
.050 IBTDC = 3.5, IABDC = 43.5

Howards Cams 120941-11 1500-5800 rpm
LCA = 111, lift = Int/Exh .527
Adv dur = Int/Exh 279, ICA = 111
Dur @ .050 = Int/Exh .225
3d overlap @ .050, 57d overlap @ .006
.006 EBBDC = 70.5, EATDC = 28.5
.006 IBTDC = 28.5, IABDC = 70.5
.050 EBBDC = 43.5, EATDC = 1.5
.050 IBTDC = 1.5, IABDC = 43.5

Clay Smith 02-013 1700-5700 rpm
LCA = 110, lift = Int/Exh .510
Adv dur = Int/Exh 274, ICA =110
Dur @ .050 = Int/Exh 224
4d overlap @ .050, 54d overlap @ .006
.006 EBBDC = 67, EATDC = 27
.006 IBTDC = 27, IABDC = 67
.050 EBBDC = 42, EATDC = 2
.050 IBTDC = 2, IABDC = 42
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
it would be very interesting to see what the software dyno results show on these cams.
the clay smith cam still looks rather good to me for the intended application
Clay Smith 02-012, 1700-5700 rpm
LCA = 108, lift = Int/Exh .542,
Adv dur = Int/Exh 274, ICA = 108
Dur @ .050 = Int/Exh 224
8d overlap @ .050, 58d overlap @ .006
.006 EBBDC = 65, EATDC = 29
.006 IBTDC = 29, IABDC = 65
.050 EBBDC = 40, EATDC = 4
.050 IBTDC = 4, IABDC = 40
 

TXChevy

Working at The Speed of Slow
I found a discrepancy in the CS cam data that I'll resolve today. Summit lists both the 012 and 013 cams at .542 lift, but the CS website lists them at .510 lift. Using 1.70 ratio.
I'll call the mfg today to ask about this and to see what they recommend for valve springs as well.
Perhaps I'm comparing apples and oranges due to different durations and LCA/ICA but I was anticipating that a bit more lift than the current Erson cam at .514 would be of benefit.

EDIT: I spoke with CS cams and both lift numbers are incorrect. The correct lift is .500, so now I think I may need to look at either a custom grind from them or going back to my other alternatives. I don't think the .5 lift will be my best choice. Is this a reasonable approach?
 
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Indycars

Administrator
Staff member
Assuming the CS 012 cam has a .542 lift, then here is the first comparison with the Crower 01295.

NOTE: The lift on the Clay Smith cam012 was found to be incorrect. Page
down to see the corrected graph in POST #15.


Sim01_ClaySmith012_VS_Sim02_Crower01295.jpg
 
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Indycars

Administrator
Staff member
SCR & DCR: Or the info to calculate SCR & DCR SCR = 10.29 DCR = 8.72 (per the calculator) These may be a bit high as I didn't have complete data on every item. My initial calculation using the V1-V5 method came out to SCR of 10:1
If you were using the CS cam 02-012 for your calcs, then I get 8.24 for the DCR and not 8.72. What cam did you use? What IVC did you use?

Even a DCR of 8.24 could be problematic if you can only get 91 octane like here in Oklahoma City.

BTW, don't worry about rows 9 and 10 in the calculator, they don't add up to much. But technically they are there, so I included them.

DCR_ClaySmith_01.jpg
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
install the cam at split overlap .. not 4 degrees advanced,



http://garage.grumpysperformance.co...ng-cam-and-shifting-the-lca.10553/#post-44949

http://garage.grumpysperformance.co...op-dead-center-1-for-timing-ignition-cam.966/

http://garage.grumpysperformance.com/index.php?threads/turning-your-crank-manually.5933/

use of different brands of lifters and obviously use of roller lifters vs flat tappet lifters will result in the need for different pushrod lengths so you need to verify rocker geometry and valve train clearances

RockerGeometry.jpg


Standard Length Big Block Intake 3/8" / .080" 8.275"
295-7941-8 Big Block Chevy, Standard Length Big Block Exhaust 3/8" / .080" 9.250"
295-7969-8 Big Block Chevy, Standard Big Block +.100" Long Intake 3/8" / .080" 8.375"
295-7979-8 Big Block Chevy, Standard Big Block +.100" Long Exhaust 3/8" / .080" 9.350"
295-7951-8 Big Block Chevy, Standard Length Big Block Tall Deck Intake 3/8" / .080" 8.675"
295-7961-8 Big Block Chevy, Standard Length Big Block Tall Deck Exhaust 3/8" / .080" 9.650"
295-7800 V8 396-454 Retro Fit Pushrod Set, Intake & Exhaust, 1965-Present
3/8" / .080" 7.725 Int. 8.675 Exh

and some of the un-needed potential compression is bled off and a bit more power in the upper rpm is gained,
all a basic improvement, in the power curve and in addition ,
you have the option of use of a marginally higher roller rocker ratio,or the stock ratio,
(personally Id use these higher ratio, on the intake valves) as they can be used to grab further mid and lower rpm gains
and reduced friction losses



you can use steel roller rockers or the cheaper and marginally less durable aluminum versions

yes as usual, much of the info you need is in links and sub=links:rolleyes::D

http://garage.grumpysperformance.com/index.php?threads/checking-piston-to-valve-clearances.399/

http://garage.grumpysperformance.com/index.php?threads/valve-train-clearances-and-problems.528/

http://garage.grumpysperformance.com/index.php?threads/rocker-push-rod-wear-issues.9815/

http://garage.grumpysperformance.co...ectly-and-get-it-to-last-cam-install-info.90/

http://garage.grumpysperformance.com/index.php?threads/check-cam-valve-lift.15893/#post-95551

http://garage.grumpysperformance.co...-pushrods-and-check-info-you-might-need.5931/

http://garage.grumpysperformance.com/index.php?threads/pushrod-length-tolerance.15189/#post-86920

http://garage.grumpysperformance.co...ng-combustion-chambers.2630/page-2#post-54342

http://garage.grumpysperformance.co...train-clearances-and-problems.528/#post-79273

http://garage.grumpysperformance.co...mble-and-swirl-quench-squish.4081/#post-12283

http://garage.grumpysperformance.com/index.php?threads/valve-to-piston-clearance.16349/#post-99047
 
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TXChevy

Working at The Speed of Slow
Hi Rick, thank you for your time to run the simulations. My mistake on the IVC, I overlooked it and left it at 57.5. Here north of Houston we can get readily 93 octane fuel but detonation is indeed still a concern, I think the cast iron heat sink heads may also contribute?

The published Clay Smith cam info is indeed in error, the lift is verified at .500 for both the .012 and the .013 cams, not .542. I'm glad I noticed this.

I'm appreciating your time so I'm not looking for endless simulations. I did some additional research and found the following that may be of consideration...

Dual Pattern
Howards Cams 120241-09 1600-5800 rpm
LCA = 109, lift = Int .527/Exh .533
Adv dur = Int 279/Exh 285, ICA = 109
Dur @ .050 = Int 225 /Exh 231
10d overlap @ .050, 64d overlap @ .006
.006 EBBDC = 71.5, EATDC = 33.5
.006 IBTDC = 30.5, IABDC = 68.5
.050 EBBDC = 44.5, EATDC = 6.5
.050 IBTDC = 3.5, IABDC = 41.5

Single Pattern
Howards Cams 120991-10 1400-5600 rpm
LCA = 110, lift = Int /Exh .533
Adv dur = Int/Exh 275, ICA = 110
Dur @ .050 = Int/Exh 221
1d overlap @ .050, 55d overlap @ .006
.006 EBBDC = 67.5, EATDC = 27.5
.006 IBTDC = 27.5, IABDC = 67.5
.050 EBBDC = 40.5, EATDC =.5
.050 IBTDC = .5, IABDC = 40.5

I could very well be all wrong here but my perception of general quality in the off-the-shelf is that Howards, CS, Crower, Lunati cams seem to receive more favorable reviews/comments than Comp. Of course it could be that Comp sells many more cams and therefore the proportion of good/bad reviews will be higher as well. But I just wanted to explain why I had leaned more towards a particular brand. In all cases I plan to use the GM 12371044 lifters with the hardened base, and the appropriate recommended valve springs.

When I plug in the Howards 120241-09 cam numbers into the chart, using 0d install, I get an IVC of 68.5, resulting in DCR = 8.02, SCR = 10.29, CP = 192.

When I plug in the Lunati 10110702 cam numbers into the chart, 0d install, I get an IVC of 63, resulting in DCR = 8.37, SCR = 10.29, CP = 203.51.

When I plug in the Crower 01295 cam numbers into the chart, 0d install, I get an IVC of 74.5, resulting in DCR = 7.61, SCR = 10.29, CP =178.64. I noticed that if I change to 4d advanced install, DCR =7.88 and CP =187.64, still a workable range.

If I'm on the right learning curve, it seems that the Crower cam yields good duration/lift but also a liveable DCR and CP?

I appreciate all of the help, this stuff is of great interest to me, goes so much further than guessing.
 
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TXChevy

Working at The Speed of Slow
Grumpy, yes it looks like the data reinforces your advice on 0d install - split overlap.

I'm going to read through all of the links you kindly included - thank you. I never thought (knew about) about mixing the rocker ratios.
 

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
CROWER, AND LUNATI BOTH MAKE GOOD CAMS, personally Id try to stick with those or CLAY SMITH,
(since you did not include ERSON and CRANES NO LONGER AN OPTION,
I have only used a couple HOWARDS cams over the decades ,
(nothing bad or exceptionally good to report, they worked fine)
I generally avoid COMP CAMS as their tech guys are HIT & MISS ON GOOD INFO IF YOU ASK QUESTIONS,
and the ones IVE dealt with seem to want you off the phone as a goal more than solving problems or answering questions
(a big strong point of the old , CROWER, ERSON AND CRANE CAMS, TECH DEPARTMENTS,,, which is why I tended to like dealing with them.

remember reading links and sub-links may take some time and effort but,
:wink:


its sure to save you a bucket of wasted cash and weeks of wasted effort:like:

and help avoid potential problems:worried:
yeah it might take days to wade through , links and sub--links
but you'll be FAR better off having done so!









https://www.chevyhardcore.com/tech-...zing-your-cams-potential-with-better-rockers/

http://garage.grumpysperformance.co...s-and-improved-oil-flow-mods.3834/#post-52402

http://garage.grumpysperformance.co...ing-down-a-valve-train-noise.6237/#post-31799



http://garage.grumpysperformance.co...ring-installation-questions.12833/#post-66380

http://garage.grumpysperformance.co...er-rockers-and-stud-girdles.12208/#post-59297

http://garage.grumpysperformance.co...ch-is-best-steel-or-aluminum.3124/#post-12385

http://garage.grumpysperformance.co...train-clearances-and-problems.528/#post-44534

http://garage.grumpysperformance.co...fit-under-stock-valve-covers.6641/#post-21035

http://garage.grumpysperformance.co...per-valve-spring-seats-shims.1005/#post-15534


 
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TXChevy

Working at The Speed of Slow
I'm going through all of this info, thanks. Even with a budget build I'd be a fool to just guess at parts or throw it together.

If there's no issue, I'll move to order the Crower cam, GM lifters and then verify correct valve springs.:thumbsup:
 
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Indycars

Administrator
Staff member
Hi Rick, thank you for your time to run the simulations. My mistake on the IVC, I overlooked it and left it at 57.5. Here north of Houston we can get readily 93 octane fuel but detonation is indeed still a concern, I think the cast iron heat sink heads may also contribute?
You are very welcome, even if you are from Texas ! :)
Mistakes happen and that's why it's sometimes better to have an another set eyes looking things over.
If you could stay closer to a DCR of 8.0, then if you go out of town a 91 octane shouldn't be a problem if all you need to do is get home.

The published Clay Smith cam info is indeed in error, the lift is verified at .500 for both the .012 and the .013 cams, not .542. I'm glad I noticed this.
Yes, that was definitely a good catch.

I'm appreciating your time so I'm not looking for endless simulations. I did some additional research and found the following that may be of consideration...
It's very little work now to just change camshafts, so don't hold back. Besides I enjoy doing these simulations, you're not the only one learning something.

Where do you want to go from here?
 

Indycars

Administrator
Staff member
I have to post the correct info, I don't want someone using the info above in POST #7
to make a decision based on false data.

Below is the corrected graph for the Clay Smith 02-012 camshaft where the lift value
was corrected from .542/.542 to .500/.500.

Sim01_ClaySmith012_VS_Sim02_Crower01295_Corrected.jpg

I think you might be jumping the gun if you have already decided on the Crower, we have
just begun to explore the camshafts. You don't know what might be coming ahead in the
discussion that could change your mind !
.
 
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Indycars

Administrator
Staff member
Dual Pattern
Howards Cams 120241-09 1600-5800 rpm
LCA = 109, lift = Int .527/Exh .533
Adv dur = Int 279/Exh 285, ICA = 109
Dur @ .050 = Int 225 /Exh 231
10d overlap @ .050, 64d overlap @ .006
.006 EBBDC = 71.5, EATDC = 33.5
.006 IBTDC = 30.5, IABDC = 66.5
.050 EBBDC = 44.5, EATDC = 6.5
.050 IBTDC = 3.5, IABDC = 41.5

Should the IABDC = 68.5° ???
 

TXChevy

Working at The Speed of Slow
Rick, you're right, I got that IABDC wrong, it is 68.5. Thanks for spotting it. I also revised the Crower rpm curve to 2100-5700, which is what their website shows. I corrected these.

I thought about it after I posted and have to agree that there's a benefit in looking further at an optimum cam. What I didn't want to do is overstay my welcome doing endless simulations so please tell me when good is good enough :) I do like seeing them on the same sheet as it's a great visual comparison of their p/t curves, if I'm looking at it right. Also, the block is currently at the machine shop so there's not a big rush to get a cam, I think better to wait to get it done just to be sure there's no deal breaker, like a crack or similar failure. I highly doubt it but you never know,

I think the Howards 120241-09 and the Howards Rattler 128001-09 may be worth a look on the simulation. I'm going to also revisit the Crower website.
I spent more time thinking about the curves and it seems that there's a good amount of torque, peaks at about 3500ish rpm. Power peaks at about 4700ish rpm but that looks like there's room for improvement. But if I'm remaining realistic with the engine components that I have, I think there's a limit to what can be expected if we are essentially tweaking the cam profile and not changing heads etc. I'm ok with that, but that brings me back to your comment about not making the cam selection too soon. There may be a better selection that can bring the power up a bit more, do you think it's also feasible to consider trying to change the curve so the power is coming a bit sooner? Or does that mean it's also going to drop off sooner?

At the end of the day, I'm ok with a driveable combination that provides good p/t without being a twitchy beast that's miserable at low speeds. I'll also go back to my original cam considerations and see if there's some that may be worth another look based upon the data you've kindly provided.

EDIT, I did go and look up Erson but I'm not really sure of their current quality. I can say that their cam was in the engine for 34 years (but low miles) and looked great upon removal. But that may have been a different company then. I also looked at another Crower.

Erson E120018 2200-5600 rpm
LCA = 109, lift = Int/Exh .544
Adv Dur = Int/Exh 292, ICA = 109
Dur @ .050 = Int/Exh 230
12d overlap @ .050, 74d overlap @ .006
.006 EBBDC = 75, EATDC = 37
.006 IBTDC = 37, IABDC = 75
.050 EBBDC = 44, EATDC = 6
.050 IBTDC = 6, IABDC = 44

Crower 01296 2400-5500 rpm
LCA = 110, lift = Int .535, Exh .557
Adv Dur = Int 294/Exh 304, ICA = 110
Dur @ .050 = Int 233/Exh 240
16.5d overlap @ .050, 79d overlap @ .006
.006 EBBDC = 82, EATDC = 42
.006 IBTDC = 37, IABDC = 77
.050 EBBDC = 50, EATDC = 10
.050 IBTDC = 6.5, IABDC = 46.5
 
Last edited:

Indycars

Administrator
Staff member
Rick, you're right, I got that IABDC wrong, it is 68.5. Thanks for spotting it. I also revised the Crower rpm curve to 2100-5700
Not a problem, again two sets of eyes are always better then one. Just trying to keep the data correct
for those that come after us. The RPM curve is subjective, it's not so important, but always better to
get it right to best of our ability .... thanks !

NOW, I WOULD LIKE TO SAY ..... WOAH NEELY !!!!

You have quoted about 12 camshafts specs above (some maybe duplicates). I'm not sure where you
are going. Now I'm NOT saying I don't won't to do that many simulations, far from it, but that many
simulations without a logical progression/plan will JUST BE OVERWHELMING data, and nothing will
be gained in the long run by bombarding our senses with so much data. It's already starting to turn
my mind to mush !

Answer a few questions ......

1.) Is the Crower 01295 at the top of your list now, if not what is ? (This is always subject to change. )
Is this the cam going forward that we should compare all others to until we decide to change ?

2.) The Intake Valve Closing angle (IVC) needs to be 67° to 71° , this will keep your DCR between
8.11 to 7.85. Now this is an example, IT IS YOUR RESPONSIBILITY TO DETERMINE THE ACTUAL NUMBERS.
If you are not willing to change the physical dimensions of your engine, then your only choice is the
IVC. The IVC can be moved (typically retarded 4°), depending on the camshaft manufacture and model.

3.) Have you considered a hydraulic roller, why have you not consider them ??? Let's don't get down
the road a couple of weeks, then wonder ..... how about a roller camshaft ??? If you are not going to
consider a roller that's perfectly fine, but let's decide now or should we look at some rollers before
counting them out ???

Before you say NO. Consider the benefits.
- More area under the lift curve, meaning better performance.
- Don't have worry about break-in. If you have to replace the flat tappet cam, then what is your cost?

Cons
- Cost is considerably higher
- Might delay the completion of my project by a few months until the money is available.
 

Indycars

Administrator
Staff member
When I did a search on your pistons, I got a Speed Pro number. Guess TRW has been gobbled up
since I was in high school when my 64 Nova had TRW pistons.


Anyway, the number comes up with a slightly different dome volume of 29.4cc instead of the 28cc
you quoted.. This does change things alittle.

Did you measure the dome volume or do you have documentation ?

1635478121836.png
 

TXChevy

Working at The Speed of Slow
NOW, I WOULD LIKE TO SAY ..... WOAH NEELY !!!!
You're absolutely right. I was getting the "I'm getting a bit too far from shore" feeling. I've learned a couple of things along the way - make the best plans you can but be prepared to change them as reality affect them and take knowledgeable advice.

I think if there's a simulation to be looked at as a known baseline, it's the Erson cam that was in the car. It worked quite well.
Erson TQ20H 1500-5000 rpm
LCA = 112, lift = Int/Exh .514
Adv Dur = Int/Ex 292, ICA = 112
Dur @ .050 = Int/Exh 214
-10d overlap @ .050, 68d overlap @ .006
.006 EBBDC = 78, EATDC = 34
.006 IBTDC = 34, IABDC = 78
.050 EBBDC = 39, EATDC = -5
.050 IBTDC = -5, IABDC = 39

1.) Is the Crower 01295 at the top of your list now, if not what is ? This is always subject to change. )
Is this the cam going forward that we should compare all others to until we decide to change ?
So far yes, it seems to provide a reasonable improvement from the original Erson cam in the 1800-5700 rpm range. It would be good to see a comparison of these two cams on the simulator.

2.) The Intake Valve Closing angle (IVC) needs to be 67° to 71° , this will keep your DCR between
8.11 to 7.85. Now this is an example, IT IS YOUR RESPONSIBILITY TO DETERMINE THE ACTUAL NUMBERS.
If you are not willing to change the physical dimensions of your engine, then your only choice is the
IVC. The IVC can be moved (typically retarded 4°), depending on the camshaft manufacture and model.
Agreed. At this time there's no plan to change heads and based on measuring taper/out of round the only work needed on the cylinders was a fresh hone. So I will be glad to use the calculator to verify the IVC especially now that I see how it impacts the DCR.

Have you considered a hydraulic roller, why have you not consider them ??? Let's don't get down
the road a couple of weeks, then wonder ..... how about a roller camshaft ??? If you are not going to
consider a roller that's perfectly fine, but let's decide now or should we look at some rollers before
counting them out ???
I had thought about a retrofit hydraulic roller, especially looking the ones from Howards, but had initially decided that for my budget and for the need, a hydraulic tappet cam would be ok. I had looked at those costs, and of course I was considering cost of block/head machine work and parts as well. However it seems that the Howard retro HR's with lifters are in the $700-800 range which I think is reasonable for what I think are decent quality parts. And I understand that there's still rockers, springs, etc to buy, but I'd have to do that anyway so it's mainly the cam/lifter cost difference.
Here's where the advice part comes in so I'm listening to avoid being penny wise and dollar foolish. I understand about the break-in requirements and have considered the possibility of a failure and the complete rebuild of the engine. An HR cam purchase would not delay anything, its simply a cost factor. But also looking at the p/t curve, I think your comment about considering a HR cam is feasible. It would be much easier to run the engine in and greatly reduce the break-in issues related to hydraulic tappet.

So yes, would be very useful to see any HR cam compared with the baseline Erson TQ20H and the possible Crower 01295- that would give me a real world comparison since I remember clearly how the car drove with the Erson.
As you mentioned, I don't want to get to the completion and wonder why didn't I spend the extra for the HR cam vs the $350 or so I spent for the HT cam.
When I did a search on your pistons, I got a Speed Pro number. Guess TRW has been gobbled up
since I was in high school when my 64 Nova had TRW pistons.

Anyway, the number comes up with a slightly different dome volume of 29.4cc instead of the 28cc
you quoted.. This does change things alittle.

Did you measure the dome volume or do you have documentation ?
You are correct, this was another mistake on my part. Dome height on my pistons is .221 which does translate to the 29.4cc. I'm not sure where the 28cc number came in - I had a lot of numbers flying around. No excuses though, I'll correct this in my data. Thanks again for cold eyes look at this.

I used the calculator to look at the 2 cams at 0d installed:

Erson TQ20HCrower 01295
Bore4.2804.280
Stroke4.0004.000
Combustion Chamber116.0116.0
Deck Height0.0140.014
Gasket Thickness0.0390.039
Gasket Diameter4.5004.500
Dome (-) / Valve Relief (+)-29.40-29.40
Top Ring Height0.3000.300
Ring Land to Cyl Bore Clearance0.00700.0070
Connecting Rod Length6.1356.135
Intake Valve Closing Angle78.076.5
Atmospheric Pressure14.714.7
Dynamic Compression Ratio7.437.55
Static Compression Ratio10.4010.42
Cranking Pressure (Gauge)173.09176.93

So when I look at data and remember the fun factor of the actual drive, it helps me to focus on what do I actually need, which can be a bit more power than what I had. There looks to be gobs of torque which gets the car up and going quick and I remember that.

My ongoing spare time homework has been going through the links and sublinks that have been posted. A lot to process but that's ok, when I step back a moment it starts to slowly seep in.

For me, this is a discussion of huge help.
 
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