Assembled Head or Cam Kit ???

[Indycars]

I'm in the planning stages for a new engine in my street rod. Concerning the aftermarket heads and cam, which direction should I take.....assembled heads, and a camshaft OR bare heads and camshaft kit (cam, springs, lifters, etc).

The assembled heads would have a complete multiple angle valve job done by the manufacture, but the valve springs may not be exactly what the cam company recommends. On the other hand if I buy the cam kit then I'm assured of having the correct components, but then I have to decide how to get a quality multiple angle valve job done locally. If I had a long history with a local machine shop, then this would not be a problem, but I don't.

There are more pros and cons to both sides, but this seems to be the biggest one to purchasing the best components. Which direction would you take???

Thanks!!!


Rick Miller

 

[grumpyvette]

the question as to if assembled heads or buying bare heads and adding your selected components to match your application comes up frequently
that's a common question and the answer unfortunately is.. that the most effective route to building a quality engine ,is to buy the bare heads and cam kit with matched springs and let a experienced machine shop assemble the components and do the required machine work and clearance work, because it makes little sense to pay for springs,retainers and valves that you, discard,and won,t be using, if your planing on upgrading those components.
assembled heads generally provide a good start point for a generic engine build, but once you carefully check the components used by the manufacturer, and find they don,t match your requirements the assembled heads don,t look like as much like an attractive choice
its unfortunate because finding an experienced machine shop that does work at a reasonable cost and in a timely manor is not easy to do, in most areas,
and because you take a significant chance of getting your project totally screwed if your machine shop doesn,t do good work, plus the total cost tends to be higher than just slapping heads you get assembled onto an engine and installing a cam, and trusting to the manufacturers specs and LUCK that it will function as intended, simply because it takes a good deal of time and knowledge, and specific tools, to check all the clearances, spring heights,coil bind, valve guide clearance,etc.etc.
that's mostly because assembled heads are sold at a price point, and the manufacturer will not know which cam or engine combo it will be used with,so the manufacturer won,t be selecting the best valves,valve guides, retainers, and springs available, but a component that's a compromise between cost and quality to maintain both a decent quality product but a low total price.
and components that will work with a fairly broad range of engine combos, while keeping the price as low as he can to remain competitive in the market place.
while you can select better valves and springs and retainers that exactly match your needs.
obviously you can build a similar hp level engine several different ways, and you could use similar components from different manufacturers to get similar results

threads with a good bit more related info, and useful sub links

viewtopic.php?f=52&t=534&p=1042&hilit=bare+assembled#p1042

viewtopic.php?f=52&t=2826&p=7296&hilit=bare+valves#p7296

viewtopic.php?f=52&t=181&p=2342&hilit=bare+valves#p2342

viewtopic.php?f=52&t=975&p=1700&hilit=+bare+valves#p1700

viewtopic.php?f=50&t=321&p=2931&hilit=track+notes+pad#p2931

viewtopic.php?f=52&t=401&p=698#p698

viewtopic.php?f=52&t=389&p=6855&hilit=shrouding#p6855

viewtopic.php?f=52&t=2630&hilit=shrouding

now IM not saying you can,t get a good deal on assembled heads because obviously in many cases the out of the box assembled heads from name brand manufacturers like AFR,BRODIX,DART,EDELBROCK,TRICKFLOW,etc. will provide good service, or that you can,t get similar results from, a few different components, but if your serious about maximizing a heads potential it should be rather obvious that exactly matched components with the correct clearances, spring load rates, flow rates,and designed rpm band characteristics etc. that match your application,provide some benefits over a random collection of similar parts, machine work done, a generic valve spring,and clearance work.
now if your building a fairly generic 383 SBC with, 10:1 cpr and a dual plane intake designed to spin in the 3000rpm-6300rpm band, with a mid range hydraulic roller of flat tappet cam,for a basic hot street combo then by all means go with a basic 195cc-210cc head designed to match your components after checking the valve train,springs etc. against your requirements, because your very likely to find what you need in an off the shelf head,but if your building a 13:1 cpr roller engine your very unlikely to get the same performance from an assembled head as you could get from a properly prepped head and valve train with light weight valves and springs on a solid roller combo designed to hit 7000rpm plus.

your thoughts? questions?

 

[grumpyvette]

when I built my last 540 BBC combo we had to price out both routes and compare

bare heads cost $1620 per pair

http://www.summitracing.com/parts/TFS-4 ... /?rtype=10


assembled, cost $2460....roughly $800 more than bare heads
http://www.summitracing.com/parts/TFS-4140T808/

but by the time you added,
quality valves ,
rocker studs,
adjustable guide plates,
springs,shims,
retainers,keepers,
valve locks,
valve seals
valve springs
and machine work,
the assembled price didn,t look nearly as bad, as it was several hundred dollars LESS than the cost of our finished heads, at nearly $$2870
but keep in mind having the better springs and valves seemed like a better idea

 

[Indycars]

when I built my last 540 BBC combo we had to price out both routes and compare

bare heads cost $1620 per pair

http://www.summitracing.com/parts/TFS-4 ... /?rtype=10


assembled, cost $2460....roughly $800 more than bare heads
http://www.summitracing.com/parts/TFS-4140T808/

but by the time you added,
quality valves ,
rocker studs,
guide plates,
springs,shims,
retainers,keepers,
valve locks,
valve seals
and machine work,
the assembled price didn,t look nearly as bad

Do you have a number for the bare heads and separate components??? Or suffice it to say it was so close the actual number doesn't matter.

I'm still reading your first post with links before I respond.

Thanks again!!!


Rick

Sorry I see where you have added more info, I'm guessing after I clicked on "Reply"

 

[Indycars]

Maybe a little about my expectation for this engine will help with this conversation. Since I'm not competing in a class where I have to stay within the rules and make the biggest HP, I'm not concerned about getting every last pony out of this engine. Sound and looks are of some concern, but I will not do something that is ONLY for appearance. I have totally rejected the thought of using CompCams Thumper for the sound. I want to think to some extent(pretend) that I built this engine with performance as my only goal. I enjoy the process of learning the details and then putting them in to the final product, just like I would if I was racing. Racing is my first love, so I use the street rod as vehicle for this purpose....no pun intended. I've never built an engine with this kind of sophistication and it will take me most likely until next spring to find my way to the end result.

I'm pretty sure I'm going with a Solid Roller, I don't mind adjusting the valves. Besides if done right and with the limited miles (~4000 miles/yr) that should only be needed once or maybe twice a year, at the most. It will be more like spending quality time with my baby, my other two babies are in the limbo state called college.

This is what I have in mind at this point:
- Max RPM = ~6200
- Use pump gas
- Intake Manifold Type = Dual Plane.....probably
- Aluminum Heads
- Compression Ratio = ~ 10:1
- Rotating Assembly from Scat, Eagle or Ohio Crankshaft for a 388
- Late 60's, Chevy 350 with 4 bolt main block
- Block as been bored far enough to determine what piston size to purchase (0.060 over size)
- Street Solid Roller with lift about .525 to .550, Duration = ???
- Car weights 1800 lbs w/ TH350 Automatic (To be rebuilt and torque converter purchased with stall in 2400-2800 range)
- Budget = $4500-$5000

The question as to if assembled heads or buying bare heads and adding your selected components to match your application comes up frequently. That's a common question and the answer unfortunately is.. that the most effective route to building a quality engine, is to buy the bare heads and cam kit with matched springs and let a experienced machine shop assemble the components and do the required machine work and clearance work, because it makes little sense to pay for springs, retainers and valves that you, discard, and won,t be using, if your planing on upgrading those components.

I'm looking at the Brodix IK180 or IK200, so if the spring pressures are Ok for the cam I select, then I don't plan on upgrading anything on the assembled head. I will be comparing their valve lift specs with the cam also, then measuring for coil bind, rocker/retainer, etc to confirm.

That's mostly because assembled heads are sold at a price point, and the manufacturer will not know which cam or engine combo it will be used with, so the manufacturer won,t be selecting the best valves, valve guides, retainers, and springs available, but a component that's a compromise between cost and quality to maintain both a decent quality product but a low total price and components that will work with a fairly broad range of engine combos, while keeping the price as low as he can to remain competitive in the market place.

After verifying that the spring pressures are reasonable, I'm not sure I could do a better job of selecting components. I've built 3-4 engines in the last 30 years and the last one was 15 years ago, so I don't have the experience to backup my selection of retainer, keepers, etc.

Now if your building a fairly generic 383 SBC with, 10:1 cpr and a dual plane intake designed to spin in the 3000rpm-6300rpm band, with a mid range hydraulic roller of flat tappet cam, for a basic hot street combo then by all means go with a basic 195cc-210cc head designed to match your components after checking the valve train, springs etc. against your requirements, because your very likely to find what you need in an off the shelf head, but if your building a 13:1 cpr roller engine your very unlikely to get the same performance from an assembled head as you could get from a properly prepped head and valve train with light weight valves and springs on a solid roller combo designed to hit 7000 rpm plus.

I think I'm closer to the first one.

I don't how you find the time for everything else and still answer questions, but I'm sure glad you do....thanks!!!

Rick Miller

 

[grumpyvette]

This is what I have in mind at this point:
- Max RPM = ~6200
- Use pump gas
- Intake Manifold Type = Dual Plane.....probably
- Aluminum Heads
- Compression Ratio = ~ 10:1
- Rotating Assembly from Scat, Eagle or Ohio Crankshaft for a 388
- Late 60's, Chevy 350 with 4 bolt main block
- Block as been bored far enough to determine what piston size to purchase (0.060 over size)
- Street Solid Roller with lift about .525 to .550, Duration = ???
- Car weights 1800 lbs w/ TH350 Automatic (To be rebuilt and torque converter purchased with stall in 2400-2800 range)
- Budget = $4500-$5000


your correct , given the info youve just posted that the brodix IK 200cc heads with the optional springs will match your intended goals admirably, having a car that light weight will make this almost an unbelievably responsive combo,just keep in mind your goal is not just peak hp.
, theres no reason to go with other than a hydraulic roller cam, as they perform just fine up to 6200rpm and tend to be slightly more durable on a street car than a solid roller cam due to lower valve train loads and a bit better oil flow IF set up correctly, get the 2800rpm stall converter and a 3.73:1 -4.11:1 rear gear will match perfectly in that car,
get an ignition with a rev limiter that can be set at 6300rpm

http://www.brodix.com/heads/ik.html
optional springs, and possibly the 7/16" rocker studs
1.470 Hydraulic Roller Valve Spring - CC 987,
125 lb Closed, 325 lb Open,
1.900 Installed Height,
.575 Maximum Lift
(IK 180, IK 200)
a cam like this, matches your converter stall and cpr, ID strongly suggest you don,t get seduced into a larger duration cam as although you'll gain a bit more peak hp, you'll lose enough of the mid rpm power curve doing so, to make the increased duration a bad choice in a street driven car, this cam kicks butt in a combo like this in a light weight car , Id suggest a BILLET CORE for durability and talk to crower, about the lifters, again don,t get seduced into a larger duration cam as its not going to be a good swap in a street combo, youll have all you can handle if you follow these tips, but if you really want more later a 150hp nitrous kit can be added, although I don,t think even slicks will contain the torque, increase youll have trouble with most street tires with the N/a combo power curve
http://www.crower.com/misc/cam_spec/cam ... 1&x=30&y=9

with 1.5:1 roller rockers similar to these, but Id use a rocker stud girdle or upgrade to the 7/16" rocker studs, or both.
http://www.summitracing.com/parts/CCA-1601-16/

intake manifold, and a good 750-800cfm Holley or demon carb
http://www.summitracing.com/parts/WND-8501/

If you can find some or weld up some 1 5/8" headers with about 36"-38" primaries and a 3" collector about 14"-18" long and mated to a low restriction 3" exhaust/mufflers with an (X) pipe it will increase low and mid rpm power

read these, keep your cpr around 10:1 and quench at about .040-.042
http://www.brodix.com/heads/ikdyno.html

http://airflowresearch.com/articles/article031/A-P1.htm

optional only if your goal is simply destroying tires

http://www.summitracing.com/parts/NOS-05001NOS/

 

[Indycars]

there's no reason to go with other than a hydraulic roller cam, as they perform just fine up to 6200rpm and tend to be slightly more durable on a street car than a solid roller cam due to lower valve train loads and a bit better oil flow IF set up correctly

I thought the solid roller would provide a little more lift with the same duration, since the solid roller lifters are lighter and the stresses would then be roughly equal. The durability of the solid on the street seems to be a question in your mind......correct???

your correct , given the info youve just posted that the brodix IK 200cc heads with the optional springs will match your intended goals admirably, having a car that light weight will make this almost an unbelievably responsive combo,

I was kinda on the fence about which head IK180 or IK200......Is it the light weight car that gets me by with the IK200 and 2800 rpm stall converter??? Another words if this car weighed 3200 lbs, then the IK180 and higher stall converter would be better.

get the 2800rpm stall converter and a 3.73:1 -4.11:1 rear gear will match perfectly in that car,

The car has 3.7:1 Ford 9 inch Posi now. How is driving with a high stall converter on the street different from the stock converter??? I've always had 4 speed manual trans before, so I don't have experience with the high stall converter. My wife will be driving the car also, so I'm just wondering how this might affect her.

Id suggest a BILLET CORE for durability and talk to crower, about the lifters

What concerns do you have about the lifters??? I'm not sure what you are suggesting, please clarify.

but if you really want more later a 150hp nitrous kit can be added, although I don,t think even slicks will contain the torque, increase youll have trouble with most street tires with the N/a combo power curve

I think this car will be scary enough, besides I don't know where I would put it......this car is a T-Bucket. Not much room except for the essentials!

If you can find some or weld up some 1 5/8" headers with about 36"-38" primaries and a 3" collector about 14"-18" long and mated to a low restriction 3" exhaust/mufflers with an (X) pipe it will increase low and mid rpm power

I would like to do something different than the others in this area, but not sure what it would be at this time. I already have a set like these...
http://www.summitracing.com/parts/PTE-H8070/
With turnouts like this, except they might be slightly shorter with mufflers inside...... http://www.summitracing.com/parts/DOU-H3817/

Do I need to order a small base circle cam to clear the 3.75 inch stroker crankshaft and better rods from Scat, Eagle...etc???


Rick

 

[grumpyvette]

there's no reason to go with other than a hydraulic roller cam, other than the cost, as they perform just fine up to 6200rpm and tend to be slightly more durable on a street car than a solid roller cam due to lower valve train loads and a bit better oil flow IF set up correctly

I thought the solid roller would provide a little more lift with the same duration, since the solid roller lifters are lighter and the stresses would then be roughly equal. The durability of the solid on the street seems to be a question in your mind......correct???

Keep you goal of high durability, ease of street driving and reasonable cost in mind!, most solid roller lifters are lighter in weight than most hydraulic roller lifters ,a hydraulic roller valve train, with its matched lower valve spring loads and cam lobe design has somewhat lower stress, but because your limiting your engines rpm to under about 6400rpm , where piston speed starts to become a factor in durability and because you expect to drive mostly on the street where low and mid rpm power is your major concern and because of the dual plane intake design theres no reason to use the higher valve spring loads and lighter lifters that allow higher rpms, that the solid lifter provides, and the hydraulic roller valve train will provide all the lift and duration you can use, the 200cc ports better match the 388 displacement.
slightly more lift than the .555/.560 on those heads in that rpm range will have little or no benefits, IN YOUR INTENDED APPLICATION
theres no quest that you could gain a few more peak hp with a cam like this crane design Ill list below, IF your willing to trade peak hp for less drive-ability, but that's not usually a great idea in a street car,because to reach its potential a 3500 stall converter and a single plane intake
like this,
http://www.summitracing.com/parts/HLY-300-110/
and 10.5:1 cpr would be a better match
http://www.cranecams.com/index.php?show ... vl=2&prt=5

It makes little sense to build in a 7500rpm potential if your not spinning the engine above about 6400rpm or to sacrifice low and mid rpm potential you will use constantly to gain high rpm power in an rpm range you won,t be using.
that crower 00471 cam with its .555/.560 lift and 236/240 dur. at .050 lift, pretty much maximizes the 200cc cylinder heads potential in your intended rpm range
read these, again pay attention to cam specs, and power curves
http://www.brodix.com/heads/ikdyno.html

http://airflowresearch.com/articles/article031/A-P1.htm

your correct , given the info youve just posted that the brodix IK 200cc heads with the optional springs will match your intended goals admirably, having a car that light weight will make this almost an unbelievably responsive combo,

I was kinda on the fence about which head IK180 or IK200......Is it the light weight car that gets me by with the IK200 and 2800 rpm stall converter??? Another words if this car weighed 3200 lbs, then the IK180 and higher stall converter would be better.

the crower cam I selected and your 3.71/1 rear gear ratio are a good match, the higher stall (2800rpm) in that light car will place you in the power band quicker and have no drive-ability issues in a light car on the street, having a 2800rpm stall DOESN,T mean the car wount move well below that rpm under part throttle, it simply maximized the power curve

get the 2800rpm stall converter and a 3.73:1 -4.11:1 rear gear will match perfectly in that car,

The car has 3.7:1 Ford 9 inch Posi now. How is driving with a high stall converter on the street different from the stock converter??? I've always had 4 speed manual trans before, so I don't have experience with the high stall converter. My wife will be driving the car also, so I'm just wondering how this might affect her.

iIt should not be an issue after she gets used to the car,she will need to learn NOT to stomp , on the throttle because it will respond far faster, and more spectacularly than most street cars especially if shes not blasting off every stop light, it simply means the car will rev a bit higher than stock, as she accelerates, its just not as big an issue as you might imagine

Id suggest a BILLET CORE for durability and talk to crower, about the lifters

What concerns do you have about the lifters??? I'm not sure what you are suggesting, please clarify.

cam cores come in cast or billet core, billet steel is stronger

but if you really want more later a 150hp nitrous kit can be added, although I don,t think even slicks will contain the torque, increase youll have trouble with most street tires with the N/a combo power curve

I think this car will be scary enough, besides I don't know where I would put it......this car is a T-Bucket. Not much room except for the essentials!

if you have the desire, youll find a way, many guys mount the tank behind the seats, under the car or in the trunk area.

If you can find some or weld up some 1 5/8" headers with about 36"-38" primaries and a 3" collector about 14"-18" long and mated to a low restriction 3" exhaust/mufflers with an (X) pipe it will increase low and mid rpm power

I would like to do something different than the others in this area, but not sure what it would be at this time. I already have a set like these...
http://www.summitracing.com/parts/PTE-H8070/
With turnouts like this, except they might be slightly shorter with mufflers inside...... http://www.summitracing.com/parts/DOU-H3817/

those should work just fine if the collectors fairly long

Do I need to order a small base circle cam to clear the 3.75 inch stroker crankshaft and better rods from Scat, Eagle...etc???

that depends on the connecting rods selected, in most cases a small base cams NOT required, but clearances can be close, so verifying clearances is mandatory, I have used a small base billet core hydraulic roller cams in most of my builds with scat cranks/rods , designed as stroker kits and had no clearance issues
Ive used both these cams, in similar engine combo

http://www.crower.com/misc/cam_spec/cam ... &x=27&y=10
http://www.cranecams.com/index.php?show ... vl=2&prt=5



Rick

yes IM only too aware most guys want bragging rights on a 550-600hp engine, while that might sound impressive its hardly what your going to want to be driving in a 2000lb t-bucket, youll be able to destroy the tires and run very impressive times with an engine as described above, in fact if you build it as suggested Id strongly suggest HUGE 4 wheel disc brakes, and lots of tire tread on the pavement
this may be of interest
viewtopic.php?f=44&t=38

http://ohiocrank.com/chev_sb_shortb.html

assume ONLY 425- 450 rear wheel hp (which you should easily exceed) and a 2000 lb weight and use these calculators

http://www.wallaceracing.com/et-hp-mph.php

http://www.ajdesigner.com/fl_horsepower ... d_time.php

and before someone brings it up, yes you could reduce cost with a slightly longer duration, solid lifter, flat tappet cam
http://www.cranecams.com/?show=browsePa ... e=camshaft

and while it would tend to reduce the power curve, and drive ability it would also reduce the cost easily $600-$700


questions?

 

[Indycars]

Grumpy Said:
there's no reason to go with other than a hydraulic roller cam, as they perform just fine up to 6200rpm and tend to be slightly more durable on a street car than a solid roller cam due to lower valve train loads and a bit better oil flow IF set up correctly

Rick Said:
I thought the solid roller would provide a little more lift with the same duration, since the solid roller lifters are lighter and the stresses would then be roughly equal. The durability of the solid on the street seems to be a question in your mind......correct???

Grumpy Said:
Keep you goal of high durability, ease of street driving and reasonable cost in mind!, most solid roller lifters are lighter in weight than most hydraulic roller lifters ,a hydraulic roller valve train, with its matched lower valve spring loads and cam lobe design has somewhat lower stress, but because your limiting your engines rpm to under about 6400rpm , where piston speed starts to become a factor in durability and because you expect to drive mostly on the street where low and mid rpm power is your major concern and because of the dual plane intake design theres no reason to use the higher valve spring loads and lighter lifters that allow higher rpms, that the solid lifter provides, and the hydraulic roller valve train will provide all the lift and duration you can use, the 200cc ports better match the 388 displacement.
slightly more lift than the .555/.560 on those heads in that rpm range will have little or no benefits
It makes little sense to build in a 7500rpm potential if your not spinning the engine above about 6400rpm or to sacrifice low and mid rpm potential you will use constantly to gain high rpm power in an rpm range you won,t be using.
that crower 00471 cam with its .555/.560 lift and 236/240 dur. at .050 lift, pretty much maximizes the 200cc cylinder heads potential in your intended rpm range
read these, again pay attention to cam specs, and power curves
http://www.brodix.com/heads/ikdyno.html
http://airflowresearch.com/articles/article031/A-P1.htm

Rick Said:
I think you read me wrong, let me try to explain better. I'm talking about keeping the duration and spring loads the same but having more lift with the SOLID roller and still not exceeding the ~6200 rpm. But like you said above, if the heads can't flow any more, then more lift is a moot point.

------------------------------------------------------------------------------------------------------------------------------------------------
Grumpy Said:
Id suggest a BILLET CORE for durability and talk to crower, about the lifters

Rick Said:
What concerns do you have about the lifters??? I'm not sure what you are suggesting, please clarify.

Grumpy Said:
cam cores come in cast or billet core, billet steel is stronger

Rick Said:
Above you referred to the lifters, that's what I'm asking about. I understand the Billet Core being stronger.

------------------------------------------------------------------------------------------------------------------------------------------------
Rick Said:
Do I need to order a small base circle cam to clear the 3.75 inch stroker crankshaft and better rods from Scat, Eagle...etc???

Grumpy Said:
that depends on the connecting rods selected, in most cases a small base cams NOT required, but clearances can be close, so verifying clearances is mandatory, I have used a small base billet core hydraulic roller cams in most of my builds with scat cranks/rods , designed as stroker kits and had no clearance issues
Ive used both these cams, in similar engine combo
http://www.crower.com/misc/cam_spec/cam ... &x=27&y=10
http://www.cranecams.com/index.php?show ... vl=2&prt=5

Rick Said:
How do you know what the clearances are until you order the cam and check, then you need the small base cirlce. Can you return the cam for another???

If the crankshaft is internally balanced, is it likely to have more clearance issues than a externally balanced crank???

Thanks!!!


Rick

 

[grumpyvette]

its always a good idea to select the cam and lifters and valve springs and as much of the valve train as you can from a single manufacturer, and to follow that manufacturers suggested installation process,simply because if you mix and match components from several manufacturers it voids any warranty, and theres a very strong tendency for each manufacturer to blame the mis-matched components supplied by the other manufacturers as the source of your problem if anything bad happens to the valve train.
crower,isky and crane all have decent cams and valve train components, but each has at least two different hydraulic roller lifter, or spring designs for every cam they sell,so you need to discuss your goals, components,expectations and options with the tech dept.

theres no reason to not use a small diam. billet cam to gain additional connecting rod clearance with a roller cam,or to not select connecting rods designed for extra cam clearance if your building a 388 sbc stroker, but yes you always need to verify clearances during the trail assembly clearance checks, a .060 cam lobe to connecting rod clearance is all thats required, as always discuss your combo with the manufacturer supplying your components
I posted earlier these threads that may help

viewtopic.php?f=44&t=38

viewtopic.php?f=52&t=2166&p=5840&hilit=+cores+cast#p5840


has a good deal of info and useful sub links

internal balance crank assemblies tend to have larger counter weights and less internal stress but its the connecting rod to cam clearance not the counter weights your normally concerned with on clearance issues

obviously the connecting rod on the right has significantly more cam lobe clearance than the left rod bolt rod design provides

why you need to verify the cam to rod bolt clearance

 

[Indycars]

theres no reason to not use a small diam. billet cam to gain additional connecting rod clearance

When do you start to worry about a small base circle cam having too much Torsional Twist??? Is it when the spring pressures rise above a certain level that creates this problem???


Rick

 

[grumpyvette]

theres no reason to not use a small diam. billet cam to gain additional connecting rod clearance

When do you start to worry about a small base circle cam having too much Torsional Twist??? Is it when the spring pressures rise above a certain level that creates this problem???


Rick

thats a potential valid issue with a cast iron cam core, with its lower torsional shear strength, but of less concern with a steel billet core, but I would suggest staying in the .900 or larger diam. range on a small base circle cam, keep in mind that the valve springs push on both the opening and closing cam lobe ramps and theres 8 cylinders, with two cam lobes each so theres always opposing forces, , trying to equalize as the cams rotated, yeah it would be beneficial to have a larger cam bearing diameter and more rod clearance, but we are forced to work with the basic design, unless your willing to do extensive machine work and install larger roller cam bearings, so use of a billet core is a wise precaution if your valve spring load rates exceed about 320 psi, and certainly by 400 psi, as the wear increases with the spring load rates

viewtopic.php?f=52&t=788&p=1142&hilit=play+core#p1142

viewtopic.php?f=52&t=282

 

[Indycars]

Many thanks for the help Grumpy!!!


Rick Miller