Isky Mega 270 Vs Crower 00256

All,

Putting together a mild 355. Going in a 69 Camaro. 9.5:1 compression, 3.73 gears, automatic with a 2500 converter or so. World product heads, 64cc, 180 runner, pocket ported. Nothing extravagant. Wants a good lumpy idle. I was thinking these cams were decent candidates. What's your thoughts? Street car. 3" exhaust and 1 3/4 full header.
https://www.crower.com/searchresults/
(Type in 00256). Lots more info on the 270 isky. Can't find the valve events on the isky though. What's your thoughts or suggestions? Thank you as always.
 
Chris,

Looks like Grumpy missed your post/questions, he is getting old and cranky so when he sees this
post he should offer his opinion.

I don't find a WP head with both 64cc chamber and 180cc intake runner, what is the part number ?
Is this just a camshaft swap or a new engine build?

You have two conflicting goals when you say Mild with a Lumpy Idle, so you are going to have a compromise
somewhere. At this point it looks like you are on the milder side.

You also need to consider .....
- Your static CR and your Dynamic CR, which hinges in the Intake Valve Closing angle at the advertised duration.
- What octane fuel you will be using.

If you can supply most of the info below, I can run a Dynomation 6 computer simulation on your selection of parts.

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:
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 .....

Are these the camshafts you are considering ???

Crower_HF_00256_450_453.jpg
Isky_HF_201271_270Mega_465_465.JPG
 
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Thanks Rick. I guess when I say mild I mean not radical but want some cam sound to it. Both grinds are mild in my opinion. Those are the 2 grinds.
Bore:4.030x3.48
355 cubic inch
.039 head gasket thickness, 4.100 gasket bore
-7cc dish piston
Deck is even.
2.02/1.60 valves
Edelbrock airgap
650 or 750cfm carb. I have both.
No blower
93 octane
Cam cards have the timing events.
Thank you
 
I still need the Cylinder Head Flow Numbers and preferably also the Model #.

DCR looks abit too high for the Crower 00256 unless you retard it some. Maybe install with a split overlap, same as retarding it 4°.

DCRwCrower00256&Isky270.jpg
 
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yeah, the isky 270 looks like a better match of the two listed choices,
but Id have selected a crane 114142 and installed it at split overlap
\(4 degrees or a bit more retarded from the dot-to-dot location)

and ideally, used that Crane cam installed with a set of 1.6:1 ratio rockers and a set of rhodes lifters
yes they have a sewing machine mild clicking noise at idle when properly adjusted a bit like properly adjusted solid lifters

(BE DARN SURE YOU VERIFY PISTON TO VALVE CLEARANCES)
once again I wish scotty had the transporter working so I could beam over and help with the cam install
j8XcNHXm8J8vbqExRvwGzF-320-80.jpg

crane114142.jpg

related info
that should be read through carefully along with related sub links


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

http://garage.grumpysperformance.co...g-cam-and-shifting-the-lca.10553/#post-100190

http://garage.grumpysperformance.com/index.php?threads/cam-break-in-procedure.130/#post-160

http://garage.grumpysperformance.com/index.php?threads/cam-degreeing.9010/#post-35474

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

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

http://garage.grumpysperformance.co...s-tool-swapping-to-1-6-1-ratio-rockers.14761/

http://garage.grumpysperformance.com/index.php?threads/rhodes-lifters.1552/#post-6067

http://garage.grumpysperformance.co...train-clearances-and-problems.528/#post-57678
 
Last edited:
yeah, the isky 270 looks like a better match of the two listed choices,
but Id have selected a crane 114142 and installed it at split overlap
\(4 degrees or a bit more retarded from the dot-to-dot location)

and ideally, used that Crane cam installed with a set of 1.6:1 ratio rockers and a set of rhodes lifters
yes they have a sewing machine mild clicking noise at idle when properly adjusted a bit like properly adjusted solid lifters

(BE DARN SURE YOU VERIFY PISTON TO VALVE CLEARANCES)
once again I wish scotty had the transporter working so I could beam over and help with the cam install
j8XcNHXm8J8vbqExRvwGzF-320-80.jpg

crane114142.jpg

related info
that should be read through carefully along with related sub links


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

http://garage.grumpysperformance.co...g-cam-and-shifting-the-lca.10553/#post-100190

http://garage.grumpysperformance.com/index.php?threads/cam-break-in-procedure.130/#post-160

http://garage.grumpysperformance.com/index.php?threads/cam-degreeing.9010/#post-35474

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

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

http://garage.grumpysperformance.co...s-tool-swapping-to-1-6-1-ratio-rockers.14761/

http://garage.grumpysperformance.com/index.php?threads/rhodes-lifters.1552/#post-6067

http://garage.grumpysperformance.co...train-clearances-and-problems.528/#post-57678
Grumpy if you ever make it to North Alabama stop by! Thank you for the other choice I will look at it shortly. Let me figure out what heads these are, I just got out of work at the hospital.
Rick, what dynamic compression did you have with the t-bucket? I can't remember, didn't you run into a detonation problem? I was concerned about the early intake valve closing on the Crower, I have had that cam on the shelf for several years and never used it. Lemme check those heads.
 
I still need the Cylinder Head Flow Numbers and preferably also the Model #.

DCR looks abit too high for the Crower 00256 unless you retard it some. Maybe install with a split overlap, same as retarding it 4°.

View attachment 15398
Rick,

It looks like they are 200cc. WPI011250-1. I'm looking for a flow chart. Oh and I don't mind running 1.5 or 1.6 rockers or mixing it up. I'm not sure how efficient the exhaust port is on these heads. The profiler heads I last used and we discussed really ended up making a nice engine. But they were more efficient.
 
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Rick, what dynamic compression did you have with the t-bucket? I can't remember, didn't you run into a detonation problem?
Yes I do believe I had some detonation problems, but never did find any signs of it. I did retard
the camshaft 3.5° and never heard again what I thought was detonation.

I went from "Engine #1" to "Engine #3" when I made the change.

DynamicCompressionRatioCalculatorWithCrankingPressure05-TBucket.jpg
.

I was concerned about the early intake valve closing on the Crower, I have had that cam on the shelf for several years and never used it.
You would have to retard it about 6° from Dot-to-Dot or 2° retarded from a split overlap.

With the pistons and heads (64cc) you have, then you need to close the IV at 65° - 67° assuming you have aluminum heads.
Can you change the pistons or is this an existing build already ???

DCRwCrower00256&Isky270.jpg
.
 
Yes I do believe I had some detonation problems, but never did find any signs of it. I did retard
the camshaft 3.5° and never heard again what I thought was detonation.

I went from "Engine #1" to "Engine #3" when I made the change.

View attachment 15399
.


You would have to retard it about 6° from Dot-to-Dot or 2° retarded from a split overlap.

With the pistons and heads (64cc) you have, then you need to close the IV at 65° - 67° assuming you have aluminum heads.
Can you change the pistons or is this an existing build already ???

View attachment 15400
.
Rick,

It's an existing build I was brought the parts for
 
.
These numbers include a higher CR than may be possible on 93 octane without detonation. I suspect the intake flow
numbers might be abit too high since the numbers are for the 72cc chamber.

Sim01vsSim02.jpg
.
 
.
These numbers include a higher CR than may be possible on 93 octane without detonation. I suspect the intake flow
numbers might be abit too high since the numbers are for the 72cc chamber.

View attachment 15403
.
I will look in the shop and see what other heads I have. I may need to find some with a 70cc or 72cc combustion chamber. Pretty sure I have a set of AFR and a set of profiler heads that would fit this build well, I just really didn't want to use them for this build, but it's no big deal. I suppose I could switch over to 4 eyebrow pistons but the rotating assembly has already been balanced for these pistons and connecting rods. Thank you! I appreciate your help! Will let you know what I end up using.
 
Keep in mind that we are splitting hairs when we are talking about EXACTLY when the IV closes. The
Isky uses .007" of lift, but most cam companies use .004. When using .004" the cam timing numbers
would be LATER (takes longer to get from .007" to .004" when closing the IV) . The valve is moving
VERY SLOW at this point in it's displacement cycle. It's about a soft landing so the valve does NOT
bounce off the seat. For some safety margin, retard the cam a couple of more degrees.

I think you might be able to make the Isky work, BUT check this out with Grumpy.

GRUMPY what do you think about the Isky being retarded 2° from split overlap ???

Bottom Line ....... IVC of 63° @ 0.007" lift (Isky 280), could easily be 66° @ 0.004" of lift when
compared to other camshaft ratings.

I hope this makes sense !
 
the only major difference between the isky and crane is in the crane cams increase lift and yes
this combo of increased rocker ratio and rhodes, rapid bleed down lifters that bleed, off a bit of , off idle duration,
tends to result in a bit more consistent upper rpm valve control and lower and mid rpm breathing potential,
just as it would to a bit lesser extent if you put 1.6:1 rockers on a isky cam,
and even with a 1.6:1 ratio rocker I've never had issues with the crane cam.
the crane cam listed .454/480 which with the 1.6:1 rockers, that becomes .490/520 lift , with the rocker ratio change,
which is a very noticeable advantage (yes you need to verify spring bind,
thats also why I recommended the rhodes lifters as the lifter smooth out,
and make the lower rpm range valve control smoother, as you don't get the full duration or lift until after about 3000rpm,
where everything in the combo comes awake very noticeably,
and other valve to piston and spring bind and retainer to valve seal clearances
yes I've run that combo in several of my personal engine builds and for engines built for friends , and everyone has been impressed
 
All simulations thus far have been done with Rocker Ratio of 1.5

Both scales on the graph are the same as before. Also the colors are the same with
Sim03-Crower00256 being Gray and Yellow lines.

Sim01vsSim02vsSim03.jpg

So before you ask I went ahead and did a comparison of the Isky 270 with the only change
being the Rocker Ratio change from 1.5 to 1.6. The two graphs cross each other at 3500 RPM. See graph below.

Sim01vsSim01a_RR1.6.jpg
.
 
All simulations thus far have been done with Rocker Ratio of 1.5

Both scales on the graph are the same as before. Also the colors are the same with
Sim03-Crower00256 being Gray and Yellow lines.

View attachment 15407

So before you ask I went ahead and did a comparison of the Isky 270 with the only change
being the Rocker Ratio change from 1.5 to 1.6. The two graphs cross each other at 3500 RPM. See graph below.

View attachment 15408
.
Those 1.6 rockers look favorable. Seemed to like the lift.
 
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