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Hey guys so I’m rebuilding the top end of my 88 corvette. I’ll be adding a mild cam Isky cam with these specs:
• Valve Lift Int/Ext. 0.465/0.485
• Valve Lash Hot Int/Ext. 0.000
• ADV Duration Int/Ext. 257/265
• 0.050 Duration Int/Ext. 209/217
• Lobe Center 112
I plan on using 24 pound injectors, porting and polishing the heads, edelbrock manifold, and aftermarket runners. What size should my push rods, roller rockers, retainers, and valve springs be? Thanks guys always a huge help.
Your pushrod length will have to be determined once you have everything assembled. I would ask the camshaft manufacturer what weight springs they suggest with their cam. Roller rockers require guide plates, I'm not sure if your heads have them. Hopefully someone with your year will chime in on that one. (I have an 85 with AFR heads so I'm not much help there.)
Stock rocker ratio is 1.5, 1.6 ratio rockers would get a little more lift.
I would suggest looking at a Miniram instead of aftermarket runners and an Edelbrock base. The bigger runners and base are difficult to find, expensive when you do, and won't gain you much power or RPM before the TPI "cliff".
My 85 has ported and siamesed SLP runners and an Edelbrock High Flow base but the horsepower still peaks right at 5,200-5,300 RPM (verified on the dyno) even with my cam. I will be switching to a Miniram this winter off season. (However, I will be selling my intake then.)
Last edited by Mixednuttz; Oct 9, 2021 at 03:05 PM.
The last time I bought a Camshaft I basically let the Manufacturer of the cam suggest the settings I needed to use. I bought "Bare" heads and they were rebuilt using all new valves and valve train and getting the porting work done when possible became a PIA and expensive.
Ask Isky what you need to do (if anything) to your "rebuilt" stock Aluminum heads. If they need a special spring strength or anything unusual then they start to get expensive. Then when you take your heads over to a shop who will "Rebuild" them properly and they can help "set them up" for the cam (if needed). The 1988's have good Aluminum heads and don't seem to have the issues of some years. Just flush the coolant and brake fluid every Five and stay safe with your aluminum parts and the brake parts.
Using the Corvette regularly will keep the fuel lines from rusting internally as fast thanks to Ethanol in our gasoline.
Did you do a Leak Down Test to verify that your Rings are still sealing well? As far as you are going into this engine you might do it all at once.
Your pushrod length will have to be determined once you have everything assembled. I would ask the camshaft manufacturer what weight springs they suggest with their cam. Roller rockers require guide plates, I'm not sure if your heads have them. Hopefully someone with your year will chime in on that one. (I have an 85 with AFR heads so I'm not much help there.)
Stock rocker ratio is 1.5, 1.6 ratio rockers would get a little more lift.
I would suggest looking at a Miniram instead of aftermarket runners and an Edelbrock base. The bigger runners and base are difficult to find, expensive when you do, and won't gain you much power or RPM before the TPI "cliff".
My 85 has ported and siamesed SLP runners and an Edelbrock High Flow base but the horsepower still peaks right at 5,200-5,300 RPM (verified on the dyno) even with my cam. I will be switching to a Miniram this winter off season. (However, I will be selling my intake then.)
i already have the manifold and the base so I don’t want the mini ram and I’m fine with 5300 redline I just don’t want it to be 4600 like it is stock. And let’s say if I used the wrong rockers or pushrods what could happen negatively? I’m new to this stuff that’s why I ask.
The last time I bought a Camshaft I basically let the Manufacturer of the cam suggest the settings I needed to use. I bought "Bare" heads and they were rebuilt using all new valves and valve train and getting the porting work done when possible became a PIA and expensive.
Ask Isky what you need to do (if anything) to your "rebuilt" stock Aluminum heads. If they need a special spring strength or anything unusual then they start to get expensive. Then when you take your heads over to a shop who will "Rebuild" them properly and they can help "set them up" for the cam (if needed). The 1988's have good Aluminum heads and don't seem to have the issues of some years. Just flush the coolant and brake fluid every Five and stay safe with your aluminum parts and the brake parts.
Using the Corvette regularly will keep the fuel lines from rusting internally as fast thanks to Ethanol in our gasoline.
Did you do a Leak Down Test to verify that your Rings are still sealing well? As far as you are going into this engine you might do it all at once.
yeah I’ll inquire with the manufacturer about the proper stuff. Basically my car got a HG leak so I said ok it’s higher mileage let’s rebuild the motor and do some stuff to it while it’s open. Yeah I know the heads are solid I mean I don’t think they’ll need extensive work cuz the cam is mild it’s not crazy and only would need slightly bigger injectors I’ll have them machined. And yeah I was very good with regular maintenance I did the fuel pump and a plethora of other things to it.
i already have the manifold and the base so I don’t want the mini ram and I’m fine with 5300 redline I just don’t want it to be 4600 like it is stock. And let’s say if I used the wrong rockers or pushrods what could happen negatively? I’m new to this stuff that’s why I ask.
Which runners are you using? You can siamesed the SLP ones (and plenum to match) to get a little bit more RPM out of it.
Using roller rockers without guide plates will allow the rocker to rotate off the valve stem. Incorrect pushrod length will cause improper contact between the rocker and tip of valve. Either can cause pretty severe engine damage.
Checking for proper pushrod length isn't difficult. You would need one similar to this https://www.compcams.com/magnum-chec...ct-length.html or (as I did when I changed heads and cam on the 85) a selection of pushrods of different lengths to swap out to figure the correct length. The benefit of using real pushrods instead of an adjustable is that you can keep the real valve springs on while checking instead of a weaker one as there is no threaded portion on the pushrod to wreck.
Yeah the runners I have are Siamese runners much better than stock. And the motor doesn’t come with guide plates? Yeah I heard about that I don’t want adjustable either I’ll have it measured etc when we get there.
You could also run the self aligning roller tip rockers if you're dead set on a roller style rocker. They don't require the guide plates. I ran them on my 85 before I installed new heads. They worked great until I switched the heads out.
My runners are siamesed 1/2 way down the runner. The SLP runners are cast one piece with the runners in pairs so there is plenty of material for me to remove. (Unfortunately, I can't find any of the picture of my siamesing/porting work.)
I'm running the Comp Cams XFI 08-466-08 which has an operating range of 800-5,800 rpm. With the intake I have it tops out at 5,300 rpm. (Nice flat torque curve though.)
If you don't want to use the adjustable pushrod, you could see if there is a local engine builder. One near me lent me rods in different lengths so I could figure out which ones I needed. I was sure to buy the pushrods from him as he didn't even charge me to borrow them.
Help on parts spec
