C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

help from SR guys

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Old Jun 15, 2009 | 03:34 PM
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Just finished a cam, and heads job on my 88, top off with a SR manifold, heads are patriots 195 runners 2.02/1.65 valves 64cc comb. chbrs 1.6 R Rlrs.
Cam is a crane 214/221 with 488/518 lift 12 dgrs lobe separation.
Manifold super ram with a 58mm thrtle body by Arizona speed marine
headers headman ceramic coated 1 5/8 dumping to 3inch collectors 2 1/2 pipes all the way to magna flow cat back.
problem is Car is not running well idling is all over the place, part throtle surges, runs great between 3and 6000 rpms.
I am runing stock injectors and chip has not been modified I am trying to get a dyno tune and go from there, problem is must shops will do c5's C6's but not first gen C4's
any tips ut there ?
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Old Jun 15, 2009 | 04:02 PM
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Check with PCM4Less. They'll do C4s by mail. Your combination should be pretty straight forward.
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Old Jun 15, 2009 | 04:09 PM
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Convert to an Accel DFI. You'll be able to tune your car dead on and won't have to depend to a tuner when you make additional changes.
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Old Jun 15, 2009 | 04:24 PM
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SR's can be notorious for vacuum leaks.
Get yourself some starting fluid, fire the car up and let it idle and slowly spray
the SR. You will be able to tell if there is a leak when the idle increases.
Just be very careful with the starting fluid.
I think you can use WD40 as well, others can chime in.
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Old Jun 15, 2009 | 06:15 PM
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I always see these posts.

I asume you have an 88. I have a 90 and it runs fine on a stock chip and stock injectors, even though I have a tune. I have similar mods.
My cam is the tpis ZZ9 cam.
I have a map sensor and people always say the MAF cars will respond better. if this is the case I would say you have a vacuum problem with the super ram since mine runs just fine on stock tune, just not as powerfull.

Are you certain the MAF sensor is all sealed up after the sensor to the TB? no leaks?

It's always hard, or at least for me to offer help for a new combo.

Does it idle at all, and what does it do exactly when idleing?
have you tried to set the timming even though it is very hard to do so?
What about the AIC reset?
were all the sensors working fine before the rebuild? IAC and what about the TPS, did you set it?


This is kind of a vicious circle. you have to get the idle down and the timming set to the idle, then you can do the idle reset, and it may have to go another round of this after you set the aic to get it locked in.

Any details on how you installed the super ram? did you install the runners loose, then put the plenum on, then tighten up the runners, then back to the plenum?
are you using stock bolts, did you do any mods to the super ram to make the install easier?
I do it this way everytime and never had a vacuum leak.

Did you block off the egr?

the surge when driving, does anything change between running cold and running hot (open/closed loop)
I had some issues when in closed loop and an exhaust leak with the O2 sensor.

as you can see, there are lots of posibilities.
First thing I would do if not done already, try to set the idle and timming, then do some starter spray around the super ram to look for a leak.

what about the injectors being installed? any O ring issues? did you oil them at all to install?

Last edited by bill mcdonald; Jun 15, 2009 at 06:17 PM.
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Old Jun 16, 2009 | 07:54 AM
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Sure does sound like a vacuum leak. How well did the EGR part of runner gasket, seal to the base/runner ? I had heard about poor gasket match there, and sure enough mine could have been on that list. Since I don't run EGR, I gave it a good dose of the "Right Stuff".
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