Frustrating!
Frustrating! I wont throw the tuners name around at this particular time but I'm pissed. My vehicle is a 78' Malibu that I've swapped a 396 LT1 into. My LT1 is running modded sbc AFR210's, Ross domed pistons, 6" lunati rods, dragon slayer crank, pp'd lt1 intake with a holley 58mm tb, msd opti, comp pro mag 1.6rr's, with a custom hyd roller cam 230's/240's duration .5xx lift int/exh on a 115lsa. The engine begins to break up in the mid 5grand range and its still not hitting the 400hp level, what gives? The compression is 13:1 and I'm feeding it c16 per the tuners instructions but I'm pissed that we cant get this thing sorted out completely. Minus the shortblock, everything else was installed onto the engine by the tuner. Oh yeah, and the starter that was installed by the tuner just took a crap on me too, its the PowerMaster pwm-9202. So can I hear some suggestions as to where do I go from here with this project and what starter are you high compression guys running. Sorry for the long post but I needed to vent guys and I'm sure theres someone here whos experienced the same frustration one time or another.
The msd opti is new, its the 2nd new one, the first was a dynaspark. Mind you the car has only dyno time, I havent had a chance to beat the streets in it. Check your pm's for the tuner.
Where to start?
Far as breaking up, are the springs truely appropriate? Comp in particular usually recommends too little spring for the LT1 because they under rate rpm ranges.
Might try a different ignition module.
First you came here asking questions way too late, your build is a bench racer's wet dream and a colossal mistake in reality.
The rods, crank and rockers are the only things right with this build.
115lsa????????? you know the actually fast NA stuff is running 110 and below??? ONLY way I would consider 115lsa would be on a turbo build
Far as breaking up, are the springs truely appropriate? Comp in particular usually recommends too little spring for the LT1 because they under rate rpm ranges.
Might try a different ignition module.
First you came here asking questions way too late, your build is a bench racer's wet dream and a colossal mistake in reality.
The rods, crank and rockers are the only things right with this build.
115lsa????????? you know the actually fast NA stuff is running 110 and below??? ONLY way I would consider 115lsa would be on a turbo build
What plugs are you running and what's the gap? Could it be something as simple as too much gap and consequently blowing out the flame at higher rpm? Are the valve springs correct for the cam? Not at all trying to insult ya, just seen AFR heads before with the supposed correct valve springs only to find out otherwise. Also I've seen first hand several bad MSD optis in a row. I run an AC opti with MSD cap/rotor with great success.
Also, my Dad's LPE 383 Corvette was experiencing very similar issues and it wound up being a bad wire in the harness. When LPE installed the motor they crushed a wire, or series of wires, resulting in a break up at 5500 rpm...We replaced the entire wiring harness and all was good as new. Granted this was in a 2003 Corvette, so its not an apples to apples comparison, but just tryin to help. Good luck with it. And as for a starter..I use the LT4 style from a 1996 Corvette. I think even at 13:1 it should turn your motor over just fine. It's a factory gear reduction type. I've never had good luck with aftermarket starters...
--Alan
Also, my Dad's LPE 383 Corvette was experiencing very similar issues and it wound up being a bad wire in the harness. When LPE installed the motor they crushed a wire, or series of wires, resulting in a break up at 5500 rpm...We replaced the entire wiring harness and all was good as new. Granted this was in a 2003 Corvette, so its not an apples to apples comparison, but just tryin to help. Good luck with it. And as for a starter..I use the LT4 style from a 1996 Corvette. I think even at 13:1 it should turn your motor over just fine. It's a factory gear reduction type. I've never had good luck with aftermarket starters...
--Alan
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Where is the rev limiter set at? If you're running a 6AL you might wanna change your pill to a step higher and see if that helps out, if not change it back over to the stock ignition just to eliminate the MSD box as your issue. Once again, this is all assuming you're running an after market ignition...
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Verdad Gallardo The springs are from Comp, they were recommended by them to match the cam. I maybe wrong about the cams lsa I need to dig out my papers just to be corrrect. Also im unsure about the spark plug gap but I will pull one of the plugs to verify. Im not running a 6AL, Im running a Crane Hi6 with msd coil, also unsure of where the rev limiter is set. The tuner has played around with adding and removing components to see where the weak link is. Even the springs were an add on because the original springs that was on the heads were too stiff for the cam and supposedly was creating valve float. I'll also tell them to recheck the wires in the harness but the harness is a brand new Painless harness.
Launching!
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From: Michigan
The springs are from Comp, they were recommended by them to match the cam. I maybe wrong about the cams lsa I need to dig out my papers just to be corrrect. Also im unsure about the spark plug gap but I will pull one of the plugs to verify. Im not running a 6AL, Im running a Crane Hi6 with msd coil, also unsure of where the rev limiter is set. The tuner has played around with adding and removing components to see where the weak link is. Even the springs were an add on because the original springs that was on the heads were too stiff for the cam and supposedly was creating valve float. I'll also tell them to recheck the wires in the harness but the harness is a brand new Painless harness.
Far as the 115LSA there definitely are people out there who misinterpretation information and are just plain missguided enough to do such a thing. If you let Comp spec the cam I would fully expect it to be 113-114LSA.
People hear things like "a wider LSA makes more average power" but never stop to ask "wider than what". Then they take cams with already too wide LSA for the sake of manners and then spread them wider.
10 Second Club
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If they were AI parts he'd be singing praises and blaming the tuner. 10 Second Club
Joined: Oct 2007
Posts: 2,630
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To the op, I would have suspected the opti since mine did the same thing, but my rpm breakup point was 6000. It ran great from idle up to 6k, but I see you've recently installed an MSD unit. I would run a fuel pressure gauge and see if it fluctuates at higher rpm. what valve springs are you running? Do you have a part number?
Besides the questionable parts being used(particularly that cam, wtf? 
), there is obviously something wrong that has nothing to do with the engine.
- What spring did they recommend, what are the open/closed pressures?
- What is the spark plug gap set to? Like stated with 13:1 CR you could be blowing out the spark at high RPMs. Even for my modest 11:1 CR build my tuner wanted me to drop from stock gap down to .035. Surprisingly to me it helped a TON.
- What fuel pump are you using? Stock FPR? Have you measured the fuel pressure going WOT?
Honestly I would change the cam even after the gremlins are sorted out...thats not exactly an optimal grind for an NA 396.
EDIT: Joel had the same ideas as I was typing.
), there is obviously something wrong that has nothing to do with the engine.- What spring did they recommend, what are the open/closed pressures?
- What is the spark plug gap set to? Like stated with 13:1 CR you could be blowing out the spark at high RPMs. Even for my modest 11:1 CR build my tuner wanted me to drop from stock gap down to .035. Surprisingly to me it helped a TON.
- What fuel pump are you using? Stock FPR? Have you measured the fuel pressure going WOT?
Honestly I would change the cam even after the gremlins are sorted out...thats not exactly an optimal grind for an NA 396.
EDIT: Joel had the same ideas as I was typing.
Still ooking for the spring and cam pt numbers, I wont be able to pull a spark plug until tomorrow to see what the gap is. I pitched a bitch with the tuner about the size of the cam, I felt that with the ci of my motor combined with the heads, and pistons that I could run a .600" lift cam in the 230-240's duration range with 113 or lower lsa. The car runs damn good before it starts to break up. The fuel pump is a GSS-340(255lph). I chose the domed pistons because they were the correct bore and available at an extremely reasonable price. The AFR heads were modded for the pistons.
Last edited by deuce4935; Jan 1, 2011 at 07:49 PM.
So you what had to open up the chambers to fit the dome?
Far as the cam yeah I would have expected mid 230s intake low 240s exhaust and over .600" lift, only reason to stay even up around 113LSA would be emissions but seeing as you are running race gas that is not a concern.
Far as plug gap, I run mine out around .040-45", maybe I should try .035, cranking compression on mine is up around 240psi and if anything the car is faster with stock ignition vs the Accel 300+ box I tried. So you might pull the aftermarket "upgrades" out and see how it runs. A LOT of us have had no gains and if anything issues with aftermarket ignition stuff.
Far as the cam yeah I would have expected mid 230s intake low 240s exhaust and over .600" lift, only reason to stay even up around 113LSA would be emissions but seeing as you are running race gas that is not a concern.
Far as plug gap, I run mine out around .040-45", maybe I should try .035, cranking compression on mine is up around 240psi and if anything the car is faster with stock ignition vs the Accel 300+ box I tried. So you might pull the aftermarket "upgrades" out and see how it runs. A LOT of us have had no gains and if anything issues with aftermarket ignition stuff.
if your running c-16 im assuming you are planning on nitrous?
i wouldnt thinkg "breaking up" would be an issue with the valvesprings, more like an ignition or fuel problem. valvesprings would normally cause power to fall off a cliff around 6k or something a good bit lower than the peak is expected to be. i believe my nitrous cam is on a 113 in regards to the 115 you have. i wouldnt worry about the guys bashing your stuff because its not the same stuff they are running.
i wouldnt thinkg "breaking up" would be an issue with the valvesprings, more like an ignition or fuel problem. valvesprings would normally cause power to fall off a cliff around 6k or something a good bit lower than the peak is expected to be. i believe my nitrous cam is on a 113 in regards to the 115 you have. i wouldnt worry about the guys bashing your stuff because its not the same stuff they are running.