Cannon007

Ok ive been searching around and looking through just about everything to do with TPI fuel issues and ignition related and just wonder if anyone has experianced what my engine is doing: Ive got a 406ci sbc with an 85-86 corvette TPI topend and old double hump heads with a mild cam. Ive got it in a 68 chevy C10 with a TH350 tranny. The problem is everytime i excellerate hard after around 3k RPM its like it hits a rev limiter and bogs and cuts off, no backfires or anything like that, just like it hits a rev limiter and cuts out. However I can have in it park and rev it past 4k just fine. I've put in newer 24lb injectors and an adjustable fuel pressure and it Idles in drive much better now, I dont have to put it into nutral at a stop light but it still has the problem of cuting out at higher RPM's. Anyone have any idea what to look for? I will check the fuel pressure ASAP when I get a gauge.

Apeiron

You mean it shuts off entirely and stalls?

Cannon007

no it just acts like a rev limiter and comes back down in RPM and keeps on going, I just back out of the throttle.

Apeiron

What do you have for a valvetrain?

Vader

400+ cubes, camel-hump heads, heaven only knows what cam grind, and a TPI might not be the best combination for delivering fuel at higher RPMs. Unless fuel pressure is way off spec, some of the problem might be the intake reaching its limits. That doesn't normally happen to a 350 until around 4,500 RPM, but with 15% more engine to feed, it will likely be lower. If the engine has good VE, it would be even lower yet.

Cannon007

I noticed some magnum roller rockers, harder springs for the cam and dont know what pushrods or lifters? I belive its stock valves and 64CC chambers so compression is probably a bit high.

Cannon007

UPDATE!

ok Ive installed a fuel pressure gauge and it holds pressure at 48-50psi pretty well when its running but when I turn it off, it bleeds within 15seconds down to 0 and I've found out I have a leaky injector, I can see it leak out a drop or two ever 10 seconds, now I still dont get why the engine would behave this way though, I can rev it up past 5k RPMs when in park but in drive it just chokes up and cuts out just like a rev limiter after about 3k rpms and so I let off and it settles back down into a good running engine under 3k.

Cannon007

bump

anyone have any similar problems?

Scout

I'm going to agree with Vader on this. I don't think the intake can flow enough air.

I'd like to run tpi on a 400 but based on some searching even a 383 would be on the ragged edge.

VincentZ28

iTrader: (2)

How new is your fuel filter. A clogged fuel filter will cause that everytime. Take off the filter and see can you blow through it. Check the timing, make sure its at 6 degrees. Check spark plug wires for arcing.

Cannon007

fuel filter is fine, it was all rebuilt within 5k miles so I doubt a fuel filter would be causing the problem and I reved it well past 4k in park and watched the fuel pressure gauge and it held it in 46+psi all the way so I dont think thats it. I'm thinking maybe ignition problems, cause if the intake isnt giving it air, its just not gona make power pask 4k, but what mine does is just completely cut off for a split second like a rev limiter, like its cuting spark, but the engine isnt knocking as far as I can tell and yet in park it will rev past 5k easily with no signs of it? just under load in drive will it act up???

DAVECS1

iTrader: (2)

have you done any tuning to the ECM? Are you running a 730 or 165?

Cannon007

I have no idea and no its not been tuned as far as I know, and obviusly that would help alot but what gets me is how can it rev in park just fine but when in drive it messes up? I plan on sending the ECU to this place: http://www.customefis.com/flash.html and have it converted into a real time flash chip so I can tune it in real time.