My old 350 tpi broke a valve spring and I built a basic flat top 350 with pocket ported, gasket matched 882 heads. I used a crane compucam with 210@.050 on the intake and 1.6 RR's and the same TPI. The new motor runs fine and idles way smoother than the old one. It just doesn't have the same low end and it doesn't pull on the highway like it used to. It used to spin posi for like 5 feet and now it has nothing. What could be wrong?

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86 Iroc, 383 Ported Sportsman II, Ported RPM Airgap, 750 Holley Vac. Sec., Slp 1 3/4, Comp Cams roller 218 224, 10" 2600 stall, Fairbanks 700r-4 W/superflow pro pump, 9" disk 3.70, 12.969@106.54 1.991 60', new times in spring
87 K30 Chevy P/U 355 TPI Crane Compucam, Ported heads TH400, headers and 2 1/2 duals, flowmasters, 8" lift, 36" super swampers, 4.10 detroit lockers,

 

I checked my codes today and found a code 43, any ideas?

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86 Iroc, 383 Ported Sportsman II, Ported RPM Airgap, 750 Holley Vac. Sec., Slp 1 3/4, Comp Cams roller 218 224, 10" 2600 stall, Fairbanks 700r-4 W/superflow pro pump, 9" disk 3.70, 12.969@106.54 1.991 60', new times in spring
87 K30 Chevy P/U 355 TPI Crane Compucam, Ported heads TH400, headers and 2 1/2 duals, flowmasters, 8" lift, 36" super swampers, 4.10 detroit lockers,

 

Spinning 36" Super swampers with a 350ci in a 1 ton truck with a full locker is pretty impressive to me!!! Those swampers REALLY stick! What was the duration of your old cam??? You lose approx 20-25 ft-lbs of torque @ 1500-2000 rpm for every 10 degrees more duration you add to your cam. If you had a stock truck type cam it probably had around 190 degrees intake duration so you could easily lose 40 ft lbs at low rpm with your new cam. You can gain some back if you install the cam advanced 5 degrees to get the intake valve to close sooner, but you wont get it all back. Thats the price you pay for more duration in your cam. The other thing that affects torque output down low in rpm is compression, did this change???

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Dave Zelinka

 

I went from dished pistons to flattops, around 8.5-9 compression now. I know it didn't have the stock cam in the old motor but I don't know the duration. I looked at the instructions on the timing chain today and I think that I may have installed the cam 4 degrees retarted which looses low end. Do any of you think it would be worth it to take the front of the motor apart to do this. I would hate to do it and not notice a big difference if I changed it to 4 advanced. I also put it on a snap on code scanner and found the code was that my knock sensor wasn't working.

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86 Iroc, 383 Ported Sportsman II, Ported RPM Airgap, 750 Holley Vac. Sec., Slp 1 3/4, Comp Cams roller 218 224, 10" 2600 stall, Fairbanks 700r-4 W/superflow pro pump, 9" disk 3.70, 12.969@106.54 1.991 60', new times in spring
87 K30 Chevy P/U 355 TPI Crane Compucam, Ported heads TH400, headers and 2 1/2 duals, flowmasters, 8" lift, 36" super swampers, 4.10 detroit lockers,

 

OK.....you're running 882 heads....882 heads are 76CC heads so you most likely lost compression when you switched heads and therefore you lost power! I'd almost bet you $10 that your heads are the problem....check it out!

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1986 Trans AM
305 TPI
Completely Stock
Soon to upgrade to a 327 TPI with pocket ported 64CC heads, comp cam, TPI air foil, Adjustable Fuel Pressure Regulator, possibly bigger injectors!
Current project: Keeping my car running until I get the money for the above mentioned project! :-)