I just finished put L98 Corvette heads, an LT-4 production cam, Edlebrock headers, and a flowmaster muffler on my 1987 LB9 Engine and lost a lot of low end throttle responce. From 2000 RPM's up the engine pulls good, but is a dog from a dead stop. My car has a 5-speed so it is really noticeable. I checked the TPS and it was OK. How much time does it take for the computer to relearn what to do? The engine timing seems to be right on after checking. Does anyone know what might have happened?

 

i don't think there is anyting wrong with your engine at all. u r runnin a 305 right? cuz if u r, vette heads may be a little extreme for a 305, and i would say that the cam is over kill also, but i could be wrong. big heads and cam are gonna move your power peak up in the RPM range, sounds like that is exactly what happened. someone back me up on this though.

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86 IROC-Z
40,000 miles!!
305 TPI
1 gutted maf/airbox
2 k&n filters
3 manual cooling fan switch
4 headers, no cat, cat back flowmaster
700R4 tranny
1 shift kit
2 manual converter switch
BF Goodrich radial TAs
3.23 gears
georgous car repainted by my dad and assembled by me

FASTER THAN YOU THINK FOR A "STOCK" 305 hehe.

 

You'll probably need to further advance the base timing, as well as increase the fuel pressure some to keep up with the cam and new exhaust

 

I'm with 8Mike9.

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We need Perry Mason

 

The timing right now is 15 degrees at itle. I found this using a dial back timing light. Should I try 17 degrees? Is there any special way to time this tpi (LB9) motor?

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1987 Camaro IROC-Z w/ 305 tpi/5-speed/9 bolt 3.45 gear
1969 Camaro with '96 350 vortec truck engine

 

I think I may see your problem...in order to set base timing, you need to disconnect the EST bypass first...what you're seeing is the amount of timing added in with the computer contolling it.

Disconnect the EST (single wire connector, forget the color code off hand, but on my '89 it's behind the pass. side strut tower) and set the base timing to 6* (stock setting) first. Shut the car off, and reconnect the connector, fire it up and take it for a run.

Increment the advance in 2*'s at a time until it feels right, without any ping/knock (using the above procedure only).

Get a fuel pressure gauge and check the fuel pressure (did you install an adjustable fuel pressure regulator? if not, you should before going much further) and check the current pressure to give you a baseline of where to start at with the new regulator.

Good luck.

 

I try retiming it tonight the way you said Mike.
I did check the fuel pressure and have 46 PSI, but I do not have a adjustable regulator thought. I will post what happened.

 

After work I retimed the motor with the distributor wire disconnected and after a short drive all I can say is WOW what a difference. It runs great now. After all the changes and the right timing, the throttle responce is even greater then before all the mods. Thanks Mike for the help!

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1987 Camaro IROC-Z w/ 305 tpi/5-speed/9 bolt 3.45 gear
1969 Camaro with '96 350 vortec truck engine