I just finished put L98 Corvette heads, an LT-4 production cam (not the hot cam), Edlebrock headers, and a flowmaster muffler on my 1987 LB9 Engine and lost a lot of low end throttle responce and torque. From 2000 RPM's up the engine pulls good, but is a dog from a dead stop. I tryed flooring it from a rolling start and the motor acted dead. My car has a 5-speed so it is really noticeable. How much time does it take for the computer to relearn what to do after being disconnected? How will timing effect these changes. Does the engine need more (timing)? What did I do???


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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

 

The only thing i can think that may be the problem now is that the bottom end doesn't have enough in it to make power with the much freer flowing heads/cam combo that you put in. If it were a 350 you would see a BIG performace jump, but the 305 just doesn't have enough to push it.


Brendan

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1987 IROC-Z L98,SuperRam,EB 6085's,LPE 219/219 Roller, Crane 1.6RR, EB TPI Base, 58mm TB, ADS 24#, AFPR, K&N, EB TES, Catco Cat, 3" Borla Cat-Back, Accel cap,rotor,distro/other crap, MSD 6AL, MSD Blaster 3, Aluminum DS, 94 Disk Rear, Adjustable Valve, Precision 3.73 Gears, Sub-Frame Connectors, Hotchkis Lower Control Arms, KYB Shocks/Struts, Suspension Techniques Lowering Springs, Polyurethan Bushings all over the place, Moog Upper/Lower Ball joints and Tie Rods ends/Idler Arm,

To see the ROC, Check out the webpage Here

 

did u have the heads milled? i believe its a must when putting 350 heads on a 305 due to the loss of compression....

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1989 pontiac firebird
bright red exterior(just repainted)
grey interior
5 spd
305 TBI (stock)
WS.6 formula wheels
3.73 posi rear end
http://members.aol.com/j007golden/Mikey89.html
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1985 trans am
factory bright yellow
4 wheel disks
16 inch wheels
305 TPI
power antenna and mirrors
t tops

 

well the TPI vette heads have 58cc chambers don't they? cuz if they do, then he is fine.

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86 IROC-Z
40,000 miles!!
305 TPI
gutted maf/airbox
k&n filters
manual cooling fan switch
headers, no cat, cat back flowmaster
700R4 tranny
shift kit
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.

 

The problem I had was timing. I did not disconnect the distributor timing wire when the motor was first timed. After retiming the motor the right way, WOW what a difference. The motor now runs great. The Corvette heads have 58cc chambers, the same as the 305's. I used a GM head gasket with a compressed height of .028". This kept my compression very close to stock (9.5 to 1).

 

What are the specifications on the LT-4 cam, and how dead is the bottom end? Torque loss below 2000 rpm is pretty common when you swap in a larger cam. I have a 1988 LB-9 and mine really doesn't start to pull until 2500 RPM, and that is with the stock cam. With a stick shift you should be able to overcome a loss of low end torque.

The computer should relearn it's paramaters immediately or very quickly. Set the timing at the stock 6 degrees and slowly advance it until maximium performance is acheived. I would not advance your timing any higher then 10 or 12 degrees initial advance.

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1988 Formula 5L/5sp 3.45 gears, SLP cold air kit, MAS gutted, TPIS air foil, TPIS AFPR, MAC headers, Mac under drive pulleys, MAC cat back, Relocated MAT.
Best ET street tires 13.85
Best 60 FT street tires 1.930
Best MPH street tires 99.29

 

LT4 production cam:
Duration @ .050
I:203
E:210
Lift w/ 1.6 rocker arm
I:.476
E:.480
centerline: 115 deg.

this cam is simular to the stock cam but has more lift. It is mild and some guys on this web sight do not like it. For the mods I made on my car I thought it might work ok for me. For the price ($135 from Jim Pace) it was all I could afford at this time. If I really wanted a fast car I would build a 350, but then I would have to get a stronger transmission and rearend ($$$). I would rather spend the money on my '69 Camaro.
I am happy with results after modding my 305 and glad I did them.

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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

 

That combo should work OK. There must be some other prob. Are you setting codes?


[This message has been edited by JoelOl75 (edited April 03, 2001).]