I have a 1989 GTA Trans Am. The motor was a 305-TPI with a 5spd. To make a long story short the motor spun a bearing and I have decided to swap to a 350. Here is the plan so far..

I am having a 350 built with the usual low end stuff...forged pistons, factory rods and sealed power bearings. My machinist has suggested using the stock 305 heads to push up the compression. We have talked about keeping the cam just a step above mild. (I am not sure of the exact numbers on it yet.) It will be a lunati full roller cam and valve train. The lower intake is going to be port matched to the heads and I am getting the TPIS runners. I am sticking with the stock throttle body, but I am going up to SVO 30lbs p/hr injectors. I have been looking over everyones postings and have garnered the following info regarding the ECM.

I can still use the stock computer and chip, although having a custom burned chip is something to look to in the future. I will need to replace the knock sensor for one off of a 350 motor. Do I still need to replace the ESC or is that part of the ECM? If not then will an MSD 6a unit work in its place? Is going with a later model speed density setup better and what would be involved to do it. Parts and Cost.

If I have missed anything please let me know and your suggestions and advice are welcome. This is my first FI car most of my expeirience comes from 2nd gen birds.

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1989 GTA TRANS AM
305 TPI, 5 SPD
SWAPPING TO TPI 350 NEXT MONTH.

 

Rob,

The stock 305 heads will certainly push up the static compression. And they may even increase dynamic compression at low RPM ranges. However, since the ports and valves are miserably small, you will likely lose compression pressure at higher RPMs (2,500+) since the chambers will tend to be starved, causing lower initial charge pressure (but higher vacuum). In short, the heads barely flow well enough to feed a 305 at 4,000 RPM. They will really hurt the potential of a 350.

Instead of using the 305 heads, try doing a little machining on the 350 heads, if for no other reason than to provide a flat surface. I installed larger Manley Race-Flo SS valves and had the bowls cut on 350 heads for under $400.00. The rest of the port machining, stud installation, and spring seat cutting only cost me my time What 350 heads do you have (casting numbers)? They might not be as bad as you expect.

If you're planning to use the 305 heads, don't waste your money on larger runners. It will be like trying to funnel a fire hose through a 1/4" copper tube. You'll have less cash and no benefit.

My feelings on the MAF versus Speed/Density is to keep the MAF system whenever you can. The system is a lot more accurate, more reactive to actual conditions and tolerant of engine modifications. The only real advantage to Speed/Density is the ability to eliminate the air intake ducts and install a conec filter on the TB. The same can be done with a MAF if you're clever.

The ESC is not part of the ECM, but you should be able to retain the existing unit if you install a proper knock sensor.

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Later,
Vader
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"Make Me Bad"
Adobe Acrobat Reader 4.0

 

I'm not sure how its going to run w/ the larger injectors and the stock chip... Certainly won't be up to potential. I wouldn't go w/ the 305 heads either.

Is that darn TPI intake for Vortec heads out yet? If so look into that and a set of the Vortec heads, around $400 for the set of heads, great performance, and good for ~.470ish lift w/ the stock springs on em. Problem area is the intake w/ TPI, stock one won't fit. So if the Vortec TPI intake from Scoggin Dickey isn't out yet you can ignore this section. But look for something other than the 305 heads regardless.

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Ray87Z
-Vortec headed 350.
86 IROC w/ a cammed 305 TPI.
Formerly Ray86IROC.
www.inter-scape.com/Ray

 

I am doing a similar swap and was just wondering why do you have to change the knock sensor? Please e-mail me thanks, Mike