OK, here it goes. Last winter i did a complete rebiuld of my 305 TPI. The mods are listed below. Before the rebuild the car ran 16.3 stock. (that was my first time ever at the track so im sure it could have done bettter) Well about a month or so ago a bunch of us went down to the track to do some racing. With all the mods i was expecting at least mid 14's. Well i was wrong. The car ran a 16.9, a 16.7, then a 16.5!!!!! What could the problem be??? I know i need a new torque converter. But that cant be slowing up the car that much. I think i might a problem with the ECM. Any ideas out there? Once i get this straightend out and add a few more mods this winter i want to be hitting high 13's.

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1987 IROC-Z 305 TPI
S/R Torquer heads,Compucam,Edelbrock TES,SLP Runners,52mm TB,Ported plenum & intake,Hypertech Thermomaster chip,plus a bunch of other mods.

 

There's definantly something BIG wrong with it because my car can do 15's easy with the totally nothing mods it has, it's basically stock. I'd start with the basics and check all the systems one by one...

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www.TransAmGTA.com
1992 GTA (226 made), 1 of only 18 "Dk. Jade Met." 92 GTA's, My Window Sticker, 305 TPI, 700R4 4-Speed, T-Tops, Grey Leather, every option except rear disk brakes and CD.
Current Mods/Upgrades: 80 Series Dual Outlet Flowmaster, TPIS Air Foil, K&N Air Filter, and Mobil 1.
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"If it ain't broke, fix it til it is!"
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[This message has been edited by 92GTA (edited November 09, 2000).]

 

I agree, I ran a 15.24 with nothing but the free mods on my 305 TPI, check,check, and double check everything.

 

timing? that will kill an engine, as it did my 383... and a random for you guys/girls that dont have much luck with timing lights, or dont trust them.. sit there and just rev the engine(via the throttle on the carb or throttle body) quickly.. and adjust the timing until it revs the quickest, i tried that after not being satisfied with how the car felt on acceleration from using a timing light, and now it'll smoke the mess out of my tires.

 

Thanks for the replies. I did play with the timing and thats how i got from a 16.9 to a 16.5 Any other ideas on what to check out? Does anyone think i could have a problem with my ECM?

 

Ok, lets go over what you have.
Heads S/R Torguer are ok.
Compucam? What lift, duration, etc.
Edelbrock TES Headers for a 305 is ok.
SLP Runners? No good for a 305. These should only go on 350 or larger with aggressive cams. These supply too much air for a 305 plus the velocity of the air coming into the heads is slowed down not letting the fuel mix well with the air. Try putting on the stock runners again and see what you do at the track.
52mm TB? Well this is questionable. But see what happens with the runners.

The last thing is your chip. Depending on the cam you may need a custom chip, it probably could hurt. You could tell the guys in the "PROM" form your mods and if you should get a custom chip. Just tell them your mods and cam specs. They'll probably tell you to burn your own chip but that is another story.
I hope this helps you.

Good Luck!

 

The compucam is a 208/214 @ .050
I was told that the slp's would be ok because i have better heads and i ported my intake and plenum. I really dont want to put the stock runners back on, they have a few dings in them. Same reason goes for the 52mm TB. And i will be putting on a 2400 torque converter in the spring.

 

The cam seems good but like I said before the SLP runners are wrong for a 305 motor, sorry. It doesn't take long to swap the runners maybe 45 minutes. I would try doing it on the weekend and see if you feel a noticable difference. I think you will.
I know you paid alot for them but unless you are going to put a really more aggressive cam and custom chip in it you're hurting the preformance.
The 2400 torque converter is a good idea (go with a Vigilante) but it would work better with the SLP cam #51006. Then maybe the performance will be better with the SLP runners.
Maybe you can find someone who has LARGE TUBE RUNNERS and swap your SLP's for them.

The main thing to do with these cars (thirdgen cars) is to match up the parts. BIGGER is not always better and the big companies who advertise the most is not the best. I learned the hard way also bought a ZZ9 cam and paid $400 for it and there are better ones for half the price and that wasn't the only thing, oh well. Now I do searches on this web site for products I want to get before I buy.
Good luck! and keep us informed!