raulgta

Hey guys, I have a 88 GTA with a 383 with a flat tappet cam and stock tpi. When I first installed the engine I set timing at 6 BTDC (With computer out of loop) and it pinged like crazy. I had to set it to 4 ATDC. It has a 8 balancer, fuel pressure at 50, and a re-programmed chip. My best time so far is 14.8 @ 94mph. So my question is whats going on with the timing?? and is this way to slow?

Cam specs are .468/.480 - 220/231 with a 109 lsa. Idles like crap!

ZEEYAA

Just a guess if its a solid lift flat tappet cam your knock sensor could be picking up the valve noise and causing it to retard the timing thinking it might be spark knock. also your LSA may be to wide for the gearing you have for the car and converter. comp cams speced me a 114 LSA for my 383 with almost the same lift and duration a yours. they said that is so it has a good power curve and idle quality.GOOD LUCK.......

raulgta

It does it with or without the knock sensors connected. Right now I have it disconnected. When I installed the distributor, I had to install it in a new direction and reposition the spark plugs. The old cam was a roller cam. Could it make a difference in timing?

91Z28-350

Are you using an aftermarket balancer?

It could also be that your balancer's timing marks are not where it's supposed to be. May have to get a TDC piston stop and find TDC to verify that it is at 0*. If not, timing tape or memorize an offset from your balancer's marks.

Edit: Is this an audible ping? Too much compression?

brutalform

[QUOTE]Originally posted by raulgta
[B]Hey guys, I have a 88 GTA with a 383 with a flat tappet cam and stock tpi. My best time so far is 14.8 @ 94mph. So my question is whats going on with the timing?? and is this way to slow?



A 383 engine is not well suited with a "stock" TPI setup. They were designed for a 305. A stock system can become flowlimited on a 350. You will never get enough air into the engine with the stock TPI.

ZEEYAA

HI did you build your engine yourself, did you degree your cam, or just install it straight up. I dont think its your TPI becacus i have an old 5.7 with 196k on it an it runs 14.60s at 96mph. also i know some guys that are running low 13s with real mild 383 pump gas motors with stock TPI. also did you check your fuel pressure, you might want to bump it up to 46/48 lbs. pull your plugs and see what they look like. also what RPM does it pull to. when you installed the cam you did put new springs on it right. hopefully you can get it sorted out. let me know.THANKS....

speed88

That seems a little slow to me.

I put a 383 in my '88 GTA last year with a LT4 hotcam, WP Torquer heads and a Miniram and went 12.8's at 105+mph. I am only going to start playing with the tuning this year.

ZEEYAA

HI that was my point about the stock TPI, when I said mild I ment very mild. They were 89 oct. pump gas engines that did not even hit a lick. I mean sounds bone stock. limited by traction and still run real low 13s. with miserable 2.10 60ft times, but that was first trip out with no tune. so it should not be a problem to run low to mid 12s with a TPI that maybe has been cleaned up and port matched ect. of course you would turn a better time than mph because of the tourque. good luck with your project.....

raulgta

I got the engine as a longblock package from Portland. It came with the balancer. Its rated at 420hp, 9.5:1 compression, 2.02/1.60 valves. Fuel pressure is at 50 psi. It pulls to about 4300 RPM. Ill pobably check the plugs this week. I'm having serious thoughts about switching over to a LT1 intake. What do you guys think?