ok very odd problems I can't get fixed. My timing is 20 degrees slower on the motor with a timing light than the computer shows that it is advancing have pulled the opti off it was installed right checked the cam installation, have tried another computer with stock tune. Still nothing has changed. If anyone could help or if you need additional information about the car let me know. Thanks

 

What timing mark are you using? lt1s dont come with timing marks? Are you sure your timing mark is accurate?

 

yes I know they are acurate we marked the balencer hub with the engine out of the car, took a dial indicator and found top dead center, the balancer is also keyed now for the supercharger so it only goes on one way, also I have went in the computer and added 20 degrees to everything in the timing just to try it car ran perfect, but that still doesn't fix the problem

 

No msd or anything that can do timing retard?

 

no ignition box what so ever on the car yet

 

Are you absolutely sure the splines on the Opti driveshaft are correctly aligned? Both the one in the cam sprocket and the one in the back of the Opti? One tooth would be about 20deg.

 

sorry I forgot to mention it has been converted to vented opti, and I am 100% positive it is correctly installed I even pulled it off to check it out about 200 miles ok

 

ttt

 

Whats a compression test show? Maybe your timing chain is a tooth off compression test + a quick calculation based on your DCR would reveal this.

 

as i stated in the first post i have pulled it apart and checked the cam install, i have also done a compression check about a month ago before i figured out that it was out of time, the lowest was 180 the highest 190.

 

Did you mark the damper in "crankshaft" degrees or "camshaft" degrees?

 

Your timing problem is unusual. If you find out what's going on please post.

I checked actual timing compared to PCM timing on an LT1 a while back to satisfy my own curiosity. What I did was set up a pointer to TDC with an ATI damper (timing marks on the damper) and checked with the engine on an engine dyno at idle and a bit off idle and the PCM timing was pretty close to the timing light timing. I did not check timing at WOT and I should have but was too busy and scatter--brian with other things at that session, (trying to get my home made wiring harness to communicate with the laptop datamaster).

You might see 3, 4 or 5 degrees off from the PCM commanded timing but 20 degrees is very weird. And you added another 20deg to the PCM and no change? That is double weird.

What is your timing set at right now at WOT??? 55 deg?

This is very interesting so please post your findings.

Karl

 

I didn't mark any degrees on the balancer just TDC then used a degreeable snap-on timing light, and started at what the computer showed for timing on the light and backed it down until TDC and my pointer lined up. computer was showing 35 advance light showed 15 advance. as far as the other question about timing at WOT it is set at 44 for the motor to see 24 it is supercharged that's why the low timing at WOT.

 

well dang me. Now I just saw that you are not using the stock PCM but you are using the F.A.S.T.

Forget what I said on my last post.

Give the guys at F.A.S.T. a call and please keep posting here with the answers and findings.

Karl

 

The FAST appears to be only a dual-sensor wideband.

It's totally beyond me how people can post complex technical problems and include little, if anything about the engine, mods, etc.