Problems with TPI/TBI
02-18-2008, 06:02 AM
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Problems with TPI/TBI
Hi guys
Pleas help me out. First I describe you what Iam dealing with. The car is `84 Pontiac Trans-Am. It have 305cid motor. Now I rebuilded the motor - block is overbored/honed, new Keith Black pistons, new bearings, mild ported heads, Holley Stealthram intake and some other new parts. CR is now 11.0 BUT my problem is that after I put this Holley Stealthram intake on then my oldser version TPI distributor dont fit there anymore cause it`s too big (diameter) Now I put newer TPI ditributor (from `89 TPI motor) on it and it fit.
My biggest problem right now is that I need to do cam brake in first cause it`s new hydraulic flat tappet. I know cam brake in procedure BUT how I set timing now. As I told I can only use newer version TPI distributor now. As I know then ECM is on older and newer version same? How I set timing and what degree? (I think myself that 30-35 degrees should be fine?) Also where is the timing mark on block? Is it up (12 o`clock) or on driver side (2 o`clock)?
Please help me out
Thanks
Georg
Pleas help me out. First I describe you what Iam dealing with. The car is `84 Pontiac Trans-Am. It have 305cid motor. Now I rebuilded the motor - block is overbored/honed, new Keith Black pistons, new bearings, mild ported heads, Holley Stealthram intake and some other new parts. CR is now 11.0 BUT my problem is that after I put this Holley Stealthram intake on then my oldser version TPI distributor dont fit there anymore cause it`s too big (diameter) Now I put newer TPI ditributor (from `89 TPI motor) on it and it fit.
My biggest problem right now is that I need to do cam brake in first cause it`s new hydraulic flat tappet. I know cam brake in procedure BUT how I set timing now. As I told I can only use newer version TPI distributor now. As I know then ECM is on older and newer version same? How I set timing and what degree? (I think myself that 30-35 degrees should be fine?) Also where is the timing mark on block? Is it up (12 o`clock) or on driver side (2 o`clock)?
Please help me out
Thanks
Georg
Last edited by Olds; 02-18-2008 at 06:35 AM.
02-19-2008, 06:49 AM
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Re: Problems with TPI/TBI
What engine was in the car originally? (carb, or CFI) What ECM did you put in it? What wiring harness?
Timing is timing. It's just the relationship of when the spark occurs, to where the piston is in its cycle. The lump of aluminum the air flows through to get from the outside world into the cylinder, the part number of the ECM, and the diameter of the distributor, will not affect the correct setting, by themselves. However many other details about how the engine is built, may alter the ideal setting.
Your engine originally had the timing tab at the 12:00 position.
The "correct" timing setting will be affected by the programming you put in your ECM. In an electronic FI setup, the ECM has COMPLETE control over that; all you do with the distributor, is to set it to where the ECM is expecting it to be, so that it can control it from there. Obviously you aren't able to use any stock programming, since your whole setup is so different from stock. What do you have your timing tables in your PROM set up for? (that is, what is the ECM "expecting" it to be) That's where you want to set it.
Not to be mean or anything, but it's ALL BUT IMPOSSIBLE to get a 305 up to 11:1 compression. Needless to say, an ACCURATE estimation of that, might help in designing an appropriate timing curve. What heads do you have? What pistons? What head gaskets? What machine work has been done to the heads and the block, either milling the heads or decking the block? What cam did you use? How does it run, up to this point? Any problems or complaints with it?
Timing is timing. It's just the relationship of when the spark occurs, to where the piston is in its cycle. The lump of aluminum the air flows through to get from the outside world into the cylinder, the part number of the ECM, and the diameter of the distributor, will not affect the correct setting, by themselves. However many other details about how the engine is built, may alter the ideal setting.
Your engine originally had the timing tab at the 12:00 position.
The "correct" timing setting will be affected by the programming you put in your ECM. In an electronic FI setup, the ECM has COMPLETE control over that; all you do with the distributor, is to set it to where the ECM is expecting it to be, so that it can control it from there. Obviously you aren't able to use any stock programming, since your whole setup is so different from stock. What do you have your timing tables in your PROM set up for? (that is, what is the ECM "expecting" it to be) That's where you want to set it.
Not to be mean or anything, but it's ALL BUT IMPOSSIBLE to get a 305 up to 11:1 compression. Needless to say, an ACCURATE estimation of that, might help in designing an appropriate timing curve. What heads do you have? What pistons? What head gaskets? What machine work has been done to the heads and the block, either milling the heads or decking the block? What cam did you use? How does it run, up to this point? Any problems or complaints with it?
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