Timing problem - ZR-1 Net Registry Forums

8upZR1 · 06-20-2006

After fixing a blown head gasket on my 90 it has been unable to start. Many good suggestions were made on the other thread I started. Today I cranked the car with the plenum removed to check out the injector spray pattern and I was greeted by combustion from the injector housing ports. All 8 cylinders are firing, its just that the combustion occurs in the ports and not the chamber. Can anyone tell me if this is an ignition timing issue or if this is a cam timing issue? I am stumped.

ZR1 MK · 06-20-2006

Based on information here and your previous post, I would check the combustion chambers with a scope viewer to see if any valves arent fully closed or bent at TDC due to a slipped cam. Or check compression and or leak down if you dont mind cranking the engine, but Id go with the other option first. If all checks machanically, start diagnosis on the ignition timing again.

8upZR1 · 06-20-2006

I have a boroscope, just need to find all the pieces. I dont think any valve damage occured, before firing the motor spun nicely by hand, and while cranking I have never noticed anything that would be worrisome. I cant think of anything that would cause my timing to be so far off though. For combustion to exit the ports, the spark is occuring sometime while the intake valve is open. About as far as you can get from correct timing. Compression has always looked good, leakdown I have yet to do.

ZR1 MK · 06-21-2006

If all checks mechanically, it should be an electric issue. What is the MSD box you mentioned in your other post?

8upZR1 · 06-21-2006

I use an MSD DIS 4+ box. It converts the ignition to a cd setup and ups the voltage from the coils. It has some nice features like multiple sparks, rev limit, 2 step, high speed retard, tach output. IMO it is a necesity if you are running nos. I have been running this igntion on my mustang for years now and have no complaints about it. I am surprised that more ZR1 people do not know about this box. I mentioned it to Haibeck and he kept asking me how I run an MSD without a distributor.

I am beginning to think that it would be impossible for the timing to so far off from an electrical problem. I am going to pull off the valve covers and recheck the cam timing. I was told that when using a crank locking device that it would only fit into one of the slots machined into the reluctor wheel, but now I am thinking that this advise was BS and that I locked the crank down in the wrong location. I did not even think to check this because the info came from a source who has always received the highest praise from the people on this forum. I am beginning to think this was a load of bs.

ZR1 MK · 06-21-2006

My engine builder uses that same ignition box.
The crank has a variety of slots, but only one that is deeper than the rest. It lets the crank locating tool make contact with the block, where the other slots wont let the tool set 100%. Its at 51 degrees. This could be the problem. Do you recall?

06-20-2006	#1
8upZR1 Join Date: Jun 2006 Location: Thunderbolt, Ga. Posts: 253	Timing problem After fixing a blown head gasket on my 90 it has been unable to start. Many good suggestions were made on the other thread I started. Today I cranked the car with the plenum removed to check out the injector spray pattern and I was greeted by combustion from the injector housing ports. All 8 cylinders are firing, its just that the combustion occurs in the ports and not the chamber. Can anyone tell me if this is an ignition timing issue or if this is a cam timing issue? I am stumped.

06-20-2006	#2
ZR1 MK Join Date: Aug 2005 Location: NY Posts: 143	Re: Timing problem Based on information here and your previous post, I would check the combustion chambers with a scope viewer to see if any valves arent fully closed or bent at TDC due to a slipped cam. Or check compression and or leak down if you dont mind cranking the engine, but Id go with the other option first. If all checks machanically, start diagnosis on the ignition timing again. __________________ Mike 427 cu in LT5 [URL="http://zr1mk.weebly.com"]http://zr1mk.weebly.com[/URL]

06-20-2006	#3
8upZR1 Join Date: Jun 2006 Location: Thunderbolt, Ga. Posts: 253	Re: Timing problem I have a boroscope, just need to find all the pieces. I dont think any valve damage occured, before firing the motor spun nicely by hand, and while cranking I have never noticed anything that would be worrisome. I cant think of anything that would cause my timing to be so far off though. For combustion to exit the ports, the spark is occuring sometime while the intake valve is open. About as far as you can get from correct timing. Compression has always looked good, leakdown I have yet to do. __________________ IT IS THE FATE OF THE INNOCENT TO MEET WITH DEATH!!!

06-21-2006	#4
ZR1 MK Join Date: Aug 2005 Location: NY Posts: 143	Re: Timing problem If all checks mechanically, it should be an electric issue. What is the MSD box you mentioned in your other post? __________________ Mike 427 cu in LT5 [URL="http://zr1mk.weebly.com"]http://zr1mk.weebly.com[/URL]

06-21-2006	#5
8upZR1 Join Date: Jun 2006 Location: Thunderbolt, Ga. Posts: 253	Re: Timing problem I use an MSD DIS 4+ box. It converts the ignition to a cd setup and ups the voltage from the coils. It has some nice features like multiple sparks, rev limit, 2 step, high speed retard, tach output. IMO it is a necesity if you are running nos. I have been running this igntion on my mustang for years now and have no complaints about it. I am surprised that more ZR1 people do not know about this box. I mentioned it to Haibeck and he kept asking me how I run an MSD without a distributor. I am beginning to think that it would be impossible for the timing to so far off from an electrical problem. I am going to pull off the valve covers and recheck the cam timing. I was told that when using a crank locking device that it would only fit into one of the slots machined into the reluctor wheel, but now I am thinking that this advise was BS and that I locked the crank down in the wrong location. I did not even think to check this because the info came from a source who has always received the highest praise from the people on this forum. I am beginning to think this was a load of bs. __________________ IT IS THE FATE OF THE INNOCENT TO MEET WITH DEATH!!!

06-21-2006	#6
ZR1 MK Join Date: Aug 2005 Location: NY Posts: 143	Re: Timing problem My engine builder uses that same ignition box. The crank has a variety of slots, but only one that is deeper than the rest. It lets the crank locating tool make contact with the block, where the other slots wont let the tool set 100%. Its at 51 degrees. This could be the problem. Do you recall? __________________ Mike 427 cu in LT5 [URL="http://zr1mk.weebly.com"]http://zr1mk.weebly.com[/URL]