CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.
Thinking of doing the unthinkable... *Rotor to cap gap. Normal?*
- Thread starter y5mgisi
- Start date
You need a piston stop tool that screws into the cylinder head in place of the spark plug. I like the brass one with the hole through it. Just make sure to take the two rockers off that cylinder when you do it so the valves don't collide with it.
If you don't find true TDC with a piston stop then you can't trust your results degreeing it in. The cam can rotate quite a few degrees with very little piston movement right around TDC.
That's a good idea too, I like that, assuming you have a ball tip on your indicator that fits it nicely. All the cams I've degreed with the heads on were solid lifters (can just adjust to zero and degree away on the valve retainer), and all the hydraulics I've degreed were before the heads were on. I'll probably try that one in the future. I usually do it at least twice anyway to double check repeatability.
The white one would be lean and I would look for a vacuum leak near that cylinder. Of course a vacuum leak will make you run rich, making other plugs look rich...
Does that plug smell like gas or oil? It looks wet.
y5mgisi
1 ton status
I got a lot to explain here! So hang tough as its going to be a little bit before i can offer my FULL lengthy explanation. Quick tidbits, that one plug is wet like it wasnt firing. When i did compression test it was all even but all low like around 135psi. Vacuum reading varies. If you watch my videos most of them have vacuum gauge readings. Some times its fairly stady but low, other times its really jumpy, other times its fairly decent and fairly steady. Bad plug wires very possible, bad cap possible, bad plug possible. Finding TDC with the heads on was done by using a "piston stop" aka large screw driver. About the dail indicator, i hadnt thought about removing the rocker and putting the needle in the oil hole but i think thats what i'll do. Thanks for that tip!
y5mgisi
1 ton status
A little more stuff that im concerning myself with. I think that in the middle of ship tuning and so on, i developed a miss. It used to be that it would start and run perfectly and run just right until it was actually warmed up at idle. Well now, even with the stock computer plugged back in, it runs "rough" all of the time. from a cold start on to forever. Obviously, that one plug isnt doing much of anything. BUT here lies the trouble. I dont know if the problem lies between the rotor and the plug OR in over tightened valves from when i re adjusted the valves some time ago. What i haven't done yet to figure it out, is re compression test it. My last two compression checks were done on the first and only valve adjustment i did on the motor. along with adjusting the valves. another thing i did at some point was replace a couple burnt plug wires with a couple old spares that i have. ANOTHER strange thing about this truck is that ever so randomly it will blue smoke. Never at a WOT pull or anything like that but backing out of the driveway or something. Only does it about once every 4 monthsish or so. The more to that little story is that i suppose its possible to have an internal intake manifold vacuum leak like a cracked manifold that sometimes sucks oil up in threw the crack. of coarse thats just a little theory i had at one point. The smoke could just be a result of oil rings being spun wrong on the pistons or something like that i suppose. It doesn't use hardly a drop though is the strange part. Anyway. As you can tell, there is a lot of **** still going on with this motor and i just need to do one thing at a time. Degree-ing the cam i think is just a good idea and i would like to get that one off my mind as a possibility. There was one guy on here telling me how a retarded cam will cost you 4"+ of vacuum and 20psi of compression. That falls perfectly in line with my poor vacuum and low compression.
y5mgisi
1 ton status
Little video of the plugs also.
Couple other ones just for fun cause i like videos!
[YOUTUBE]-JwD0eov00k[/YOUTUBE]
Couple other ones just for fun cause i like videos!
[YOUTUBE]-JwD0eov00k[/YOUTUBE]
Last edited by a moderator:
Dude!
y5mgisi
1 ton status
y5mgisi
1 ton status
Ok, so, heres what transpired today. Had my buddy Scott(who's pretty much my best friend) come over and help me out with rotating the motor while i watched the dial indicator and we determined that the cam is 10* retarded! So, we pulled the timing cover off assuming that that amount of error would mean i was off a tooth when i put the cam in. Turns out it was right on. Then doing some calculations we determined that being off a tooth would give about 8* advance/retarded so naturally, we advanced the cam sprocket a tooth. Which SHOULD put me at 2*retarded. Im going to re check it with the degree wheel now. If it turns out it is in fact 2* i might just go ahead and get those bushing sets and advance it the final 2*. We'll see. I still have to re-adjust the valves and check the compression for the hole with the plug that looked like it wasnt firing. When all of that is done i'll put it all back together and fire it up. Going to be interesting to see what happens...
Its the super common SUM-1102 cam.
Here's how it looked before,
And after. I think this was the right direction to go to advance,
Its the super common SUM-1102 cam.
Here's how it looked before,
And after. I think this was the right direction to go to advance,
Before you button it all up, the timing cover and such, check the cylinder pressure. You are aiming for around 160#'s.
As I mentioned in a previous post way back, cylinder pressure is the foundation of a good running motor. From there you can tune it, but you can't tune out low cylinder pressure.
If you advanced it 8 degrees, you might be close to 155#'s now which will be a big improvement in idle quality, idle vacuum, and low end response.
Best of luck.
As I mentioned in a previous post way back, cylinder pressure is the foundation of a good running motor. From there you can tune it, but you can't tune out low cylinder pressure.
If you advanced it 8 degrees, you might be close to 155#'s now which will be a big improvement in idle quality, idle vacuum, and low end response.
Best of luck.
y5mgisi
1 ton status
Thanks a lot man! Yea I'm going to check at least a couple and see how they do. Will post results tomorrow I think. It's going to take a couple days before work to re set the valves and check the spark on that hole and everything. And then I'll get it all wrapped up and see how it runs... Fingers crossed.
Something doesn't add up there, you are double checking, so that's good, but either the cam was ground wrong or some lobes were, or the sprocket marks are messed up, I have never seen a cam that far off. That doesn't mean it can't happen though. I hope it double checks exactly as you hope it will.
y5mgisi
1 ton status
So i adjusted the rockers, rolled the motor over and all was well. Turned it over with the key and all was well. Checked compression, 150-155 depending on what one I checked... So that's a solid 25-30 psi increase over my last check. Keep in mind that it might actually be higher then that as last time I checked the motor had been ran for several minutes before hand and it was a summer day. Today it hasn't been ran in a couple weeks and It's about 50* out. So, I'm interested to check the degree again and see what I got. Then I'll button it all back up and start it and see what i have for results.
I went back and reread all the threads.......My brain hurts.
I really hope you get this fixed. Its going to haunt me if you don't. Don't feel too bad about the time. It took me 8 years to find a problem with my old Jeep. But it was a really weird one.
I think you may be on to something with the cam timing. But if it works, I suspect that you are correcting a "factory" fault. In other words, either the timing mark on the crank gear, is wrong, or there is something wrong with the cam.
Plus, I really suspect that you have a structural problem somewhere. Either a cracked intake, block, or head. You never did get the engine to stall with the air closed off.
With the IAC and the bleed screw off, that engine was getting air from somewhere.
I'm glad you cranked it over by hand after you moved it one tooth. That is not a lot of change, but it would have sucked to have the valves hit the piston when it cranked.
I'm looking forward to see what happens when you get it running.
Hey, that crankshaft gear can't go on facing the other way can it? Even if it could, there should not be a timing mark, but if someone put it on backwards, did not see the mark, and marked where they thought it should be.........
I really hope you get this fixed. Its going to haunt me if you don't. Don't feel too bad about the time. It took me 8 years to find a problem with my old Jeep. But it was a really weird one.
I think you may be on to something with the cam timing. But if it works, I suspect that you are correcting a "factory" fault. In other words, either the timing mark on the crank gear, is wrong, or there is something wrong with the cam.
Plus, I really suspect that you have a structural problem somewhere. Either a cracked intake, block, or head. You never did get the engine to stall with the air closed off.
With the IAC and the bleed screw off, that engine was getting air from somewhere.
I'm glad you cranked it over by hand after you moved it one tooth. That is not a lot of change, but it would have sucked to have the valves hit the piston when it cranked.
I'm looking forward to see what happens when you get it running.
Hey, that crankshaft gear can't go on facing the other way can it? Even if it could, there should not be a timing mark, but if someone put it on backwards, did not see the mark, and marked where they thought it should be.........
y5mgisi
1 ton status
Yeah, they are usually too lengthy........
Maybe we can. I suspect that there just might be someone else here who has replaced the cam and gear set on a GM engine....
Surely someone here either knows if it will fit both ways, or maybe even has one torn down and can try it.
If it won't actually go on but one way, then we know its not wrong. But if it goes on both ways, then its possible.
If no one chimes in in the next couple of days, I'll start a thread on just that question.
Maybe we can. I suspect that there just might be someone else here who has replaced the cam and gear set on a GM engine....
Surely someone here either knows if it will fit both ways, or maybe even has one torn down and can try it.
If it won't actually go on but one way, then we know its not wrong. But if it goes on both ways, then its possible.
If no one chimes in in the next couple of days, I'll start a thread on just that question.
y5mgisi
1 ton status
Never too long! I enjoy them!
Maybe we can. I suspect that there just might be someone else here who has replaced the cam and gear set on a GM engine....
Surely someone here either knows if it will fit both ways, or maybe even has one torn down and can try it.
If it won't actually go on but one way, then we know its not wrong. But if it goes on both ways, then its possible.
If no one chimes in in the next couple of days, I'll start a thread on just that question.
I am just going off of memory, but I believe those double roller crank sprockets are machined in the back so the sprocket slides on to the crank further since the chain is wider, they aren't flat on both sides. So it would fit both ways, but it would stick out further and the timing cover probably wouldn't fit on and the sprockets would be out of alignment and you wouldn't see the flat side anymore. But my memory could be wrong.
Last edited:
