Yes!
Not stubborn, just persistant in attempting to understand..... I was stating it WOULD put the opti IN time, not out of time.
Well, (and I dislike complicating this, geez) if by checking a couple/few other lobes, to be satisfied, or to insure they are in line with the #1 lobes that were used to degree with, then it is a good possibliity the cam/crank linkage is the culprit. HOWEVER, this does NOT totally rule out a screwup, on the part of the cam grinder, to make sure the drive dowel was correctly indexed in cam grinding machine itself, before the lobes were ground. 7º is alot for the linkage itself to be off.

IF, and I repeat IF, the cam was indeed ground with the drive pin/dowel out of location, this will cause the drive pin (the opti drive pin) to be out of location, when the lobes are put in sync with the crank. Follow me? IOW, you would be moving the pin OUT of location, to get the lobes INTO proper location/sync. One will end up being off. Which do you want to sacrifice? Follow me here?

If the cam is not ground correctly, in respect to the drive dowel, how would one know this? Something such as a cam doctor, OR, if the same linkage is being used now as with previous cam... to check (degree) to find out how well the other cam was timed with the same linkage, OR easier yet, to check THIS cam with a different linkage set. My gut feeling here? I'll state it again, 7º is alot for the linkage itself to be off......

 

That is exactly the problem I am seeing. I do not care if the pin is out of location and in fact thats what I was counting on. What I am having trouble with (still) is when I read moving the cam (with respect to the crank) will CORRECT the spark timing instead of retard it because the TDC reference via the opti pin would have to be off 7 degrees. And what is worse is a timing light is useless with a stock balancer so I cant even check the advance.


The timing set used now has been on the motor the day this mess started couple years ago and has not been off since. I suppose its possible the timing set is off but that would mean we would need to find one to compare it to now. It is an extreme duty LT4 set if that matters...

 

I hope to see some good gains. The only thing that worries me is someone i was talking to said that if my cam is retarded and i advance it the cam will peak earlier. It already peaks at 5500 it can't get any lower than that. I'm hoping it will run like an AI heads and cam car should. I do appreciate everyones help and adding some thought and imput. I should finish buttoning up tom and then i'll probably get to test it.

 

Honestly, you should just have the advance ground in the cam and install it straight up. If it's a 108 ICL and 112 LSA, then obviously it's ground 4* advanced.

Fix your cam problems and redyno.

Mike

 

FWIW, don't over complicate the matter. Your car is running like poo poo, and the cam is obviously installed incorrectly. Is it 7* retarded with everything lined up 100% correct? If so, sounds like the cam is the problem, but to be sure, get a stock cam and install it for a minute. Confirm the specs on its installation to eliminate the timing set. Don't worry about the opti right now, you need to get the cam installed right. I say get the cam correct, put it back together and see how it runs. I bet you will be surprised.

 

*I do not care... Why would you want the pin location off deliberately?
*What I am having trouble... With the (any) cam ground correctly, this would result in the lobes being 'in proper sync', or 'proper relationship' with the drive pin. If you were to then move this correctly ground cam.... the move would result in the lobes being off location, AND the pin would be off location, same amount, same direction. When you move the body, the head goes with it.
*And what is worse... When going thru the cam degree process, you will establish true TDC. At that time make some reference mark on the damper, and one corresponding mark on an adjacent stationary location, to line up to, be it an add on brkt., or an existing surface.
My understanding is, it IS ground that way. Desiring to install it 'straight up' is how the 7º figure originally came about. Agree?
I agree..... Either try a different timing chain/gears, or a different cam. Although, with the cam, ideally, you'd want to use as a standard, a cam of known accuracy. But yes, doubtful an oem cam would be off more than a degree or two, good enuf to verify wheither or not THIS cam is garbage.

 

I don't have access to a different timing chain setup and i don't have access to a diff cam. What does it matter if its actually the timing chain thats off and not the cam. As long as i correct it with the cam pin bushing it should be ok right?
For an update i just installed the right bushing last night and am waiting for my dad to return home so we can finally degree it one last time and make sure we are in the 108 range. Then i'll button it back up and should hopefully have it done today.

 

It wouldn't matter...... IF you were assembling a std. SBC. However, those of us with LTx engines, have a unique situation/problem. With the LTx engine you'd rather, that it WOULD be the gears/chain linkage. If the cam is degreed and you find it's off, you'd WANT the problem to be the linkage. Then there would be no problem at all. Put is the offset bushing, (or offset key in crank) and you're home free. Sew it up, let's run it.... It needs to be understood however, that with the LTx series of engine, the dowel used to index the cam to the cam gear, is also the same dowel pin used to index/locate/drive the opti. When the engine assembly is together, all the mating components are designed to be in sync.

:Scratching head: Where the hell is my mentor 'Yogi' when I need him. I think he'd do a better job of wording this than I can. :still scratching head: I judge the effectiveness of an instructor by the understanding gained by the students. Doesn't matter how knowledgeable the instructor is, but how much of that knowledge rubs off on the student.

OK, let's try something. Throw a tire/wheel assembly on the ground (lying on sidewall). Chalk an 'X' somewhere (anywhere) on the tire sidewall. Chalk up one (any one) of the lug nut holes. With a little imagination, view the chalk 'X' as the location of the cam lobe. View the lug nut hole as the drive dowel pin. Now grab the tire and rotate it some. Now step back and look at it. What you have done is rotate the 'X' a number of degrees, and ALSO rotate the lug nut hole a like amount. Well duh Arnie, move one the other moves a like amount. Now clean off the chalk from the lug nut hole previously marked. Pick out and chalk up a lug nut hole right next to it. View this hole as the new drive pin dowel location. Quick math here; 360 divided by 5 = 72. The new hole (er pin) is in a different location by 72º. The previous hole is where the cam grinder would have put the pin if it were correct. The new hole is where the cam grinder ended up putting it. Yea, the new pin is now off 72º. Now put this pinned cam into the cam sprocket. The cam lobes are off 72º. OK you say, no problem. I'll put in an offset bushing. Cam lobes now in the correct location. I agree, yes they are. One minor problem, now the drive pin is off 72º. This means the opti is off 72º. Without some idea as to what component is off location, you won't know for sure how far off the opti is.

[Well, with a timing lite, a marked TDC, and an accurate determination of how many degrees the pcm is commanding, a person could determine just how far off the dowel really is. However, this is not relevant to the subject of this thread.]

 

Exactly.. Time to toss that cam in the garbage and buy a cc306 off the shelf.

Mike

 

If you toss it, don't nick up anything. Still haven't determined which is at fault for the degreeing error, or if both are at fault, to what degree of fault for each. Have we? That was the point of this conversation/posting frenzy.

 

Glad I was right with the cam being in way off..... Kinda felt that was el problemo.

As for Why it's off....

Two things can happen here....

Comp could have ground the cam without advance in it..... which would put it at 112ICL.... They either do it with or without, one or the other. If it's 7* retarded send the cam back, but only way to tell is with a timing chain you know is accurate or a Cam DR.

Most likely is the timing chain is the problem.

Bret

 

Poor man's Cam Dr. = spare block w/crank and piston rod assy., and standardized timing chain/gears on spare engine stand.
Without knowing the wear n tear on that chain assy., 'spose it could be off that far, seeing that it IS retarded.

Hmmm, be interesting to know the srpring pressure used, and the # of miles on short block. Makes more sense to figure it is the chain, rather than a cam being off. Bad cams aren't THAT common. They are human, but not bumbling idiots.

 

How common is the chain being off? I would put it at installation error before a manufacturing error. Its a LOT easier to THINK you have the cam installed dot to dot, and it not be. 7 degrees retarded could be off a tooth on the cam right? Remember to KISS.

 

The reason for the spring pressure and mileage comment above, was to acknowledge the possibility of significant chain stretch. When stretched, timing will retard.

 

Well i just got done running it. I was forced to just use a cam bushing in my LT4 ED chain. This is my daily driver and i needed it to head back up to college. If not i probably would of ordered a diff cam and installed it or sent mine back. By the way i'm running the oversized crank gear offered with it and there almost absolutely no stretch in it after 20k+ miles. Afterwords The car has a lot more pull down low. I can take off from idle with out giving it any gas and slipping the clutch like i was forced to before. Also cam surge is almost non-existant, it use to be pretty noticable. I hammered it, and it seems a lot stronger. I don't have my scanmaster anymore and have been meaning to get a laptop but haven't yet. Hopefully next week me and turbo_Z can get together and do some datalogging and see whats up. I'd say even if its all in my head and the car didn't gain anything just doing this for better drivability was almost worth it.