What caused this cam Gear damage?

[Linda]

Have you considered getting a new chain, if the old one is stretched?

Linda

[svwilbur]

Have you considered getting a new chain, if the old one is stretched?

Linda

I am not sure how much it is stretched. it only has about 18,000 miles on it since the engine build in 1989. at that time it had new chains and new cam sprocket and jack sprocket and chain.

I did think about it but that is more work to get at it in the front. next time I have to pull the engine for a rebuild or clutch I will do that.

[Gregs672000]

Yes, we're talking about such small degree changes it is hard to know what is the "correct" position, and that's gonna vary engine to engine, cam to cam. My goal was to get as close to stock as possible and see how it did... And it was much better! If I'm happy with my dyno numbers I may just leave it, but knowing me we'll likely try a degree or two change each direction and see what the results are... But dyno time costs money! And my results will likely only apply to my (modified) engine. It's fun though!

[svwilbur]

Yes, we're talking about such small degree changes it is hard to know what is the "correct" position, and that's gonna vary engine to engine, cam to cam. My goal was to get as close to stock as possible and see how it did... And it was much better! If I'm happy with my dyno numbers I may just leave it, but knowing me we'll likely try a degree or two change each direction and see what the results are... But dyno time costs money! And my results will likely only apply to my (modified) engine. It's fun though!

it will be interesting to see how your dyno runs do with and without cam adjustments. what mods do you have now to your engine from stock?

[Gregs672000]

Mods: 11.7 to 1 compression on forged pistons, Total seal rings, custom 49mm intake 38-40mm exhaust valves (not sure on exhaust, will have to look it up again), adjustable cam gear (the missing element from the last dyno run!), ported head, Isky cam, aluminum flywheel, crank fired megajolt programable ignition, electric fan, balanced and lightened (some) rods, balanced assembly, ceramic header (deans, not sure which one as I don't think there was a choice before), 2.25 exhaust thought the frame and 2.5 out the muffler, 45mm Dellorto carbs with 37 chokes, standard Mikuni stacks with foam socks. I've had her for 30 yrs and have a hard time not tinkering! Last dyno run was only 131hp at the wheels, which was disappointing and we couldn't get a good air/fuel ratio (due to the cam timing).

[svwilbur]

Greg,

Lots of mods there! So are you hoping for 140+?
That will be interesting to see what a cam adjustment does.

[svwilbur]

OK so back to my cam sprocket project that started as a valve adjustment.........

Many people on the list have been saying I should play it safe and not run the older Indian based aftermarket chain that someone installed 18,000 miles ago. They recommend changing all the chains and the jackshaft sprockets as well. I was hoping to wait on doing that but maybe that is a foolish idea?
If I do it I would be doing it with the motor still in the car. Not wanting to pull the engine for it.

Does anyone know of an good existing writeup on the forum or wiki that explains in detail everything I would need to be concerned about?
It is not something I would just want to go into without knowing what all is involved. Any special tools for pullers or anything required?

[JT68]

Don't rush the job...
Have to be careful not to damage the head gasket when the cover comes off. Have to clean it up REALLY well to get sealants to work.
Easy to break the front cover- there are two studs at the front of the head that must come out. Most people break the cover by prying on it. Alternator/WP all have to come off of course.
May need a puller for the harmonic balancer, but may not.
An impact wrench is the easiest way to remove the crank bolt, or lock it in 4th, set the brake and use a breaker bar.
DO NOT rotate the crank without the cam sprocket in place. (Remove all the rockers to be safe...it is impossible to bend a valve with the rockers removed
Number the rockers, and Number the lash pads.
You'll replace the lower tensioner of course.
Use loctite on the JS bolt for obvious reasons.
Photograph how the oil slinger in installed.
There is a lot more...It is a PIA, but you can certainly do it. It is the safer bet..jt

[Gregs672000]

Hoping for? 200!... And then I woke up
I'd be happy at somewhere in the 140s, and I think that's a reasonable expectation. And dynos vary as many will attest to here. I just expect it to be improved considerably (same dyno, so I'll be comparing apples to apples). I KNOW it's much better, as it struggled to reach redline before and would go way rich and now it's fine... I think it could be better though, so that's part of the reason I'm willing to mess with it. We built the ignition timing map with the cam way off too (doh!) so we may be able to tweak that some as well. But right now she only rarely pings, mostly on hot days and at heavy, low speed load if I'm not careful with the throttle and ask too much below 3200 rpms. I may throw in some octane booster to protect things, just in case. My A/F ratios have been perfect (she cruises at 14.7), and richens to 12.5 when I'm on it without going into the high 10s like before. That was all cam timing, and it drove me nuts trying to jet the carbs... I learned a lot! And despite all the mods, it's not a bitch to drive normally at all, and will poke along at 2500 rpms in 5th in town no problem. I love my car.

Not sure what to tell you about your chains. I've never had one break, but it would not be a fun moment! Does it look worn from the cam gear? You MIGHT luck out and get the front cover off, not wreck the head gasket seal, etc, but Will didnt. If I were doing the chains, I myself would pull the head (and knowing me have some work done to it, ha!), but it's up to you! You could try, and if it doesn't leak, you're golden! But if it does, well, you live with it or pull the head. My engine has some oil leaks... I just clean them off from time to time
Good luck, I'm confident that you'll handle it regardless!

[svwilbur]

I have started reading through the service manuals for a U20 and seeing what they do to pull the engine, although I am not planning on pulling it i was reading it just in case.

I am more interested in all the little steps if I decide to go with trying to chain all the sprockets and chains and lower tensioner etc.

But I have a dumb question. I was wondering what the difference is between the crankshaft pulley, harmonic balancer and vibration damper???
Are they all part of the same thing where the timing marks are?

They talk about removing the vibration damper with a special tool which appears to be a basic puller.

Am I missing something? The pulley has the timing marks on it and I thought it was all part of the harmonic balancer or do they just call it a vibration damper???

[JT68]

Nope, for your purposes, all referring to the same big crank pulley with the timing marks on it//j

[SLOroadster]

I have started reading through the service manuals for a U20 and seeing what they do to pull the engine, although I am not planning on pulling it i was reading it just in case.

I am more interested in all the little steps if I decide to go with trying to chain all the sprockets and chains and lower tensioner etc.

But I have a dumb question. I was wondering what the difference is between the crankshaft pulley, harmonic balancer and vibration damper???
Are they all part of the same thing where the timing marks are?

They talk about removing the vibration damper with a special tool which appears to be a basic puller.

Am I missing something? The pulley has the timing marks on it and I thought it was all part of the harmonic balancer or do they just call it a vibration damper???

Pulling the engine is easy. Remove the radiator, unhook the driveshaft, unbolt the transmission crossmember, pull the carbs (not the intake manifold) unhook the header from the pipe. undo the electrical connections and fuel lines. Lift the engine and transmission out as one. It takes about an hour and a half, perhaps two the first time.

Yes, the front pulley is the harmonic damper, vibration damper ect. Same thing. To remove it you do need a puller that screws into the center threads, do not pull from the outside rim as the pulley will come apart. Once that is off, you will have to remove the cylinder head, then remove the timing cover. (Yes you will need a new head gasket and timing cover gaskets as well as an oilpan gasket.) Make sure the engine is at TDC when you start taking things apart.

Will

[svwilbur]

Another question.... I am just investigating and seeing what is involved and what the hard or tricky parts are when trying to remove the chains and sprockets with the engine in the car.


I am guessing that one of the issues with trying to replace the chain and sprocket replacement in the roadster (no engine pull) is that the front of the head also is fastened to two upright studs in the front of the cover. In order to take the timing cover off you have to pull those studs out or pull the head so it does not keep the cover from pulling straight out to the front????

I think those are the studs that people often break off accidentally?
And also are what people often replace with bolts so it is not so hard the next time?

Or is that at a different location?

I have included a picture that family_2k had posted (IT IS NOT MINE, I AM JUST IN INVESTIGATION PHASE).
It looks like one stud on left may be broken or just the nut is off, the one on the right seems to have the nut loosened. But are these the ones that cause issues?

If so what is the best way to go about loosening the studs?
Use a lot of Kroil or other penetrating oil and a little pressure?
It appears that the non-threaded part of stud is below the head so do you try to take that off with Vice Grips on the threads?????

What are the other tricky steps that may cause harm?

I assume trying to remove the timing cover you may damage the part of the head gasket that is between the head and the top of the timing cover below those studs? Is that the tricky part with the head gasket and not pulling the head?????

How do you prevent the damage to the head gasket????

[JT68]

If the engine needs to come out for any other good reason, I'd pull it.

If it is only for chains project, you can do it in the car far easier than pulling the engine.

yes, those two 6mm studs you have circled have to come out. NO vise grips. remove the nut and remove any washers. replace the nut and lock a second nut against the first. then turn the lower nut CCW to remove. Since the nuts are tight against each other, the stud will turn with the nuts. (If not I can tell you some other good tricks)...just don't mess up the threads with pliers!

The front cover has two alignment dowels, so it cannot go up, or down, it comes straight off for about 1/4", then will be off the dowels and can drop down a little.

There isn't much you can do to prevent damaging the HG// really depends on the method used to assemble it originally. It may come off w/o much damage, maybe not.

If you damage the HG, it isn't the end of the world, and you do not need to remove the head. I can share two different methods to repair that problem effectively w/o removing the head. j

[JT68]

"And also are what people often replace with bolts so it is not so hard the next time?"

6mm socket head cap screws are a nice option....Just don't over tighten - common error/sucks if you do.

You can also use 6mm set screws (allen drive studs basically) & nuts, making them very easy to install/remove if needed. j