Cam Timing
 

Not exactly a new topic but I'm checking in to make sure I'm not screwing up.

Here's the pics of my cam timing. Pretty sure I have the cam marks lined up right and if so my cam timing is about 1 degree or so retarded. Am I reading this right? If so I'll need to order up an offset key. I wouldn't be surprised if this has never been checked.

Is there any performance advantage to advancing the cam a bit ahead of stock? How much does a whole tooth on the cam sprocket yield?

Thanks
Dan

Advancing the cam moves the power band lower and retarding the cam moves the power band upward.

As an example, my parents had a Camry and they had the dealer replace the timing belt. When we got the car back, the dealer had goofed up the install and retarded the cam timing by one tooth. The car had very little torque down low and came on strong up top with a power band that felt much like a 2 stroke dirt bike.

The dealer fixed the problem and the car felt normal again.

I wasn't sure if a Diesel followed that same rule of thumb (though it seems like it would). I'll plan to return the timing to stock and start there. When I drove the engine in the 300SD it was a real pig but who knows what state the engine was in. Maintenance did not seem to be a priority for the PO.

Dan

That's a good way to do a quick rough check, akin to twisting a distributor and listening to the timing.

A $20 dial indicator will yield a dead accurate timing stretch reading, I'd recommend going that route. Akin to using a timing light to time a distributor.

It is possible to have a chain with very little stretch on an old engine-if they regularly maintained it or if it was replaced in the past.

If I remember correctly, each tooth advanced/retards your timing ~18° which is way too much

Thanks Simpler!

I have a dial indicator. Just thought I'd try the cheap & dirty method first. If I have the dial indicator method in my head correctly I take the valve lash out of the system, compress #1 intake 0.080, and read the balancer which should show 11 degrees. I'll try that today. Why couldn't you just use a feeler gage to take the lash out and rotate the engine instead of messing with the valve adjustment? Seems simpler (but maybe it isn't).

So is there any performance advantage to advancing the timing past stock?

Dan

You're on the right track, taking the valve lash out (just on intake #1) just to make sure that the valve isn't getting pushed down by the lobes at all when you're measuring. FYI 2mm= 0.0787"

As I understand it, you want the cam->crank to be at the factory setting (0 stretch).

Setting the injection pump timing you want to advance it a little, some people have been able to run as advanced as 28°BTDC (stock is around 24°). You will want your injectors to be popping at the proper pressure with a good spray pattern before you advance the IP.

So MAYBE advance the pump timing but leave the valve timing stock? After the first run I'll do the injector check. I want one data point pretty much as I started with the engine. I'll be adding an intercooler and other enhancements as I go along. I think I have a line on a guy with a pop tester so that's one of the things to do.

Dan

Greazzer will do your injectors on the cheap ($60-$100? total) it is definitely worth it. If you can get a pop tester and don't mind taking the time to mess with the shims, it's definitely doable on a CLEAN bench.

I would definitely advance the pump timing, but not until the chain stretch has been corrected and the injector pop pressures are confirmed. Other people have had success with 28° but it can vary from engine to engine. If it knocks, retard the timing a degree or two.

In other news, you can look into boring the prechambers out a little, but that requires a special tool to pull them and can be done later(engine in car is definitely doable). the 1985 PCs are larger than the pre-85, and the 60X PCs are larger too-so the theory is that bigger is better.

Bigger is better - the Hot Rodder's creed! Sounds like something for later on but I'll need to get ahold of Mr. Greezer for sure.

Dan

He would need a holder for the DI + some sort of extended rod on it to reach from above the cam down to the top of the valve keeper. There is no room for a DI next to the cam and directly above the valve. I've been wanting to check my chain stretch using this method but no DI I've seen has a long enough rod.

From what I've read here, people are fabricating there own extensions for this. If I'm wrong about this, please post a photo showing how it's otherwise done. :)

Oh, and advancing the IP timing 4 degrees will make the car fast but idle like a dog schitting chicken bones. I've done it--bad idea IMO.

Funny

Idle quality isn't THAT important to me but I am running the automatic for now so I'll need to be careful. Maybe split the difference at 2*?

Dan

2 deg. is the most I'd do. Just experiment with it, not like it takes too long to adjust IP timing if you know what you're doing. Dedicate an afternoon to messing with it and see what you come up with. :)

How long does it take if you don't know what you're doing? That would be me, at least for now. Bet there's a thread on this......

Dan