Installing used camshaft

[z-ya]

So I now have attempted to operate this cam with my new MegaSquirt install. I'm glad I cam back to re-read this thread, as this "mystery" cam is acting retarded. After timing the thing nuts on the number 2 cam gear position, it won't idle as there is no vacuum. I advanced it a single tooth, and it was a little better but still crap.

 

Before I give up on it completely, I may have some luck advancing it more than 1 tooth, say 2 or so here goes.

 

Is the head shaved much? Have you shimmed the cam towers at all? are you running a stock thickness head gasket?

 

What I am getting to is if the distance from the cam center to the crank center is just about stock, then just time the cam as you would normally do to take up any stretch in the chain. In other words, don't advance or retard the cam. From your cam specs it looks like it is a non-symetrical cam, so you can't use my directions from the "How to Degree Your Cam..." thread. My point is just to get the cam as close to being "straight up" as possible, and then tune your Megasquirt. Until you have your timing and AFR tuned, you can't assume that the reason it isn't running good is cam timing. Once you getting it running decent, and the AFRs are correct across the VE table, then start experimenting with cam timing. I am also assuming that you are running dished pistons. If you are not, be careful changing cam timing!

 

Pete

[SleeperZ]

Yeah, I have tweeked the MegaSquirt so that my ignition timing is dead on, and although it is still running very rich, I am sure it's not the reason for the poor vacuum and idle. And I have a stock bottom end with dished pistons.

 

I think I was brain dead when I initially timed the cam. I am certain the camshaft is ground retarded relative to TDC. It did not come with a cam card, but when I had my degree wheel attached with TDC set with the piston stop, I made my own cam card for it. I measured and documented the intake and exhaust lobes for opening, closing and duration, but did not pay much attention to the absolute timing.

 

Here is my finding from looking back at what I measured: the lobe spacing and intake/exhaust durations are similar to my Schneider stage II, the exhaust duration at 0.05" is virtually identical, the intake duration at 0.05" is 220, 20 degrees less, but the intake doesn't open until 24 degrees AFTER TDC, where the Schneider intake at 0.05" is 8 degrees BEFORE TDC.

 

It appears I need to advance the cam by at least 3 teeth !!! Yes, the cam is ground ok and should work, but relative to the index, it's way off.

Edited September 12, 2012 by SleeperZ

[SleeperZ]

BTW Z-ya, the head is resurfaced, nothing more, just a rebuild factory head with Schneider springs and a Felpro gasket.

 

To put a cherry on this project, I looked at the cam specs I previously measured with the degree wheel and dial indicator, and finally giving it some thought, I verified my TDC pointer with a piston stop and hooked up the dial indicator. I referenced the old Schneider cam that has the intake opening at 0.050" at 8 degrees BTDC, then measured the current cam, and it was so advanced it had the 0.050" lift close to 30 degrees BTDC.

 

I retarded it by two cam gear teeth (gotta get the adjustable cam gear....) and advanced the gear from 2 to 3. Rechecked the 0.050" intake event, and it's dead on 2 degrees BTDC, so it's close to the Schneider, and with its slightly shorter duration, I've windowed the new cam's duration within the old cam.

 

I checked the index at TDC, and the cam is retarded by a bit more than the notch width from the factory reference. Oh well, the cam was definitely ground off the factory index. But I started the engine, and what do you know?

 

Even cold it fired right up and idled.

 

 

Now on to the MegaSquirt tuning....

[SleeperZ]

It's not yet where I want it. I still have very low vacuum, so I wrote Bill Gude again, and he was kind enough to email back with the cam card. He has made all of his valve lift checks at 0.025", not 0.050", so it's back to the dial indicator to see if I can get this adjusted right.