Author Topic: cam timing help please (Read 6654 times)

flyinglizard · « **on:** January 21, 2010, 08:53:39 AM »

This M42 had a fresh Head gasket, and bad radiator. Fixed the rad but the head warped. Now have the head off,etc.
The cams seem to be off time. Does someone have the opening point RE crank time? Or how about the actual marks? This engine has been apart enough to make me think that the cam gears may have been swapped or the cams .
I could resort to TDCing the cams if I have to but any actual info would help.
TIA. Mike Ogren, FL.
Trade 91- 318IS for corvette, Please

DesktopDave · « **Reply #1 on:** January 21, 2010, 10:36:25 AM »

Do you have the Bentley manual? The e36 one should help as well.

flyinglizard · « **Reply #2 on:** January 22, 2010, 09:06:45 PM »

What are the correct marks? The square end of the cams dont point square to the head.
Thanks, MM

monko141 · « **Reply #3 on:** January 22, 2010, 11:13:08 PM »

The cams themselves are at TDC when the two dots on the end of the camshaft are facing up. The camshaft gears have small arrows on them that point strait up at TDC.

flyinglizard · « **Reply #4 on:** January 23, 2010, 07:33:32 AM »

Thanks a lot.
This head has been cut about 025 and I would like to get the timing advanced back to zero or maybe + 3.
I dont have the E 36 book as I dont service those cars. Mostly Vw street and race cars.
Does the 36 book have the valve opening specs?
If it does Iwill get that book.
Are the cams supposed to be the same ?

I think that there are more E 30s around here than 36. The 30 has a very nice drive quality. Better turn in stock for sure.
Still slower than the 16V Dubs that I have, but all are cool.

I see that VW lifters fit this engine also. They must be the common replacement at 8$ea vs 14$ ea for BMW

TIA, Mike Ogren , FL.

monko141 · « **Reply #5 on:** January 23, 2010, 09:42:15 AM »

Only valve specs in the bentley are for the diameter of the valve head valve stem diameters and valve seat dimensions. Valve head diameters are 33mm for intake and 30.5mm for exhaust.
Cams are not the same. E for intake.

flyinglizard · « **Reply #6 on:** January 23, 2010, 10:04:52 PM »

Thanks for your time.
Mike Ogren,FL.

flyinglizard · « **Reply #7 on:** January 27, 2010, 08:57:58 PM »

What I found out. Bently and Haynes have the same info, not much.
The cams are timed by a plate on the rear of the cam. This plate has the tolerance stack of 4 cuts. If you C clamp a flat bar onto each cam, you may then use a T square to check against the head surface. This is a lot more accurate than making a cam plate by hand. The engagement area is much more accurate also. My cams were off by about 6 or more degrees on the intake, and retarded about 10 degrees on the exhaust. Some power may be gained by advancing the intake about 4-6. That value works well on the Miata race cars.
For a quick refence, set the flat bar on the top sqaure, surface of the cams. You can tell in you are close that way just fine.
FWIW: I had all of the valve grinding tools for this head. It was marked
"907" That must be from the old Lotus days. The heads are about the same design, cam bucket tray, inverted lifters, lots of little tiny valves. Many parts ,little speed. Still fun to keep running tho. IMHO.
The head work ,plus the cam timing setup is worth about 900$ for anyone that wants it done in Central FL.
R and R head , clean and Mill, Hand lap valves, grind any that need it, fluid check the seats/valves, check spring values, clean and time cams, change oil and antifreeze, etc. Change to Mustang injectors, etc. MM

4banger · « **Reply #8 on:** January 28, 2010, 06:26:04 AM »

you can get 35mm x 14.5mm solid VW lifters for $8.00 a peice??

DesktopDave · « **Reply #9 on:** January 28, 2010, 08:40:05 AM »

Quote from: flyinglizard;85862

This plate has the tolerance stack of 4 cuts. If you C clamp a flat bar onto each cam, you may then use a T square to check against the head surface. This is a lot more accurate than making a cam plate by hand. The engagement area is much more accurate also. My cams were off by about 6 or more degrees on the intake, and retarded about 10 degrees on the exhaust. Some power may be gained by advancing the intake about 4-6.

I'm not exactly sure what you're talking about here. :confused: Did you double check cam timing with the head installed? Using the top surface of the head? I'd expect that having timing off that far would definitely cut into power. Now I'm interested in checking mine closely to see how far they're off.

You're right about the car being slower than the 16v vee-dubs. Our little M42 will need a lot of work to be as quick. Parts aren't as cheap either. But I still like it much more than my old Golf & Jetta. More substantial, more tossable, easier to work on. Different kind of ride all the way around.

Choking Hazard · « **Reply #10 on:** January 28, 2010, 09:53:14 AM »

I've got the intake advanced about 4 degrees on one of my M42s, and it is NOT an improvement. Sounds cool, but power is shifted even farther up the rev range (4.5 K), and does not feel any stronger than when it comes in closer to 3k. I'm going to set it back once I finish the head replacement on the other M42.

flyinglizard · « **Reply #11 on:** January 28, 2010, 09:55:40 AM »

The books tell you to cut a timing plate.
All of the cutting is subject to a flaw in precision. The very short, square sides of the cam lead to a tolerance of a couple of degrees at least,plus any tolerance of the plate.
This amount of accuracy( not a lot) can be just as easily measured by laying a flat bar across the rear of the cams.
The most accurate way, is to measure the cam for centerline, with two dial indicators, rocking the cam, finding cam TDC,IMHO.
If you mill the head, you should reset the cam timing, as now it will be a little late.
Clamping two short flat bars to the side of the cam works very well. Project them vertically, and square with a T square, to the head surface. This reduces the flaws, to measuring the square, and the grind of the cam end.
With a 6 in bar the angle is very visible to the eye, two degrees off shows easy.
This car is to replace My 16V Jett for the street. The 16V Jett, will be a FSP race car to take on the Grass Roots FSP car, here in FL.
The 318 is not yet dependable enough for my Son to drive all over Florida to play Ultimate Frisbee, for UCF. He has my Wife's PT cruiser, (car dominoes) etc.
They do drive very well. I thought that it was worth some cash,but I guess not. With that in mind, we are going to change the color to frost blue, from silver. I already cut the front springs so that I can look at it. Big improvement in turn in, just from that. I raced a 320I and a 2002 . The 320 was my favorite ITB car. Solid chassis, good brakes. The 02 was too weak to deal with the new tires. MM

DesktopDave · « **Reply #12 on:** January 28, 2010, 10:53:35 AM »

I might have to try that. I don't have dial indicators but I might be able to rig something up...I'm no racer or machinist by any stretch of the imagination.

Post some pics...I'm sure there's someone looking for a Stage 1 head on here too.

JP 91iS · « **Reply #13 on:** January 31, 2010, 12:05:16 AM »

I used a ruler to eyeball the squareness of my cams:

I don't know how close to true square I achieved but I don't have driveability problems.

edit: you cut the springs?

dwtaylorpdx · « **Reply #14 on:** January 31, 2010, 02:26:30 AM »

This is why having a real experienced engine builder assemble is such a good investment. Mine degreed the cams to the crank then installed the chain, and pre-pumped up the tensioner. Not on the 318, but same idea.

But its good to do your own work to learn the insides...

Dave