My mechanic is stumped (MFI 2,2) Help!

[72doug2,2S]

HELP!
My MFI is advanced by ˝ a tooth! Is this a problem? Is there anything I can do?

Background:
My mechanic is scratching his head. My engine, a 2,2S according to the engine number, is in a top-end rebuild with new exhaust valves, guides, springs, and cam chains. The old exhaust valves looked straight, but were bent somewhat because they would not go back in the new guides. As it went back together, the valve timing adjusted only to a 2,2E not the S my engine block said it was.

Cams:
The Cams are stamped SE on the drivers side and S on the passenger side. He believes these cams make the engine a Type 2000S (901/02 901/08)…(page 41 of the Hayes manual) from his dial gage and he makes the valve timing to be 2,2 911E. The cams match to each other. The intake at 360degrees is .225 on #1 and #4 cylinders. The cams are too “tight” straight up and down so he advanced them slightly to the .225. He believes straight up to be .215 and retarding at .205.

MFI:
The MFI has two lines that do not match with the belt on. I don’t know that they matched before, but now the line sits ˝ a tooth advanced. He said to match the lines he would have to retard the timing a lot, this is not a good thing. My mechanic is stumped, what can I do?

[Zeke]

From a post awhile back: "Being off by 2mm on the pump timing won't make a big difference, but if you loosen the allen bolts on the pump sprocket, you can turn the pump shaft until it is perfect."

If you want to read more, search for Tyson Schimdt as the poster and belt as the search word.

[72doug2,2S]

That is a relief. I'll do the search.
Thank you!

[72doug2,2S]

I sent Tyson an email on this, but my mechanic is really at a loss on what kind of cams are in this engine and how to time them.
I have a 1971 case that says it's a "2,2S" but I think my cams ("SE" stamp driver side and "S" stamp on passenger side) are not original because the cam timing ends up like a 2.2E and then the MFI is advanced 1/2 tooth. They are currently straight up (slightly advanced) at .225 thousands of an inch (360 degree rotation). If the MFI was set back to be even, via the cam timing, the timing would be way retarded (.205) to 2.0S spec (I Guess). Can the cams be exaggerated that much (advanced or retarded)? I guess I'm concerned I don't know what these cams are and how I should time them. How should I approach this to not mess up the valves 2MM and 1.5MM clearance?

[BK911]

Can't you put a degree wheel and a dial indicator on them to determine exactly what profile they are?

[72doug2,2S]

I know that there is .448 lift cam intake lobe. Does that help?

[72doug2,2S]

We can't do a real profile without another tear down. Can we avoid this. Does the stamped SE and S mean anything.

[Bobboloo]

inre: MFI advanced by 1/2 tooth:

As pointed out in Milt's post (Zeke) you can adjust for this but the adjustment is on the sprocket that is mounted to the left cam of the motor, not the MFI pump cam.

[tobluforu]

About a year ago I checked the same markings on my MFI pump. It was also about 3 mm off. I was able to get them lined up. Car ran worse-go figure..

[Kevin G.]

Doug -
Your valve timing needs to be adjusted correctly based on the cams you have installed, then you can properly adjust your MFI pump to line up. If you haven't got it already, find a copy of the MFI bible - I think it's called 'Check / Measure / Adjust' or something like that. It explains the proper sequence to be followed when making adjustments to your MFI system.

I wouldn't worry too much on the different stampings on the ends of your cams. I believe my 2.2S has different stampings for each as well. You can identify lift and duration of your cams without taking them out using a dial indicator on the valve stems. Post your information and someone here can probably tell you which cams you have and whether they match.

BTW -
Half a cog out on the MFI adjustment is nothing. I doubt anyone could notice any difference in the fuel delivery from that small of a deviation. I had forgotten to tighten down my pump at one time after an adjustment with the result that the belt slipped and was off by 90 degrees. Now THAT was noticible, but the car still ran.

OTOH - small valve timing differences have a large impact on how your motor runs, and with an S motor you can run into valve / piston significant relationships if you fiddle with the timing too much.

[BK911]

You do not have to tear down the engine. Make/buy a degree wheel. Install it on the pulley. Remove the left side intake valve cover. Install a dial gauge on #1 valve retainer. Rotate the crank and record degrees when valve opens and closes as well as total lift. This should give you a pretty good idea what cams you have. If that isn’t enough to tell, you can do the exhaust and the right side as well. DO NOT go by any markings on the cams, the cams could have been reground.

Good luck!
BK

[72doug2,2S]

Is 2mm exhaust and 1.5mm intake the clearances for 1971?
I told my mechanic this yesterday from a post I read, but now I can't find that information in any of the manuals.

Thanks,
Doug

[jstobo]

Doug,
From memory so I may be wrong. The E cam timing spec is about 3mm. There are slightly less that 40 thousandths in a mm. Lets use 40 thousandths. So the overlap on the E cam timing would be about .120 inches or 120 thousandths. The S had a 5mm spec.(actually a range I think 5-5.25mm) Anyway 5mm is equal to .200 inches or 200 thousandths. It appears your cam timing is correst for an S. The MFI timing is adjusted with the pulley at the FE mark. You adjust at the MFI pump not with cam timing. I hope this helps.

Jim

[jstobo]

I forgot. All valves are adjusted at 4mm. No difference between intake and exhaust valves.

[john walker's workshop]

i think your tech is a bit mixed up. if the left cam has SE stamped on it, then it's a S cam, and needs to be set to S specs. what does he mean that the cam timing only adjusted to E specs? you can adjust it anywhere you want!. the pump timing marks should line up, but a hair off won't make any difference. the upper wheel is adjustable for lineup purposes. if the cam were turned more, to the S spec, it may line up on it's own. the pump timing is done at the FE mark on the pulley as you turn the engine clockwise, just past #4 timing mark, not after #1.

[Peterfrans]

You time the cam at the number 1 intake valve to have 5.2mm lift (+ or - 0.2mm).

This is crucial, especially on a S engine. As said the timing on the mfi pump is much less critical and can easily be adjusted by loosening the sprocket bolts on the pump.

I have two S cams right in front of me now and neither of them has any S or SE markings. They probably mean nothing.

I am a bit worried about your mechanic though as he seems to have little experience with 911 engines in general and probably none with MFI engines.

E engine:
hight of the intake camlobe: 36.50mm
hight of the exhaust camlobe: 36.20mm
Intake valve opens at 20 deg before TDC, closes 34 deg after TDC. Exhaust opens 40 deg before TDC and closes 6 deg after TDC

S engine
hight of intake camlobe: 37.20mm
hight of the exhaust camlobe: 36.20mm
Intake valve opens at 38 deg before TDC, closes 50 deg after TDC. Exhaust opens 40 deg before TDC and closes 20 deg after TDC

[72doug2,2S]

My tech says to get the "S" spec would retard the cam bock off the lobe so much that he is concerned about bent exhaust valves (We had bent exhaust valves when we did the top rebuild). He would really like to know the Porsche Piston to Valve clearance for the 2,2S. We can't find it anywhere. Does anyone know?
Are they are supposed to be aggresively timed to retard?

On Jim's comment on the 4MM exhaust and intake, was that overlap clearance and not piston to Valve?

[john walker's workshop]

it's already predetermined that S cams work with S pistons, without contact problems, as long as the timing is correct. do you have S pistons? E pistons don't have deep enough valve reliefs for S cams. bent valves are usually caused by over-revving the engine beyond the point where the springs can accurately control the valve. retarding the timing to E specs on an S cam would make for a bigtime low rpm power problem. S cam don't start to pull until the RPM gets up there, and are not that much fun to drive around town, so retarding them would be a big mistake.

[72doug2,2S]

When I bought this car last November I knew the engine was not the original 2.4T, and the engine block numbers made it be the 2.2S . I assumed, so did my mechanic, that everything else was there. When my mechanic thought the "S" spec timing was too tight he thought we had "E" Cams.

At this point, is there a technique to determine whether the Pistons are "S"? The heads and rockers are already back on.

[john walker's workshop]

a mechanic familiar with these engines would know instantly if it were a S,E, or T piston. the S has a tall crown, with very deeply cut valve reliefs. the E has a shorter crown, with shallower reliefs, and the T is barely crowned, with mini reliefs. a borescope would probably allow you to see enough of the crown to decide, but not by your guy.