HELP! Our Homecoming trip could be in danger!

[nolastyankee]

The Spence car is on track to make a debut at Homecoming this year with one, significant glaring exception that is placing our trip somewhat in jeopardy - the car is undrivable.

We are running an Accel DFI fuel injection system and the motor is only developing 7" - 12" of vacuum (idle to run) which is driving the MAP sensor nuts. I can re-scale the entire fuel strategy to match the low vacuum, but this really does not seem right for the motor. I'm looking for any advice or suggestions that the group may have on why my vacuum may be so far off. Here's what we know to date:

1. 351W, 0.030 over, 9.1 compression
2. 224/232 at 0.50 cam with .555/.565 lift on 1.6 rockers. 108 intake centerline with 112 degree separation. Both Comp Cams and Cam Motion have validated the grind for the combination. Comp indicates 13" of vacuum is normal for the cam, everyone else in the world I have talked to says no way, cam should pull at least 18"
3. Auto trans with 2500 stall
4. Cranking compression is 155# or 160# for 6 holes, other 2 holes are at 150# and 152.5#
5. Valve covers are not pulling vacuum, propane tests suggest no vacuum leaks
6. Vacuum readings on the MAP have been validated by a gauge
7. Only vacuum pulling off the plenum is for the MAP and fuel regulator, everything else is sealed up
8. I think I recall degreeing the cam, and definitely remember installing it straight up and even getting a second opinion to ensure the cam was installed on the right tooth. I haven't gone back to validate this yet because I am trying to avoid yanking off the timing cover.
9. I have taken the car from 20 degrees to 45 degrees of initial timing to see if there was a serious retard issue. (A serious issue with the timing that is. We know there is a serious retard issue with the mechanic. )

I'm at my wit's end and looking for some help. If you have any advice or know anyone I can call please let me know!

(Funny story - I did get the car around the block a few times with a seriously modified fueling strategy...I got into the throttle a little farther than planned and outside of my adjusted fuel map. The EFI dumped a bunch a gas into the motor and the backfire in the manifold launched one of the breather covers over the top of the car. Once I cleaned my pants and determined nothing was hurt as a result my neighbors and I all had a good laugh!)

[Tony Radford]

Brian, you might want to post your data on the FFR forum. It seems most of those guys run fuel injected engines and I see posts regarding FI configuration all the time. Collectively, they seem to have an awful lot of experience.

[pbrown]

Some of the smartest tuning people I've seen are here. http://www.innovatemotorsports.com/forums/

You can also contact Accel and get a referal to a local tuner.

[pbrown]

Double check your rocker nuts.

[TurnpikeBoy]

+1 on Patrick's suggestion. Did it run fairly smooth, even with lo vacuum? I assume hydraulic lifters - and also assume you went only 1/2 turn on the nut after the pushrods were snugged up between the lifter and rocker arm. While you can go more, there's not really any advantage to do so.

Head/manifold gaskets were glued on? - and manifold bolts are tight? Gaskets are in, between stacks and manifold? Any block-off plugs missing?

A slow easy surveillance of the whole upper tract might give rise to something.




-Roger

[nolastyankee]

Rocker nuts? You mean like overtightening the nuts on a hydraulic lifter and holding the valve open? Check, in good shape. My rocker specs suggested 0.030 preload which corresponds to 60% of a turn based on my thread pitch. (How's that for anal?)

Head gaskets on with copper adhesive. Intake gaskets on with sealant. Everything is tight.

Only block off plugs on our intake are right in the center on the plenum, and all are closed up.

The prevailing theory is that the cam timing is off and that the cam is either mismarked or installed one-tooth-off. Looks like the timing cover is coming off. Yuck.