Need some help with regard to vacuum leaks. We have very poor vaccum on our 914-2.0 (carb conversion). This results in poor idle and very lean running. The local (expert) 914 mechanics state that the intake manifolds are prone to leaking at the head.
Has anyone else experienced a similar problem? Is this common? And what were your fixes? Any other areas that could be leaking by?
Anyone know the torque values for the locking nuts on the intake manifold to head nuts?
(Thanks to xsboost90 for his previous help....picture was worth a thousand words!)
BTW... take a look at the attached file...3000 dollars..worth it or not? (1975-2.0, converted to carb, roll bar, chassis braced, 911 suspension upgrades, adjustable shocks....)

How can it have 911 suspension upgrades? It has 4lug riveras and 911 stuff is all 5lug?

We had this problem with the four cylinder engine in my race car. It seems the manifolds get warped when they are tightened to the head. The fix was to remove them, remove the carbs and then use a huge flat file to level the metal surface out. I then polished it with fine emery cloth on a flat surface. I found the stock gaskets were like paper so I made some from thicker material and never had any more leaks at the head joint.

QUOTE (DanPMan @ Jun 7 2005, 12:23 PM)

Has anyone else experienced a similar problem?

yes, what you need to do is, first make sure the mounting surface on the manifolds is flat and clean,
then used the stock FI gaskets and put a thin layer of hightemp silicon on *both* sides and bolt the manifolds back on.

it is also crucial you get the thicker gaskets where the carbs bolt to the manifolds!

you can easily test for vacuum leaks by spraying some carb cleaner at the area in question while the engine is running.
if you get any change in idle, you have a leak. (careful, carb cleaner is flameable!) ...

once you're sure this is all tight, make sure your vlaves are adjusted correctly, as that can obviously also influence the vacuum your getting on the carbs ...

Andy

PS: oh, and while you're in there, port-match the gaskets before you assemble everything ...

If you're okay with longer manifolds, CB sells a new set with gaskets and all the hardware for a very reasonable price (~$80).

BTW.... how do you know you have a vacuum leak? Are you measuring it? Hearing a whistle?

The torque value should be in the Haynes manual.

Equal flat surfaces are a gud thang....check for leaks by LIGHTLY spraying carb cleaner in the suspect area and listening for a change in idle.

The carb cleaner thing is an easy way to find leaks. Just make sure you do it outside, and stand clear of the exhaust. Now there's some fumes there!

-Josh2

Silicone fills a lot of gaps besides boobie implants.

We hooked up a vacuum gauge at the top of the manifold (large port with white plastic plug) and my vacuum gauge read in the "intake manifold leak " zone (a very fluctuating 5 Hg vacuum) at idle. We'll be resurfacing the manifold faces tomorrow......
Not sure what is part of the 911 suspension upgrade, but the mechanic and 914 specialst it was bought from mentioned some sort of cross tube or bar in th front end(????) Haven't been able to confirm any of this yet, since we just got the car a few days ago.....
This weekend, we'll reset the Weber 32/36 DFEV and set the valve clearances...Any suggestions on valve clearance limits?

sounds like someone put a 911 swaybar on your car maybe. hey, that looks like my truck!

QUOTE

BTW... take a look at the attached file...3000 dollars..worth it or not?

Its hard to tell if $3k was worth it by the photo. If it is rust free(or very little rust) then I would say yes. Need more info on the condition.

Near 100% rust free. Minor surface corrosion in baterry box area. Both rockers original and solid!

A near 100% rust free 914 that runs with some upgrades is a good buy for $3k. I also noticed that the bumpers look like they were backdated.

Don't neglect the battery box rust.