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Fuel rails changed during 1987 run, with different mountings. IIRC. The rail covers may be particular to the year and mounting heights of the rails. But this is a guess at best.
Fuel rails changed during 1987 run, with different mountings. IIRC. The rail covers may be particular to the year and mounting heights of the rails. But this is a guess at best.
It's entirely possible you have the wrong covers for the wrong year. They are the same part #s but are different between the early and late S4s.
Originally Posted by dr bob
Fuel rails changed during 1987 run, with different mountings. IIRC. The rail covers may be particular to the year and mounting heights of the rails. But this is a guess at best.
Originally Posted by Kevin in Atlanta
That has to be the issue.
There are at least two different fuel rail versions: early-'87 and post-early-'87 with the former needing rubber stand-offs to mate with the early-'87 intake.
There are at least three different fuel rail covers: early 'hollow' covers and two late 'insulated' covers. I don't recall in which MY they changed, but definitely by '91. All replacement covers are now of the second 'insulated' type and require excess insulation to be trimmed away.
I don't have an early-'87 on hand to look at right now, but it may have been the case that those covers were notched OE.
One thing is for sure: if you mix early and late fuel rails with early and late intakes you will be in a 'fuel' situation since the lower injector o-ring won't be correctly seated in the intake bore.
It may be possible to use late rails on an early intake if the rubber buffers are removed and replaced with studs. Note the use of "may". It's not going to be possible to use an early rail on a late intake unless you can make a rubber buffer with a negative height.
Edit: the hollow covers with the separate insulation were still used through mid-'89. I think '90s had the insulated covers.
I am only aware of two revisions of the fuel rail. One needs the aluminum spacer and one does not. Regardless of that, the elevation of the rail has to be the same to connect to rest of the fuel plumbing.
So given that early or late rails play no role in the interference, I say this because the rail covers bolt to the rail and rail elevation is always the same. That assumes the injector rail mounts are the same.
Given that either the rail cover is different or more likely my rail cover is warped down.
I have compared the relationship of the injector position in the manifold to a couple of other cars (87 and 90) and the injector is correctly placed.
Sometimes I find weirdness where it isn't really there.
Car runs fine with no leaks. It just was a strange observation.
Since Porsche went to a metal-to-metal interface with the later rail and intake, it doesn’t really matter, but the original spacers were ‘bonded rubber buffers’ identical - same part number - to the ones used for the airbox supports.
My December '88 built '89 had insulation on the rail, and the cover fit over that. No insulation in the cover itself. Insulation is there to help with heat transfer into the rails, and maybe to help with muffling a little of the noise passed from the injectors. Seems that addressing the noise issue more started in the 1990+ covers, from memory. Although there was a parade of clinic cars while we were in SoCal, only a few have cycled through the workshop here. None newer than mine. The area has a high per-capita Porsche population, but a pretty low capita number.
I can't remember even half of the stuff I've forgotten. That may be a good thing under certain circumstances, IIRC.
02-08-2019, 03:37 PM
Notching the DS fuel rail cover
