The Porsche 951 Exhaust Header FAQ (4/28/03)
Early 951's had a high-grade tubular steel header (1-4, 2-3), without any provision for expansion. This quickly became an issue, as numerous early cars had the headers crack in numerous locations. There were a couple of different generations of factory replacement headers produced, none that completely solved the problem.
The 1985-1986 early (pre-July 86 build) came from the factory with the expansion-less headers.
Original Early Factory 1-4 Expansion-less Header
(951.111.131.01)
Original Late Factory 1-4 with
Expansion Bellows (951.111.131.05)
Early (Pre-July ’86) 2-3
Headers (951.111.133.01)
Later (post July ’86) (951.111.133.05)
In addition the expansion joint, the flanges
that attach the header to the head were change. The mounting holes on the 1-4 pipe were changed from slotted to
large round. On the 2-3 header, the
round were changed from round to slotted and large round. Both of the newer flanges were heavily
reinforced at that the union of the pipe.
Early Late
Late Non-insulated Headers
Sometime in 1989, Porsche discontinued the
Insulated Headers (probably due to Asbestos concerns). The basic header remained the same, sans the
insulation. Part numbers continued on
with (951.111.129.05
for the 2-3 header, and 951.111.127.07). I don’t have details on what changed on
these very late, post North America’s
model headers. Below is a picture of
one from a euro model. From what I have
seen in the past, it appears to be a standard header without the asbestos
insulation and metal heat shields.
Failure
Even within the first 10-15K miles the first generation headers would crack, as did mine. The pictures below are from my vehicle. It had 15K miles on it at the time.
The 2-3 header cracks at the "Y"
joint
The 1-4 cracks right at the flange
Identifying a Header Failure
From the outside, neither of these cracks are at all visible, due to the heat shielding. They can be tested for cracks, in place on the vehicle by a number of methods:
1. Look for tale-tail signs of exhaust soot
2. When the car is first is cold/cool, start the engine and "feel" for hot exhaust emanating from the edges of the heat shielding.
3. Using a rubber/silicone hose, listen for hot gases leaking out of the cracks.
4.
The vacuum cleaner
method (More on that later.)
Alternatives
I read all the "Rennlist" threads and spoke to a number of people on the horrors of replacing and maintaining the Header. I decided against repairing the original faulty header, and instead had a set of custom headers built. (I tried a set of "advertised" stainless headers, but they weren't even close to being able to fit!!!)
Custom Header Current, Late Factory Headers
The new custom header were built out of 1.75” Stainless Steel and feature a slip coupling, which not only provides for expansion, but made installation very simple (Can you every say that about a header install??!!). They are Cermachromed inside and out. The fittings are all 316 stainless steel. Thus far they have been great. The fellow who made these is no longer in business, but the design appears to be now manufactured by B&B.
Return to main 951 page:
Copyright Vaino P. Narma