1975 450SL Exhaust Manifolds Question...

[Jay Gibbs]

My current job on my 1975 450SL rejuvenation involves replacing the troublesome exhaust manifolds with the integral catalytic converters...

I have seen that the recommended fix is to replace them with pre-1975 "cat-less" manifolds. The problem however seems to me that the pre '75's do not have the provisions for the EGR fittings on the left manifold. Is the EGR system just ditched/plugged, or should I use a catless manifold from say a '79which has the provision for the EGR?

As I've finally got the injection system running pretty good, I am afraid of deleting the EGR for fear that I'll throw off the damn injection system...Can the cat manifolds be replaced without throwing off the D-jet system??

Also- The early manifolds that I have seen are single piece and do not have the expansion joints. I've read that these manifolds are prone to constant cracking due to the inability to expand/contract at the rate of the aluminum heads...should I be concerned about this, or is there another pre '75 catless manifold that actually HAS the expansion joints???

Thanks.

J.G.

[Graham]

Originally Posted by Jay Gibbs

Also- The early manifolds that I have seen are single piece and do not have the expansion joints. I've read that these manifolds are prone to constant cracking due to the inability to expand/contract at the rate of the aluminum heads...should I be concerned about this, or is there another pre '75 catless manifold that actually HAS the expansion joints???

Thanks.

J.G.

The engine shop manual has a survey of all the manifold types. But, so far as I know, all North American D-Jets did have expansion joints. My '72 has two per side, if I recall correctly. But this did not stop the passenger side from cracking several times in 20 years. I eventually drilled out the manifold bolt holes slightly, and touch wood, have not had any further problems. I think some sedans had the solid manifolds. Any 72 or 73 should have the same as mine.

I can't help you with the EGR. Don't have it on the early cars, so I guess you could do without it too!

[rowdie]

Both my '72 and '73 have solid manifolds. No expansion joints.
Look at the '77 manifolds. They may be what you need.

[Jay Gibbs]

Originally Posted by rowdie

Both my '72 and '73 have solid manifolds. No expansion joints.
Look at the '77 manifolds. They may be what you need.

Yeah...there are a couple solid manifolds for sale on e-bay...I am more inclined to go with the multi-piece to retain the EGR setup unless I can get away with deleting the whole EGR setup without throwing the calibration of my D-Jet injection system off...

Do you know if the '75 was the only year the cats were integral with the exhaust manifolds, or was is 75 and 76??...

J.G.

[rowdie]

It is my understanding '75 and '76

[Graham]

Originally Posted by rowdie

Both my '72 and '73 have solid manifolds. No expansion joints.

That is strange. Do you think they may have been swapped at some time?

I have had three passenger side manifolds. One I bought new, the others were off parts cars. All had two expansion joints on each side.

I "thought" it was just the 116 sedans that had the solid manifolds. I thought about using them, but never could find any.

Ron, if you read this, what does your '72 have?

[rowdie]

I don't think they were changed. It would be unusual for both. But I have been wrong before.
#2913 and #8906.

[Graham]

Originally Posted by rowdie

I don't think they were changed. It would be unusual for both. But I have been wrong before.
#2913 and #8906.

2592 here. It would be interesting to ask on BW where there are more owners of the early cars. I am interested, so will do it. Maybe mine originally had solids?