Headers?

[jimustanguitar]

Are there any other buick cars like the regal that would have aftermarket tube headers that would bolt in with no problems? Nobody has anyhting for the reatta in the aftermarket arena.

[padgett]

Really all you need is to replace the rear manifold with something better, front is not that bad considering that the whole engine is really designed for low speed torque.

Have often wondered why the rear manifold is so bad. Only thing I can think of is so that the engine can be removed by just disconnecting the head pipe.

[Barney Eaton]

There were some pictures posted of the intersection of the two pipes on the rear manifold and it looks very bad. I enlarged the photo and did a quick calculation that showed about 30% restriction. This can be cleaned with a grinder or mayby a Dremel tool and should be a help.

Some say that will not help performance, but it cannot hurt. I believe Hal posted an answer to the question if the later manifold will fit and I think the answer was the head flange bolt pattern is different.

[Guest Greg Ross]

May be a "Senior Moment" but I cannot recall if this was ever clearly settled. Certainly the 3800 Series I ('91-'95) manifolds were much improved but I don't remember a definite whether they would match up to the earlier 3.8L or not. The EGR outlet was relocated so that would be a nuisence! I'd made the suggestion back whenever that aftermarket exhaust gaskets be compared to see if they'd match.

Dropping in the Series I there was no problem mating the existing exhaust down pipe to the new rear manifold.

[2seater]

Are we talking 3.8's or the later 3800? There 3.8's which were used as fwd in '86 look like a hybrid of Grand National and 3800 parts. The intake is clearly different than the Series I which came out in '88. Two intakes on each side are side by side, like a small block Chevy, where the 3800 are all evenly spaced, so the intake stuff will not interchange. The exhaust is a little murky. I have a set of old cast iron manifolds from a Riviera, and I believe the bolt pattern may be the same, I would have to check to be sure. The exhaust port design of the 3.8 is not as good as the 3800. I have seen data on head flow and the stock Series I 3800 head flows almost as well as the Stage 1 heads for the GN's and better than stock 3.8's which have been ported. I do believe all the Series I intakes and exhaust will interchange, through whatever year the were made, '95? The electronics to run some of the items, like the EGR are different though. I agree with Padgetts assessment that the rear manifold was done as a compromise for space consideration, although if the engine is indeed installed from the bottom, installation at the factory would not be a problem . Removing it afterwards may not be possible. It really needs to be longer at the outlet to make a nice smooth transition and join the front and rear pipes near the outlet. This could be done and I have seen some fine looking aftermarket headers for the Series II. I do not know if they would fit as the heads are closer together due to a lower deck height on the block. The crossover pipe may be the only thing that needs to be modified? For a naturally aspirated engine, I am not sure it would be worth the cost unless other changes are made, such as a cam to extend the rpm range where high flow headers would be more worthwhile.

[padgett]

Just think the whole rear manifold is crude, when you open up the restriction, you can see that they just stuck the tubes in and welded without bothering to cut them off (the triangle showing at the bottom of the attachment is an adjacent tube).

[DTakas]

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Edited January 2, 2019 by DTakas (see edit history)