any performance in P6 exhaust manifolds ?

multi

New Member
Hello everybody.
I have these P6 exhaust manifolds . ( see pickture) I really like the look of them but i understand that they are a bad choice in a performance perspective.
But where are the limit? does any have some experience with them in a high performance matter? is possible to port them to better performance or are they just plain hopeless?
any dyno sheets out there :)
Best regards multi
 

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with exhaust manifolds a lot depends on cam, with standard or fairly mild cams they are not that critical.

that manifold looks like an auto one to me, manual "s" ones are bigger bore and worth having
 
Hi, They are not ideal compared to tuned length or extractor manifolds but because of the space constraints in the bay they are a good compromise. As said try and get hold of the bigger (exit) bore ones.

Colin
 
2" from the manifold, 2 x 90 deg bends, 1 1/2" connecting balance pipe between, 2 x 2"onward to two straight through cans which are 4" x 18 " then 45 deg out to side in front of rear wheels all in 2".
I did not fit the cam, it was in the motor when I purchased it. I was told it was a Kent 224 that had been re profiled and had had one dyno pull on a development engine.
 
2" from the manifold, 2 x 90 deg bends, 1 1/2" connecting balance pipe between, 2 x 2"onward to two straight through cans which are 4" x 18 " then 45 deg out to side in front of rear wheels all in 2".
I did not fit the cam, it was in the motor when I purchased it. I was told it was a Kent 224 that had been re profiled and had had one dyno pull on a development engine.


cool thanks for the info
 
There a good article called "Improving the P6" which goes thru performance gains of a flowed header, used to be on this site.
Also some rather good work backed up by rolling road tests done by a few regular contributors here on this forum.


Graeme
 

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Thank you. that was the answer i was looking for. you see aim planning to make a 200-220hp engine so now i know that those 3500S manifold will not be the restriction on that :thumb:
Cobraboy: i really like the dyno graph. must be a lot of fun to drive. lots of torque from 1400rpm. but what is the rest of that engine? how many ccm.
intake manifold. carburetor. cylinder heads . compression ratio. and how is idle?
Again thank you all. this is very helpfull to me.
Cheers.
PS. is there any of those S manifolds lying around for sale and will any have the trouble sending them to Denmark.
 
I would tidy up any 3500 s manifolds you get, the more you do to them the better they will be.
I think there are before and after overlays on that graph, the trouble is being colour blind I just have to read the numbers, if it says blah de blah hp or blah de blah torque, I just think either OK or o dear. I cannot actually see which line is which, although I could figure it out, but that would take up drinking time.
4.6 litre
Offenhauser 360 intake
Autolite 4100 1.12 carb
Ported and polished SD1 heads
Kent 224 cam
10.0 : 1 CR
Idle is good, not too lumpy

Anything can be posted to anywhere, you just need to fund it.
 
I read some where that the later auto manifolds were the same, I have a pair of manifolds that have an 1 3/4 inch opening, I am guessing these are the larger 3500S ones, unfortunately they are broken !
 
If I did find some 35500s manifolds where do I get the larger downpipe bit to fit ?


You would have to use the top part of the 3500S downpipes, so that's either buy used, or go to the expense of buying a new set of 3500S frontpipes and cutting and shutting them.
 
Thank you, I think if I get a pair I will machine up a pair of mushroom tops most likely easier than getting frontpipes. - had a look they are £60 each at Wadhams £102 in Stainless.
 
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IIRC the 3500S that had the larger manifolds was credited with an extra 6bhp, but some of that is probably because of the rest of the sytem being larger bore than the equivalent auto at the time, so as you already have the large bore system, is it worth all the effort fitting the larger manifolds?
 
IIRC the 3500S that had the larger manifolds was credited with an extra 6bhp, but some of that is probably because of the rest of the sytem being larger bore than the equivalent auto at the time, so as you already have the large bore system, is it worth all the effort fitting the larger manifolds?
Its got a 4.6 engine.
 
Just checked over the manifolds I got at the start of the year at an autojumble and they are the 3500s larger ones, I am gutted though as when I got them home one of the bottom lugs was cracked and when I touched it, it fell off, also the other one has a crack welded up on the back, only good thing is I only paid £10 for them so havent lost a lot !
 
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