2" exhaust

[superfragl]

Hi all.
I plan on doing the 318-to-440 engine swap on my 68 Fury. I got a 440 engine/transmission out of 73 Polara police interceptor. The car currently has a 2" aluminized dual exhaust that is about 4 years old and appears to be in a good shape. Due to limited budget I was thinking about keeping the 2" exhaust system and, maybe, adding H-pipe to increase the flow. Is it a good idea? Or should I go with bigger pipes?
I also have a set of full length headers with 1 7/8 primaries. Should use them?
Thanks

 

[68Bigred]

I am not the expert by far on this but here is my experiance. I had a 67 coronet that I had a 273 commando motor in it (I was young and that is all my father allowed me). However about 10 years later I put a pretty much stock 440 in it. I also had 2" duals on the SB and tried to run my 440 with it. The motor always seems to bogg so I put set of headers and 2.5" pipe with crossover in it. With out touching anything else the car had a very noticiable improvement (also had flowmaster 40's). As far as the headers I will never run headers again. I had to lift the dam motor up once just to change the starter. On my 68 300 I am just running stock manifolds and duals (2.5") with FM 40s no crossover. Even with very mild cam car run nice and smooth and makes enough power for me.

 

[polara71]

The big block pipes are 2 1/4 the bb with HP manifolds run 2 1/2" pipes.

The 440 is taller than the 318. .... Just run a new system. A custom system isn't THAT expensive....

 

[superfragl]

Dual or single?

 

[68Bigred]

Dual! I bought the front 4 pipes for my 300 off ebay, have to find the guy but they were perfectly bent to factory specs. I didnt want to change my fufflers and tail pipes as I have them tucked under the rear bumper angleled out, looks better then where chrysler had them.

 

[superfragl]

Thanks folks. 2.5" system it is!
I have a TIG welder. Now I have to find pre-bent pipes and route them the way I want. I think tit will be cheaper then buying a ready-to-go exhaust.

 

[1970FuryConv]

Very helpful thread. I have a 2" H-exhaust system for a 318 and was wondering the same thing. 440/727/8.75 conversion coming.

Question: If I have the factory log manifolds now and decided to go HP later, would the HP manifolds bolt on to the new exhaust or would the front pipes need to be bent to a new exhaust manifold outlet location?

 

[polara71]

I am certain they dump at the same location. The size of the pipe will be your concern. Your logs are a 2 1/4 dump and the HP's are a 2 1/2 inch dump. the flange isnt going to work from one to the other

 

[bajajoaquin]

I am certain they dump at the same location. The size of the pipe will be your concern. Your logs are a 2 1/4 dump and the HP's are a 2 1/2 inch dump. the flange isnt going to work from one to the other

Is that why TTI asks for the manifold casting number when you order? I thought it was because the manifolds dumped in different places. Good to know.

 

[thrashingcows]

Very helpful thread. I have a 2" H-exhaust system for a 318 and was wondering the same thing. 440/727/8.75 conversion coming.

Question: If I have the factory log manifolds now and decided to go HP later, would the HP manifolds bolt on to the new exhaust or would the front pipes need to be bent to a new exhaust manifold outlet location?

Yes they will need to be changed. The angle, and orientation of the bolt holes on the flange changed from LO Po to HP manifolds. As well as the location of the flange...closer, or farther from the ground?

I am certain they dump at the same location. The size of the pipe will be your concern. Your logs are a 2 1/4 dump and the HP's are a 2 1/2 inch dump. the flange isnt going to work from one to the other

See above comment...;)

Is that why TTI asks for the manifold casting number when you order? I thought it was because the manifolds dumped in different places. Good to know.

Different manifolds have different flange locations and bolt hole orientation.

 

[polara71]

My only experience is from my own ignorance. Presuming they would bolt right up I was able to get one bolt in and not the other .

 

[kawdude]

My 68 newport 383 2 bbl has 2 inch pipes comin out of the manifolds. I did 2 1/4 all the way back for a lower tone through the glass packs.

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[1970FuryConv]

"Your logs are a 2 1/4 dump and the HP's are a 2 1/2 inch dump. the flange isnt going to work from one to the other"
"Yes they will need to be changed. The angle, and orientation of the bolt holes on the flange changed from LO Po to HP manifolds. As well as the location of the flange...closer, or farther from the ground?"

Great Info!!! Hardly worth doing a 2.5" exhaust if you have logs. I have looked at some c-body HP manifolds. On the left side, the exit seems more angled to the side than straight down. Why do you think that is?
Also would you consider "shorty" block hugger headers over HP manifolds?

Pictures below are LOL. They are right side and left side bends in my 2 inch 440 exhaust system. No wonder it ran slow, it couldn't exhale.

 

[thrashingcows]

The driver side manifold exits at a bit of an angle...almost 90* to the side of the block. It does this so the pipes can be directed around steering linkage and shift linkages.

Personally I would never run headers...nor will I ever run them as long as I have a choice. ;) They are way more problematic then the old HP manifolds.

 

[1970FuryConv]

Yet the outlet from my left side log points straight down and both log and HP outlets are between cylinders 5 and 7. Could 1/4" of increased diameter necessitate such a turn?