[kernalcorn]

hello,

I am looking to replace the manifolds(believe on has a hole in it in the drivers side.) on my 70 gto it has a 400(350 c.i.) with auto trans. How can do you tell if the manifolds are Round or D shaped?
any pictures/drawings would be appreciated.
and what would you recommend for replacements?


Also while I have all the pipes off for the manifolds do you guys have any suggestions on what is a good pipe to replace them as well and what would be the recommended size?(3 " or 2.50")

thanks
Don

[kernalcorn]

hello,

I am looking to replace the manifolds(believe on has a hole in it in the drivers side.) on my 70 gto it has a 400(350 c.i.) with auto trans. How can do you tell if the manifolds are Round or D shaped?
any pictures/drawings would be appreciated.
and what would you recommend for replacements?


Also while I have all the pipes off for the manifolds do you guys have any suggestions on what is a good pipe to replace them as well and what would be the recommended size?(3 " or 2.50")

thanks
Don

[WDCreech]

Post the numbers (letters) cast over the center exhaust ports and the date code if you can find it and we'll tell you whether they are round or D port. Chances are that they are more than likely D port, but you never know.

[kernalcorn]

Bill,
thanks for the info here is what I found

the only letter & numbers found were right above the manifolds on the drivers side E150 was above the center exhaust ports. (might I need to remove the heat riser?) if this is not it can you post a picture as to where I can find them? any help is apppreciated.


Don

[bonneville Joe]

D port manifolds will look like the center ports are basically one large oval shaped port. Never heard of a E150. Should be something in the realm of 7K3 or 16 or something like that.

[Held for Ransom]

E150 is the casting date. He probably has standard D-port exhaust manifolds.

[4SLASH6]

only wish there were a bigger swap area for muscle car show sunday.... would like to score a set of ram air exhaust for my 70 350hp gto hfr , maybe you have a spare set??

[Held for Ransom]

You would have to go to Spring or Fall Jefferson Car Show/Swap Meet to find a pair. Ram Air Restoration Enterprises, Inc. now sells out of Chicago also and has a van set up at the show for buying the reproductions.

[4SLASH6]

will be there with bells on,..now, where is it?

[Held for Ransom]

Jefferson, WI near Milwaukee. 5-1/2 to 6 hour drive, one way.

[kernalcorn]

ok my manifolds look the the ones that Held for Ransom showed the numbers on the center port is E050 hope this sheds some light.

so next step what do you guys recommend? replace with Headers or back to manifolds?

I plan on driving this car but showing alittle too. nothing serious.


I really do appreciate the help from all of you this is why these forums ROCK!!

thanks again....

Don

[sleeper]

GO with headers. up to 40 mre hp. They sound much better. They have summit ones that work ok for $80

[gtoformula]

Original message quote:

"I am looking to replace the manifolds(believe on has a hole in it in the drivers side.) on my 70 gto it has a 400(350 c.i.) with auto trans. How can do you tell if the manifolds are Round or D shaped? any pictures /drawings would be appreciated. and what would you recommend for replacements?"

I assume that you meant 350 HP (not 350 c.i.). Hole in the manifold? Not very common. Could be cracked, but might just be a bad gskt or loose bolt.
Regarding the pipe size: unless you are running the car at the strip go with the 2 1/2" system. 3" is great for max HP, but not cheap and not easy to install due to clearance issues.
Cast manifold vs. headers: kind of depends on what you want from the car. Headers are less expensive and produce more power. On the flip side they are SOB's to install on Pontiacs as the head ports face more towards the ground than straight out horizontal like Chevy's.
I like the sound of the headers on my 1970 GTO. It runs a RAIII type cam, Q-Jet, Flowmasters with 2 1/2" pipes. To install headers you need to tweak the trans cooler line routing (if you have an automatic), remove the starter, undo the engine mounts on each side as you install the headers, perhaps slightly modify the brake proportioning valve to avoid contact with the driver's side header, etc. The header bolts need to be tightened with a succession of 1/4, 3/8 drive sockets, combination wrenches and a 90 degree wrench. It isn't an easy install, but I like the results. The bolts need to be retorqued a couple of times at 200 mile intervals to ensure a snug fit, but I have never had a leak since installing them about ten years ago. I went with Hooker Competition (not Super Comp), but there are lot's of good alternatives out there.
Also, way unlikely that you have round port manifolds. Don't know how they might have found their way onto your car, but without round port heads they wouldn't bring anything to the party anyway.

[kernalcorn]

yes GTOFormula ,

I meant 350hp looks like they are D shaped (compared them to the photo above.) I will have to look at the Manifolds more closely to see if it is a crack or if the gaskets are blown. the manifold have gotten really pitted since it sat (for 4yrsin a garage.) however now I have the money and time to get it "back on the road"


Thank you all for your imput I will look at the pypes complete kit(2 1/2) however I guess the
RPE630KAT 2 1/2" PY USA Thunder system W/X pipe and X/RPE659LC -Pypes V-Force Mufflers....

any one have this complete system and have any suggestions?

pls let me know.

Don

thanks again all this help is great for someone with little exhaust experience.