Exhaust Manifolds and are you Pleased

[ir3333]

this argument will go on forever.
Tuned equal length headers can help nasty long duration race cams at hi rpm because of the scavenging effect.For the street a shorter duration cam will provide more lo rpm power and headers might not help much at all on this type of engine.
Manifolds should be fine for all but the open header racers.

 

[rumblefish360]

Sounds like it to me. It's YOUR car, do it the way YOU want!

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[andyf]

Who has put their original exhaust manifolds (instead of headers) back on after a complete engine rebuild and are you happy?

Reason I'm asking is we are at the final stages of my stroker (505) rebuild and the original exhaust manifolds we took off look fantastic. I'm just questioning the investment of headers when it's never going to see the track. Will any loss of HP (20-40?) without headers be that noticeable when street driven.

Also we are using the original 915 heads that have been machined and ported. Thx.
View attachment 676614

From what I see of your build I'd think that the original manifolds would be a good match. If you aren't racing the car you will probably not notice the difference in power. I have manifolds on the 512 inch stroker in my Coronet with ported heads and a hyd roller cam. It makes 485 rwhp on the chassis dyno and it accelerates fast enough on street tires to get into trouble in just a few seconds. Bottom line is that I don't really need anymore power in a street car. If I stomp on it I'll be doing 100 mph by the end of the average freeway on ramp so what would be the point of having another 30 or 40 hp? I don't need to hit 105 mph to merge onto the freeway.

Here is a video of my car on the chassis dyno. This was taken while were were testing the new Sniper fuel injection system. If you already have the manifolds then I'd take the money that headers would cost you and buy a Sniper EFI kit with the Hyperspark distributor. You'll notice a much bigger improvement to performance and fuel economy with the EFI kit than you would with headers.

 

[vintage chromoly]

I’ve done it both ways lately.
I had the HP manifolds on my 446 and now I have 1-7/8” TTI headers.

My combo is relatively mild (solid cam 240 246 .540 lift)
Holley 750 DP, Holley street dominator intake and ported 906 heads. 9.5:1

I will say, the headers seem to have much more punch across the entire RPM range.

If I was doing a strict OE type car, I’d run manifolds. If not, headers all the way. (Good headers, not Chinese junk)

 

[rumblefish360]

What’s the best manifolds for a B body big block?
Any different choices for a 400/440/470/500+cid

 

[33 IMP]

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Don't drop phone when girlfriend's dog jumps on you while texting and hit power button, losing what you were

 

[m79ded]

There was a thread on moparts recently....... 500”, 6bbl, TF240 heads, hyd roller cam........ headers and hp manifolds...... on the dyno.

Headers......90hp better than manifolds.

How much you can gain or lose is totally dependent on the combination......but on any decent 500” type build, don’t kid yourself into thinking you’re only leaving 10-20hp on the table.
It’s def going to be well over that.

I totally agree, been there done that, you will leave so much on table especially with bigger motor it's crazy. I did a 493 with manifolds and the thing would get the manifolds red hot and whatever I did just wouldn't stop pinging, it was not fun unless retarded it. Put headers and easily picked up almost a second on E.T. Needed to put a really wide LSA cam as well. Needed to lazy up the engine to make it work well with those many cubes corked up. I'm speaking from experience, I wouldn't do it again.
Good luck with your build

 

[rumblefish360]

Don't drop phone when girlfriend's dog jumps on you while texting and hit power button, losing what you were

Just trying to help, don’t be a dick.

 

[BSB67]

........ Put headers and easily picked up almost a second on E.T............

Sounds like great info. Can you you share the et and mph difference between manifolds and headers and a little about the build? Were there other changes made?

 

[ir3333]

If your headers or manifolds are red hot it might be timing.Too retarded and the big part of the fire is burning exiting the heads and in the exhaust manifolds instead of the cylinders.
Pinging is too much compression for the fuel octane you are using or tuning / timing.
Larger exhaust pipes are required for big cubes.

 

[PeteBell68]

Sounds like your building a pretty stout motor that probably needs headers to flow .
I've had that motor with headers and it was loud , fast , hot in the car but was it worth it hell ya .
Now I'm in a pretty much stk 440 HP manifold car that's not as loud not as fast but fun and I can actually hear my radio - although it's a mighty 2 watt AM .
Manifolds are great depending on the motor .

 

[m79ded]

Sounds like great info. Can you you share the et and mph difference between manifolds and headers and a little about the build? Were there other changes made?

That time the car with Manifolds went 13:10 @107 mph with the Cooper radials and switched to headers and went 12:39 @ 112Mph. The motor had a racer brown cam (very old) and ported iron heads 453 castings.With the presence of nice modern grinds it can be much better. Car Now has a 451 with TFS240 and a huge difference. My opinion is stick with headers.

 

[rumblefish360]

What’s the best manifolds for a B body big block?
Any different choices for a 400/440/470/500+cid

 

[Dennis H]

Confused. Why would less weight and less heat be bad?

 

[BSB67]

That time the car with Manifolds went 13:10 @107 mph with the Cooper radials and switched to headers and went 12:39 @ 112Mph. The motor had a racer brown cam (very old) and ported iron heads 453 castings.With the presence of nice modern grinds it can be much better. Car Now has a 451 with TFS240 and a huge difference. My opinion is stick with headers.

Thanks

 

[wyrmrider]

What’s the best manifolds for a B body big block?
Any different choices for a 400/440/470/500+cid

Rumble - what year 73 and later B is different left side takes like a C body manifold as the stearing gear is in a different place
aside from that all the HP manifolds work about the same IMHO
I like my stereo so no headers
and you know I go short on the cams anyway
stock heads extra duration on the exhaust
good exhaust you can run single pattern cam -or less extra exhaust duration with or without headers
keeping the overlap down really helps with ex heat

 

[m79ded]

Thanks

Another point I would like to make is I really believe now that I know better I really had the wrong cam in it. Truth to be said I had a wrong combination in it. Seen many F.A.S.T cars run manifolds with big engines but they really put alot of work in them.This was my 1st time and like I said didn't know what I know today.It was a single pattern with about 241 duration, and a TQ carb. I wanted the thing to look completely stock when I did that build. I'm sure if I had a wide LSA like 115 to 116 and a dual pattern cam with 8 degrees more exhaust it would have made a difference. Compression @ 10.7 didn't help either. I had to tame the engine down to be manageable. Good luck with your build and I hope by me sharing my mistakes with our forum buddies can help someone else not make the same mistakes I did.