[dataway]

Is there much to be gained using RA/HO exhaust manifolds on a stock build compared to the standard logs?

Looking to keep the car as correct as possible and it's a YS engine ... so no RA/HO manifolds.

Did the 326/350/400 in 68 use the same standard log manifolds?

Did all the 68 GTO with standard manifolds have the exhaust flapper valve on one side?

Thanks,

[b-man]

All the different engine displacements used the same exhaust manifolds and intakes as well.

You'll gain right around 8 HP with the RA/HO manifolds over the logs on a stock engine.

Pretty sure in '68 the flapper valve was still being used, by '69 it was gone.

[dataway]

Jeez, 8 hp is quite a bit to give up. But they probably ding you pretty good in a show if you have the wrong manifolds.

[b-man]

I'd say 8 HP wouldn't even be noticeable in the seat of the pants while driving it hard, for the roughly $400 cost to install a set the juice ain't worth the squeeze.

Not to mention they'd be incorrect if correctness is your aim here.

[dataway]

LOL, I like that phrase

Ok ... another decision made. It's great hearing from people that know more than me.

I could probably get the same performance effect from only putting in a 1/4 tank of gas

And yes, correctness is my aim.

[dataway]

Come to think of it .... anyone know the proper part numbers for left and right exhaust manifolds ..68 YS400 GTO.

[grandam1979]

We just took a set of log manifolds off a 68 GTO and will be for sale. I have not looked at part # I dont think either one has a flapper in it.

[dataway]

I can't remember if mine had the flapper when I took them off many years ago. Wonder if it's a "late/early" thing in 68. My 68 is July 68 ... doesn't get much later than that.

[ilo]

Originally Posted by grandam1979

We just took a set of log manifolds off a 68 GTO and will be for sale. I have not looked at part # I dont think either one has a flapper in it.

I would be interested in them if the OP does not want them...

James

['ol Pinion head]

Pass side had the flapper for '68, flapper was gone for '69.

[ponchjoe]

Mine has flapper (stuck open of course) After I pick up the motor GrandAm1979 is talking about and install it they will be for sale.

[goatless]

Originally Posted by dataway

Ok ... another decision made. It's great hearing from people that know more than me.

I could probably get the same performance effect from only putting in a 1/4 tank of gas

And yes, correctness is my aim.

I think you made the right choice. If you want to get a little more performance while still looking "correct", do a search- B-man and I have made a bunch of posts on modifying log manifolds. One more thing on switching to RA manifolds- you may pick up a few hp, but you'll also be adding 20 pounds, or so, that'll negate any gains.

[dataway]

Originally Posted by goatless

I think you made the right choice. If you want to get a little more performance while still looking "correct", do a search- B-man and I have made a bunch of posts on modifying log manifolds. One more thing on switching to RA manifolds- you may pick up a few hp, but you'll also be adding 20 pounds, or so, that'll negate any gains.

Very good to know about the weight ... and the experimenter in me immediately started wondering what could be done to improve the logs ... the port openings certainly aren't anything to be proud of, I assume port matching would help.
I'll see if I can find those posts.

Ponchjoe ... I might be interested in those.

Thanks guys.

[goatless]

Here's one of them- http://forums.maxperformanceinc.com/...t=log+manifold

[dataway]

Excellent, thanks for the link.

Wish I could narrow down when exactly they stopped using the flapper. I have a very late 68 and would love it if I didn't have to have the flapper to be correct. I'd weld it open or remove the flapper and leave the parts on the outside anyway.