BILL DEMMER

i ordered a set of x/w repop manifolds from opgi during a recent sale. the pic on their website clearly shows the center port as having a divider. the ones i received did not have a center divider. i called jeff at opgi to see wtf was up. he said that the manufacturer knows that what they made are wrong, but they won't do anything about it. opgi sent me a call tag, for them to pay to get the manifolds back and credit me. opgi also says the their w/z manifolds are missing the center divider-same deal, manufacturer doesn't give a f.
clearly, opgi is just a reseller of thornton manifolds.

so, wtf is up with repop x/w and w/z manifolds?


thanks,
bill

BILL DEMMER

here are some pix of the x/w manifolds that opgi sent me, before they went back.

https://classicoldsmobile.com/forums...1&d=1420315298

https://classicoldsmobile.com/forums...1&d=1420315298

https://classicoldsmobile.com/forums...1&d=1420315298

https://classicoldsmobile.com/forums...1&d=1420315298


bill

oldcutlass

If you don't mind me asking, what benefit would a divider have?

joe_padavano

Absolutely nothing on those manifolds. Unfortunately, the aftermarket manifold vendors seem to think it's magic and thus worth more money.

To recap: The factory W/Z manifolds used on the 1969-72 big block cars are INTERNALLY DIVIDED. That means that inside the casting, they actually have individual runners. That's why the W/Z manifolds are physically larger than others (and why they don't fit SBOs) and why they flow better.

The earlier manifolds, like the ones discussed in this thread, are NOT internally divided - they physically are not large enough for separate internal runners. The center divider the OP seeks is cosmetic at best (especially if you haven't welded up the divider in the ports on the heads!) and only runs an inch or so into the casting, like the ones on the ersatz "W/Z-like" manifolds for the SBO. Arguably that divider only serves to add turbulence (though without a real flow test, that is only speculation on my part). The factory versions of the X/W manifolds do NOT have dividers, for this reason. The ones with the divider actually are incorrect repros. The short center divider adds nothing to the performance of the manifold. It does, apparently, add to the selling price, however.

oldcutlass

Which was my point in asking the question. I just could not see any physical benefit to it being there.

Octania

Exceedingly good input, Joe, as usual.

Does this mean that my old broken real factory W/Z units are still worth resurrecting?

Dammit my '68 is supposed to have the undivided x/Y set anyhow.

BILL DEMMER

thx for the replies!

i had a set of original w/z manis on ernie before i pulled the motor. the originals are cracked/eroded at the center divider, would cost about $250 to get them fixed, and they may continue cracking. the g-heads i'm using now have been modified for the w/z manis to work as designed(exhaust crossover filled, divider built up to mating surface, etc.) just like real f-heads. the reason i went with x/w repop manis was: it appeared in pic that they were properly divided like real w/z manis, and there was a problem with the lh mani only being about 3/4" away from the steering shaft(heat).

does anybody make proper w/z repop manis now? or am i relegated to fixing the originals? originality doesn't matter to me one bit, getting the max out of the 425 does(without headers).


bill

jensenracing77

Here are the repops you are looking for.

http://gawain.membrane.com/~thornton/70_72manifold.html

73aussie455

Sort of related
I recently saw a set of w/y manifolds for sale. The seller said they were factory manifolds from '73-'78 big block B & C bodied cars with factory dual exhaust, supposedly very rare he said?

Could someone who knows comment about these manifolds and if true, what are the differences between w/y and the OP's w/z manifolds?
Apologies for the hijack.

BILL DEMMER

thanks, jensen... for what they want for those, i can fix my old ones, and have money left over.


bill