Yea or nay?
Rebuilt engine, Isky performance cam, everything else is stock, SU carbs.
Can't decide on stock or 4 into 1 headers. I have both ready to install. Any thoughts?
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'61 PV544 - '65 PV544 - '64 Lincoln Continental

Consensus when this topic came up before is that the stock manifold into the twin downpipe is as good or better than the IPD headers, as an example. Further, if available for your car, you can try the twin dp manifold with the Simon's 2" sport exhaust. I just put one in my '62 Amazon (this car had a B20 w/twin manifold already). Some issues with clearance, but I'm working on it and it's not a big enough problem to pack it up and ship it back. Sounds good and looks COOL, IMHO. Good Luck.

Pretty much anything is better than the single downpipe manifold the PV would have come with.

From what I understand the 4/2/1 header styles work better at the RPM's most of us would normally use on the street, the 4/1 style works better at really high rpms.

The dual downpipe manifolds are quite nice, basically a cast 4/2 portion of a header, with the downpipe being the 2/1 portion. Only issue being the diameter on the single pipe section if you have a lot of HP.

For whatever reason, Volvo somewhat choked the heads in the exhaust ports. Probably intentional, to keep the HP levels down in a hard to change spot. But that means that you can't really 'uncork' a lot of power just by swapping the exhaust. Until you've sunk some effort into improving the flow in the head, that is.
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'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)

I'd be tempted to try the 4 into 1 headers, I know that design is quite critical on these and that Volvo R sport did recomend the cast iron manifold but when you look at its design, specifically the way no 2 and 3 ports are only separated by 15-20 mm I'm a bit dubious about it. I've heard it described as a rev limiting design and its possible for one cylinder to suck in exhaust gases from its neighbour. But I don't really know and I suppose you should try both.

I'd pick the stock one if it is the twin outlet one. 4 into 1 headers only good for much higher state of tune with the engine running at the top of it's range, 5k+. 4-2 into 1 needs to be a good one to match the factory twin outlet. Most won't be as good. Factory used the cast one for the tuning kit that gave 145 bhp, you won't be getting anywhere near that.