Sampson

I am contemplating a set of Thorton's JR Manifolds for my 350. The engine is just back from the machine shop. Some details of the build:
Speed Pro flat tops 30 over. Comp 268. 280 Cam, #6 heads w/ performance valve job and bowl blending, rpm performer intake and Edlebrock 650 com carb.
I wonder if the JR's would make a noticeable difference vs stock. Would it be better to invest is some headers instead? I am trying to balance the performance gain of headers vs the stock look but want to get the most out of the ride.

oldcutlass

You have a great stock looking car. It probably is not going to see the track much, I would stick with that theme and go with the Thornton's.

joe_padavano

The Thornton SBO manifolds are nearly identical in size and configuration to stock. The only differences are the blanked-off crossover port, slightly larger outlet ports, and the 1" deep divider between the two center ports. Any difference in performance will not be measurable. If you want a performance increase, get real equal length headers sized for your combo.

DoubleV

They are internally bigger too. Just a fact, NOT an endorsement for the Thorntons!

joe_padavano

But not THAT much bigger, since the space under the SBO ports is limited. More to the point, bigger does NOT mean "higher flow" or "more HP"

jag1886

I don't understand why you trash this product every time it comes up. I admit it is still a stock type manifold that conforms to stock type head pipes but Thornton's have notably larger internal volume the outlets are larger and they eliminate the mixmaster on the rear of the pass side manifold and they are quiet.
I have a set and it is a good product.
Samson you have a very similar build to mine expect a little more cam, if max power is important get headers, if keeping the car quiet and totally dependable go with the Thorntons.

70cutty

IMO You did all that work to the engine, got the rpm intake why choke it on the exhaust. Put some full length headers on it and let it breathe, let that cam come to life. You will notice the difference in sound and performance. Personally I like Hooker. others will disagree but like I said JMO.

Sampson

Thanks for the feedback guys. I would love to put this thing on a dyno when I get it back together and do a comparison. My gut tells me I probably will not feel the difference between the JR's and the stock manifolds in the seat of my pants and Eric has it right that I would like to keep the stock look. I will probably go with the stock manifolds for now and if I get bored with the performance I know I will be able to find a few more ponies with some headers.