[Bull]

If my goal is to make some MILD upgrades to my '69 Cat convertible to make it a cruiser with nice performance (no races or anything) is it necessary to run anything other than the stock log manifolds? I am considering the factory long branch manifolds, but if they are overkill and I can save money, then I'll stick with the logs. Basically, I guess my question is how restrictive are the log manifolds as compared with the long branches, and at what point do you need to upgrade from the stock manifolds? Thanks for your guidance.

Dave
Amherst, MA

[Bull]

If my goal is to make some MILD upgrades to my '69 Cat convertible to make it a cruiser with nice performance (no races or anything) is it necessary to run anything other than the stock log manifolds? I am considering the factory long branch manifolds, but if they are overkill and I can save money, then I'll stick with the logs. Basically, I guess my question is how restrictive are the log manifolds as compared with the long branches, and at what point do you need to upgrade from the stock manifolds? Thanks for your guidance.

Dave
Amherst, MA

[bonneville Joe]

I think going from log manifolds to long branches is a signifigant improvement in performance just by itself. The log manifolds don't flow worth a crap. I have an original set of LBs that Im going to be installing on one of my cars in the near future and I can't wait. I plan on stepping up the cam shaft a bit but just installing the LBs will help a ton.

[Coach]

Just MHO, but Pontiac was pretty good about wringing performance out of their motors. I would think the stock manifolds would do you well, at least till you opened up the cam a bit. A set of high flow mufflers on the other hand should give you a big improvement over the stock units.

Now I have to admit that if someone dropped a set of long branchs on me I would install them in a moment, but considering how much they are selling for and the fact that I have a bone stock motor I don't think it would be worth it, at least not for me.

-harry

[bonneville Joe]

The smoother and better you can get the exhaust out of the motor, the better it will run and perform. The exhaust gas is obviously the hottest as it leaves the heads, you need to give it as much room and possible to move. Look on ebay and see if there are any stock log manifolds for a big car on there. They look pretty pathetic.

[Bull]

Thanks for the input thus far. Do you guys know whether the long branches fit without any issues on a '69 Cat? Are the ones in the Perf. Years catalog identical to the original factory long branches?

[b-man]

Stick with the logs, you'll only gain about 10 HP with the long-branch manifolds on mild 400/428/455 engine. A good 2-1/4" or 2-1/2" dual exhaust will work fine with the stock logs for a mildly hopped-up street Poncho.

By the time you get a set of repro long-branch manifolds and the filter adapter you will have spent half a grand. You'll have to decide whether or not a 10 HP gain is worth $500 to you.

[goatless]

Dave, for what it's worth, I've still got log manifolds on my '69 Lemans convertible. It just ran a 13.30 1/4 at a weight of 4050 lbs. with a 3.08 gear.
Yes they are a restriction but not as bad as you'd think and not something I'd worry about unless you're trying to get every last bit of power. I'd say for your stated goals the long branches aren't necessary.

Jeremy

[bonneville Joe]

Im pretty sure they fit '65-'69 big cars. They are supposed to be exact repops of the originals. I have an original '66 pair that I am going to use on my 4dr pretty soon. A smooth flowing exhaust is not going to benifit the motor if it experiences alot of resistance when it leaves the heads. Its more or less forcing the exhaust out as opposed to it flowing out. There is a reason the HO cars had the Long Branches.

[buwalda]

From the pics, the repro long branch manifolds look really good, but more importantly, efficient. I have the RA/HO manifolds on my GTO. I only wish that the long branch manifolds fitted. The LB's have straighter runners with less sharp bends, plus the runner lengths' are closer to being the same length.