73 Exhaust on a 79

Hello, I am switching out my ZS carb to dual HIF's using a pre ZS exhaust manifold. Would I run into any problems then if I used the down tube and exhaust system from a 73 B?

If you're transferring the complete system without taking it apart you will probably find the exhaust hangs low in the centre, this is because the RB exhaust exits lower at the back to clear the rubber bumper. I just did the opposite, I transferred an exhaust from a 79 to a 73 and because of the differences the centre muffler sits tight against the floor.

If you can take the system apart you'll get a much better fit.

Remember there were 2 early stock exhaust manifolds. One matched the thinner 7/16" flanges of a HIF-4 intake and has the number "12H 3911" cast into it, the other more common version matched the thicker 9/16" HS-4 "12H 709" intake . Both can be made to work with extra washers, but a match is better. AFAIK, matching all of the exhaust parts from the head to the tail pipe to one year is best.

FWIW the stainless Falcon big-bore system looks/sounds great, and will not rust. However, it is expensive vs. other options.

HIF-4 is a great choice as they look cooler, and were stock for other later UK spec cars.

You might have clearance issues under the rear axle if you don't lower the car. a RB exhaust has a bend in it that the CB doesn't

If you dont lower it, you will need to use the CB manifold and downpipe and attach it to a RB system from that point on

Jon.

The rear hanger for the rubber bumper car hangs down about 1 1/2" lower than the chrome bumper one. This will drop the tail end of the exhaust down a bit, but as Paul noted the RB resonator assembly has a bit more kick right under the axle for clearance.

If you were going to lower the car, this would not be a problem. If the car is staying at factory ride height then the clearance between the rear axle and hand brake lines is going to be tight.

If you use a three piece system, you should be able to juggle it enough to give you what you need. But if you are going to this amount of trouble, I'd recomend dropping the car an inch with spring/lowering blocks to give a bit better handling as part of the package.

kelvin

I just did this. I have a 1978, and used a header from a 1972. Bought a stock three piece exhaust from the B-Hive, but the front pipe is from a pre 75, the middle and end is for a 1975-1980. Fits like a glove. As the posters state above, an earlier exhaust would have clearance issues on a RB car.

Paul

Thanks for the info. I had planned on lowering but just not right away. Guess I will add that to the list, probably should do the bushings at the same time?