LancePearson

Just as a new owner curious...what makes the ram's horns oem type exhaust manifolds crack? Is it movement of the exhaust system while the car is hot, age (metal fatigue), defective castings?

Can you replace them with individual headers but not have to go to side pipes and true duals on a 76 with cat converter? I have one with a filled crack...I filled it with the 1200 degree epoxy...and will replace it and the exhaust next year...learning what among the choices I want.

The ease of changing plugs looks better with individual pipe type headers versus the ram's horns which hide things, have heat shields, etc.

Any wisdom appreciated. If I put one new ram's horn back on then, wonder if it will crack again or if the one on is an original 1976 and it's just metal fatigue.

Lance Pearson

earthquake68

Anything is possible, but epoxy isn't the best repair on an exhaust manifold. A good welder can weld the crack permanently. Any exhaust manifold is susceptible to a crack. Heat, vibration and the exhaust pipe trying to twist it all contribute. It is, after all, cast iron. Very hard, but very brittle. Some manifolds are worse than others. DO NOT run one header on one side and a manifold on the other. That's just silly. Yes, you can run headers without true duals or side pipes. They make shorty block hugger headers that kind of resemble the rams horn manifold. You just need to adapt the pipe ends to the headers. ...or you can use long tube headers and cut the pipes further back.

Every performance part you put on the car is only PART of a complete system. Headers into a stock exhaust system makes absolutely no sense. You're trying to increase exhaust flow, but then bottle the gases back up with the stock 2 into 1 exhaust system. Just find a replacement manifold or find a qualified welder to repair it properly. That's my .02.

LancePearson

Thanks, earthquake 68. I know the two sides need to be the same. If I replace the exhaust sytem in 2011 as original but with new high flow cat converter will just replace cracked manifold and leave as it is both sides. However, since I have to do something with one side and the exhaust system is near the end of its life I will rethink my options for all of it. What I really would like is straight duals and not old mild steel pipes but something more long lasting like stainless and no cat converter at all which is possible with antique license. If I do that then it makes sense to put headers on so it can breathe better all the way through the exhaust system I believe. Will read more and be sure that doesn't have engine implications. Can always put same type header on and just 2:1:2 exhaust pipes and high flow cat converter. Suspect timing settings would change slightly with true dual setup. The epoxy is holding so far but I know it's only a short term fix at best. PO did a good job on some things, not such a good job on others.

I don't ever plan to put diff. cam, roller lifters, new heads, new intake. Too much trouble for an occasional use car and that would run the mpg down too I believe with that much more power. No drag race aspirations either.

earthquake68

Well, as long as you're doing the whole exhaust, I don't see headers and bigger pipes to be a problem. Don't go over 1 5/8" or even 1 1/2" primary tubes. That's the critical part for you. You need to keep exhaust velocity up. With bigger primary tubes in the headers, the exhaust velocity drops and you actually hurt performance. The reason headers work is, when a cylinder fires, it creates a vacuum in the collector and actually pulls the next exhaust pulse out of the head. When exhaust velocity drops, this process is far less effective. I would go with Heddman headers into a single 3" pipe into your dual mufflers and tail pipes. You shouldn't have to do anything with the engine. ....nothing at all.

highschool67

Most cast exhaust manifolds were meant to be used without a gasket. Sometimes a cylinder head can be machined on the exhaust surface incorrectly causing a few thousands bind over the whole surface. A lot of old timers suggest you use gaskets when servicing the manifolds. It gives a little cushion to surfaces that might not mate perfectly over time. Weak castings can cause cracks as well.

bucky-katt

theyre really not too hard to weld properly. drill out the ends of the cracks (so it doesnt migrate any further) you just need to pre-heat the cracked area (after bead or sand blasting the crack) get it glowing dull red before hitting it with a mig welder set on the highest setting. this method always worked for me anyways and never had any complaints about it leaking or cracking again.

LancePearson

The 69 I bid on and lost before getting my 76 had hedman headers on it. Wondered what they were at the time. Sure made getting to the plugs easier than the rams horns. I will probably go to coated hedmans and true duals since I have to take one exhaust rams horn manifold off anyway to repair or replace it. I'll probably replace it as noted and just haven't fully decided what exhaust configuration I'll use. With antique license I can junk the cat. converter or go modern with a high flow one. Haven't fully decided yet. Will do hedmans if I go true duals, rams horn if I go high flow 2:1:2 and keep it essentially original engineering..

Aflac

I would think that over time, the heat cycles could cause the iron to grow brittle too...