LeaningTowerOfPowr

Hello

My Valiant has a crack in the exhaust manifold for the 3rd time in 6 years. I am going to replace it again soon. Im wondering which manifold I should choose as far as material. Ive seen a variety of metals available with an array of price ranges. Heck, I have even seen plastic. Anyway, what do yall think? Tired of replacing manifolds.

1970 Valiant, 3.7 Slant Six. Completely stock. 60k orig miles

RacerHog

That s odd???? Were is it cracking? Is it the same spot every time?
I will have to say. Here in SO-CAL.. I have not had any of those type problems..

LeaningTowerOfPowr

Hey Racerhog
It seems to crack in different places every time. I was told once that its due to the block and manifold being of different materials and thus expanding and contracting at different rates. Plus living in Phoenix in extreme heat then going to the mountains where its much colder helps with the cracking. At any rate, it needs replacing again as my car is getting louder and louder.

LeaningTowerOfPowr

The crack usually happens between the inlets in the manifold.

RacerHog

Are you using new or used manifolds?

LeaningTowerOfPowr

I am using junkyard manifolds. I wanted to buy new this time and see if that would help. I was just concerned about what material to get.

Iowan

This is a good one for the leaning tower of Bob /////////

RacerHog

Thanks Tom...lol
LTOP:... I agree with you on the temp change... Phoenix and a place like Prescott (PressKit) are and can be challenging when dealing with temperatures....
Most of the Cast Iron stuff your dealing with is more than seasoned to be up for using without having an issue! At least thats what I think.
Here is where I think you might be able to do some improvements....
Use the 5 minutes rule when starting the car, Let it warm up for 5 Minute.
And for shutting off the car, Let it Cool at idle for 5 minutes.
This will help the temperatures on both side of the heat cycle, cool down and warm up.
Know, I'm going on this info guessing that the tune up is all in good working adjustments. Not lean... Not rich... Not heavy in timing one way or the other.
Just food for thought. and something to try....

Just my 2 cents....

Iowan... What do you think?????

Iowan

Iowan... What do you think?????

DANGER DANGER

I think it's in the tune up!

Drag Pak

I've seen v8's with this problem.

Might be a good idea to put a straight edge along the head and then along the manifold before assembly next time. Both may need surface grinding to true them up.

TVLynn

MAKE sure you are using the correct fasteners. They are designed to allow the manifold to move with expansion

Iowan

I forget that not everyone would know to cut let alone check a used manifold prior to installation, it's automatic with me, but check a head that's good.

70newport

If this is the 3rd manifold you have had crack I would be confident that Drag Pak is on the money with the head not being straight. any update on this though?

Im curious.

TVLynn

Just a additional thought, Make sure the exhaust pipe it supported and not just flapping in the wind