340 manifolds and Magnum heads

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AdamR

AdamR

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I know this has been brought up before but I dont think anyone could answer for sure. Do 340 Hi po exhaust manifolds seal up ok to Mag heads or do they leak ?
 
Adam I can't say positively but I think they'll be fine. The 340 heads did have larger exhaust ports but I don't think it was over 1/8" diff and there should be enough meat on the head to seal things up. On my 93 Dak with the 318 magnum I used exhaust gaskets for a LA 360 and they worked fine.
 
Ive read a few times that the Magnum port is a bit higher ? and leaves a small gap at the bottom with manifolds.

I just dont want to buy a $500 set of manifolds and a set of EQ Mag heads have have an issue.
 
I thought I read threads on here where people made them work on EQ heads but they had to make an adapter plate out of thick sheet metal because of the port mismatch. So its been done but you have to do a little work to get them to seal up.
 
The magnum exhaust port exit is some higher I believe but I think by the drawings I have looked at all 4 ports are the same amount higher than LA ports but their shaped the same with the same amount of sealing surface area. This being the case I can't see why LA headers won't bolt up properly but it probably will raise the header by the amount the ports are higher. I know the LA ex. manifold gaskets I used on my Magnum heads were dead on. The only thing problem with raising the headers is room is limited in an A-body chassis as I'm sure your aware of. I understand your point that you don't want to buy something that may not work without a big modification. Wish I knew somebody that had a set of Magnum heads cause I have a couple sets of LA header gaskets I could compare them too.
 
I have a 340 with the EQ magnum heads and they bolted up. But I had to make sheet metal adapters to seal them up. The port mismatch left an open gap, as the manifold was open below the heads sealing surface.
If you want a photo of it Adam, I could post it Sunday.
 
bobscuda67 said:
I have a 340 with the EQ magnum heads and they bolted up. But I had to make sheet metal adapters to seal them up. The port mismatch left an open gap, as the manifold was open below the heads sealing surface.
If you want a photo of it Adam, I could post it Sunday.
Click to expand...

If you can that would be great !
 
Great to see Bob's post. This is contrary to what I thought but the only exp. I had was using the LA gaskets on the Magnum heads. It's odd that they worked unless the EQ heads are a little different than standard Mag heads. Or maybe I just got lucky that the brand of gaskets I used were a match.
 
Here's a picture of the back of the motor. I hope you can see that the manifold is sticking down lower than the head's mating surface.
I herd that someone makes a copper gasket to fix this problem, but I don't know who has them.

0720081217.jpg
 
Yep, drivers side the same way. I used some 16 gauge steel and made some adapters to fix it. It just took some time to fit them.
I also had an issue with alternator. I am using a square back late 70's alternator and it hit the freeze plug boss. I had some leftover alternator spacers from a van and cut them down to line everything up.
The left side manifold hit the heads deck where the head bolts are. A little grinding took care of that.
 
Good luck finding copper header gaskets that work. I tried a few different pairs and had no luck with any of them sealing. I think it would have sealed just as good as no gaskets than with the copper ones I tried.
 
I used Hughes Engines new "Iron Ram" Magnum castings along with a set of 1970 340 HP manifolds. They must be beefier in that area because there was no gap like the pictures that Bobscuda67 posted. I used a set of stock gaskets. But I also had to grind a bit off the head where the manifold tucks up tight. Hughes claimes better flow numbers than factory heads and more meat for porting reducing the chance of heat cracking around the seats. Its been running now for about 6 months and there have been no problems so far. I thought the cost was reasonable.
 
AdamR said:
I think the Iron Ram heads are the same as the EQ heads.
Click to expand...

Yep, I think all the aftermarket replacement magnum heads were made in New Zeland. They are a much better casting than the stock Chrysler heads.
 
I was planning on aluminum Edelbrocks but got a tip on the Iron Rams. Didnt have to use aftermarket rockers either. The stock rockers and pushrods went in perfectly.
 
Too bad you're not close enough, I have a set of Magnum 5.9 exhaust manifolds you could have for free, not sure if that would work with you're a-body chassie though. Dan
 
bobscuda67 said:
I have a 340 with the EQ magnum heads and they bolted up. But I had to make sheet metal adapters to seal them up. The port mismatch left an open gap, as the manifold was open below the heads sealing surface.
If you want a photo of it Adam, I could post it Sunday.
Click to expand...

What is an "EQ"
 
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