I think I am just hosed now!! Head Issue!

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superdart360

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I found a nice set of 71 J heads on craigslist for my 92 360. Heads came with Double Springs, Long Stainless Valves, All the work had been done to them. Just need to be assembled. So I had the machine shop check them out and assemble.

I also ordered a cam now that I could accommodate for a higher lift cam with these heads. So everything is back and ready to go. I put the cam in bolt the heads on. Measure for the proper length push rods. Push rods came yesterday. So I got up early today to get done with work and get half the day off so I could finish putting the motor back together and fire this beast up. I was very excited.

I drop a pushrod in and set the roller rocker set on and things just don't line up. After a few hours of measuring with the calipers. I have determined that the 92 roller cam heads have a 5/8 Diameter hole for the pushrod and the 71 heads I bought have a 7/16 hole. So sounds easy enought lets just drill out these holes a bit bigger. Nope it seems the hole is offset 1/4" and I just don't think I have the room to cut out that much.

So anyone that may have some advice to get a set of heads, or use these heads, or have the stock heads machined to work. Please chime in. I am looking for what route to go. I spent 600.00 on the heads it was a steal. So I can easly get my money back if I need.

Thanks! Here are some pics of the issues.

head%20problems%20001.jpg



head%20problems%20004.jpg
 
You're putting LA heads on a magnum block? I think I am a little confused. What is the setup? Cam, pushrod length, rockers, etc.?
 
This is a 92 Roller cam la block. Not a magnum. Pushrods are 6.35 in length. Harland and sharp 1.5 ration roller rockers. The problem is that with the roller cam the lifters are much longer than that of a non roller cam. So by making the pushrods shorter it takes more angle for the pushrods to move up and down.

This is why the diameter of the push rod holes are different from the 71 to the 92. Heads line up in every other way just fine.

Thanks!
 
AAAAAAAAH. Ok now I'm a little clearer on the situation. It still looks like the pushrods are a little short
 
Yes they are but that is a separate issue! lol. If they where the right length they would not line up. I was showing that picture to show how much the offset difference between the heads are.
 
just a wild thought im not an engine builder. im wondering what the offset is on 340 ta heads if their rockers would straighten up your geometry. are you sure your left and right rockers are positioned right?
 
You could take the heads back to the machine shop and have them cut the holes more toward the rockers with a end mill thats 1/2" diameter, then get the right length pushrods and you should be set. The pushrods that we use are 7.070 for hyd. cams and 7.340 for mech. cams. If your shop can't help you I can.
 
BJR Racing said:
You could take the heads back to the machine shop and have them cut the holes more toward the rockers with a end mill thats 1/2" diameter, then get the right length pushrods and you should be set. The pushrods that we use are 7.070 for hyd. cams and 7.340 for mech. cams. If your shop can't help you I can.
Click to expand...
Yeah the stock heads that came off the 92 had 5/8" holes for the pushrods. The rockers are in the same place as stock. I threw the stock set of rockers off the 92 onto the 71 head and had the same issue. The issue with drilling it out to 5/8" is the 92 5/8" hole is offset about 1/8 inch toward the rocker. I don't think I have enough metal to move the hole around that much.

But yeah I would like to do that BJR if possible. But not sure at this point.

Thanks!
 
Call up Dave at Hughes Engines. He and his guys are rocker arm Guru's. If you cant figure it out, I'm sure they'd be happy to help. They are really good to talk too...just an option.
 
Stock 92 Roller cam head with 5/8 Push rod holes. Look at the distance from the edge of the head. Then look at the other picture. Not only is it smaller on the 71 but its closer to the edge.

100_2356%5B1%5D.jpg



71 J Head. 7/16 push rod hole. Hole is right against edge of head.
100_2357%5B1%5D.jpg
 
Take them off and drill them. There is enough meat there. Even doing it by hand. But I would also disassemble the heads for cleaning after. Also, longer valves, but no lash caps? The rocker tip doesnt look right to me. Make sure everything clears and the sweep is good. It looks to me like they might hit the retainers without caps.
 
BJR Racing said:
There should be about 3/16 of material there and you only need about a 1/8.
Click to expand...

Not to mention the direction the pushrod needs to move is AWAY from the cover gasket surface.

The hole needs to be elongated towards the rocker shaft.
 
You need rocker shaft spacers to correct the geometry with the longer valves. The longer valves raises the roller tip and pushes it too far to the outside of the valve and it also drops the pushrod end of the rocker and rotates it in, toward the rocker shaft and away from the stock pushrod location.

Shim it up the shaft to give yourself the correct roller tip/valve stem contact and the other side will should be in a more stock location. Then measure for new pushrods. With a bit hand drilling on the pushrod holes, you should be right on target. :)
 
Ok..what is the actual stem height measurement?

Geometry then push rods.
Which way do the push rods need to go in relation to the holes?
Lastly did you drill for oiling to the heads? Or did you use oil through push rods?
 
Great advice. Thanks for the help. I think I will focus on trying to keep the heads and get them drilled out. I really appreciate all the help! I will keep you posted with the progress.
 
forgive me if i'm missing something here. but why not use the 308 heads that came on the 92 block originally. unless cracked, 308 heads are nice heads.
 
Here's the spec's on his new cam just installed .520-.544 lift 222*-228* @.050.
What would need to be done to the 308 heads to work with this cam?
 
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