516 head question

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qkcuda

qkcuda

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I did a compression test on my 361 and found one low cylinder, so I am getting ready to have the original 516 heads redone. Nothing fancy, perhaps change out the 1.60 exhaust valves for 1.74's. I was thinking just a 3 angle valve and a plunge cut, and then just blending out any ridges left behind. I have been doing some reading indicating you have to be careful or you can get into water on these heads. I am enclosing a picture I found showing the kind of plunge cut I am talking about. There seems to be quite a hump in the stock exhaust port right next to the intake valve. Is this where they are thin, and should I be concerned about the plunge cut?

516 plunge cut.JPG
 
Going to 1.74 shouldn't be a problem unless the head has a bad case of core shift. I've done it a few times never had a problem. Even went to 1.81 a few times. Blend the sharp edges and you will be fine. 2.14s and 1.81 on these heads.
67hp black.jpg
 
Thanks, I am not as concerned with the seats themselves, as the area in the throat that the arrow is pointing to. I did this previously with a set of 452 heads, where I also installed 2.14/1.81 valves. Just a bit concerned that the 516's may be different.
 
There seems to be quite a hump in the stock exhaust port right next to the intake valve.
Click to expand...

If you had to guess....... what do you think is on the other side of that bulge....... considering it’s on a wall in the exhaust port(the hottest part of the head).
 
qkcuda said:
I did a compression test on my 361 and found one low cylinder, so I am getting ready to have the original 516 heads redone. Nothing fancy, perhaps change out the 1.60 exhaust valves for 1.74's. I was thinking just a 3 angle valve and a plunge cut, and then just blending out any ridges left behind. I have been doing some reading indicating you have to be careful or you can get into water on these heads. I am enclosing a picture I found showing the kind of plunge cut I am talking about. There seems to be quite a hump in the stock exhaust port right next to the intake valve. Is this where they are thin, and should I be concerned about the plunge cut?

View attachment 1715665651
Click to expand...
I have done a number of sets of 516 heads and they can be made to work pretty good. The flow characteristics are totally different than the 915 and 906 heads and if you know how to port, they can work good. You have to be careful on plunge cutting those exhaust ports because that is the area that goes into water. Any core shift and you can have a hole.
 
Sounds like it will be more hand work, but that's OK I've done it before. My main objective will be flow under .450 lift, since it will be getting a pretty small cam.
 
Dave, when u consider that a small block only has 1.60 ex valve even for a 408 build u will be good as u r. I myself wouldn’t go bigger on the ex valve. Kim
 
Just thinking about that too. Less material to remove under the valve. A lot will depend on the condition of the seats.
 
RustyRatRod said:
@IQ52 May can shed some light. What say you, Jim?
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Cody fiddled with the 516's a little bit on the low compression 440 tests. He is in the mountains with his wife today or I could ask him more. I believe we put stock 1.74 valves in the heads and he did some porting.

Lift..............IN/EX
.200........160/132
.300........210/182
.400........237/203
.500........250/216

The engine had a 509 cam with a MP M1 single plane, a 850 Mighty Demon and our dyno headers.

Test (1) stock 906 heads @ 7.45:1 compression. Test (2) ported 516 @ 7.9:1 compression.

RPM...........#(1)HP...............#(2)HP.........HP gain/loss
4,900..........387....................428.................+41
5,300..........377....................449.................+72

Peak to Peak gain (387 to 449) was 62 HP. So under the above circumstances ported 516 heads made a significant difference.
 
won't you end up,spending more money on heavy iron than something new aluminum, lighter, cooler, & flow much better, I bought a set of 440source heads $1000, had them checked out & they needed nothing. I had a machine shop quote me over $1200 to redo some iron heads. Read that as I had the iron head quote 1st lol.
 
I have a rough quote of $500 on the valve job. The problem is here in Canada you have to add about 40 percent between exchange and shipping to anything you order. The extra porting work will be done by me. I'm not going to go crazy, I just can't leave anything alone.
 
MOPARMAGA said:
won't you end up,spending more money on heavy iron than something new aluminum, lighter, cooler, & flow much better, I bought a set of 440source heads $1000, had them checked out & they needed nothing. I had a machine shop quote me over $1200 to redo some iron heads. Read that as I had the iron head quote 1st lol.
Click to expand...

Yeah but you have to have that thousand all up front to buy heads, while you can pay a little along for a shop to build a set.
 
qkcuda said:
I have a rough quote of $500 on the valve job. The problem is here in Canada you have to add about 40 percent between exchange and shipping to anything you order. The extra porting work will be done by me. I'm not going to go crazy, I just can't leave anything alone.
Click to expand...
Yep, I get that. That's not a bad price either.
 
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