Milling Heads

TB2

TB2

New member
Alright Guys, I got an unbeleivable deal on a fresh set of World Products Sportsman heads for my 350 LT1 SBC. The only problem is that they are the 72cc, vs. the 64cc combustion chambers that I should have. I need to get some of my compression back. Whats your opinion on getting these cut. And who can I take them to thats really good at angle milling a set of heads, and would know what I need?
 
You should be able to mill the heads about 0.080 at a safe deck and angle mill them no more then 2-3 degrees. Will this get you close to 64cc ??? I don;t know enough about the head to be sure. I know a competent machninist capable of doing it but your gonna spend a couple hundred with milling the intake. If your willing to bring it Pontiac area then i can give you his number.





TB2 said:
Alright Guys, I got an unbeleivable deal on a fresh set of World Products Sportsman heads for my 350 LT1 SBC. The only problem is that they are the 72cc, vs. the 64cc combustion chambers that I should have. I need to get some of my compression back. Whats your opinion on getting these cut. And who can I take them to thats really good at angle milling a set of heads, and would know what I need?
Click to expand...
 
I am not sure what your plans are with this engine, but if you ever plan on selling the heads....good luck (if you get them angle milled). Also, the money you saved on the heads will be spent milling the intake to match the heads on top of the cost to mill the heads themself. Now in doing this, you will also be changing the valvetrain geometry, meaning new pushrods, not that you could have avoided that one anyway with the changing of the heads.
 
QuickLX said:
I am not sure what your plans are with this engine, but if you ever plan on selling the heads....good luck (if you get them angle milled). Also, the money you saved on the heads will be spent milling the intake to match the heads on top of the cost to mill the heads themself. Now in doing this, you will also be changing the valvetrain geometry, meaning new pushrods, not that you could have avoided that one anyway with the changing of the heads.
Click to expand...


:stupid: but I was going to wait to say this until i got my answer about application. Also if you got them so cheap, resell them and buy what you actually need, it'll be better in the long run
 
Yea, its old school 69 LT1. I'm not too concerned about resale if I can them to perform to what I need. I realize that getting them all the way to 64cc is probaly not realistic. If I did my math right, with the 72cc chambers I am right about 9.6 to 9.7:1. If I can get somewhere mid 10:1 I'd be happy.
 
TB2 said:
Yea, its old school 69 LT1. I'm not too concerned about resale if I can them to perform to what I need. I realize that getting them all the way to 64cc is probaly not realistic. If I did my math right, with the 72cc chambers I am right about 9.6 to 9.7:1. If I can get somewhere mid 10:1 I'd be happy.
Click to expand...

If you can get them all the way down to 64cc, you'll end up around 10.5:1 at best. Then you'll need to make sure your cam will not have clearance issues, at which point if there isn't enough, you'll have to cut the pistons (lowering the compression). So lets say, you get it to 10-10.25:1......

To be quite honest, I would be shocked if you could tell the difference. Besides that, if your cam guy is good enough, the .5 or so point of compression delta won't make a hill of beans difference. I mean we are talking about 5-10 HP here TOPS. Is the extra $500 or so worth even 10 HP? Not unless you have bottomless pockets.


Now, if what Sean said is correct about the .080" milling allowance. You could potentially get the chambers to around ~60cc. This would put you around 11:1, but with and iron head you may have fuel issues. If fuel is not an option, I would say if you are going to do it, get all you can for the money. But again is even (in the 11:1 case) worth it for say 15 HP?
 
So it sounds like my best options are to give up on trying to get the heads milled, and either sell em, and get something that will work with my pistons, or get some pistons that will like working with these heads. Am I missing anything? If I run these heads as is, how much cam can I put to it with about 9.7:1? What kinds of problems would I expect to see.
 
TB2 said:
So it sounds like my best options are to give up on trying to get the heads milled, and either sell em, and get something that will work with my pistons, or get some pistons that will like working with these heads. Am I missing anything? If I run these heads as is, how much cam can I put to it with about 9.7:1? What kinds of problems would I expect to see.
Click to expand...

If your going to sell them. I'm interested. It's all SEAN's fault for showing me a S400 turbo!!!!
 
TB2 said:
So it sounds like my best options are to give up on trying to get the heads milled, and either sell em, and get something that will work with my pistons, or get some pistons that will like working with these heads. Am I missing anything? If I run these heads as is, how much cam can I put to it with about 9.7:1? What kinds of problems would I expect to see.
Click to expand...

Designing a camshaft around 9.7 or 10.2 compression will not make a difference. Especially if you plan on buying a shelf cam. If you go with a custom cam guy, they will make sure you are getting the most power possible with the setup. Meaning, a shelf cam from comp or any other company and the possible added compression (10.2-10.5:1) could potentially make less power due to shelf cam being given a "general" compression ratio suggestion.

What type of cam are considering? SR, FT, HT, HR???
 
I've got a Comp cam hyd. flat tappet that I'd like to run. Ive got the #'s at home. Its a dual ramp 530/540 lift, 110 lobe sep. I think the duration was advertised 320/330 if I remember right. I'll post the actual #'s when I get home.
 
The cam is a Comp cam 12-254-3. .519/.523 lift. .250/.256 duration. I've been thinking that 9.7:1 compression would not be enough for this cam. Do you think I could/should run this cam with the compression that low, or should I be looking at raising it so this cam would work right? Being able to run this motor on pump gas has been a goal that I'd like to stick with. Thanks for your help.
 
TB2 said:
The cam is a Comp cam 12-254-3. .519/.523 lift. .250/.256 duration. I've been thinking that 9.7:1 compression would not be enough for this cam. Do you think I could/should run this cam with the compression that low, or should I be looking at raising it so this cam would work right? Being able to run this motor on pump gas has been a goal that I'd like to stick with. Thanks for your help.
Click to expand...


That cam will make this engine run like a turd. The duration is definately a bit on the high side for the compression. I looked at the full spec sheet of that cam and the lobes are about as fast as 1-legged turtle. I would suggest getting a mild solid roller (lash will only need to be checked in the spring when you first set it) with relatively fast ramp rates. You are going to want a cam that produces a good amount of cylinder pressure since won't have a ton (even 10.5:1 isn't much). The newer lobe profiles will allow the cam designer to use less duration and faster ramp rates to achieve the same results as a cam with much more duration yet keeping it from bleeding off all your cylinder pressure. There have been some killer hydraulic cams that have been done in recent years, but they do require a ton more compression than you have.

Since your goal is to run this thing on pump gas, I would check to see how much relief is in your pistons, get a rough idea for how much lift it can take, get a cam with as much lift as you can fit in there. If the heads peak flow occurs at .600" lift, don't hesitate to get a cam with a max net lift of .050" or so more than that. This way you get greater average flow out of the heads which results in more power. Once you have the cam, degree it in, make sure the valve events are occuring when the cam card says they should be. After you have it in and everything checks out, start mocking up the heads for clearance checks. Once you have your clearances and you know that there is enough (if you want) get the heads flat milled to one of two points, etiher the point where you still have adequate clearance, or the point where the manufacturer says is far enough to raise your compression a bit. You may have pleantly of clearance so be sure not to take too much or you'll end up with a motor that runs on race fuel, but has only 11:1 compression.

More importantly, make sure how far the pistons are in the hole, take note and get a gasket that will keep your quench between .035" and .045", if you make a mistake here it will either break parts or lack power.
 
You must log in or register to reply here.
Back
Top