Warped Cylinder Heads... - Team Camaro Tech
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post #1 of 9 (permalink) Old Apr 3rd, 03, 05:21 AM Thread Starter
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Matt Jones
 
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My 1986 C10 with a 350 appears to have at least one warped head. With a carpenter's level and some feeler gauges, I could measure a .006" warpage (right where the gasket blew, between cyl 4 & 6). The motor is a Target 350 installed about 10,000 miles ago in place of a 305.

I believe it warped because the 305 carb was never rejetted for the 350, so it ran lean. It always ran hot because of this, but never overheated. It came with composition head gaskets.

Anyway, to the point: Is there a general limit on how much a head can warp before it should be junked? I didn't see any cracks (yet). I know the proper thing to do would have them pressure checked and magnafluxed, but I just can't afford to do that. I have the opportunity to rebuild these heads (resurface, cut valve seats, new seals) if I do it here at the university all for free.

Or am I just wasting my time with gambling with these Mexican heads?

Matt Jones
Lead Mechanical Engineer
Art Morrison Ent. Inc.
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post #2 of 9 (permalink) Old Apr 3rd, 03, 08:12 AM
 
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Check your heads and see if they are the lightweight type.

This shows up by looking at the short row of outer headbolts by the outline of the head being more "scalloped" then the older, thicker heads. If they are lightweight you might better consider getting the heavier heads or maybe a new set of W/P's S/R torquer heads with big valves or something like them..

I don't think the lightweight heads can stand milling b/c their decks are already too thin or they wouldn't warp all that easy like the older heads...pdq67



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post #3 of 9 (permalink) Old Apr 3rd, 03, 09:44 AM Thread Starter
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That's a good point. Fortunately, these are not the lightweight heads...or else I would have junked those in a hurry.

Now the question becomes...how do I mount a darn cylinder head on a Bridgeport mill?

Matt Jones
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Art Morrison Ent. Inc.
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post #4 of 9 (permalink) Old Apr 3rd, 03, 10:05 AM
 
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Dude mill those heads, I had .030 milled off mine and drilled the top of the block to match water holes in the heads between 3&5 and 4&6 using head gasket as template for top of engine 1/2" hole. The cyl's mentioned run the hotest!now mine runs cold.
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post #5 of 9 (permalink) Old Apr 3rd, 03, 10:23 AM
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A carpenters level may be good for a first check, but I would go to a machine shop and let them check or buy? A machinist tool for just that purpose.

68 Camaro~LSx ~all motor
1.54 60'--6.95 @ 98.45 660'--10.96 @ 121.53
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post #6 of 9 (permalink) Old Apr 3rd, 03, 02:17 PM
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I used to mill cylinder heads, blocks etc. Our figure of merit was always 0.003". We would only mill off enough to get get clean metal. We used a precision stainless straight edge and feelguage in various orientations accross the head as you did.

If you're dealing with aluminum heads you want a smooth surface - the mill tends to make a sharp serrated surface. A lot of shops that mill aluminum now days use what we called a wiji (wee gee) board. It's basically a precision flat surface with an abrasive and the head is moved around to remove material. Aluminum heads expand and contract enough that if the milled surface isn't relatively smooth, it will cut through the head gasket in time. Once upon a time, engine machinist though that a rough mill would hang on to the gasket. That is probably one of the reasons some of the early production vehicles with aluminum heads had so much trouble with blow-outs.

-dnult

Dave
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68 Coupe, 350 w/ Edelbrock Performer RPM heads, cam, intake, 700R4, Dave's small body HEI
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post #7 of 9 (permalink) Old Apr 3rd, 03, 02:40 PM
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Matt,
All of the later model heads (After 1979 or so) are very prone to cracking if run hot. I would have the head magnafluxed before doing anything else. You should have no problem cutting .010" off the head to get it flat, but make certain you get the proper surface finish. A Bridgeport will work if you have a large multi tooth milling head that will cover the entire surface in one pass. You need a very smooth surface finish, somewhere near 40ra.
By the way...never heard of a "weejee" board ?? Most up to date automotive machine shops are using a single cbn (or pcd) bit cutter in a high speed milling machine to get the required surface finish.
Hope this helps,

Bill Koustenis
Owner
Advanced Automotive Machine
Waldorf Md
1971 Chevelle "Heavy Chevy" original owner


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post #8 of 9 (permalink) Old Apr 3rd, 03, 04:21 PM
 
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Bill,

CBN = cubic boron nitride.

But what does pcd mean?

Poly-crystaline diamond??? pdq67



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post #9 of 9 (permalink) Old Apr 3rd, 03, 04:26 PM
 
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Back again,

Has anybody ever used a "Blanchard" with a diamond wheel?

I used to get our BSM plastic refractory material gunite machines that came from Germany's feedwheels surfaced at APGreen when I was there years ago..

We had one wheel flame sprayed with tungstun carbide and the guy used a worn out diamond/metal matrix grinding wheel and he said after grinding the hardface overlay off, the old diamond matrix wheel came back to life b/c the matrix was removed by the hardface material moreso then the diamonds!!! He, He!!! pdq67



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