Cylinder head tricks.

[1955 plymouth]

I have recently came into a couple extra mopar heads:rolleyes:, the 23.5" versions, was just wondering if anyone had the "magic" formula to re-work these heads, mill.050" from the gasket surface? port? I would like to play with one and try to install on one of my other engines once ready. Thanks for any sucessful stories re-working a head.

[Reg Evans]

Go to this thread and scroll down to the chart that shows how much gain in compression ratio you can achieve by milling the head.

http://www430.pair.com/p15d24/mopar_forum/showthread.php?t=15185&highlight=Head+milling

[greg g]

Would either of them be the ever so elusive "P" head there has been so much discussion about lately???? If so it may behoove you to contact a certain party on the car board.

Any way, I had .040 taken off my head and .010 off the block. So I estimate that on my 56 engine I am running around an 8.0 to 1 CR. If you go to the specs area of the carnut website and look at the engine specs, you will see that each increase in HP is accompanied by an increase in CR. Over the years the flat head went from 6.0 to 8.0

The 59 230 was rated at 132 HP with 8 to 1 CR. So we all know cams was cams, and pistons was pistons, so most of the hp increase was likely related to CR.

George Asche suggests that you can go .090 on the head, and .030 on the block. He mentioned when I spoke with him that any thing more than .090 total will need premium fuel.

I believe it will wake up a engine pretty good. Several discussions have stated that relieving is counter productive, as it will reduce some of the gain made through milling.

Some one suggested that rouding the ramp from the area above the valves to the area above the piston is worthwhile. and ther was some discussion about a "V" shaped grove being machined into the surface of the head in the area above and between the valves is also productive. It is apparently one of the things they do to the Briggs and Stratton flatheds they use on racing go carts.

Below is a pic of an edmunds head showing the shape of the combustion chamber of a head rated at 9.0 to 1. As you can see the area over the piston is not flat across.

[grey beard]

I'm afraid some of you gents may have a few things mixed up here, in all this local wisdom dispensing activity, here.

First off, the only reason for anyone to cc a head chamber is in blueprinting a precision race motor, to get the volume exactly the same in each cylinder. This would be a collosal waste of time on our MoPar flatties. You simply do notr need this information. It is totally useless in this situation.

Don's chart is a good rule of thumb to follow, in a perfect world, where no head had ever been resurfaced before, or no block deck was ever trued.

What you DO need to know is how close the valves come to the cylinder head when they're fully opened. Here's the only way to find out - unless you're really quick and can get in there and measure it.

Lay a three-inch long piece of solder over the top of each valve and pinch it down with something so it will not fall off. Now bolt your clean head onto the clean block surface with two or three bolts and torque 'em down. Now roll the engine over two full revolutions, so that each valve has opened and closed one time fully.

When you pull the head off and measure the thickness of the solder crump from each valve, you will know the true clearance you are working with.

My own head and engine assembly measured .110 thou clearance using this test, without the gasket in place. I removed .100 thou from the head and installed a FelPro gasket. Runs great, and no problems.

Just remember we're working with sixty year-old-plus iron here, and no one can be sure what was done to any parts in their past lives. The next guy who pulls my head better not take ANYTING off, or he'll be in trouble.

Good Luck and Keep 'em Crankin'!

__________________

[1955 plymouth]

One of the heads is from a P20 dated 1954 it is a "P" head.the other I really haven't looked at too closely yet. I will post some pictures of the heads soon to this thread.

Thanks for the link to the compression ratio milling chart. I can cc the head no problem and set up the mill to take the surface down, might do the block on the spare engine from the '54 Plymouth I have too.