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#1
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cc's of 452 head: need to get it between 75 and 81
I have a set of 452 heads and am trying to get my compression to 9.5:1 to 10:1. According to the mopar compression calculator I downloaded from here, the heads need to have a cc of between 75cc (10.02:1) and 81cc (9.51:1)
What cc are these heads to start with? If they don't fall in this range, how much can you safely mill them without running into problems? Also, if that is the case, how much would they have to be milled to put them in that range? |
#2
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These heads are usually around 88ccs.Mopar heads vary alot so you must cc a couple of chambers in each head.Were you using the .020 mopar head gasket for your calculations? For each .004 th cut from the head you loose 1 cc.How much can you cut? Boy thats a loaded question as the deack height etc adds variables.For sure a safe cut is .020 ( for a 5 cc loss),but you must be sure the heads have not been previously cut or valve geometry changes alot.I have a 440 +.030 with a .050 deck flat tops 906 heads cut.016 (88cc ctualy after cut) with .020 head gaskets for 9.6cr.
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#3
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Yes, was using the .020 for head gasket calc. So would it be better to mill the block instead? If so, what's your calculation for that? For every .00xth milled, loose x cc's. What's the safest max to go if I currently have a .088 piston to deck clearance right now? It almost seems to me it would be better to mill the deck/block as it wouldn't interfere with the valvetrain geometry.
Only concern will be piston to valve clearance as these pistons don't have valve reliefs...guess those could be flycut also. What do you think? Quote:
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#4
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The machine shop I deal with is doing a 440 dakota right now and that engine had a.120 deck.They milled it down to .060 but you have to realy be careful on intake fitment as the block gets wider.My pistons are also flat no reliefs lots of clearence with .070 total(.020 gasket/.050 deck) 509 cam 1.5 rockers.
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#5
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After I sat out in the garage tonight (my smoke hole), and thought about it, milling the deck would effect valvetrain geometry because the rocker will now be closer to the pushrod which means I need to run a shorter pushrod setup.
How much clearance do I need to get in the 9.5-10.0:1 comp range? I see you have .070. I'm running the M1 intake, can't I mill it also to fit the heads after all is done? But then again, milling the block, heads, intake...I'm sure that costs a pretty penny. Would prefer just to mill the block...or heads. Either way to get to what I want will require different pushrods. Thoughts? Suggestions? Quote:
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#6
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Milling the block deck makes the block narrower. The intake face of the head should be milled .0123 for every .010 removed from the heads surface. Rocker shaft pad shims can be used instead of shorter puchrods. By milling the intake face of the head your manifold can retain stock dimensions.
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#7
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RadCuda, where did you get the compression calculator that you said you downloaded from this site? I must have missed it and would be interested in looking at it.
Thanks |
#8
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Go to the homepage here and there's a small menu on the left. Click on the "Download" link and you'll get a choice between software and wallpaper...choose software. There's also an RPM calculator.
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#9
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Thanks for the specs on the intake face. Do you have the specs for milling the deck? In other words for every .00x milled from deck will reduce combustion chamber ccs by x.
It would be really nice to have this information posted here on the website somewhere so it's easy to find and reference. I have it now, but what happens two years from now when I want to build another motor...have to dig it up again. What would be even better is if you can provide the specs/formulas, I could write a program that figures this stuff out, like the compression calculator on here. Kind of a 'milling' calculator? Quote:
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#10
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The correct answer to this posted question is a book called "Building the Big Block Chrysler" and is available at performance shops.
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#11
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If you have a stock bore 440 with a deck height of .088, 80cc heads, .020 gasket, compression will be 9.5....reduce the deck .010 so that deck height is .078, compression will now be just a hair under 9.7....reduce by another .010 for a deck height of .068, compression will now be 9.9....another .010 for a total of .030 off the deck, compression will be 10.1
Also, do a mockup with the intake to see how it fits before cutting the intake or the intake side of the head. Sometimes an aftermarket intake fits better than before and you won't have to cut so much off. The .004 is about right for each cc off the heads...and the most I've ever milled off of heads was .100...but you need to check the thickness of the deck side as heads, like blocks can have core shift problems too. The thicker the deck, the better it will take a big cut. |
#12
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A couple of other options (that may be even more simple and less expensive) would be to get higher compression pistions or use a pair of closed chambered heads.
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#13
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I've got a pair of bare 452 castings that [supposedly] have 82cc chambers. Never actually cc'd them myself.
They've been machined for the 2.14/1.81 valves and the ports have been hogged out pretty well. Sell 'em to you cheap. Such a deal. Problem is, one exhaust port has a 3/16" hole through to the water jacket. = The porter got a little carried away. Ran for 10 years with less that 1mm material to the water jacket before it gave out last summer. I scrapped them and used the parts on my 906s. Now they just keep the dirt out of the cylinders on my spare motor. Darn shame. I'd bet there are a lot of hours in those heads. |
#14
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Have them welded up...no big deal.
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#15
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What do you want for them? Send me an email offline to rad@learn2.com (days) or rad@rodsbyrad.com (nights).
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#16
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Maybe someday I'll have someone knowledgable look at them. For now, they do a fine job keeping the rodents from nesting in my spare block. |
#17
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Yes, you're using the comp calculator also. Same figures, but my 440 is .030, but I got the idea.
New Question: Is it better to mill the block or the heads to achieve this desired result? I'm trying to keep costs down, so I don't want to have to mill heads, intake and block if possible. Would prefer to just do the block, or heads...maybe I can leave the intake alone. I am going to cc the heads in the next couple of days to find out for sure. Quote:
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