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#1
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Does the MP .509 cam typically give you piston / valve clearance problems on a 440.... I currently have the 915 stock heads. I want to shave my new 906 heads( 2.14 / 1.81 ported/polished) down as much as I can to get some more compression. (Have TRW 10:1 pistons) I've heard because of the long duration of the .509 cam that clearance is usually a problem.... I know I have to measure but I'm just curious if other people have had problems. The block deck has only been cleaned up for straightness according to the guy who put it together. Any thoughts?
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#2
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I have a 509 with flattops and stock 906s, had I had valve reliefs in the pistons, my 440 would still be running. Hope this helps!
------------------ Nitro 69 Coronet 440 90 W250 4x4 00 Avenger ES |
#3
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You really should measure to be sure, but for what its worth about five years ago I had a shop do a 1972 440 for me using TRW 10:1 pistons, the .509 cam, stock crank and rods from the '72 engine, and some 906 heads from a '69 440. I was concerned about a lack of piston to valve clearance. The builder checked it and told me I had plenty of clearance. Plenty of clearance he said. I didn't ask how much at the time but now I wish I had of. I've got two 440 engines with the TRW 10:1 pistons and I guarantee neither of them have 10:1 compression. I'm quite sure you wouldn't have a problem with valves meeting the pistons, but if I were you I'd measure how far down in the hole the pistons are just be sure, and I'd cc the heads to make sure you have enough compression to do that .509 cam justice.
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#4
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The problem with the P to V is these older MP cams have a relatively slow ramp and a lot of overlap, and usually it's the exhaust valve getting slapped by the piston on its way back up. Too many variables, ex: cam not degreed correctly, factory deck height variances from bank to bank, etc. so you always need to check. But many times it's valve float (often undetected, maybe one out of your 16 valves)that's the culprit and the valves "hang" just long enough to get slapped. From my experience, this is more common on stick cars that have been overreved and consequently the valvesprings loose the required tension leading to eventual disaster.
BTW, MP "933" springs (the ones MP has recommended for these cams for OVER 30 YEARS) are murder on your seats and lobes. I can always tell a "933" head by the way it disassebles because the seats are hammered. There is a Comp spring that is ~120 on the seat and ~295 open is much better for hydraulics up to about .560" lift and your cam lobes, seats and rocker arms will thank you for it. 933's were developed for the hemi which has a much heavier valvetrain than the wedge. The Valve Float problem is part of the reason that Mopar's clearance recommendations are so liberal (.110 clear! ) ; of course valvetrain parts are a whole lot better today. I know, you asked what time it was and I told you how to build a watch! Yes, you need to check!! Wize [This message has been edited by Streetwize (edited December 22, 2000).] |
#5
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The problem with the P to V is these older MP cams have a relatively slow ramp and a lot of overlap, and usually it's the exhaust valve getting slapped by the piston on its way back up. Too many variables, ex: cam not degreed correctly, factory deck height variances from bank to bank, etc. so you always need to check. But many times it's valve float (often undetected, maybe one out of your 16 valves)that's the culprit and the valves "hang" just long enough to get slapped. From my experience, this is more common on stick cars that have been overreved and consequently the valvesprings loose the required tension leading to eventual disaster.
BTW, MP "933" springs (the ones MP has recommended for these cams for OVER 30 YEARS are murder on your seats and lobes. I can always tell a "933" head by the way it disassebles because the seats are hammered. There is a Comp spring that is ~120 on the seat and ~295 open is much better for hydraulics up to about .560" lift and your cam lobes, seats and rocker arms will thank you for it. 933's were developed for the hemi which has a much heavier valvetrain than the wedge. The Valve Float problem is part of the reason that Mopar's clearance recommendations are so liberal (.110 clear! ) ; of course valvetrain parts are a whole lot better today. I know, you asked what time it was and I told you how to build a watch! Yes, you need to check!! Wize |
#6
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i just went through this with trw flat tops with no valve reliefs.i had a stock cam 220 duration .435 lift ,.091 deck hieght on front cylinder &.084 on rear cylinbders so clearence are quite different.but i checked it on front i had .190 intake &.236 on exhaust .with a260/271 .540/563 lift i had .150 intake &..140 exhaust so i could only mill heads .040 to stay safe.but that would only give me about8.8 to 1,my engine needed .060 off to get 9.5-1.or closed chambers 74cc.so you will probibly be close with the 509 .i think i would go with the 915 closed so you can get ratio up with out milling to much .or you may have to cut inreliefs or do what i did and put in some ross pistons.you need to measure you deck to piston wieght and go from there.
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#7
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It's always a good idea to check the piston to valve clearance with the 509 cam.Usually as already posted, factory tolerances are not up to par and with 30+ year old parts,you really don't know what has been done to them in the past.I'll disagree with StreetWize about the 933 springs though.I've used them for over 25 years and have never had any problems with the heads,in fact I have a set that was installed in 1972 and they still are holding very good pressure after hundreds of 6500 rpm passes.Just a difference of opinion.
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#8
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Disclaimer: I have not measured this combo!
In my opinon, the TRW "10:1 CR" pistons, L2355F, will be close with the MP 292/0.509 cam. The compression height is 2.061 which yields about 0.019 piston to deck on a spec block. With no valve reliefs, this is marginal. Many people must have tried/used this, what is the real word measurements? Lets hear it! |
#9
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You should give the number for those 10:1 pistons, usually the 2266's are referred as 10:1 pistons. We have those in a 440, they sit .090" in the hole and with .060" milled heads and steel shim gaskets there were no signs of hitting in the pistons with '933' springs. Didn't measure the clearance, but it seems to be enough. I believe the 2355 pistons have the reliefs already, so that cam shouldn't be a problem with them either.
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#10
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Thats right, the L2355F have valve reliefs (4 I think).
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