Piston to valve clearance question

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efriedrich

69 383S
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If I put a MP 509 in my 383 will their be any piston/valve clearance issue with the TRW cast flat top pistons. I have 906 heads with the heavier springs and the valve trane is stock.
 
How far from the deck are the pistons?
What head gasket? (compressed thickness?)
Are there any valve reliefs in those pistons?
 
71DartGuy said:
How far from the deck are the pistons?
What head gasket? (compressed thickness?)
Are there any valve reliefs in those pistons?
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There are no valve reliefs in the pistons (thus my question), the head gasket came in a basic felpro rebuild kit and I dont know the deck of the piston. It comes to the top of the cylinder. Yes I'm no engine tech.
 
So, clay is needed to check, even the cam degree affects it, Dollar store modeling clay, no head gasket, turn over twice with a pull bar, and measure; then factor in head gasket.
 
If you are at zero deck (top of piston flush with top of block at TDC) and you have no valve clearance pockets in the pistons then if you use a .509 cam you are going to be VERY VERY close. Probably to close, under .050". You definately have to check it beforehand.
 
demon seed said:
If you are at zero deck (top of piston flush with top of block at TDC) and you have no valve clearance pockets in the pistons then if you use a .509 cam you are going to be VERY VERY close. Probably to close, under .050". You definately have to check it beforehand.
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minimum for no valve shrouding is what .75-.10??
 
green1 said:
I decided to sidestep that,,
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I'm just looking for more power, it currently has a 474 hemi grind and a M1 dual plain and a edelbrock 750. Its runs ok but I have had the 509 for a while and was thinking about putting that in and adding a single plane and a 850 Holley DP for more juice.
 
efriedrich said:
I'm just looking for more power, it currently has a 474 hemi grind and a M1 dual plain and a edelbrock 750. Its runs ok but I have had the 509 for a while and was thinking about putting that in and adding a single plane and a 850 Holley DP for more juice.
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well there is your problem... hemi's have a very different attitude to cam timing, lift, duration, adv... everything, thats why chevy lobe cams suck in mopars... because it wasn't designed for it...

demon seed said:
I'd use those numbers Kid .075 In. and .100 Ex.
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i thought so! thx
 
efriedrich said:
I'm just looking for more power, it currently has a 474 hemi grind and a M1 dual plain and a edelbrock 750. Its runs ok but I have had the 509 for a while and was thinking about putting that in and adding a single plane and a 850 Holley DP for more juice.
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I run a .509 in my 383 but I'm .020-.025" below deck at TDC and I'm right at the minimum. As far as your choice of manifolds go I'd recommend a Edelbrock RPM Performer over the single plane, night and day difference at the bottom end and just as strong up top. I'm also running at 750DP and had to knock it down slightly so a 850 DP might be to much in your case without some further tuning. What are your gears and tranny/stall numbers. What's your timing set at, initial and mechanical total.

You may want to consider talking to Dave Hughes about a hotter cam but he to will need to know all the particulars of the power train. He might come back with something between what you're running now and the 509.

http://www.hughesengines.com/Index/index.php
 
demon seed said:
I run a .509 in my 383 but I'm .020-.025" below deck at TDC and I'm right at the minimum. As far as your choice of manifolds go I'd recommend a Edelbrock RPM Performer over the single plane, night and day difference at the bottom end and just as strong up top. I'm also running at 750DP and had to knock it down slightly so a 850 DP might be to much in your case without some further tuning. What are your gears and tranny/stall numbers. What's your timing set at, initial and mechanical total.
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singles only make more power above... what.... 6000-6500??
 
805moparkid said:
well there is your problem... hemi's have a very different attitude to cam timing, lift, duration, adv... everything, thats why chevy lobe cams suck in mopars... because it wasn't designed for it...



i thought so! thx
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hemi grind is the same as the MP 280/480 cam today...it has nothing to do with the cam timing of a hemi....just back in the 70s...they only had 474 lift with the older style MP...

just like sb and bb has a 284/484 cam...a 292/509 cam...it was the smallest in the series of the Purple shafts...

still got one in my AAR...
 
70aarcuda said:
hemi grind is the same as the MP 280/480 cam today...it has nothing to do with the cam timing of a hemi....just back in the 70s...they only had 474 lift with the older style MP...

just like sb and bb has a 284/484 cam...a 292/509 cam...it was the smallest in the series of the Purple shafts...

still got one in my AAR...
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might be the same numbers but i bet that the valve openings/closing are alot different...
 
805moparkid said:
might be the same numbers but i bet that the valve openings/closing are alot different...
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the valve timing and lift were the same as the 70s hemi....aka hemi grind...

ground to fit big blocks and small blocks...

very popular camshaft back in the 70s and 80s...
 
70aarcuda said:
the valve timing and lift were the same as the 70s hemi....aka hemi grind...

ground to fit big blocks and small blocks...

very popular camshaft back in the 70s and 80s...
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interesting! always heard that hemi's need a very correct cam where are wedges are more forgiving...
 
just remember...when you are talking about valve to piston clearance ...it is not the max lift that is the problem...it is during the overlap period of the camshaft ...went the exhaust valve is closing and the intake is opening while the piston is near the top...
 
70aarcuda said:
just remember...when you are talking about valve to piston clearance ...it is not the max lift that is the problem...it is during the overlap period of the camshaft ...went the exhaust valve is closing and the intake is opening while the piston is near the top...
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the cam card should have a TDC checking height tho to right??
 
Not enough compression for the cam. It will work, but a smaller cam would work better. I have an old 340, advertised 10.5. I wont put a cam like that in it unless it was a trailer queen.
 
efriedrich said:
3000 rpm at 35 degrees, and no headers.
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First thing I'd do is bump her up to 12 initial (37 total shouldn't bother it) and respring the dizzy to get the timing to be all in at 2100-2300 try that it might make a slight difference up top. Next see if you can borrow someones Holley or Demon 750 DP'r and test it against the edelbrock you might be surprised. Lastly headers!!!!!!!!!!!!!!! and minimum 2 1/2" exhaust out back.

You gotto be able to get it in and out before fiddling with the cam IMHO

What's your ride BTW
 
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