Valve relief depth, stock 10.5 to 1 v/s cam lift

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340doc

340doc

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I'm using a stock 10.5 to 1 piston and wondering how the valve pockets compare to a replacement TRW piston in depth. I'm hoping to run a 540 lift cam and wondering if the stock valve pockets are going to be a problem. I know duration plays a part. Just wondering what people have gotten away with with the stock slug. My heads are not an issue, previously set up for 600 lift. Piston is .025 out. If anyone has a TRW laying around and could measure depth of pocket, that would be helpful. Thanks!
 
I ran a .572 solid lifter with stock pistons stock heads not milled. I think it was .550 at the valve.
 
not sure why you think Cam lift has anything to do with it ? The reliefs are for when the valve are closed thats when the piston is up top , the valve follows the piston opening as it goes down and closing as it comes up .
 
cannucky said:
not sure why you think Cam lift has anything to do with it ? The reliefs are for when the valve are closed thats when the piston is up top , the valve follows the piston opening as it goes down and closing as it comes up .
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unbelievable ^^^^^^^^^^^^^^^^^^^^^
 
I ran the MP .590 solid in my stock 340 with 10.5:1 TRW replacement pistons, no problems with VTP, .039 fel-pro's...from memory only as a long time ago reliefs were approx .200thou.
 
Should be fine. Your results may vary. If it was me I'd measure it even if I thought it was ok...
 
Put some clay on the piston with a used head gasket and turn it over a couple of times.
 
several cam companies give the lift at TDC or before and after TDC use a similar cam
Isky for one VOTC
who else?
 
moper said:
Should be fine. Your results may vary. If it was me I'd measure it even if I thought it was ok...
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I had planned to measure it, just hoping to use a cam I have on hand and wondering what others results were. I don't have the motor together yet. Appreciate all the replies.
 
Measure it to make sure. What my engine has for clearance won't be what yours has.
 
340doc said:
I had planned to measure it, just hoping to use a cam I have on hand and wondering what others results were. I don't have the motor together yet. Appreciate all the replies.
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Do you have a stock piston for reference already? I'm getting right at .200" max depth on an old stock 340 piston.
 
OK.... all I can say is that looking at the pix, the Speed Pro's 'look' to be at least that deep. (For whatever that may be worth...)
 
Still need depth info? .232" deep, BUT this is using a depth gauge that has a shank diameter of .167" so the total depth will have to be mathed out by our geometry pros using the 18* valve pocket angle and an assumption of 72* for the other angle. Then the total depth may be calculated. Pictures to follow about what i did for the measurements.
 
Max1196 said:
Still need depth info? .232" deep, BUT this is using a depth gauge that has a shank diameter of .167" so the total depth will have to be mathed out by our geometry pros using the 18* valve pocket angle and an assumption of 72* for the other angle. Then the total depth may be calculated. Pictures to follow about what i did for the measurements.
Click to expand...
That's a TRW/Speedpro piston? If so pretty close to the stock piston in post #14
 
Is it later yet?
100_2031.JPG
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I measured the old stocker in the same way.... straight down from the top surface. So it is roughly 1/32" deeper than the stocker.
 
Excellent, thanks for all the replies. I know the TRW's will take a decent cam and was wondering what I was up against with the stock piston. From all the replies, it looks like there not going to be a road block.
 
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