Will this have PVC? - Ford Bronco Forum
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post #1 of 15 (permalink) Old 04-20-2017, 05:16 PM Thread Starter
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Will this have PVC?

Ok so I'm trying to figure out if these aftermarket heads I picked, and after market cam will have PVC with stock 351W piston heads. I know there is an equation to solve this, but I forgot it. If you could help me out with this problem I'd greatly appreciate the help.

Head specs : Combustion Chamber Style Heart Combustion Chamber Volume (cc)58
Intake Valve, 1.900'' x 4.903'' o.a.l.
Exhaust Valve, 1.600'' x 4.955'' o.a.l.


Cam specs : Lift .531int/.515exh
Duration at 050 inch Lift: 227 int./241 exh.

Head gasket specs :
Bore 4.100''
Compressed Thickness .041''
Compressed Volume 9.0cc


Thank you

Edit :

Rocker ratio is 1.6,

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post #2 of 15 (permalink) Old 04-20-2017, 05:50 PM
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Pretty sure whoever can figure this out will need deck height, rocker ratio, valve length, and valve diameter.

4.100 bore is huge, why such the overbore?

I know that my .480 lift cam, with 1.7 rockers, 58cc afr165 heads, near zero deck height, and 19 cc dish pistons (stock are 22 cc dish) had no issues. But I don't know really what valves it had.

94 Bronco XLT. Beefy 351, 6" , 37's, 4.88: burnt
85 Bronco custom, 4" 37's, locked 4.56, 300 i6 4 bbl, np435/208
96 f350 XL, rclb, 351, c6, BW4407 xfer
78 f150 Ranger, 351m, t18, np205, rusty
90 f150, 95 f250, 96 f350 psd: stolen, sold, and burnt, respectively.
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post #3 of 15 (permalink) Old 04-20-2017, 05:58 PM
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Wait, how are you using factory pistons with a .100" overbore?
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94 Bronco XLT. Beefy 351, 6" , 37's, 4.88: burnt
85 Bronco custom, 4" 37's, locked 4.56, 300 i6 4 bbl, np435/208
96 f350 XL, rclb, 351, c6, BW4407 xfer
78 f150 Ranger, 351m, t18, np205, rusty
90 f150, 95 f250, 96 f350 psd: stolen, sold, and burnt, respectively.
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post #4 of 15 (permalink) Old 04-20-2017, 08:23 PM
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Quote:
Originally Posted by BigBlue 94 View Post
Wait, how are you using factory pistons with a .100" overbore?
He listed Head Gasket specs, not overbore. HAHA got me at first too!
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post #5 of 15 (permalink) Old 04-20-2017, 08:27 PM
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I believe he listed the bore of the head gasket, not the cylinder.

Piston to valve clearance needs to be checked, there are alot of variables.

Lift doesn't have much to do with it, duration is more of a factor.
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post #6 of 15 (permalink) Old 04-20-2017, 08:28 PM
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Ha! I type too slow!
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post #7 of 15 (permalink) Old 04-20-2017, 08:32 PM
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And I apparently can't read!

Lift has enough to do with it that it matters. However, as said above, duration, and timing as well will play a factor. The piston is only at TDC for a fraction of a second, while the valves are open for a significantly longer time.
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94 Bronco XLT. Beefy 351, 6" , 37's, 4.88: burnt
85 Bronco custom, 4" 37's, locked 4.56, 300 i6 4 bbl, np435/208
96 f350 XL, rclb, 351, c6, BW4407 xfer
78 f150 Ranger, 351m, t18, np205, rusty
90 f150, 95 f250, 96 f350 psd: stolen, sold, and burnt, respectively.
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post #8 of 15 (permalink) Old 04-20-2017, 08:33 PM
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HAHA Norm beat you to it! It is a race to show up Big Bleu!
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post #9 of 15 (permalink) Old 04-20-2017, 08:38 PM
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The intake valve chases the piston down the hole so when it opens is the critical thing. The piston is long gone by the time it reaches max lift.

Radial clearance of the valves can be an issue with bigger than stock valves and stock pistons.

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post #10 of 15 (permalink) Old 04-20-2017, 08:44 PM
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BTW @norm that is a sick 79 you've got
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post #11 of 15 (permalink) Old 04-20-2017, 08:51 PM
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Thank you sir. It's the main reason i'm addicted to overtime :)

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post #12 of 15 (permalink) Old 04-21-2017, 02:56 AM
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I don't know of any equation that will determine piston-to-valve clearance.

Quote:
Originally Posted by RLVBronco View Post
Ok so I'm trying to figure out if these aftermarket heads I picked, and after market cam will have PVC with stock 351W piston heads. I know there is an equation to solve this, but I forgot it. If you could help me out with this problem I'd greatly appreciate the help.,
Huh???
WHICH heads are you asking about, and I know of no equation. You have to check/verify piston-to-valve clearance during build.
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post #13 of 15 (permalink) Old 04-21-2017, 08:00 AM
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Agree with the above. Always good to check. Also agree on the WHICH heads as the various heads available, some move the valves around to get the best flow, therefore the stock pistons may not have the relief in the right spot. the Trick Flow Twisted Wedge is example of this.
However I also "think" you will be fine as there was no issues at all on the last 351w I put together which has a bigger cam and more of a flat top style piston then what you have listed. The block had been decked and was an earlier block as well.
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post #14 of 15 (permalink) Old 04-21-2017, 09:27 AM
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Quote:
Originally Posted by the Son View Post
I don't know of any equation that will determine piston-to-valve clearance, but none of this helps.





Huh???
WHICH heads are you asking about, and I know of no equation. You have to check/verify piston-to-valve clearance during build.
And none of your post helps at all. Thanks for your ten quote post about nothing.
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94 Bronco XLT. Beefy 351, 6" , 37's, 4.88: burnt
85 Bronco custom, 4" 37's, locked 4.56, 300 i6 4 bbl, np435/208
96 f350 XL, rclb, 351, c6, BW4407 xfer
78 f150 Ranger, 351m, t18, np205, rusty
90 f150, 95 f250, 96 f350 psd: stolen, sold, and burnt, respectively.
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post #15 of 15 (permalink) Old 04-21-2017, 09:36 AM
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Quote:
Originally Posted by BigBlue 94 View Post
And none of your post helps at all. Thanks for your ten quote post about nothing.
Couldn't have said it better myself.
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