Head Change

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Head Change

Post  ROAD RAGE on May 31st 2015, 12:36 pm

Going from doves to PI heads.
About how much will it lower the comp??
Also what is the cc of the PI;s???
Thanks...............

Edit: It's a 12:1 "501ci"


Last edited by ROAD RAGE on May 31st 2015, 2:44 pm; edited 2 times in total
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Re: Head Change

Post  Dave De on May 31st 2015, 1:26 pm

Compression reduction depends upon the original displacement. Use Diamond pistons calculator to determine the change but probably a reduction of 1.5
D20E volume is 85cc but some claim to have measured them at 90cc.
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Re: Head Change

Post  torino501 on May 31st 2015, 4:19 pm

are the pi worked over? is it worth the hassle over the doves...?

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Re: Head Change

Post  Dave De on May 31st 2015, 5:20 pm

Assuming that your D0VE's are 72cc and the D2OE's are 85cc then you will loose 1.5 compression. If the heads are 90cc you loose 2.0
The losses here may not be worth the change on the heads unless you are looking to run pump gas.
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Re: Head Change

Post  ROAD RAGE on May 31st 2015, 5:40 pm

Yes on the pump gas.
Thanks Guys..........................
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Re: Head Change

Post  gt350hr on June 18th 2015, 1:38 pm

Road Rage,
I did the same thing. I had some DOVE Cs. I looked at the amount of work and the dish volume I needed to run regular 87 octane and chose to get some PIs. Once I got the PIs and sat them side by side, I saw several differences in the intake port near the manifold face that made me happy I decided to change. My cylinder head guy agreed. With the larger chamber I can run a -28 cc dish and have 9.2-1 , a number I am comfortable with for my 521. I did exhaust work per Scotty's site and will see the results in a few weeks when I go to the dyno with it. 500hp /600+tq is the goal.
Thanks for all your help with small parts I neeed. I wouldn't assembling now without your excellent help. Glad you could use the SCJ valve cover!
Randy

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Re: Head Change

Post  BigRigTech on June 18th 2015, 1:42 pm

My old PI heads were 90cc when we checked them. I had KB137 hypers which yielded 10:1 compression.
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Re: Head Change

Post  gt350hr on June 18th 2015, 1:54 pm

Mine are 88 with the OEM ( somewhat tulipped) valves , after the hard seats were installed and a .006 cut on the deck. The exhaust valves sit higher in the chamber now. "Flat faced" valves would make it around 85 cc's. Another side benefit is smaller plugs than the DOVE's use. Thanks to Glen Evans in Utah for these heads.

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Re: Head Change

Post  lghting94 on June 18th 2015, 2:06 pm

I had a set of PI's I sold on here they measured 88 cc and had been cut .010. Also I installed them in place of a set of dove-c's and would do it again. They have a better intake port and not as large as the cj port. The exhaust was almost the same as a cj port on mine and after some port work it flowed the same as the cj's I purchased later.
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Re: Head Change

Post  IDT-572 on June 18th 2015, 5:01 pm

The PI head is a very nice head, and probably the most over looked................

Killer bowl and port stock, Good flow numbers with a port that is small enough to keep the air speed up.

I just did a set that flowed right at 340 with a 2.190 valve and had very good low numbers................

.300 221
.400 284
.500 320

Mill them and adjust your compression to what it needs to be or at least get close.
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