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My 915's cc'd pretty big, is this typical? #2906727
04/05/21 09:06 AM
04/05/21 09:06 AM
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Northeast Indiana
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73DAD Offline OP
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I finally cc'd a set of 915's I had rebuilt at the local machine shop a couple years ago. I had the 1.6" exhaust valves replaced with 1.74"s & new seats obviously. They skimmed the decks to square them up. I gauged the retainer to spring-seat height with the stock locks & retainers at 1.880".

One head came in at 80.5cc & the other at 82cc. I thought that seemed pretty big for closed chambers. Is this what you guys have typically seen?

I have a pretty high quality 100ml glass burret & can be confident in my measurements to +/- 0.1cc
The chambers are as-cast.

Re: My 915's cc'd pretty big, is this typical? [Re: 73DAD] #2906757
04/05/21 09:47 AM
04/05/21 09:47 AM
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fast68plymouth Offline
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Not uncommon at all.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: My 915's cc'd pretty big, is this typical? [Re: fast68plymouth] #2906861
04/05/21 12:54 PM
04/05/21 12:54 PM
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Originally Posted by fast68plymouth
Not uncommon at all.
iagree


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: My 915's cc'd pretty big, is this typical? [Re: 73DAD] #2906870
04/05/21 01:25 PM
04/05/21 01:25 PM
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Rio Linda, CA
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Kinda funny that the closed chambers are closer to the advertised volume of the open chambers. (79.5 cc)


I'm supposed to respect my elders, but its getting harder and harder for me to find one now.
Re: My 915's cc'd pretty big, is this typical? [Re: 73DAD] #2906885
04/05/21 02:29 PM
04/05/21 02:29 PM
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Originally Posted by 73DAD
I finally cc'd a set of 915's I had rebuilt at the local machine shop a couple years ago. I had the 1.6" exhaust valves replaced with 1.74"s & new seats obviously. They skimmed the decks to square them up. I gauged the retainer to spring-seat height with the stock locks & retainers at 1.880".

One head came in at 80.5cc & the other at 82cc. I thought that seemed pretty big for closed chambers. Is this what you guys have typically seen?

I have a pretty high quality 100ml glass burret & can be confident in my measurements to +/- 0.1cc
The chambers are as-cast.


Factory parts from that era were all over the map. If you want a factory big block engine to meet factory specs you have to re-machine a bunch of parts.

Re: My 915's cc'd pretty big, is this typical? [Re: 73DAD] #2906888
04/05/21 02:43 PM
04/05/21 02:43 PM
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Prospect, PA
BSB67 Offline
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Originally Posted by 73DAD
I finally cc'd a set of 915's I had rebuilt at the local machine shop a couple years ago. I had the 1.6" exhaust valves replaced with 1.74"s & new seats obviously. They skimmed the decks to square them up. I gauged the retainer to spring-seat height with the stock locks & retainers at 1.880".

One head came in at 80.5cc & the other at 82cc. I thought that seemed pretty big for closed chambers. Is this what you guys have typically seen?

I have a pretty high quality 100ml glass burret & can be confident in my measurements to +/- 0.1cc
The chambers are as-cast.


I have 2 sets of 915s. 2.080 intake and 1.74 exhaust. They have had a clean-up pass or two on them, but minimal removal. one set is about 78, the other about 77.

Re: My 915's cc'd pretty big, is this typical? [Re: BSB67] #2907057
04/05/21 10:50 PM
04/05/21 10:50 PM
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Measure the thickness of the outer head bolt bosses and see how thick, tall, they are now and please post them.
I'll bet a nickel they are closer to .960 to.950 now than they where new scope up

Last edited by Cab_Burge; 04/05/21 10:51 PM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: My 915's cc'd pretty big, is this typical? [Re: Cab_Burge] #2907137
04/06/21 07:30 AM
04/06/21 07:30 AM
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Northeast Indiana
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73DAD Offline OP
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Originally Posted by Cab_Burge
Measure the thickness of the outer head bolt bosses and see how thick, tall, they are now and please post them.
I'll bet a nickel they are closer to .960 to.950 now than they where new scope up


I'll do that if my memory cooperates. I wish I had cc'd them before sending them out to be machined, just to have the data. What do you guys suppose unmilled open chambers cc at? 95?? 100??

Re: My 915's cc'd pretty big, is this typical? [Re: 73DAD] #2907151
04/06/21 08:33 AM
04/06/21 08:33 AM
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Originally Posted by 73DAD
Originally Posted by Cab_Burge
Measure the thickness of the outer head bolt bosses and see how thick, tall, they are now and please post them.
I'll bet a nickel they are closer to .960 to.950 now than they where new scope up


I'll do that if my memory cooperates. I wish I had cc'd them before sending them out to be machined, just to have the data. What do you guys suppose unmilled open chambers cc at? 95?? 100??
on average 88-90cc's.

Re: My 915's cc'd pretty big, is this typical? [Re: lewtot184] #2907260
04/06/21 12:23 PM
04/06/21 12:23 PM
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I had a set of 906s they cc @ 91. Some 902s I had. Only cut 10 cc @85.

Re: My 915's cc'd pretty big, is this typical? [Re: 73DAD] #2907474
04/06/21 09:19 PM
04/06/21 09:19 PM
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Prospect, PA
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Originally Posted by 73DAD
Originally Posted by Cab_Burge
Measure the thickness of the outer head bolt bosses and see how thick, tall, they are now and please post them.
I'll bet a nickel they are closer to .960 to.950 now than they where new scope up


........What do you guys suppose unmilled open chambers cc at? 95?? 100??


From the factory in 1967 -9, or in 2021 after 120,000+ miles and a valve gind or two. Some folks seem to think these are the same.

Re: My 915's cc'd pretty big, is this typical? [Re: BSB67] #2907622
04/07/21 10:10 AM
04/07/21 10:10 AM
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Northeast Indiana
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73DAD Offline OP
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I'm not sure its realistic to think that folks out there are cc'ing worn out high mileage heads just for the heck of it. But just in case, here's how much it would matter...

Hypothetically speaking, lets say I cc a worn out set of heads with valves sunk 30 thou into the seats...

[(2.08"/2)*3.14*.030"+(1.74"/2)*3.14*.030"]*16.39cc/1ci=2.949cc...

Not even 3 whole cc's.

Re: My 915's cc'd pretty big, is this typical? [Re: 73DAD] #2907625
04/07/21 10:26 AM
04/07/21 10:26 AM
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When you want to know what the chamber volume is for your heads........ you check them.

This is just engine building 101.

I recently had two sets of brand new TF270’s in the shop. The chambers are CNC machined. The chamber volume spec is 78cc.

On one set the chambers were 78cc......... the other set was 76cc.

I hear of people checking 516 heads that are well under 80cc.

I’ve never seen an uncut set under 81cc........ and have seen a few at closer to 84.

You check them........ they are what they are.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: My 915's cc'd pretty big, is this typical? [Re: 73DAD] #2907690
04/07/21 01:34 PM
04/07/21 01:34 PM
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Ontario, Canada
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Originally Posted by 73DAD
Originally Posted by Cab_Burge
Measure the thickness of the outer head bolt bosses and see how thick, tall, they are now and please post them.
I'll bet a nickel they are closer to .960 to.950 now than they where new scope up


I'll do that if my memory cooperates. I wish I had cc'd them before sending them out to be machined, just to have the data. What do you guys suppose unmilled open chambers cc at? 95?? 100??


My 906 heads measured out at 92cc.


1970 Super Bee prostreet. 383, SMR 727, Dana 60 4:88. Building a 512 low deck.
Re: My 915's cc'd pretty big, is this typical? [Re: 500ciBee] #2907827
04/07/21 08:08 PM
04/07/21 08:08 PM
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Originally Posted by 500ciBee
Originally Posted by 73DAD
Originally Posted by Cab_Burge
Measure the thickness of the outer head bolt bosses and see how thick, tall, they are now and please post them.
I'll bet a nickel they are closer to .960 to.950 now than they where new scope up


I'll do that if my memory cooperates. I wish I had cc'd them before sending them out to be machined, just to have the data. What do you guys suppose unmilled open chambers cc at? 95?? 100??


My 906 heads measured out at 92cc.

How thick are the outer head bosses now? scope
I had a set of "516" close chamber heads converter to 1.74 exhaust and some bowl work done for a 440 bracket motor years ago, I ended getting a use set of 906 heads that had some poring work and bigger valves in them and swap them onto that motor, I ended up checking the CC on both sets of heads while doing the swap and the 516 had right at 90.0 CC and the 906 had right 74.0 CC shock The 516 set had taller outer head bolt bosses than the 906 did shruggy
I ended up learning from that you can tell if a heads has been cut very much based off of the head bolt boss thickness up scope
EDITED: One of the older Mopar HP bible section on BB stated that to remove 1.0 CC form a open chamber head like the 906 to remove .010, I think, from the head surfaces for each CC and to remove .012 from the intake side of the heads to keep the intake manifold fitment correct confused luck
I should have dug that book out before posting this but I can't remember which book and where all those books are stored now, CRS whiney shruggy whistling

Last edited by Cab_Burge; 04/07/21 08:12 PM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: My 915's cc'd pretty big, is this typical? [Re: Cab_Burge] #2907866
04/07/21 10:44 PM
04/07/21 10:44 PM
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Originally Posted by Cab_Burge
Originally Posted by 500ciBee
Originally Posted by 73DAD
Originally Posted by Cab_Burge
Measure the thickness of the outer head bolt bosses and see how thick, tall, they are now and please post them.
I'll bet a nickel they are closer to .960 to.950 now than they where new scope up


I'll do that if my memory cooperates. I wish I had cc'd them before sending them out to be machined, just to have the data. What do you guys suppose unmilled open chambers cc at? 95?? 100??


My 906 heads measured out at 92cc.

How thick are the outer head bosses now? scope
I had a set of "516" close chamber heads converter to 1.74 exhaust and some bowl work done for a 440 bracket motor years ago, I ended getting a use set of 906 heads that had some poring work and bigger valves in them and swap them onto that motor, I ended up checking the CC on both sets of heads while doing the swap and the 516 had right at 90.0 CC and the 906 had right 74.0 CC shock The 516 set had taller outer head bolt bosses than the 906 did shruggy
I ended up learning from that you can tell if a heads has been cut very much based off of the head bolt boss thickness up scope
EDITED: One of the older Mopar HP bible section on BB stated that to remove 1.0 CC form a open chamber head like the 906 to remove .010, I think, from the head surfaces for each CC and to remove .012 from the intake side of the heads to keep the intake manifold fitment correct confused luck
I should have dug that book out before posting this but I can't remember which book and where all those books are stored now, CRS whiney shruggy whistling
Open chamber is .0042" per cc, closed is .0062" per cc, 286 and 518 .0064" I think.

Re: My 915's cc'd pretty big, is this typical? [Re: Cab_Burge] #2908393
04/09/21 12:43 PM
04/09/21 12:43 PM
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north of coder
moparx Offline
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as per the MP engine book, .0123 removed from the intake face for every .010 removed from the head deck surface.
you remembered pretty good Cab ! up
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