Indy 360 CNC head users, how are you making compression
#469561
09/15/09 09:36 PM
09/15/09 09:36 PM
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Joined: Nov 2004
Posts: 1,745
Maryland
340_Dart
OP
top fuel
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OP
top fuel
Joined: Nov 2004
Posts: 1,745
Maryland
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I posted the 408 motor combination in my 68 valiant race car here last week and through the responses i got, it seems i need to increase compression from 10.8 to 12.5 or 13.1 to reach my goal of 10.00's The issue i'm having with doing this is how can i get that compression considering the relatively large chamber of the CNC indy head (68-70 cc) My current 408 combo has diamond flat top pistons, set .005 below deck. I talked to RyanJ about increasing compression, and he suggested we mill the heads down to the intake valve seats, making them 59-60cc's. That will increase compression to 12.3 by my calculations. I guess you could call me a conservative, but i'm worried about doing that since the heads will never be able to be cut again. How are other 360 head users making this kind of compression? Custom domes? thanks-Andy 
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Re: Indy 360 CNC head users, how are you making compression
[Re: S/ST 3040]
#469563
09/15/09 10:05 PM
09/15/09 10:05 PM
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Joined: Nov 2003
Posts: 10,384
Upstate NY
Bigcube
I Live Here
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I Live Here
Joined: Nov 2003
Posts: 10,384
Upstate NY
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Cut them, not sure about a smallblock but on a big block it also helps to un-shroud the valves and will help flow.
Jim
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Re: Indy 360 CNC head users, how are you making compression
[Re: 340_Dart]
#469564
09/15/09 10:28 PM
09/15/09 10:28 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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we have pistons specific to the Indy heads to get your compression up without cutting the daylights out of your heads. that's the easiest way to get where you want to be.
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Re: Indy 360 CNC head users, how are you making compression
[Re: RyanJ]
#469568
09/16/09 01:53 PM
09/16/09 01:53 PM
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Joined: Jan 2003
Posts: 11,711
Portage,michigan
B3422W5
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 11,711
Portage,michigan
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If more compression is your aim, and doing it affordably is much of a factor, then i would mill the heads. I did exactly that on my eddie heads a few years ago to up my compression about the amount you are wanting to do on my old 416 motor.They were flattops 5 in the hole.
The fact is, if you cut them and even decide down the road to build a different motor using those same heads, just spec the NEW pistons to where the new milled heads would be chamber wise..
Otherwise you have new pistons, rings, balancing, etc, involved in just wanting to raise your compression..and most likely everything else, mains, rods, etc if you have it completely pulled apart anyhow.
Milling the heads just involves head gaskets/intake gaskets and an afternoon in the garage.......and will net the desired result.
69 Dart GTS A4 Silver All steel, flat factory hood, 3360race weight
418 BPE factory replacement headed stroker, 565 lift solid cam
Best so far, 10.40 @127 1/4
1.41 best 60 foot
6.60 at 103.90 1/8
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Re: Indy 360 CNC head users, how are you making compression
[Re: B3422W5]
#469569
09/16/09 06:25 PM
09/16/09 06:25 PM
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Joined: Jan 2003
Posts: 4,616
Kissimmee Fl.
dusturbd340W5
master
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master
Joined: Jan 2003
Posts: 4,616
Kissimmee Fl.
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my chambers came from Indy at 74cc so I used a dome
70 duster full chassis super pro 416 CNC Indybrock heads 727 w/brake
best so far 1.212 60 6.219 in 1/8 at 110.88 9.768 at 137.81 1/4
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Re: Indy 360 CNC head users, how are you making compression
[Re: B3422W5]
#469570
09/16/09 07:04 PM
09/16/09 07:04 PM
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Joined: Nov 2004
Posts: 226
lino lakes,MN
onebaddakota
enthusiast
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enthusiast
Joined: Nov 2004
Posts: 226
lino lakes,MN
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Quote:
If more compression is your aim, and doing it affordably is much of a factor, then i would mill the heads. I did exactly that on my eddie heads a few years ago to up my compression about the amount you are wanting to do on my old 416 motor.They were flattops 5 in the hole.
The fact is, if you cut them and even decide down the road to build a different motor using those same heads, just spec the NEW pistons to where the new milled heads would be chamber wise..
Otherwise you have new pistons, rings, balancing, etc, involved in just wanting to raise your compression..and most likely everything else, mains, rods, etc if you have it completely pulled apart anyhow.
Milling the heads just involves head gaskets/intake gaskets and an afternoon in the garage.......and will net the desired result.
True, but at some point you have to worry about intake alignment issues and pushrod lengths.
Tom
10.56 at 125.6, with a 1.43 60 ft.
E85, Hyd. Roller 410 magnum,full exhaust, 3500 race weight.
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Re: Indy 360 CNC head users, how are you making compression
[Re: 340_Dart]
#469571
09/16/09 09:59 PM
09/16/09 09:59 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Quote:
I posted the 408 motor combination in my 68 valiant race car here last week and through the responses i got, it seems i need to increase compression from 10.8 to 12.5 or 13.1 to reach my goal of 10.00's
The issue i'm having with doing this is how can i get that compression considering the relatively large chamber of the CNC indy head (68-70 cc) My current 408 combo has diamond flat top pistons, set .005 below deck.
I talked to RyanJ about increasing compression, and he suggested we mill the heads down to the intake valve seats, making them 59-60cc's. That will increase compression to 12.3 by my calculations. I guess you could call me a conservative, but i'm worried about doing that since the heads will never be able to be cut again.
How are other 360 head users making this kind of compression? Custom domes? thanks-Andy
there's no doubt that milling the heads is the "cheapest" way, for the time being at least. one of the problems is it doesn't really get you where you want to be on C/R. the other is that your basically to the limit of how much you can mill that head. what happens in the future not if, but when they need to be touched up again? another thing that happens is you affect the amount of valve to piston clearance by milling that much off any head, especially the Indy head though because of the valve/ seat placement in the chamber. you'll also be milling a ton either off the intake side of the head or the intake itself. that can be problematic to take that much off the intake side of the head since that area is already thin. sealing, or even fitting the valve cover can become a problem. as far as i know, everyone that we've done pistons for here on Moparts has been very pleased with what we've done, and that's a lot of people.
Last edited by DRAM_Perf_Only; 09/16/09 10:03 PM.
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