Indy 360 CNC head users, how are you making compression

Posted By: 340_Dart

Indy 360 CNC head users, how are you making compression - 09/16/09 01:36 AM

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

Posted By: S/ST 3040

Re: Indy 360 CNC head users, how are you making compression - 09/16/09 01:59 AM

Take most of it off the head and get the rest with a little dome.

Here's a 6.8 cc, zero effective volume dome for an Edelbrock head.

Attached picture 5485170-DSCN1786.JPG

Posted By: Bigcube

Re: Indy 360 CNC head users, how are you making compression - 09/16/09 02:05 AM

Cut them, not sure about a smallblock but on a big block it also helps to un-shroud the valves and will help flow.

Posted By: Anonymous

Re: Indy 360 CNC head users, how are you making compression - 09/16/09 02:28 AM

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.

Posted By: Ian

Re: Indy 360 CNC head users, how are you making compression - 09/16/09 04:19 PM

what comp do you get in a 410 and price and do they come with chev pins thanks

Posted By: Jacob Pitt

Re: Indy 360 CNC head users, how are you making compression - 09/16/09 04:43 PM

Quote:

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.

This what I did. Ordered some pistons from Dram that fill up the chamber. Yes they have the .927 pin in them. Should have it running Thursday.

Posted By: RyanJ

Re: Indy 360 CNC head users, how are you making compression - 09/16/09 05:06 PM

I typed out a long winded reply to several of these responses, & then realized all I was going to do was piss off everyone, so I'll bite my tongue & say "no comment"

You know my thoughts on what would be the "easiest way" so.... no sense in beating a dead horse.

Posted By: B3422W5

Re: Indy 360 CNC head users, how are you making compression - 09/16/09 05:53 PM

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.

Posted By: dusturbd340W5

Re: Indy 360 CNC head users, how are you making compression - 09/16/09 10:25 PM

my chambers came from Indy at 74cc so I used a dome

Attached picture 5486813-raceparts017.jpg

Posted By: onebaddakota

Re: Indy 360 CNC head users, how are you making compression - 09/16/09 11:04 PM

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

Posted By: Anonymous

Re: Indy 360 CNC head users, how are you making compression - 09/17/09 01:59 AM

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.

Posted By: B1MAXX

Re: Indy 360 CNC head users, how are you making compression - 09/17/09 04:11 PM

My major concern with milling would be the valve to piston clearance. I have a Batten w-2 right now that had a new seat put in on an intake valve and it's going back to be sunk for that very reason. But if your getting pistons a special deep pocket could be specified. The ones I'm dealing with are .280 deep from plane.