HOME FORUM RULES CONTACT
     
   
   

Go Back   CLASS RACER FORUM > Class Racer Forums > Stock and Super Stock Tech
Register Photo Gallery FAQ Community Calendar

Reply
 
Thread Tools Display Modes
Old 02-11-2012, 03:10 PM   #1
428tom
Junior Member
 
Join Date: Aug 2010
Posts: 54
Likes: 0
Liked 3 Times in 3 Posts
Default maximum compression for pump gas aluminum head m

Just wondering on what is the maximum compression ratio for pump gas, you can run with aluminum heads?
428tom is offline   Reply With Quote
Old 02-11-2012, 04:33 PM   #2
FINESPLINE
Senior Member
 
FINESPLINE's Avatar
 
Join Date: Apr 2010
Location: Island of high taxes, N.Y.
Posts: 541
Likes: 0
Liked 1 Time in 1 Post
Default Re: maximum compression for pump gas aluminum head

Can only speak for myself----383 sbc with Dart 215 pro aluminum heads with 64cc chambers 6 inch rods port matched victor jr. comp cams small solid roller R 280 R. True compression at 11 to 1. Runs cool with no signs of detonation on any pump gas. Car is a stick and driven during the hot summers on cruise nights and to car shows. ALMOST left out the carb. A custom built 750 DP---money well spent here !

Last edited by FINESPLINE; 02-11-2012 at 04:51 PM.
FINESPLINE is offline   Reply With Quote
Old 02-11-2012, 04:40 PM   #3
BillK
Member
 
Join Date: Nov 2005
Location: Waldorf Md
Posts: 230
Likes: 12
Liked 30 Times in 17 Posts
Default Re: maximum compression for pump gas aluminum head

Tom,

I really dont think you can make a general assumsion about this. There are a lot of variables involved. I just read that some of the new direct injection engines are running almost 13 to 1 on 87 octane pump gas. A lot of it depends on how much time you are willing to spend optimizing the ignition and fuel curve to prevent detonation throughout all operating conditions. A fuel injected engine with knock sensors can get away with a lot more than one with a Holley and a distributor.

That all being said, I tell my customers 9 1/2 for iron heads and 10 1/2 for aluminum but I tend to be very conservative.
__________________
Bill Koustenis
BillK is offline   Reply With Quote
Old 02-14-2012, 11:06 AM   #4
Mike Croley
Member
 
Join Date: Apr 2010
Posts: 182
Likes: 0
Liked 0 Times in 0 Posts
Default Re: maximum compression for pump gas aluminum head

That would depend on which pump gas ( 87 , 91 , 93 ) and on what day . Pump gas is not consistent batch to batch , day to day . It doesn't have to be . The computer and EFI in street cars can easily compensate for the differences in ethanol content and the different blends .
As a rule , aluminum heads allow a little more CR than steel heads , but on pump gas i'd stay below 11.1 and maybe even a little lower to be safe .
Mike Croley is offline   Reply With Quote
Old 02-14-2012, 11:37 AM   #5
X-TECH MAN
Banned
 
Join Date: Dec 2007
Location: Lake Placid, Florida
Posts: 3,203
Likes: 1,047
Liked 235 Times in 110 Posts
Talking Re: maximum compression for pump gas aluminum head

My street rod with a bone stock ZZ4 crate engine with a GM rated 10 to one comp. (probably a true 9.5 to one unblueprinted) and alum. heads runs fine on todays 87 octane horse pizz.....oops. I mean todays junk pump gas. Car only weighs around 2700 lbs. Engine temp. plays a role also. Mine usually stays around 170 degrees and I run a 160 thermostat. Timing is set at 10 degrees and totals out at 36 degrees at 2500 RPM. I use a vacume advance on an HEI dist. and 3.55 gears with an over drive trans. Turns 2005 RPM at 65 MPH in overdrive. Not a lot of load on the drive train. Lots of things to consider when running pump gas and a med comp. ratio.
If its a race car around 3000 or under to 3400 lbs I would stay at no more than 10 to one with at least 4:11 gears unless its a late model with a computer, knock sensors, etc. then use 91 to 93 octain.

Last edited by X-TECH MAN; 02-14-2012 at 11:57 AM.
X-TECH MAN is offline   Reply With Quote
Old 02-14-2012, 02:27 PM   #6
FINESPLINE
Senior Member
 
FINESPLINE's Avatar
 
Join Date: Apr 2010
Location: Island of high taxes, N.Y.
Posts: 541
Likes: 0
Liked 1 Time in 1 Post
Default Re: maximum compression for pump gas aluminum head

Quote:
Originally Posted by X-TECH MAN View Post
My street rod with a bone stock ZZ4 crate engine with a GM rated 10 to one comp. (probably a true 9.5 to one unblueprinted) and alum. heads runs fine on todays 87 octane horse pizz.....oops. I mean todays junk pump gas. Car only weighs around 2700 lbs. Engine temp. plays a role also. Mine usually stays around 170 degrees and I run a 160 thermostat. Timing is set at 10 degrees and totals out at 36 degrees at 2500 RPM. I use a vacume advance on an HEI dist. and 3.55 gears with an over drive trans. Turns 2005 RPM at 65 MPH in overdrive. Not a lot of load on the drive train. Lots of things to consider when running pump gas and a med comp. ratio.
If its a race car around 3000 or under to 3400 lbs I would stay at no more than 10 to one with at least 4:11 gears unless its a late model with a computer, knock sensors, etc. then use 91 to 93 octain.
I agree with you X- Tech Man. Although I run a lot more initial timing because of the cam , I have a Be Cool radiator with twin fans on a thermostat plugged into the heads set for 180 degrees and a mechanical stat at 160 on the manifold. You have to drive the car to build heat. I have to sit in stop and go traffic during the summer to set the fans off and they don't stay on long. I do use 93 octane all the time. My trans is a tremec tko600 with a .64 od with a 4:30 rear.
FINESPLINE is offline   Reply With Quote
Reply


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 10:27 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2025, vBulletin Solutions Inc.
Copyright Class Racer.com. All Rights Reserved. Designated trademarks and brands are the property of their respective owners.