What type of pistons for 11/12:1 cr? - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum

Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
lost password?   |   register now

LinkBack Thread Tools
  #1 (permalink)  
Old 11-30-2009, 09:28 PM
Registered User
Join Date: Nov 2009
Location: Charleston
Posts: 229
Wiki Edits: 0

Thanks: 0
Thanked 4 Times in 4 Posts
What type of pistons for 11/12:1 cr?

Building a 355 cu.in.race engine that will use 110octane fuel. The heads are 040's from a 68 327 engine. I realize these heads are nothing to write home about but.....thats what we got!
Should we go with flat-tops? Or dish pistons with a postive deck height and mill the crap out of the heads? I know domes are a poor choice because of lousey flame front, although that would be the "ez way out".
Any suggestions?

Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 11-30-2009, 10:07 PM
ericnova72's Avatar
More for Less Racer
Join Date: Jan 2007
Location: S.W. Lower Michigan
Age: 50
Posts: 13,254
Wiki Edits: 0

Thanks: 140
Thanked 1,759 Times in 1,492 Posts
Flat top, zero deck the block or go a little farther and run the pistons .005-.010" above zero deck, and flat mill the heads. You should be able to get 11.5-1 easily this way, more than 11.5-1 will probably require you to angle mill the heads to get it.

You also have the option of doing the above, and using a solid dome piston mill the dome to a minimum height (say something like .040"-.070" tall) to acheive your target compression or more(like 13-1+) but the dome will be short enough to not have an impact on plug shrouding and flame propagation acrossed the cylinder. I have done this with no ill effects.

Use a forged piston, not that hyperpathetic junk.

Last edited by ericnova72; 11-30-2009 at 10:12 PM.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 12-01-2009, 05:54 PM
Last photo:
Join Date: Jun 2005
Location: St. Louis, MO
Age: 31
Posts: 9,544
Wiki Edits: 0

Thanks: 20
Thanked 404 Times in 377 Posts
It won't take much of a dome to get you there just smooth any rough edges and run it.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 12-02-2009, 07:51 AM
Registered User
Join Date: Nov 2009
Location: Charleston
Posts: 229
Wiki Edits: 0

Thanks: 0
Thanked 4 Times in 4 Posts
[QUOTE=F-BIRD'88]A lot of bother for nothing. Only extreme high compression pistons (14:1) with the largest piston dome are going to effect the combustion flame travel if at all. Most of these extreme high cr pistons have a fire slot in the dome anyways. (race piston manufactures didn't fall of the turnip truck yesterday)

Just get a 350 dome piston that gives you 12.5:1 on a 350 with your Measured cylinder head volume and a measured 0 deck height.

If you really want 12.5:1 don't guess. Don't assume the heads are 64cc. Factory heads vary a lot. CC your cylinder heads and measure the actual piston deck clearance. and calculate the actual compression ratio.

If you guess without measuring and calculating the actual finished cr , you will get it wrong and surely give up way more power than any combustion power effect from a any domed piston.

Run it on 110 octane race gasoline and give it all the spark advance timing it requires. Many, but not all high octane (especially leaded type) race fuels require a bit more spark advance for max power than pump gas.
This has nothing to do with the piston dome.

If the cam is a big duration racey cam , lock out the mechanical advance.

Will be useing the 040 heads(327/300hp..1967) How much do they flow with just a mild port clean-up and 3 angle valve job. So I will know how big to go on the duration and lift? We're stuck with the 1.94 I/1.50E valves.
Also ..could you explain "lock out the mechanical advance"?
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Please select your insurance company (Optional)


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools

Posting Rules
You may post new threads
You may 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
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Questions on floating or pressed fit pistons and rods for SBC 350 eric32 Engine 7 10-30-2015 07:21 AM
Piston type or ring size? biscuitville Engine 5 12-19-2008 11:37 AM
What kind of pistons do I have? 87SS Engine 7 08-02-2008 01:30 PM
? about dome piston's bowtieorbust Engine 5 09-19-2004 07:34 AM
383 Crank Hits Pistons 68NovaSS Engine 17 08-09-2004 02:33 AM

All times are GMT -6. The time now is 02:13 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.