Another Compression Ratio Mystery - Hot Rod Forum : Hotrodders Bulletin Board -- 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 06-10-2003, 07:29 PM
Registered User
Join Date: Jun 2003
Posts: 6
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Another Compression Ratio Mystery

To Anyone,

I have a aftermarket Chevy 350 engine installed in a 1990 C-1500 Truck that I have no idea what the static compression ratio is. Without tearing the engine to down to the heads, I would like to know the compression ratio by accessing the parts installed in the engine. I do have a few receipts for parts and labor that were from a former owner that I've listed below:

1). Center bolt Cylinder Heads- casting number 14102193 used on late model Chevy TBI engines. They have been machined (open bowled) for 2.02/1.60 valves and bowl blend(?). The combustion chamber is size is not known. The key here is to know the stock size of the combustion chamber (64cc, 76cc). No mention was made of machining or decking the heads.

2). TRW/Speed Pro flat top forged pistons were installed. Part number L2256F20 (.020 over).

3). Stock head gasket.

Well that's pretty much it. If anyone want's to use their expertise to access what they think the static compression ratio is.


Reply With Quote Quick reply to this message
Sponsored Links
  #2 (permalink)  
Old 06-10-2003, 10:51 PM
DoubleVision's Avatar
Not Considered a Senior Member
Last photo:
Join Date: Oct 2002
Location: Heart Of Dixie
Age: 43
Posts: 10,733
Wiki Edits: 0

Thanks: 19
Thanked 77 Times in 71 Posts
Your chambers are 74 - 76cc, the term "bowl blended" refers to cleaning up the bowls under the valves, removing the ridge under the valve seat and just cleaning up leftover casting flash, this is good for street engines. with your pistons and overbore, your compression ratio is likely around 9.0 to 9.5:1 which is fine for a street engine on pump gas.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 06-11-2003, 05:31 AM
Registered User
Join Date: Jun 2003
Posts: 6
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Double Vision,

Thanks for your reply.

I figured the compression ratio would have been at the lower range of 8.5 - 9.0 to 1. This brings me to ask anyone what gas octane rating should be used with this aftermarket engine? The spark plugs are picking up a deposit (dark crusty spot about 1/8" - 1/4 " diameter) on the intake valve side of the insulator tip. I've been running 91 unleaded premium with CR43TS plugs. Using colder plugs results in the same condition. The unleaded regular gas here in California is said to be "real hot", a real detonation problem in hot weather.

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

All times are GMT -6. The time now is 10:36 PM.

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 1999 - 2012. All Rights Reserved.