Enough compression? - 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
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 10-02-2006, 01:22 PM
Registered User
 
Join Date: Aug 2006
Location: connecticut
Posts: 50
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Enough compression?

I'm worried about the compression ratio my engine might have.
Im building a 383 stroker blower motor. But i wont have anough money for the blower until after next summer. So i was going to buy everything i need,run the engine until im ready for the blower.
So here's what I have for now, let me know if you think the compression will be too low without a blower for now.
4340 3.75 crank
4340 h beam 5.7 rods.
Forged speed pro pistons with 8.92:1 with 64cc heads(adding 72 or 76cc heads with blower).
blower cam: Intake Duration at 050 inch Lift: 234 , Exhaust Duration at 050 inch Lift: 244 , Advertised Intake Duration: 292 ,Advertised Exhaust Duration: 302 ,Intake : 0.488 in. , Exhaust Lift: 0.510 in., Lobe Separation:114 .( is this cam to big? i have 4.11 gears in the rear).
not sure on intake for now, probably high rise or edelbrock performer rpm.
holley 670 cfm carb.
Is the compression too low to run with out a blower, and also can some1 dyno this for me. Thanks alot.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 10-02-2006, 02:00 PM
johnsongrass1's Avatar
Race it, Don't rice it!
 
Last photo:
Join Date: Jul 2002
Location: Columbia, Mo
Age: 38
Posts: 4,232
Wiki Edits: 0

Thanks: 0
Thanked 30 Times in 28 Posts
It's likely to run, but not without the compromises from the missing part's.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 10-02-2006, 03:02 PM
Registered User
 
Join Date: Aug 2006
Location: connecticut
Posts: 50
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
what do you mean missing pats?
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 10-02-2006, 03:03 PM
Registered User
 
Join Date: Aug 2006
Location: connecticut
Posts: 50
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by 73camaro
what do you mean missing pats?
.....*parts
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 10-02-2006, 03:54 PM
Registered User
 
Join Date: May 2006
Location: cda, id
Age: 31
Posts: 282
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by 73camaro
what do you mean missing pats?
I think hes talking about the absence of the blower. Your compression is pretty low for the cam. If your gonna switch the heads for larger com chambers later why not switch the cams as well when your ready to install the blower?
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 10-02-2006, 07:02 PM
firestone's Avatar
http://teamrfc.gospelcom.net
 
Last photo:
Join Date: Nov 2003
Location: Fenton MI
Age: 32
Posts: 1,743
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
I think it might run ok. Just comparing to compression requirements from comp cams, it looks like ~9:1 will work. Below are a couple of comp cams and compression requirements for them.

286H (236 236 @.050 .490 .490 lift 110 lsa) recommeded 9.0:1 comp

XR288HR (236 242 @.050 .520 .540 lift 110 lsa) recommended 9.0:1 comp

your cam, being 234 244 @.050 .488 .510 should be ok with your compression. More would be better, but I dont think this will be horrible. I think the high lobe separation may also help with low speed torque. A hp estimate is hard to guess without knowing exactly what the heads are. As far as the intake goes, I would run the perfomer RPM.

Adam
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 10-02-2006, 07:43 PM
Registered User
 
Join Date: Aug 2006
Location: connecticut
Posts: 50
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks alot for all of your help. i really appreciate it. Im only a 20 year old kid, trying to make a big statment, as well as doin this for myself. I havent seen too many blowers in camaros around here,let alone in a 73. Thanks guys
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 10-02-2006, 08:30 PM
Member
 
Last photo:
Join Date: Dec 2003
Location: Milford, IL
Age: 28
Posts: 128
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
To answer your question, yes it will run.

53_belair is exactly right though. Why not swap the blower cam in later once youve got the blower and run something smaller for the time being?

With the cam you described, even with the gears the car will be very soggy down low. It will run, and itll lope like a harley with a miss but it will NOT be very fun to drive.

If you havent already pulled the motor from the car, Id leave it. Id pick up another 350 block (not hard to find) and build it. That way you can still drive the car while you assemble parts for the 383.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 10-02-2006, 08:34 PM
Registered User
 
Join Date: Aug 2006
Location: connecticut
Posts: 50
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by JohnyR17
To answer your question, yes it will run.

53_belair is exactly right though. Why not swap the blower cam in later once youve got the blower and run something smaller for the time being?

With the cam you described, even with the gears the car will be very soggy down low. It will run, and itll lope like a harley with a miss but it will NOT be very fun to drive.

If you havent already pulled the motor from the car, Id leave it. Id pick up another 350 block (not hard to find) and build it. That way you can still drive the car while you assemble parts for the 383.
I already pulled the motor from the car, since it is already bord .30 over, and is pretty fresh. maybe ill just go with a nitrous cam for now, then switch. What cam would you suggest.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 10-02-2006, 09:50 PM
Member
 
Last photo:
Join Date: Dec 2003
Location: Milford, IL
Age: 28
Posts: 128
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
4-speed or automatic? If auto, are you prepared to use a stall converter?
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 10-03-2006, 04:20 PM
Registered User
 
Join Date: Aug 2006
Location: connecticut
Posts: 50
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by JohnyR17
4-speed or automatic? If auto, are you prepared to use a stall converter?
4 speed rock crusher
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 10-03-2006, 08:40 PM
Member
 
Last photo:
Join Date: Dec 2003
Location: Milford, IL
Age: 28
Posts: 128
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I may have missed it, are you running rebuilt factory heads or aftermarket?

If it were mine to build Id pick a cam somewhere in the ballpark of 225 degrees duration @.050 and .475 or so lift. Slightly smaller would be better than slightly bigger.

You wouldnt have to rev it to the moon to make good power. Dont give up the torque of a 383 by stuffing in the giant cam of death. Remember, RPM stands for 'ruins peoples motors'!

If youve got factory chevrolet heads, Id look hard at a split pattern cam.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 10-03-2006, 08:56 PM
Registered User
 
Join Date: Aug 2006
Location: connecticut
Posts: 50
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by JohnyR17
I may have missed it, are you running rebuilt factory heads or aftermarket?

If it were mine to build Id pick a cam somewhere in the ballpark of 225 degrees duration @.050 and .475 or so lift. Slightly smaller would be better than slightly bigger.

You wouldnt have to rev it to the moon to make good power. Dont give up the torque of a 383 by stuffing in the giant cam of death. Remember, RPM stands for 'ruins peoples motors'!

If youve got factory chevrolet heads, Id look hard at a split pattern cam.
OK thank alot for all of your help
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

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:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

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
Compression question for the Pro engine builders.. Axelrod Engine 14 01-16-2007 11:29 AM
Compression concerns. Siggy_Freud Engine 4 07-11-2006 11:06 AM
Interesting compression question Jmark Engine 11 04-26-2006 04:27 AM
351 windsor running rich ???? ve3ham Engine 19 08-08-2005 01:48 PM
How to figure compression ratio...... classic_chevy_guy Engine 9 07-26-2005 10:59 PM


All times are GMT -6. The time now is 12:14 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.