Piston selection 377 - 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 11-13-2012, 07:09 PM
Registered User
 
Join Date: Nov 2012
Posts: 18
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Piston selection 377

Hello, I am new to the site, so.. Its nice to meet you guys and I look forward to hearing from you all.

I am in the process of building a 377 stroker motor for my 85 Monte SS. (350 block, stock bore, 3.75 stroke) Ive been looking at a few of the different rotating assemblies available, and now I have some questions about piston and ring selection.

My first concern has to do with compression ratio. (It will be a street/ occasional strip car) My block is decked to 9.010, and I will be using a set of Dart Iron Eagle heads with 64cc combustion chambers. With this combo, wouldn't a flat top piston put me out of pump gas range? Is there any reason why running a dished piston would be a bad idea? What is the max compression ratio I could run safely?

Second, I have heard good things about the reliability and temp resistance of moly faced rings, but I also just read that the cylinders need to have a special finish to seal properly with moly rings. I just got the block from the machine shop, and dont really plan on sending it back. Is it a bad idea to run iron rings in a mild performance engine? (I am hoping for 450+ hp and tq)

Thanks for the help.

PS I know dynamic compression ratio is what really determines pump gas driveability, but I don't have a specific cam picked out yet.

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 11-13-2012, 07:50 PM
vinniekq2's Avatar
Registered User
 
Join Date: Jun 2012
Location: BC,Canada
Age: 56
Posts: 7,719
Wiki Edits: 0

Thanks: 309
Thanked 745 Times in 716 Posts
what end results are you looking for? how much power,or whats the performance you want for that car
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 11-13-2012, 08:15 PM
hcompton's Avatar
Old & Furious
 
Join Date: Oct 2012
Location: MD
Age: 41
Posts: 1,074
Wiki Edits: 0

Thanks: 6
Thanked 87 Times in 84 Posts
So the machine shop looked at the block and said the stock bore was fine?

64cc heads is what you need to make the power you want but will be out of pump has range for small cam. But you will be going with a large cam anyway to hit 450+

Alum. heads would be the best way to go. 64 cc with flat tops and normal to thick gasket to get it safe on pump gas. But you need to measure it up to be sure. Just go with a large enough cam to keep the dcr low enough for pump gas.
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 11-13-2012, 10:49 PM
Registered User
 
Join Date: Nov 2012
Posts: 18
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Vinnie, I would really like to push 450+ horsepower and torque. Reasonable goal. But I want to be sure it is streetable. Am I basically forced to run dish pistons since I cant run a large enough cam to keep my dcr in pump gas range, BC I do plan to drive it on the street?
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 11-13-2012, 10:56 PM
Registered User
 
Join Date: Nov 2012
Posts: 18
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Hcompton,

would a cam large enough to keep my dcr in pump gas range w flat top pistons even be streetable? Im looking at somewhere around 11:1 with flat tops and a comfortable quench. If it were your build, would you choose flat tops and a large cam, or just go with the dish style piston?
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 11-13-2012, 10:57 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,802
Wiki Edits: 326

Thanks: 745
Thanked 959 Times in 808 Posts
Using a Keith Black #102 standard bore piston with 18cc dish, the static compression ratio would be 9.5:1. Using a cam with the intake closing point at ~35 degrees ABDC would yield a DCR of 8.4:1. Look, for instance, at the 119671 on this page.
http://www.cranecams.com/68-71.pdf
Second set of numbers from the right tell the cam timing @0.050". Notice that this cam opens the intake at 1 degree BTDC and closes the intake at 35 degrees ABDC. I'm not saying to use this cam. I'm just trying to show everyone on this board how to arrive at a cam that will work with a given static compression ratio. You can always PM me if you like the way I do things but don't want to ask on a forum.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 11-14-2012, 07:00 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
Quote:
Originally Posted by 377MONTE View Post
Hcompton,

would a cam large enough to keep my dcr in pump gas range w flat top pistons even be streetable? Im looking at somewhere around 11:1 with flat tops and a comfortable quench. If it were your build, would you choose flat tops and a large cam, or just go with the dish style piston?
"Streetable" covers a lot of ground I'm sure you know. But to use that much compression (64cc heads and FT w/good quench) will mean a lot of cam and that means a lot of stall rpm and rear gear. It might be drivable on the street but I wouldn't call it streetable, at least not on a daily basis. Maybe when I was 18....

Much better to build it w/12-18 cc dished pistons, IMHO. I'd suggest a reverse dome or D-cup piston to maximize the quench effect.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 11-14-2012, 07:32 AM
1Gary's Avatar
Registered User
 

Last journal entry: 383 dyno sym
Last photo:
Join Date: Oct 2010
Location: Roch,NY
Age: 66
Posts: 1,526
Wiki Edits: 0

Thanks: 201
Thanked 156 Times in 142 Posts
These are I-Con's which are a pretty good deal given the offset pins to help cold piston slap and are .030 5.7 rod stroker pistons.Reverse dome 18cc's with a .010 down deck and a 67cc head ends up to be 9.3ish SCR.







I'm kind of confused why when your replacing the pistons anyway you didn't take the option of boring it .030??.I don't think you would find .030 pistons costing more.You do know that bore sizing should be fitted to the pistons you going to use.So the bore/hone should not be done until the machine shop has the pistons in hand.I would seriously question the machine shop that measured your bores on a block that old why they didn't find some of the bores oval.Not a bad thing in SBC's,just pretty common wear factor.How round on center the bores are with a very good hone is very important.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 11-14-2012, 11:51 AM
Registered User
 
Join Date: Nov 2012
Posts: 18
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Gary,

I purchased the block directly from the machine shop. I didnt tell them how to prep it, it was already done. I kind of like the idea of doing something a little different, and everybody builds a 383, so i like the sound of a 377 stroker a little better LOL. They did give me a sheet w all the things that were done to the block. Clean, degrease, magnaflux, hone, and decked. I guess i may end up having to go with a 383 after all though, I didnt really know the bores needed to be matched to the piston in hand. Good thing I havent ordered the rotating assy yet.
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 11-14-2012, 12:01 PM
vinniekq2's Avatar
Registered User
 
Join Date: Jun 2012
Location: BC,Canada
Age: 56
Posts: 7,719
Wiki Edits: 0

Thanks: 309
Thanked 745 Times in 716 Posts
there is also a 377 that has the larger bore and shorter stroke.
measure the block and look around to see if you can find pistons to fit,or better yet,get the machine shop to find the pistons to fit there machine work? If the cannot,then they can bore the block for free or take back their block. different pistons require different piston to block clearances
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 11-14-2012, 12:12 PM
Registered User
 
Join Date: Nov 2012
Posts: 18
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
cobalt,

why am i under the impression that dish pistons are second best? maybe I am mistaken, but i figure lower compression by a whole ratio, maybe even more, would equal less power? Are my 450+ hp/tq goals still realistic with dish pistons?
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 11-14-2012, 12:15 PM
Registered User
 
Join Date: Nov 2012
Posts: 18
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
ahh, thanks vinnie. makes sense now. bores need to be finished to the pistons clearance requirements.
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 11-14-2012, 12:39 PM
1Gary's Avatar
Registered User
 

Last journal entry: 383 dyno sym
Last photo:
Join Date: Oct 2010
Location: Roch,NY
Age: 66
Posts: 1,526
Wiki Edits: 0

Thanks: 201
Thanked 156 Times in 142 Posts
Not sure I would want to deck a block either if I didn't have the pistons in hand.Do you know if it was decked to 0??.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 11-14-2012, 01:01 PM
Registered User
 
Join Date: Nov 2012
Posts: 18
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
gary,
it was decked to 9.010.
Reply With Quote Quick reply to this message
  #15 (permalink)  
Old 11-14-2012, 01:17 PM
hcompton's Avatar
Old & Furious
 
Join Date: Oct 2012
Location: MD
Age: 41
Posts: 1,074
Wiki Edits: 0

Thanks: 6
Thanked 87 Times in 84 Posts
so here is where i am at. i got more question than answers. I run the numbers i get 10.3:1. with 6cc flat top 4 valve relief, .043 gasket with gasket bore of 4.063, 4 inch bore and 3.75 stroke. Even with a smaller XE262H it will be around 8.8:1 dcr. with a magnum 270H its 8.5:1 dcr. I would recommend alum. heads.

That being said what type of pistons do you have and how far down in the block are they. You say your deck hieght is 9.010 but has it been cut that or is that measured at the pistons highest point.

so what type of pistons aka what cc are they

and how far down are they installed in the cylinder

Is this a new block? Your build sheet says 4.00" bore? Has the stock bore been meausred to make sure its correct? Seems to me its going to need to be bored out to atleast the first std. over bore of 4.030 if not already at 4.060.

If you havent purchased the rotating assembly yet you can just buy pistons that are .015 or more in the hole and lower compression that way. Or use a thicker gasket.

Best thing to do is measure everything and check the cr and dcr with this link.
United Engine & Machine Co. Incorporated
Reply With Quote Quick reply to this message

Tags
377, 383, piston, sbc, stroker

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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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
Piston Selection AGABE Engine 4 12-31-2011 11:26 PM
Piston Selection 31fordcoupe Engine 11 08-02-2009 05:04 AM
Piston Selection - need advice blndweasel Engine 19 03-26-2008 09:17 PM
piston selection question malibu68 Engine 6 05-16-2007 11:02 AM
Piston Selection machine69 Engine 4 05-09-2004 10:55 AM


All times are GMT -6. The time now is 11:48 AM.


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.