Brought to you in part by:

M&M Restoration & Tool Supply Store

Great deals on auto restoration supplies!

.


NOTICE! The old Mustangsandmore.com is a read-only archive.
Currently the Search function is inoperative, but we are working on the problem.

Please join us at our NEW Mustangsandmore.com forums located at this location.
Please notice this is a brand new message board, and you must re-register to gain access.

  Mustangsandmore Forum Archive
  Ford Racing
  piston to cylinder clearance - 408 stroker

Post New Topic  Post A Reply
profile | register | preferences | faq | search

next newest topic | next oldest topic
Author Topic:   piston to cylinder clearance - 408 stroker
troyp
Journeyman

Posts: 5
From:
Registered: Feb 2006

posted 02-28-2006 12:12 PM     Click Here to See the Profile for troyp        Reply w/Quote
I have found a stroker kit for my '69 coupe 351w. Hawks 4340 4" crank, 4340 6.2" hbeam rods, Probe SRS forged Al. dish pistons. I have done some investigating and I know some people have reservations about Hawk stuff and that is understood.

My specific question is regarding piston to cylinder clearance. Is .007" too much? This will probably be about 10.25:1 with no immediate plans for power adders. I have a set of ported 289 heads with larger valves to use for now (obviously a new set to be added in the near future) and an aggressive cam shaft (specs are not handy - will post them tomorrow). This will be street driven, but mostly looking for track performance. Not your typical daily driver. How loud will the piston slap be on cold startup? Does this create durability issues long-term? Hoping for some advice from the wealth of knowledge on this site.

Thanks

Troy

troyp
Journeyman

Posts: 5
From:
Registered: Feb 2006

posted 03-01-2006 08:15 AM     Click Here to See the Profile for troyp        Reply w/Quote
Hmmmm...the sounds of crickets on a quiet night...

Let me rephrase the question. Does anyone run that loose on a N/A hotrod engine? Were there any issues? The reason I am asking is because my block is already .029 (measured) over and it will end up 5 or 7 thou bigger once cleaned up - the pistons are apparently 4.030 +/- almost nothing. I suspect this will be a good setup for turning some rpm, I am looking for a quick lesson from anyone with experience.

Thanks in advance.

Troy

Hans olsson
Gearhead

Posts: 936
From: Sweden
Registered: Apr 2000

posted 03-01-2006 10:56 AM     Click Here to See the Profile for Hans olsson        Reply w/Quote
quote:
Originally posted by troyp:

My specific question is regarding piston to cylinder clearance. Is .007" too much
Thanks

Troy


Sounds good to me!

------------------

  • VIN 1F05M139343
  • 71 Mach 1 Ram-Air
  • 351C 4V 285 HP
  • E,F,G/SA
  • Stockers are way cool!

Whitson
Gearhead

Posts: 290
From: Western Canada
Registered: Dec 2005

posted 03-01-2006 11:23 AM     Click Here to See the Profile for Whitson        Reply w/Quote
Check with the people who make your pistons for specs, but normally .005 is minimum for a true forged piston.

troyp
Journeyman

Posts: 5
From:
Registered: Feb 2006

posted 03-01-2006 11:45 AM     Click Here to See the Profile for troyp        Reply w/Quote
Unfortunately, I did call Probe and the "dude" answering the phones read his sheet that said "2.5 to 4 normally aspirated" or whatever. He could not elaborate. 5 minimum sounds good. Anyone have an opinion on the other end of the scale?

Thanks again guys.

spoiler
Journeyman

Posts: 48
From: fredericton-new brunswink-canada
Registered: Mar 2001

posted 03-01-2006 06:35 PM     Click Here to See the Profile for spoiler        Reply w/Quote
mt pistons say .005-.007
ford racing would like to see .005-.006-.0065 doesnt seem like much of a difference to me? thats there opinion according to the guy doing my work-also interested in what some of these guys here think-going in a 393c stroker

troyp
Journeyman

Posts: 5
From:
Registered: Feb 2006

posted 03-02-2006 08:06 AM     Click Here to See the Profile for troyp        Reply w/Quote
Thanks to all for piping in. Not sure where the rest of the crew is at on this issue?? I thought the increased clearance would reduce friction, especially at higher rpms - maybe that's not true? Maybe skirt length is such a big factor that no-one wants to comment? Of course every application is different, I was just hoping to gain some background knowledge based on the experience of the gang here at M&M.

CometGT1974
Gearhead

Posts: 479
From: Asheville, NC USA
Registered: Jan 2002

posted 03-02-2006 09:37 AM     Click Here to See the Profile for CometGT1974        Reply w/Quote
doesn't too much clearance cause the piston to rock around in the bore??

70rancheroGT
Journeyman

Posts: 48
From: Durham, NC
Registered: Mar 2005

posted 03-02-2006 01:17 PM     Click Here to See the Profile for 70rancheroGT        Reply w/Quote
I'm surprised your pistons are 4.030. Forged Speed-pro 30 over pistons are closer to 4.027 so that they fit a 4.030 bore. I would be concerned with excessive clearance with a short piston skirt and the fairly extreme angle at BDC with your stroker.

I know you are on a budget, because all of us are on some kind of budget. But, for the minimal cost of a 351W core, I would find another block and do it right. We're talking 100-200 bucks in a $4-5000 build.

Ask your machinist what he thinks, you should trust his/her opinion. If you don't then you need a new machinist.

Good Luck

Buster
Gearhead

Posts: 1821
From: Hurricane alley
Registered: May 2002

posted 03-03-2006 12:37 AM     Click Here to See the Profile for Buster        Reply w/Quote
quote:
Originally posted by troyp:

My specific question is regarding piston to cylinder clearance. Is .007" too much?


IMHO, .007" is too loose for your setup. Most forged pistons that I've used are in the .0045" to .006" range.

Itís hard to say how loud the piston slap will be because every piston expansion rate is different. Nevertheless, I would expect you will hear it on cold startup at .007Ē.

Also, I don't care for Probe's generic answer to your question either. Kinda answers my question on whether or not I should buy anything from them.

Typically, when someone has a concern like this there is usually a problem and thatís why youíre asking the question in the first place. If you donít feel good about it now, itís not going to get better after the engine is assembled and running.

troyp
Journeyman

Posts: 5
From:
Registered: Feb 2006

posted 03-03-2006 08:09 AM     Click Here to See the Profile for troyp        Reply w/Quote
I definitely appreciate the replies - good info. I think I will reconsider this setup. Either find a deal on a block that will work with this deal, or quit drinkin' till I can afford what I want...jeez, now that just sounds foolish, don't it?

All times are ET (US)

next newest topic | next oldest topic

Administrative Options: Close Topic | Archive/Move | Delete Topic
Post New Topic  Post A Reply
Hop to:

Contact Us | Mustangsandmore Front Page

Copyright 2006, Steve LaRiviere. All Rights Reserved.


Ultimate Bulletin Board 5.47d

Amazon Honor System Click Here to Pay Learn More

[Build a free Mustangsandmore.ws Home Page!]

[Posting Pictures]

[About M&M][Members' Pics]

[M&M Conventions] [M&M Mug Shots] [Tech Articles]

[M&M Bookstore] [M&M Restoration & Tool Supply Store]