Welcome! Please use the navigational links to explore our website.
PartsASAP LogoCompany Logo (800) 853-2651

Shop Now

   Allis Chalmers Case Farmall IH Ford 8N,9N,2N Ford
   Ferguson John Deere Massey Ferguson Minn. Moline Oliver

Attention Forum Users: On the 28th of December 2023 at 9:00am Central Time, we will be taking the forums down for maintenance while we prepare the new forums for your use. Please click here for more information.

Minneapolis Moline Tractors Discussion Forum
:

JAHNS PISTONS FROM WELTERS

[Show Entire Topic]  

Welcome Guest, Log in or Register
Author 
UB-ToMMy

10-12-2006 19:06:37




Report to Moderator

I bought a set of the Jahns pistons from Welters. They are 4.375� +0.060� over. ie. essentially a 3/16� overbore. The thing to be careful about is to make sure that when the blocks are rebored the recommended diametral clearance between piston and bore is maintained. As I recall .008� is recommended. Initially my blocks were mistakenly rebored with a 0.006� clearance. The result was disastrous. The engine would seize when run wide open for any length of time. I thought and hoped the problem was something other than the pistons. Upon disassembly, I found #1 piston severely damaged well beyond usability. The others were fine. I was able to buy one more piston from Welters�it was their display piston from the counter. I had to machine a substantial amount of the inside of the skirt to make it match the other 3 in weight and I fine tuned the weight so that all 4 weighed within about 3 grams of each other. One other thing, I had to machine the wrist pin boss openings on the inside so that the rod would fit between the two bosses on all 4 pistons. I had the bores honed to give 0.010� diametral clearance except for the bad hole which was machined 0.012� over. I wasn�t too concerned about piston slop since the tractor use was for pulling not field work.

I also have 4207 heads on the tractor. With the Jahns pistons and the high compression heads I�ve finally gotten the engine to the point where it doesn�t power out-at least not easily. After 3 years of trying to get it right, this year was the payoff in that the tractor was 1st place successful in a number of pulls. And, by the way, it never, never overheats and barely gets into the run zone when run without a thermostat. One other point: it runs best on race gas.

[Log in to Reply]   [No Email]
[Show Entire Topic]     [Options]  [Printer Friendly]  [Posting Help]  [Return to Forum]   [Log in to Reply]

Hop to:


TRACTOR PARTS TRACTOR MANUALS
We sell tractor parts!  We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]

Home  |  Forums


Copyright © 1997-2023 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy

TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters

Website Accessibility Policy