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

Shop Now

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

Discussion Forum
:

G compression ratio

Welcome Guest, Log in or Register
Author 
Rob

09-10-2001 14:53:43




Report to Moderator

I have a '49 G with stock pistons and a F486 cyl. head. I think I am supposed to have an F551 head but such is how the tractor came to me. My understanding is that if I buy a new set of aluminum pistons, instead of getting 6.5:1 comp. ratio like I'd get with the F551 head, I would wind up with about an 11:1 which is too high for my toy. I just want a really stout plow tractor, not something that is going to disintegrate on me.
I'd rather not replace the F486 head as it is in great shape with a new valve job and some modest porting.

My questions are:

1)What is the difference between the engine setups on the '49 versus (presumably) unstyled G that used the F486 head? Is it connecting rod length, piston bowl shape, what?

2)If I buy a set of Deere 0.045" over pistons (assuming they are available) and keep the F486 head, what will my compression ratio be?

3)The tractor has the 1074 gas manifold and DLTX51 carb. With new pistons, about what power should I get on gasoline?

Thanks,
Rob

[Log in to Reply]   [No Email]
Gman

09-10-2001 21:19:28




Report to Moderator
 Re: G compression ratio in reply to Rob, 09-10-2001 14:53:43  
Rob the F-486 head was used with the F-485 block which is 12 1/2'long versus styled G which used the F-550 block which is 11 1/2 inches long and the F-551 head,alot of pullers like the F-485 block because it works well with the stroked crank. The only problem I see using the tall or MW styled pistons and flat head is you would have to use a high octane fuel,why not just put in a good set of flat top pistons,give the piston 10-12 thous. clearance and go plowing. Later Gman

[Log in to Reply]  [No Email]
Rob

09-11-2001 19:02:25




Report to Moderator
 Re: Re: G compression ratio in reply to Gman, 09-10-2001 21:19:28  
Thanks for the info. If I go with the flat top pistons, I assume I wouldn't need to modify them. Any ideas what the comp. ratio might be...perhaps 7-71/2:1?? I assume the 10-12 thou. clearance is just what I'd wind up with if I go with the stock pistons. I don't mind the high octane gas requirement just so long as I can use as desired. I am thinking the flat tops are the best bet. Are 0.045 over flat tops available from Deere or anyone else?

Thanks,
Rob

[Log in to Reply]  [No Email]
lynn

09-10-2001 18:49:13




Report to Moderator
 Re: G compression ratio in reply to Rob, 09-10-2001 14:53:43  
rob the styled pistons have a dish in them unstyled are flat styled head has a chamber where the unstyled is flat rods are the same length if you want a stout tractor and use 91 to 93 octane gas keep the compression around 7 to 1 the best way to do this is buy a set of .125 over aluminum pistons and mill them to get the required ratio that would be around 1.100 plus .080 head gasket set the timing around 20 degrees this will make an honest 58 to 60 horsepower lynn

[Log in to Reply]  [No Email]
Rob

09-11-2001 19:07:38




Report to Moderator
 Re: Re: G compression ratio in reply to lynn, 09-10-2001 18:49:13  
Appreciate the info relative to the high comp. pistons. If I go with the 0.125 overs, any idea about how much I have to mill off the top of the pistons? Was that the 1.100" that your note implied? Also, how much stock is there...am I going to unduly weaken the piston to remove that much stock? 58-60 hp. sounds pretty good right now.

Thanks,
Rob



[Log in to Reply]  [No Email]
lynn

09-12-2001 17:38:10




Report to Moderator
 Re: Re: Re: G compression ratio in reply to Rob, 09-11-2001 19:07:38  
rob the 1.100 inch is the distance from the top of the piston to the front of the head this assumes your piston is flat across if dished you have to calculate this out to get the compression this with the gasket will give you 7 to 1 i don't think you can get .045 over pistons from deere i looked and i have an old set of .045 over for a styled g they have a dish in them don't remember how much chamber f551r has i say this would make between 5.5 to 6 to 1 with the flat head unstyled .045 over would have a flat top but would be harder to find guessing you would have to machine between .500 and .750 inch off of the high compression pistons if you need some .045 let me know lynn

[Log in to Reply]  [No Email]
Rob

09-14-2001 15:18:49




Report to Moderator
 Re: Re: Re: Re: G compression ratio in reply to lynn, 09-12-2001 17:38:10  
Lynn, Thanks for the info. Now that I see what the 1.1" is all about, I will take the time to calculate out the comp. ratio. I got the same result from Deere as well...no 0.045 overs. I think if I am gonna do this, I am just going to go for the high comp. 0.125 overs, get the max in3's I can and mill off as needed. I have no idea how big the crater is at this point. Sounds like there is no problem with piston-to- valve clearance regardless, correct?

Thanks,
Rob

[Log in to Reply]  [No Email]
lynn

09-16-2001 07:28:03




Report to Moderator
 Re: Re: Re: Re: Re: G compression ratio in reply to Rob, 09-14-2001 15:18:49  
rob there will be no problem with valve clearance some other things to check for are the head studs make sure they are in good shape i've had some made that were between grade 5 and grade 8 these are better than john deere and cheaper if you go very high with the compression the flat head will flex where the water goes from the head to the block there is no support behind this area have cut some metal and wedged it between the casting and spot welded it this was on higher compression give plenty of clearance for the pistons .011 to .012 inch can check with a feeler gauge make sure the piston slides all the way through with the gauge between the piston and block no worse feeling than having a g seize up and have to tear it all down if you have any questions e-mail me at debbieheller@msn.com lynn

[Log in to Reply]  [No Email]
Rob

09-16-2001 12:45:06




Report to Moderator
 Re: Re: Re: Re: Re: Re: G compression ratio in reply to lynn, 09-16-2001 07:28:03  
Lynn, Thanks again. Good tip on the side clearance; I will make sure the outfit that machines the block gives me 0.011-0.012" side clearance. I don't intend to go high on compression ratio...probably 6.5- 7:1 is as high as I will go. As I have said previously; I want to be able to play with my toy in most any operating condition. I am still concerned...how thick is the piston crown between the crater and the OD of the piston; if I machine off as much as 0.75", is that going to unduly weaken the piston? I would take the pistons to a reputable shop (same place as with the block) to ensure that proper protocol is followed (minimise heat build-up, etc.). Sounds like compression ratio is my final obstacle with the unusual parts mix I have.

Again, many thanks.

Stay safe,
Rob

[Log in to Reply]  [No Email]
lynn

09-17-2001 17:58:52




Report to Moderator
 Re: Re: Re: Re: Re: Re: Re: G compression ratio in reply to Rob, 09-16-2001 12:45:06  
rob don't know how much you would have to cut off the pistons to get the right ratio friend thought they were about 1 inch taller i don't think you would get far down enough to weaken them have to get ahold of some and do some measuring could add some gaskets between the block and case and gain around .025 inch for each one make the block longer as gman was talking about lynn



[Log in to Reply]  [No Email]
[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