G Head

[Anonymous-0]

For you JD G experts. I have a 51'G. Need more hp. Is it worth the money most guys are getting for a "flat" head? Can't the stock head be planed enough to get comparable compression? If so, about how much could I go? Thought of making the rods longer. I know a lot of guys do this, but really don't like the idea. Sorry for all the rookie questions! Thanks for any help.

 

[johndeereman]

on my a we took 325 thousands off the head already had the tall high compression pistons in it no room to lengthen rods with those pistons heard of guys welding plates on top of piston i had to put in a 1000 crancking amp battery and bigger cables to start mine after i burnt one starter up that was a 150$ mistake

 

[Cabbage]

Hey w the A did ya see much difference? did ya do anything with the eyebrow?

 

[jd88640]

it depends on what power you are looking for.
it also depends on how you want to spend money.
if you have stock g with a cylonce head cutting
the head won't get you nothing. put aflat head
on and it will increase hp. but harder to start.
also not too much increase in hp. it all depends
on what you are looking for. the most power on
a g comes from stroking the crank and getting
more cubes out of it. course this a whole nother
ball game.

 

[Anonymous-0]

On another note, can someone tell me how many cc's the combustion chamber displaces in a late G head. I'm sure someone knows this or else I need to measure mine.

Thanks, LRN

 

[buckeye brierhopper]

i have a 48g,installed a486r flat head,with high alt pistons in it. with some air work on head,with a comp grind on cam, iam getting arround 70-80 hp. i can run 2nd gear in 55-6000 lb class withoutkilling engine. that is 3mph classes.the biggest thing to watch is detonation,you willneed to roll timming back to 18-20 degrees on timming,plus go to 110 oct fuel to keep from causing any un timely breakage good luck an have fun with the pulling feeeeeever

 

[buickanddeere]

Get a set of high comp pistons. And work on getting more airflow through the heads.
That's cam and/or rocker arms. Relieving the intake eyebrow with a valve seat cutter so the intake has 3/16" all around it to breath. Match the ports. Blend the rough edges and flashing out of the ports and valve bowls. Get a shop that know show to do a good five angle valve job. Yank the entire factory aircleaner off and put a K&N filter on the carb inlet.

 

[JDGnut]

Lengthen the rods until the pistons is at the deck of the block.. or even notch the pitons and push it above the deck... You will have to modify the notch in the piston for the spark plug a little.. One of my G's is less then .100 from the deck... it will be closer next time..
The nice thing is that if you don't want the high compress later, you can just put the stock rods back in...
JDGnut

 

[johndeereman]

yes i did see a difference tapered the eybrows the a has more than my 70

 

[BushogPapa]

Hey, B&D..what do you think of using aircraft pistons or lighter custom pistons and lengthened rods..?

Been hearing more and more about aircraft pistons..

Those old Pratt & Whitney engines were plenty big..up to 4,360 cu in..!!
Not sure about the bore sizes on a Continental O-520..probably not big enough..

Ron.

 

[buickanddeere]

Maybe if you get them for free and you want to custom machine them into what you want.
I would get a set of pistons made from scratch to get the pin height, deck thickness, dia wanted.

 

[JDGnut]

(quoted from post at 11:16:57 12/19/08)
Hey, B&D..what do you think of using aircraft pistons or lighter custom pistons and lengthened rods..?

Ron.

The Pratt pistons we have used have been 5.75 & 6.100.. too small for a G.. you can find CAT pistons that will work with 6.25 bore.. they have a bigger pin, with a shorter compression height.. but they are not as short as the aircraft pistons.. The other issue is if they have enough top land above the top ring to cut a notch in the piston to get a notch for the spark plug.. G's that I know running the CAT pistons.. most are running plugs in the head, to not have ot worry about the plug issue..
If you are looking for some custons pistons you can see what Bpuller has for sale on his site.. thought he might have something.. but you will still have to build a set of rods..

IF you are using the M&W style pistons.. you can have the other notch welded shut..
I have a G that I cut the block and head down on.. I wish I would have just had the rods made longer.. would have been cheaper, easier.. and I could have gone back to stock with just changing the rods...
Good Luck,
JDGnut