jd 630 head question

jdrich

Member
Is there a difference between an all fuel head, an lp head, and a gas head? Im not looking to go crazy on this...just a tad more compression without buying expensive pistons or stroking. Thanks
 
I am not sure about the 630. But, I do know about the 720 LP and GAS heads. The heads LP and GAS have the same casting number. The LP head has hardened valve seats and this changes the part number. The GAS pistons are flat. The LP pistons are domed this is the compression difference. I am considering putting LP pistons in a GAS engine. But, I do not want pinging and spark knocking. I don,t know........ Hope this helps.
 

Except for the Hard Valve Seats, the Heads are the same on the 620/630.
The compression difference is:

"All-Fuel"---Piston top Concaved Full Width.
Gas Piston---Piston top Concaved 1/2 Diameter.
LP Piston--Piston top FLAT--Full Diameter.

Clean up the Chambers, clean up the Ports, do a GOOD 3-Angle Valve Job, 0.030" off the Head is all you want if you expect to use 87 Octane Gas...
I have an F-145 4x16" I pull with my 630 and I sock it DEEP, just to Prove it will pull it in second..(in fields WITH Jack Wax).
But, I DO have good loaded tires and front weights..
Unless you are going "Pulling", I cannot see why you would feel it needs any more power than what it should already have..
Ron.
 

Cleaning up the Intake and Exhaust ports, along with streamlining the Valves increases the volume of air the engine will Pump, (changing to a Hi-Performance cam would be an advantage).
That increased air flow is what raises the RPM the Peak HP AND Peak Torque occurs (for the same Camshaft).
My 630 seems to Peak at about 950RPM and hangs on like a Bull Dog. Almost seems like the ground should be shaking..Front end just touching the ground with 300# out front..
Ron.
 
Mine pulls 4x16s deep here in south central pa. 3rd gear. I mostly pull it tho. High octane fuel is not an issue. We have a station with112 leaded at Sunoco. I just want a little more.
 
There is a free parts book on the Jd web site.
A set of LP pistons or even higher compression are not expensive.
As previously stated there is all kinds of power in a matching camshaft, port cleanup and valve/seat machining.
 
check and see if diesel pistons won't work , a fellow put a set in a 730 and it dynoed at 77 hp that's up quite a bit from 54 hp stock .
 
(quoted from post at 18:12:31 10/20/14) check and see if diesel pistons won't work , a fellow put a set in a 730 and it dynoed at 77 hp that's up quite a bit from 54 hp stock .

Maybe able to machine a 6-1/8" 70/720/730 diesel piston to fit in a 720/730 spark ignition engine with the 6" factory bore.
The 620/630 spark ignition engine with the factory 5-1/2" bore is probably going to hit water when bored to 6-1/8". Taking 312.5 thou from the cylinder walls will be rather thin if it don't leak.
 
yea, you would have to get a block from Ray at
extreme to work , but he has pistons that will bring
it up to 12 to 1
 

May as well just obtain a stock 620/630 cylinder block. Bore it to the limit and weld in some sleeves. Probably could swing some 6-1/2" pistons ?
 
Do the port matching and other work as stated. If you want a "tad" more compression, shave the head .150
 
Tonight if I get time I will post video for the haters & non believers. I think it's alot of fun & pretty cool. On the track it gets a lot of 2nd & 3rds, beats a lot of built up A's & G's, a few molines & Allis's, and a variety of Red tractors. We usually run it in 3rd gear 5mph classes lately, with 15.5 cut tires & 4-4500 pounds. 5500 on good tracks (2nd gear). 3750 class in 4th gear occasionally. I also think a 630 has great power potential without going all out.
 
Do you have any videos or pictures of your puller? What make is it? Oh & the B pulls 3-16's not 4 lol. My bad. Big difference :)
a172403.jpg
 

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