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HOW MUCH HORSEPOWER FROM A JD-G 7.5 BLOCK?

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2 cylinder

08-31-2002 19:41:00




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WHAT KIND OF HP ARE THE JD-G'S MAKING WITH THE 7.5" BLOCK WITHOUT STROKING? AND ALSO HOW MUCH HP DO THEY MAKE WITH THE 7.5" BLOCK AND 9.25" STROKE? TRYING TO PLAN A WINTER PROJECT.




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G Taylor

09-01-2002 00:43:55




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 Re: HOW MUCH HORSEPOWER FROM A JD-G 7.5 BLOCK? in reply to 2 cylinder, 08-31-2002 19:41:00  
The displacement is there but the airflow isn't due to limited breathing. Can't fill or empty those huge cylinders. A very modest 1 HP per cubic inch at 6000rpms is being reached with emissions legal automobile engines. An 817.3 cu in G or 70 should make 275HP at 2000rpm. Look at the little 520/530 JD. They made as much power stock from 190 cu inches as a G did from 412 cu in. The 520/530 could breath. A G breathing like a 520 at a 520's rpm should make 84 HP. They G/70 can't because the head ports,valves,manifolds,carb were designed to heat low grade fuels and keep it atomised while flowing at high velocity through a relatively small port. All this for while ploughing the back 40 acres while making at most 50HP. If someone would make a custom head/manifold etc a 300HP G or 70 would be "easily" achievable.

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Paul

09-02-2002 15:20:13




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 Re: Re: HOW MUCH HORSEPOWER FROM A JD-G 7.5 BLOCK? in reply to G Taylor, 09-01-2002 00:43:55  
there is one other short coming no one is talking about nomally large cyl. bores are good for larger valves but with the power block you have a step in the bore reducing the amount of valve area available the only way you are going to even approach the flow numbers possible for this kind of HP. is with four vaves per cyl. or canted valves or both. and each of those intake valves are going to need a g sized carb.an 850 inch G has a whole lota torque about 600 rpm though.

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super G

09-01-2002 17:01:48




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 Re: Re: HOW MUCH HORSEPOWER FROM A JD-G 7.5 BLOCK? in reply to G Taylor, 09-01-2002 00:43:55  
A 300 hp G by just adding in more air to you fuel equation? I definatly have a new winter project. have you heard anything about a 70 lp mag giving you more bost?



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G Taylor

09-02-2002 01:50:44




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 Re: Re: Re: HOW MUCH HORSEPOWER FROM A JD-G 7.5 BLOCK? in reply to super G, 09-01-2002 17:01:48  
Until someone custom casts a high flowing head and manifolds for any G,70gas or 70 all-fuel engine. The mid to high rpm torque/cylinder filling isn't going to happen. Even 2000 cubic inches will make little more power as it's still restricted by breathing through the same ports. You can't make more than 14.7 psi pressure drop to have air pushed into the engine. The best to date is an extrude honed 70 all fuel head and extruded cold manifolds. The factory valves are intake 2-5/8" vs 2-1/4" and exhaust 2-7/16" vs 2.06". The LP and 20/30 series distributor's rotate at 1/2 crank speed instead of at crank rpm. The early engines were crank speed mags make a better spark the faster they turn. How can a crank speed dist light the incoming charge when it sparks eg:20 degrees before TDC on the exhaust stroke of the other cylinder? The intake valve doesen't even open until TDC or later on a two cylinder. Even a MSD ignition firing over 20 degrees isn't going to cause trouble.

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Jay

09-02-2002 14:49:28




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 Re: Re: Re: Re: HOW MUCH HORSEPOWER FROM A JD-G 7.5 BLOCK? in reply to G Taylor, 09-02-2002 01:50:44  
I can't tell you hp from this bolck but from what I have seen 130 hp isn't out of the question.But you better have a thick wallet the main case that the block bolts to has to be bored to acept the bigger sleeves their is 1 G that pulls in the club I belong to that has this block also has spark plug in head cylinder head this has a bigger manifold,valves compression reliefs are in block plug holes.I hear the block is 4,500. and head is 15-1800. P/S in 6500 lb class this G can pull in 5th gear on cut 14.9 38s and not run out of power

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JDGnut

09-01-2002 08:44:03




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 Re: Re: HOW MUCH HORSEPOWER FROM A JD-G 7.5 BLOCK? in reply to G Taylor, 09-01-2002 00:43:55  
They do.. its called a 70 All fuel head, with a duplex carb on a G block.. bolts right on.. (just expensive to find.)

Maybe GMAN will chime in here he has a similar set up using the 7.5 block.
JDGnut



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Scott Boehler

08-31-2002 20:03:34




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 Re: HOW MUCH HORSEPOWER FROM A JD-G 7.5 BLOCK? in reply to 2 cylinder, 08-31-2002 19:41:00  
Not near enough to run against the Div IV tractors that are out there.



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Dawn Juneyour

09-01-2002 19:52:08




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 Re: Re: HOW MUCH HORSEPOWER FROM A JD-G 7.5 BLOCK? in reply to Scott Boehler, 08-31-2002 20:03:34  
Your right about that, boy.



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