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Tractor Pulling Discussion Forum

more hp from an h?

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jasonp

07-12-2007 18:43:51




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working with an h for pulling and need more power.bore is 3.66 w/the piston down the bore .100, these are 706 diesel flat tops, 4.25 stroke,cam ground for 2200 rpm,kerosene head milled .250 and m carb.we are changing to an lp head and adding roller rockers 1.9 int. 1.7 ex.the stock valve size is 1.5 in. and 1.38 ex., i would like to increase this to a 1.575 int. and 1.45 ex.and tune up the ports a little. would like to mill the head,but i am concerned i will get to much compression?the tractor has a mag will this effect anything?also the head gaskets are .060 compressed i would like to go thinner to help the comp. i guess would have to get a copper gasket? are we on the right path here?any help w/ how much compression to run would be great, i personally love compression but my background is automotive and i need a little direction. thanks to all.

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42Farmall

07-14-2007 22:04:33




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 Re: more hp from an h? in reply to jasonp, 07-12-2007 18:43:51  
With the pistons that far down in the block, I would get all the compression possible. I run an copper head gasket .040 thick with 0 deck height. With a 6 inch stroke and a .100 milled gas head, it runs great at 240 lbs compression. Sonny ground my cam. Just make sure you run enough octane.



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ChadS

07-14-2007 08:35:41




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 Re: more hp from an h? in reply to jasonp, 07-12-2007 18:43:51  
Did somebody lengthen the rods? I thought a 706 IH 6 cyl gas/diesil pistons was 2.02 on the compression height. If thats so, and it has stock rods in it, they would be .480 below the deck with a stock rod, and 706 pistons. (not sure what a german diesil piston specs are) so I assumed its from the IH engine. Also, might be a 460 diesil piston,,, they had a .312 taller compression height VS the longer stroke 263 and up engines. I can see that being used and within the specs if the rods are stock. If the piston you have is a .875 diameter wrist pin, and has a stock rod, you have some options. Some machine work required, but need to know a little more before telling you something that wont work, but could,, So, pull the head off, pull the pistons out and do some measuring, and or part numbers on the pistons, and see if the rods are stock. If its a 460 piston, (im thinking it is) and it has a .875 pin, and the H rod is stock. You got options. Chad

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jasonp

07-14-2007 14:01:53




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 Re: more hp from an h? in reply to ChadS, 07-14-2007 08:35:41  
chads as for as i know the rods have not been modified other than the pin bushings.as said in another post the short block won't be coming apart.we are changing to an lp head, adding larger valves,minor porting and adding the murphy 1.9 int. 1.7 ex. rockers.i guess the real question i have is how much comp. should i put in it?should i mill the heads and use a thin head gasket to get as much comp. as i can or just run it at the 8.15 ratio?will to much comp. hurt the lugging power by creating detination problems?as for the short block i don't know any more, i am going off of what i was told about it.perhaps the block was milled alot to work with the pistons? the cam was reground by isky back when the tractor was built in the early 80's.also can you make any carb recommendations?it has an m carb and turns 2200 rpm.thanks to all

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ChadS

07-16-2007 08:58:32




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 Re: more hp from an h? in reply to jasonp, 07-14-2007 14:01:53  
Id put the Lp head on it, I wouldnt mill it yet, Id put it on there and do some research. Should pick up power from the cyl pressure increase for sure, but Id bet it would be in the 150-160 psi range peak. So you may not need much octane to operate it. With flattop pistons, a LP head will be about 200 psi at cranking speed on a H, With the pistons being as low as they are in your block, I think it will be less than 200 psi, but enough of a change to know you improved it. As for carb work, Im sure it will be rejetted larger, but how much is unknown till you fire it up and run a compression test. A #27 or a 29 venturi would be good. If the wrist pin bushings are not offset, you can offset them. ChadS

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dboll

07-13-2007 10:33:16




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 Re: more hp from an h? in reply to jasonp, 07-12-2007 18:43:51  
cc the head and figure out the comp. ratio, better than guessing, then get it to what you want for desired comp. I believe in Berry cams and more stroke wouldn't hurt. IH mags. were poor to start with. I run distributors.



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jasonp

07-13-2007 19:06:20




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 Re: more hp from an h? in reply to dboll, 07-13-2007 10:33:16  
ok guys here is the deal. the old heads,casting #361479-r1 that i have been told was milled .250 have a chamber size of 119cc. the lp head casting #364017r2 has 87cc chamber.i have not seen the pistons but was told they are a flat top w/no valve reliefs and .100 down the bore.so comp. based off these numbers and using the stock head gasket gives me a 6.59 comp on the old combination. the lp head and the same .060 head gasket come out to 8.15 comp. if i use a .030 gasket and cut the heads .040 it should be around 9.5 comp. now the question is how much comp. should i put in it?

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MEHA

07-13-2007 01:03:24




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 Re: more hp from an h? in reply to jasonp, 07-12-2007 18:43:51  
Jack up the radiator cap and drive a green one under it.



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buickanddeere

07-12-2007 20:49:14




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 Re: more hp from an h? in reply to jasonp, 07-12-2007 18:43:51  
Mill the block to get the pistons 20-30 thou above the deck. There is no quench effect unless the piston/head space is less than 40 thou cold.



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jasonp

07-13-2007 14:57:51




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 Re: more hp from an h? in reply to buickanddeere, 07-12-2007 20:49:14  
i agree this would be the best route, but the short block was rebuilt last winter and the guy does not want to pull it down.the tractor was actually built in the early 80's. now the man's son is pulling it some and wants a little more power out of it.



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TWL

07-12-2007 20:38:59




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 Re: more hp from an h? in reply to jasonp, 07-12-2007 18:43:51  
I have a frind that took off the mag and put on a distributer.Gained 8hp,dynoed before and after.



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The Dukester

07-13-2007 11:30:18




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 Re: more hp from an h? in reply to TWL, 07-12-2007 20:38:59  
Yep, switching to battery ignition (dist.) was one of the cheapest ways to up the H's hp back in the everyday use days...mainly because of the ability to advance the spark in a more timely manner, it helped "wake up" the engine quickly when power uas needed.



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