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Tractor Pulling Discussion Forum

Slug on piston

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Custom King

01-15-2007 15:06:04




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Any one ever put a slug on there piston to up com? How did you? and did it hold and work ?




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Strange Brew

01-15-2007 21:40:23




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 Re: Slug on piston in reply to Custom King, 01-15-2007 15:06:04  
i wouldn't do it with your kind of rpms, just my 2 cents! Good luck!



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Bob-Wyo

01-15-2007 19:32:23




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 Re: Slug on piston in reply to Custom King, 01-15-2007 15:06:04  
Custom King, running a 1"+ .350 plate on a D right now. makes it close 8 to 1 compression. Runs on 85 or 87 octane. Been thinking about pulling them out and going to 1 3/4" plate. Problems I've seen and heard is where some one is trying to hold it on with 1 grade 5 bolt, Mopar is on the right track, use 4 1/2" or 5/8 fine thread grade 8 allen head, and like he said locktire and double nut, I even threaded the piston top. If using a aluminum make sure the plate is at least .040 less that the piston dia. Also do a little concave in the center to create a little swirl during compression stroke. I have also done 1/4" and 1" plates, was kind a waste of time and money except the 1" was a little noticeable.
Bob

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smdv806

01-15-2007 19:12:37




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 Re: Slug on piston in reply to Custom King, 01-15-2007 15:06:04  
I have a B JD I would like to try something like that on. What is the max thickness I could go with a piece of aluminum bolted on to the piston on a head with stock thickness?



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jd b puller

01-15-2007 20:27:23




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 Re: Slug on piston in reply to smdv806, 01-15-2007 19:12:37  
CC your head, then figure out how much there is above the piston. Then determine what you want your theoretical (geometric) CR to be and size it accordingly. I wouldn't just grab a piece of plate and stick it on there to see what it does.



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rpllr

01-15-2007 19:03:33




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 Re: Slug on piston in reply to Custom King, 01-15-2007 15:06:04  
I bought a tractor that had that done to it. Someone bolted a piece of piston to the top of a flat top piston. compression was high and it wanted to detonate under load. finall got it dialed in and the chunk melted off and the piston shoved it through the head. Not a good idea on someone's part.



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Mopar-Harris

01-15-2007 16:03:38




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 Re: Slug on piston in reply to Custom King, 01-15-2007 15:06:04  
Back in the Early 80"s dad bolted a piece of 3/4 aluminum on top of an A JD piston. Worked great. In fact, I plan on doing it to another engine here in the near future.

How to...drill & tap the top of the piston. Use locktite on an allen bolt and then locktite a mechanical locknut on the bottom side of the piston.



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ChadS

01-16-2007 15:48:07




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 Re: Slug on piston in reply to Mopar-Harris, 01-15-2007 16:03:38  
Why not add some sort of alignment pin(s) to help the bolts hold the plate still? Would that help take some stress off the bolts holding it together? Chad



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Mopar-Harris

01-17-2007 06:08:48




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 Re: Slug on piston in reply to ChadS, 01-16-2007 15:48:07  
Sure dowel pins would be a great idea, that would take care of any twist that might occur.



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ChadS

01-17-2007 10:06:11




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 Re: Slug on piston in reply to Mopar-Harris, 01-17-2007 06:08:48  
Years back, a fellow had made slugs for his A JD,,, they woked really good, never came apart, but,, where the 2 pieces came together, it looked as if it started to burn the edges out, like it was trying to get inbetween the parts being held together. So, we had decided to Oring inbetween the piston and the slug, eliminated the problem. If I had to do it over, I would countersink the plate or slug to the exact area on the piston, providing there is enough material on the piston head to machine some down to fit. Pin it, bolt it, mark it with a B, and hope it holds. Chad

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PGpower

01-17-2007 10:27:48




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 Re: Slug on piston in reply to ChadS, 01-17-2007 10:06:11  
why go to all that trouble and expense..machining, dowel pins, etc. how much cheaper would all that be than just ordering new pistons, even if they were custom pistons??



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JDGnut

01-17-2007 13:23:42




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 Re: Slug on piston in reply to PGpower, 01-17-2007 10:27:48  
Your looking at about 750 for a set of custom pistons.. (and sometimes that does not include rings.) vs the pistons you have + the cost and time in the slug..

The other method is the make longer rods..

JDGnut



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ChadS

01-17-2007 13:52:07




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 Re: Slug on piston in reply to JDGnut, 01-17-2007 13:23:42  
Have you ever seen the rings that was used in the deere blocks? What they were was a cast ring that sets in the top of the bores, and fills up alot of the gap inbetween the head and the pistons. I would think that if someone really redesigned them so it can add compression, and help create an air flow thats bennificial, that may be a way to go about it too??? Chad



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jd b puller

01-15-2007 16:03:32




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 Re: Slug on piston in reply to Custom King, 01-15-2007 15:06:04  
Works great. Makes for Cheap HP and any monkey can do it. But you want to Bolt it, don't weld it. Don't ask me why I know this...



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Greg_Ky

01-15-2007 15:43:02




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 Re: Slug on piston in reply to Custom King, 01-15-2007 15:06:04  
Sounds like a recipe for a hand grenade to me.



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