300 Piston skirts

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sandboxer
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300 Piston skirts

Post #1 by sandboxer » Tue Sep 11, 2018 4:51 pm

Has anyone machined off the lower skirt of a stock 300 piston to lighten and prevent future breakage?
Thanks
S

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THE FRENCHTOWN FLYER
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Re: 300 Piston skirts

Post #2 by THE FRENCHTOWN FLYER » Tue Sep 11, 2018 5:18 pm

You may lighten it and you may reduce breakage, but the stock, non-hypereutectic pistons have a steel expansion strut cast into them and this is where the stress risers initiate cracking.
But its an interesting thought. Many modern engines have far smaller skirts and live just fine.
Try it and let us know how it works.
Presumably, in several years...
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

sandboxer
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Re: 300 Piston skirts

Post #3 by sandboxer » Tue Sep 11, 2018 11:44 pm

Thanks for the feedback. I’m definitely going to give it a go.
Cheers
S

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Re: 300 Piston skirts

Post #4 by pmuller9 » Tue Sep 11, 2018 11:47 pm

Which pistons are you going to modify?
Will they be new pistons?

sandboxer
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Re: 300 Piston skirts

Post #5 by sandboxer » Wed Sep 12, 2018 1:32 am

They are the stock pistons from an 87 block. There is little bore wear with the crosshatch still visible on the non thrust sides. I was going to put new rings and trim the skirts. I’m planning on teardropping the counterweights so I thought to trim some piston weight as well.

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Re: 300 Piston skirts

Post #6 by THE FRENCHTOWN FLYER » Wed Sep 12, 2018 9:20 am

You can lighten the pistons without taking weight off the crank - and vice-versa - just be sure all weights of the piston are the same, and the crank is rebalanced.
I'd feel better about your experiment if you were starting with new pistons as the existing ones may have already started to fatigue. Good luck.
FORD 300 INLINE SIX - THE BEST KEPT SECRET IN DRAG RACING

sandboxer
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Re: 300 Piston skirts

Post #7 by sandboxer » Wed Sep 12, 2018 10:46 am

I’m not sure about the fatigue either. I don’t know if the block ever overheated or ran dry on oil. There is quite a bit of brown varnish on the bearings and pistons...
If I go new, then I’ll probably just grab an upgrade. Gramps’s Sealed Power deal is very tempting. I was not wanting to bore out the block if I didn’t have to, so therein lies the quandary.

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Re: 300 Piston skirts

Post #8 by WorldChampGramp » Wed Sep 12, 2018 11:39 am

sandboxer wrote:I’m not sure about the fatigue either. I don’t know if the block ever overheated or ran dry on oil. There is quite a bit of brown varnish on the bearings and pistons...
If I go new, then I’ll probably just grab an upgrade. Gramps’s Sealed Power deal is very tempting. I was not wanting to bore out the block if I didn’t have to, so therein lies the quandary.


Sandboxer: Don't tell me you put the Stradivarius down to start on your pletheora of 300 builds?

Most of my SP sets are +.030 but do have a few Std bore setsthat are same specs and also include New rings. If interested PM me with your shipping address as can use either UPS, FedEx and or USPS Priority Mail for all our domestic orders BTW for now I will be accepting orders only for the pistons but SOON will be posting ordering information for our SVO Jr "ready to run" heads. Bruce

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Re: 300 Piston skirts

Post #9 by WorldChampGramp » Wed Sep 12, 2018 11:40 am

THE FRENCHTOWN FLYER wrote:You can lighten the pistons without taking weight off the crank - and vice-versa - just be sure all weights of the piston are the same, and the crank is rebalanced.
I'd feel better about your experiment if you were starting with new pistons as the existing ones may have already started to fatigue. Good luck.


FTF: In my humble opinion there is no need to rebalance the crank. Being an "inherently balanced” engine bob weights are never used on the crank journals for inlines. Sandboxer will be just fine only making sure his entire piston lightening efforts result in same total gram wt throughout the entire set of (6)
Gramps

sandboxer
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Re: 300 Piston skirts

Post #10 by sandboxer » Wed Sep 12, 2018 12:50 pm

Thanks Gentlemen
I think some new pistons and rings are in order.
I plan to lighten the crank by mounting the block upside down in the Bridgeport and spinning the crank under the cutterhead to get a hopefully consistent cut...
I think I’ll take my “finished” work to a friend with a balancer, though, and see how it looks on paper.

Gramps: hot rods in the am, fiddles in the pm:)
Cheers

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Re: 300 Piston skirts

Post #11 by Lunatic Fringe » Wed Sep 12, 2018 2:34 pm

If I remember correctly, most crank throws are elliptical,not round. Won't machine well. Way before stroker kits were commonly available, I had to reduce the counterweights on a 460 crank. Ended up being easier and quicker to use a hand grinder to do it all. My 2 cents.

sandboxer
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Re: 300 Piston skirts

Post #12 by sandboxer » Thu Sep 13, 2018 12:09 am

Thanks LF
I’ll let you know how I make out.

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Re: 300 Piston skirts

Post #13 by arse_sidewards » Thu Sep 13, 2018 8:09 am

Lunatic Fringe wrote:If I remember correctly, most crank throws are elliptical,not round. Won't machine well. Way before stroker kits were commonly available, I had to reduce the counterweights on a 460 crank. Ended up being easier and quicker to use a hand grinder to do it all. My 2 cents.


Why not? Just turn it in the lathe. The might start out elliptical but they'll be round (relative to the crank center-line) when you're done.
1994 F150 4x4 8ft, engine is basically stock.

66" leafs, extended radius arms, lockers in both ends, nothing special.

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