Putting together an experimental engine to sacrifice perhaps on the alter of searching for more performance. I will assembly short block Sat and see if it has any merit to continue further
don

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8 cylinders are for folks who cant make HP

Installed bearings and crank today and the 3.5 bore pistons.
Deck height is -.050" Since I will be using a OEM steel head gasket (.019" to .022") I could have cut the block an additional .020" and still had my -.050" safety margin with the gasket in place. I will probably do that if the test engine performs and I take it to the next level. If you use the felpro then a brave soul might sneak it to zero deck and you would still have a .043" safety zone.
This combo uses the stock 225 rods and crank and requires only a resize of the piston pin bore to use the stock Slant six pins. These particular pistons are dished however they also come flat. I found them in a friends shop while helping him assemble a short block. Said he only had six and who would want only six pistons from a V8. I thought they looked about right so I cautiously raised my hand and he gave them to me. A little measuring and some research and I realized they should be about perfect. .100" overbore and 008" from the deck to clean it and here we are.
don

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8 cylinders are for folks who cant make HP

I haven't noticed a "follow" feature on this forum, so I bookmarked your thread.

What pistons are these?

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Sex, drags, and rock & roll.
Dick, 225% crazy.
Hobby (cars, that is) Photos link

Buick /Rover 215 V8 2 bbl. I was assembling a short block for a neighbour who is building a 215 V8 MGB and realized they were awful close to what a slant needed. I took them on a hunch when he offered them and was pleasantly surprised to find they were a good fit for a slant six project.
They are readily available new and can also be had in Flat top (4 bbl engines) and even forged. However remembering my Mom taught me "A bird in the hand beats two in the bush every time!" I took these 6 good used ones to make a experimental or what we call in my shop a "Dixie cup motor" (potential throw away) to explore the concept. If it proves out then I will do a serious one. So far on this one I am in about $100 out of pocket since motor was free from a Mopar guy cleaning out his garage (he gave me three /6s) Pistons were a gift. Wearables to install them were relatiely cheap being mostly someone elses unused stock they feared they would be stuck with forever. Machine work was courtesy of an old friend.
Other then a new oil pump and timing chain/gear set I have the rest (Cams , big valve head head, intakes carbs headers etc )in spares from my dragster engine development.
don

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8 cylinders are for folks who cant make HP

Interesting find on the pistons, Don. I take it the compression height was close enough to the slant pistons as to be negligible?

Roger

My brother has a 61 of this engine for a year now. we just haven't had time to take it apart. They had a turbo version in the Olds Jetfire. I may wait to finish my S6, and see how this palys out.

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AGAINST THE GRAIN IS MY WAY

Yes Roger, I saw by looking at them they looked close so I didn't second guess but accepted them and brought them home. When I looked up the specs I could see they should work. I did the pin bores with a high quality adjustable hand reamer to about .003" under and then finished them on my friends Sunnen pin hone for a drop through fit. The pin size is about .030" smaller in the Buick Rover piston but there is still enough material to be reliable.
In my dragster I use 194 Chevy 6 cyl pistons but they are now impossible to find and are around .156" over the slant six bore so you need a good casting to use them. These are a good alternative and I discovered are available because of the Rover connection world wide. At .100" over with .090" more compression distance I feel it is a good way to go. We shall see.
The 61 engine pistons should be great!
don
If I was younger and still had some ambition I would buy a few new sets and retool the pin holes then sell them. Getting someone to do that will be the biggest obstacle. You need someone with an open mind and some experimental experience. If I lived in or near California I know Tim McMaster who is an expert in Y block Fords would be up for the job. In Florida probably Dan Dvorak in Waldo. Some of the old salt flat guys and early stock car guys would be good at it to. I fear the last generation only know why it wont work. Hopefully I am wrong on that. The 194 piston also required enlarging the pin bores although not as much.
don

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8 cylinders are for folks who cant make HP

I am not far from Dan. I spoke to him about some slant stuff, twice, several years apart. He was not interested in doing what I wanted, only what he wanted. Didn't want to listen to me at all. His way was the right way. I use a Machine shop in Ocala, Fl. (Power House) that does what I ask, and has reasonable prices.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Sorry to hear that. We both used to write for the same mag. Last I heard from him his health was crap. Opinionated comes with the DD initials I sometimes think. I can be that way myself about BB Mopars which was my specialty.
Anyway thanks for the Power House tip. A machine shop that will do what you want how you want it is a very valuable asset.
don

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8 cylinders are for folks who cant make HP

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Well, now! If memory serves me, most stock slants have a TDC that's .100+" down in the hole anyway. Just a little cleanup cut on the block, with maybe a shave to the head, and it sounds as if one might end up with a rather stout engine using (mostly) stock parts.
I will be watching this as it progresses.
Good luck, Don.

Roger

Well you are right at .100+ down the hole.
NHRA minimums were -.140" and -.141" depending on the year. Production would always be more (worse) then that! So bringing it up to -.050" gives a good increase even with the shallow dished piston. Add to that the extra swept volume from the .100" overbore and I suspect it is quite decent.
don

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8 cylinders are for folks who cant make HP

Most 225s I have measured are right around 0.180" in the hole from the factory. The later (80s) motors get closer to the factory spec of 0.141", but still over.

Lou

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Home of Slant6-powered fun machines since 1988

Today I sorted through my cam pile and picked out my choice for this motor. I lubed it and slid it home. I installed a new chain set. While I have used 340 chains and gears on these engines I have leaned lately to installing the stock style set ups. I prefer the iron gear. This one is a Cloyes and these thing are not cheap anymore.( Unfortunately I still am.) I Lok-tighted the cam bolt just in case as I have done for many years. I hate surprises!
don
Re cam
lift is over .500" and duration is split (shorter on intake) Lobe split or angle is 108. I get mine cams made to my specs so it wont appear in anyone's catalog. I installed it straight up as I have no reference point for this particular engine. So any result is a data point and I will work from there.
don

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8 cylinders are for folks who cant make HP

Engine is coming together. Got my new oil pump, installed cyl head . Awaiting fresh lifters. Cyl head is one I ran successfully on my rail for a few years and has reworked 305 chev valves installed with new 343 SBI valve guides. It has been treated to porting and bowl work (but nothing like the current head on my rail.) Still it did a fine job for several years and I am sure it will again. This job is almost falling together on its own. I like that. It is usually a good sign.
don

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8 cylinders are for folks who cant make HP

Sounds interesting. I saw two Buick Rover 3.9 V8s in the Pick N Pull, those motors have a 3.70 cylinder bore. Maybe the 3.50 pistons can be used. I think the standard bore pistons would be easy to find.