Engine and Transmission Tech

Has anyone here (or heard of anyone having) experimented with using billet aluminum Deck Height spacers? It would be interesting to see how much rod length and crank throw can be obtained (understanding the camshaft location and lower block limitations). I am researching what the longstroke, low rpm (<5200) limits of the cross bolted RV* block may be.



Edited 2 time(s). Last edit at 11/11/2024 12:00PM by Moderator.

Not necessary to increase the deck height. What you can do is move the pin position up in the piston, possibly even use a thinner ring package. Gives a good bit of room for an increased stroke length.

Jim

How much stroke are you looking for?

I've heard that a 3.85" stroke crankshaft from a Buick 340 or 350 can be made to fit a Buick 215 (or Rover) block. I don't know the details on if or how much the OD had to be turned down but you may find the block deck height is not the limitation. Rather, it may be something like camshaft to connecting rod bolt clearance.

I supplied a Ford 351C XE block to Jon Kaase that he used in one of his winning Engine Masters Competition engines. The rules specified pump gas and the engine was scored on average power from 2500 to 6500 RPM. He added a very thick "head gasket" that was effectively a deck spacer but met the rules. He sleeved the bock to a smaller (than standard) bore diameter and made up the loss in displacement with an increase in stroke (using an expensive Sonny Bryant custom crankshaft). The reason he wanted a small bore diameter was to reduce the distance the flame front has to travel across the combustion chamber which allowed him to run the highest static compression ratio. Since, the canted valve Cleveland heads unshrouds themselves (valve head moves away from the cylinder wall as the valve opens), the shrouding loss due to the small bore size was negligible.

BTW, I discussed rod ratio with Jon and he said his rule of thumb is that the rod length needs to be at least 2" longer than the stroke. In practice, the piston pin height is often a limitation as you need space to fit the ring pack. Stroker math is simple:

rod length + crank stroke/2 + piston pin height = deck height

If you rearrange the equation to solve for piston pin height and assume a 3.85" stroke and 5.85" long connecting rods:

piston pin height = deck height - (rod length + crank stroke/2)
= 8.96 - (5.85 + 3.85/2)
= 1.185 inches

That pin height compares favorably with the small block Ford 3.4" stroke engines:

piston pin height = deck height - (rod length + crank stroke/2)
= 8.20 - (5.40 + 3.40/2)
= 1.1 inches

A 1-3/16" pin height is enough to keep you out of the ring package. You might have to use a smaller wrist pin (Buick used a quite large one) or you might need thinner rings. But maybe not. Do your own math.

The 215 uses the same timing set as the 340/350 so cam interference can be dealt with. Depends on rod configuration and duration specs. Might have to knock the shoulder off one or two rods. Not really a big deal. When I've had to trim one shoulder I did all 8, had to bevel the rod bolt ends on one side also. Same process as fitting long rods to the 300 and 340. The short rods should help here and it may not even be an issue. Weren't the 215 rods forged? Might give them a little polish and away you go. Don't know about block clearance in the 215, it will be close, and the mains will have to be turned down 0.700" which will move the oil holes over a bit so that will need corrected. With a .020" overbore this puts you at 5L, a very significant displacement increase.

With the custom pistons needed to do this you can go with a slipper skirt and between that and a thinwall smaller diameter wrist pin drop 200-300 grams or more off the piston weight. That will make the engine much more responsive to the throttle and should be more than enough to overcome what Carl would refer to as the long stroke limitations. Add some stiffer valve springs and you can extend the redline up towards 6500 or a bit more with hydraulic lifters. It might also be possible to use the early SBC rods, I don't think there is much difference in the lengths, and you might even find some racing take-offs on ebay of a good brand like Carrillo for around a hundred a set. Worth looking for. That gets you the smaller wrist pin size as well. It would make a very potent package, at a very reasonable cost especially with a set of late Rover 10 bolt heads. Add a good mid level cam and it'd make a heck of an engine for the B.

Doing the same thing with the 4.6 Rover block (3.7" bore) gets you to 5-1/2L.

Jim

Two other things. This will require a different flywheel. You can buy that from TA for about $400, (I don't recommend the alloy one at $500 for the street, too light with those internals.) or acquire a stock one (a bit hard to find and limited to 6K rpm) OR if you use the later Buick 350 crank it has enough weight to do an internal balance without adding Mallory metal. Then you can use a Chevy zero balance flywheel by simply elongating one flywheel bolt hole. A pretty slick trick but not really a savings unless you find a deal on a SBC flywheel, maybe a used one.

2nd, have the rear main seal journal ground down until the knurling just disappears. This will let you use the 2 piece viton rear seal. Same treatment at the front, although a speedi-sleeve can be used there if desired.

And of course I would be remiss if I did not point out that this combination requires the very expensive BOPR bellhousing which I understand now costs upwards of $600 when you can find it and if you instead choose to use the iron block 300 you dispense with much of the above as well as cutting that cost to around a hundred. Worth thinking about. With that the aluminum flywheel might be good, don't know, haven't tried that combination. (thinking stock unmodified engine here)

J



Edited 6 time(s). Last edit at 11/15/2024 05:23PM by BlownMGB-V8.

Alfred, this build is to power an LBC ? 2,400 lbs or less ? How can you justify all the $'s/labor of using a 340/350 Buick crank ?
" Might" be easier to use a Cadillac 4.9L. crank @ 3.625: stroke.
Good Luck, Art.