Building the Ultimate Short-Stroke BOPR Engine

[MGBV8]

Curtis posted this on another thread.  I thought it should have its own.

My Buick 215 shortblock has been perfectly reliable since I built it over 25 years and ~60,000 miles ago. Occasional track days. Plenty of barnstorming on mountain roads. Long road trips. I don't think I'll ever wear out the bottom end. My original build wasn't anything special. Nothing about it was balanced or blueprinted. Mundane components. (0.030" over Silvolite low compression pistons, stock timing set and valvetrain, etc.). And my only complaint is that its always dripped oil on the floor. I love this engine's light weight, and I'm determined (through other projects) to get my MGBs weight under 2000 pounds.

So, I want to build the very, very best short-stroke BOPR short block and valvetrain possible. I'll swap my Rover 4.0 heads and custom EFI / custom electronic ignition onto it. Honestly, I don't care very much about horsepower or torque numbers. Throttle response, smoothness, reliability, and durability are much higher priorities. I drive my old Buick 215 right up to 6000 rpm more often than sensible. It goes there and back smoothly and without complaint. The new engine should be bulletproof even further across the tach.

What would the ultimate short stroke BOPR short-block look like? And what valvetrain would complement it?

[MGBV8]

Jim Nichols added this:

I would start with a 3.9 block with top hat liners. 6" Chevy rods with 305 Chevy pistons. A cam like Carl has (Crower 50232)would be great in a 3.9. You could put your heads on with larger valves, Chevy Z28 springs and ported. Everything balanced and aluminum flywheel.

[pcmenten]

You might want to check out using the beehive springs found on Oldsmobile 215 engines. The shape of the spring reduces harmonics and the smaller retainer helps reduce floating the valves. Also, higher RPMs militates for a lighter valvetrain; lighter lifters and pushrods.

Yesterday I read someone's observations about the quality of machining done on engines during the changes in Rover's fate as a company. They were pointing out that quality of manufacturing became an issue during the production of the 3.9 and 4.2 engines. I have personally seen another example of this variation of machining quality relating to the health of the company while I was working on Ford Y-block engines. Late 50's Y-block engines had issues.

I would tend to want to use an old 215 because if its cast-in cylinder sleeves. That might help reliability and that design might improve heat transfer from the liner to the block.

De-stroking a 300 with a 4.0 crank is another approach. I'd guess you can use the Rover heads but the intake would need to be adapted.

[mgb260]

Better beehive springs for a high lift cam are at Alex's Parts. Chevy Vortec and retainers. Compared to Z28 springs same 100lbs valve closed 250lb at .500 compared to 300lb for Z28.

http://www.alexsparts.com/beehive-valve-springs-sbc-vortec-ls-series-stock-to-mild/

[MGBV8]

De-stroking a 300 with a 4.0 crank is another approach. I'd guess you can use the Rover heads but the intake would need to be adapted.

Lots of info on de-stroking the 300 at the link below.


http://www.v8buick.com/showthread.php?316649-300-build-for-MGB-engine-swap

[MGBV8]

First order of business is forget  "Ultimate".  That implies expensive exotic parts; cranks, main bearing girdles, dry sumps. etc.  Things get out of hand in a hurry.

Jim N. suggested using a late intermediate 3.9 that can be drilled for the cross bolted mains.  That would be a good way to go.  I have been leaning towards the 4.6, though.

I told Curtis at a V8 Meet, that if we want more streetable power, the old 3 Cs (Compression, Cam, Carb) is not the route.  We will forgo the forced induction for now,  We need a few more cubes.  A few more is all one can get within the limitations of a Rover block with a bigger bore.  That means more stroke.  I have resisted that for a long time.  Since I love the short stroke 215 as much as Curtis, my thinking is a wee bit of more stroke would be okay.  The Rover 4.2 has a stroke of about 3.03".  That is still very much a short stroke.

So.......say we use he Rover 4.6 (tophat liners, of course) with the improved oil pump drive & the crank trigger.  The crank can be offset ground to de-stroke it to somewhere near the 4.2, grinding it to utilize the NASCAR Honda rods mated to Chevy 305 ICON forged pistons.  We get a stout short block 3.736"x3.03" that is now about a 4.35L (265ci) V8. Then we ring up Art & relieve him of one of his roller cam blanks.    I would also try my best to do a Jim Stuart & use the serpentine belt setup.

Heads could be ported Buick 300 with larger valves or spring for the TA heads.

Might be more economical to just go with a LS4, like Scott did.  

[danmas]

Might be more economical to just go with a LS4,

Or a (choke, gag) Ford 289 - 4" bore, 2.87" stroke, just a few pounds more than the stock engine, and even smaller externally than the BOPR.

To hold down the heartburn, you could mill off the name "Ford" from the valve covers and stick on an MG badge.

OK, I'll go back to my room now.

[MGBV8]

Well, I do like the sound of 4.00"X2.87" even if it is an iron block.  That Ford may be smaller, but we all know it does not fit the MGB engine bay as well as the Buick/Olds/Rover.