BritishV8 Forum

Okay, it was a bit more than a few years ago. This was an exchange from the Buick Rover V8 email list over 8 years ago:


Keith: Hey all, Currently taking a 3.9 0.020 over. I'm interested in opinions and experiences of high compression pistons for this -- at least higher compression than the wimpy Range Rover pistons!


Carl: I have spent waaay tooo many hours looking thru piston catalogs trying to find an alternative for those truck slugs. I believe I actually hit on something.

Since the compression height seems to be the problem, I found a piston that would fit in the 3.9 bore, then started working on stroke & rod lengths to get the piston up closer to the top of the deck.

My solution: 305 Chevy piston with a 6" Chevy rod. This combo will put the piston .001" above the deck. Check out the specs on the KB145 piston
(hypereutectic, not forged) and try out the calculators at United Machineswebsite:

[kb-silvolite.com]

By shaving the top of the piston (or not), like Glenn mentioned, I should be able to have anywhere from 10 to 11.5:1.

BTW, I'm using the newer, small cc heads. You may need to shave your's a bit or use a thinner head gasket.

I ran this by Dan LaGrou. He said he hasn't tried this combo, but thought it would work.


Keith: Fantastic lead! I'll run this by my machinist...

Are any mods needed for the 6" Chevy rod? I'm sure those are pretty common.

When was the change to the smaller combustion chambers made? I'm mostly familiar with the 3.5 and '89-'90 3.9 engines... and far more familiar with Austin "A" and "B" series engines.


Carl: I am currently running a '63 215, but I have 2 '89 3.9L blocks (& pieces parts).

A stock small block Chevy rod is a 5.7" The 6.0" is an aftermarket rod commonly used in performance circles. Some brands and types (aluminum or forged) are quite pricey. We aren't building an all out racing engine (at least, I'm not or I would find a forged piston, too). Therefore, we can use the budget rods, like Eagle & Scat. I'm leaning toward the Scat because the small journal is only available in the more expensive H-beam. Which, I failed to mention. Older small block Chevys (283, 327) used a small journal crank (2.0"), others used a large journal (later 327, 350, 400). We need the small journal as it matches the Buick/Rover. The Chevy rod is .100" thicker than the Buick/Rover so .050" must be machined off each side of the big end.

The heads on the new 4.0 & 4.6 are factory built to compensate for the thicker composite head gasket. I played around with the calculators and to get the compression number you want, you will have to use the thin steel head gasket or skim the head a bit. Or use KB143 & be right at 11:1. Be sure to check valve to piston & rod to block clearances.

Another important number for your machinist: Deck Height is 8.960" on a stock, never decked block (per Dan La Grou).

Good luck!

Carl

I suppose you could destroke a 300 as well as any other engine. You'd need main bearing spacers to fit the 215/3.5 crank, but the bores are integral to the block so there are no liner issues. A 3.80" bore is usually pretty reasonable.

Art, you don't have to believe me. You spend time on the Buick forum. and you've read what those boys have done with the SBB. You also know that there isn't a whit of difference between a 300 block and a 350 that would affect how much power the block can handle, and that with boost and nitrous you can still exceed what the equipment will bear. So quit busting my chops on this OK? ;-)

Jim

Destroke a 300? Hmm.

The 4.0L Rover has larger mains than the 215/3.5/3.9. May be the same as the 300. Be fun to play around with the numbers.

Yep, same mains. Could be interesting!

http://www.gomog.com/allmorgan/40difference.htm

I guess I wandered off a bit, but these subjects are conducive to that.  What I have exactly, is a 1963 Olds Jetfire block. Sleeves are grooved o.d. and cast in place. I have had it 30 yrs. I am putting 3/32 sleeves in the block. Had them 20 yrs. Using 6" forged H beam small-journal sbc rods and TRW forged std. 305 Chevy pistons. Landrover heads with lower head bolt added. Would like to use all 6 head bolts, but heads would have to be modified. Front cover from Buick 3800 series II. Northstar dis ignition. Landrover  4.0 intake manifold and fuel injection system modified for dual throttlebodies. Twin KKK turbos with water-alcohol injection. And the roller cam that I bought, as soon as I can decide how it should be ground for this set-up. I will have to make the girdle myself, Art, on a Bridgeport, since that is what I have. Then, a hacked-up GM LS ecm to control the mess.
   All of this goes into a 2700lb. Fiero.

As for the sleeves and the leaks, the only reason for a leak is if there is no head gasket that the firering will bear on the top of the sleeve. A lot of the large diesel engines have wet sleeves and no top seal at all except the head gasket. I am an automotive machinist, and sleeve engines everday, some with large pieces of the cylinder wall missing from catastrophic damage, and never have leaks. I have not done late model Rover blocks, but they are just engines. I will call Lee, at English-Swedish Spares near Atlanta, (good source for parts)  and get my hands on one of those blocks. 4.0 ? What years?

The Rover 4.0 is regarded as the one with the most sleeve issues. It was built from 1995 to 2003.

Jim B., not wishing to bust anyones chops, but if you feel slighted, I apollogize. I felt to be asking pertinent questions of a presented build, that seems to be elusive. Back in 82', I put a 300" crank,(std mains), in a 215 Buick. I wanted the stronger crank,(crank pin overlap). This resulted in making billet 7075 T6 main caps, with studs. Re-sleeved block with 305" sbc forged pistons, big valve 64' sbb heads. A lot of work, with a reliable result,(likely around 300 hp) ?  Cheers, roverman.

It's all good Art. You know I have not built that engine but the drag racers on BuickV8 have gotten up to as much as a thousand horsepower out of their SBB 350s (700 on Sean's turbo'd stock motor that wasn't even torn down for freshening up beforehand I believe) and it is the same block as the 300 except for the bore, the deck height, and the lifter spacing. But it's worth noting that Perry S. has now hit over 500 with his 3.9 Rover as well. My efforts are small potatoes by comparison. I'm perfectly happy with what I got out of the 215 which I guestimated at around 300 hp. That's my target for the 340 also, and since I don't know a dyno guy I'll just compare it to how the 215 ran and if it does that good or better I'll be happy. I think an honest 300 hp at the rear wheels is more than plenty for a street driven MGB.

Larry, you might need wheelie bars on that Fiero. ;-)

Jim

Underestimate & overdeliver, Jim?  

I think 300 RWHP is plenty, as well. Until Calvin motors by on the long straightaway.

Actually, I am a very careful, conservative driver. The car has a 4 spd., but I am changing to automatic. If I were looking for big inches and big torque, and cast iron, I would build a 427 sbc with a turbo and nitrous. (YUK!) If I had my druthers, I druther have a Lamborghini. (but I don't) What I do have is a pile of oddball somewhat unique parts, some of which I have had for years, that I am go
ing to build a small, lightweight, powerful, reliable engine with. And besides, it will give me an incentive to set up my chassis dyno.

Carl! Surely you wouldn't accuse me of sand bagging would you?!!? ;-)

Jim

Let's see, you estimated your old Olds 215/blower combo at 300hp (pretty close, I believe). You wrote on your 340 thread that this combo will have 60% more cubic inches & a 25% increase in supercharger. Mike Moor's Buick 300 has been dynoed at 308 RWHP. You have 40 more C.I. & a blower. Yeah, you're sandbaggin' just a smidge.  

Larry don't forget to chamfer side of rod by counterweight for filet clearance, just debur other side.

Thanks, Jim.
     I am looking for a piece of 7075 alum. plate to make a girdle for the bottom end, but 6061 is all I have found so far. Prices on ebay not too bad. Have a good day.

Check onlinemetals.com. Did you find out anything about the 4.0 sleeve issue?

Thermal expansion differential, is the biggest problem, with the RV8. Aluminum thermal expands at approx .2.5X that of iron. Sleeves don't initially leak when their cold/warm, but when HOT. The aluminum expands away from the iron sleeve at operating temperature. Any pinholes or cracks, in the aluminum bore, will automatically leak at the top of a non-flanged sleeve.This makes it logical to use Loctite 620, or equivalent, to bond the sleeve to the block. Think about it, when you bore away the strength of the aluminum bore, and use a non-flanged liner, what is left to hold the deck rigid enough, to make a reliable seal ?  Woody had plenty of work getting his 4.02" bores to seal.  Cheers, roverman.

That would be true if the liners and the aluminum were at the same temperature. There is in actuality a great deal of temperature diferential. On the iron side, you have combustion temperatures of 1000 to 1300F. On the aluminum side, you have a constant flow of 200F coolant. With .002 interference, I'll have to let you calculate the relative expansion, since it is a constant variable from cold side to hot, and my calculus is a bit rusty. Expansion rates are academic if the sleeves are properly installed. The only seal required is the bottom ledge and the fire ring at the top.

re: 4.0 sleeve issue
Jim, I talked to Lee at English-Swedish Spares about the problem, and he had only encountered it once. He is getting me a 4.0 block to play with. It may be a while before I get up there to pick it up.

Thanks,Larry. Real curious as to what you'll find.

As for the original question, the 300 Buick and 225 Buick rods can be used with the 305 SBC pistons with some minor machine work to the wristpin end. Downside, they are still cast "armasteel". But they are cheap.

Larry, An even better choice is the 75-76 231 V6 capscrew rod. Same design as 75-80 350 but, 300 length.

Thanks, Jim.  Did not know about that one. Was that all 75-76 231, or just turbo versions?

Larry, All 75-76 Odd Fire 231. No turbo's back then.

Yeah, I guess turbos were a couple of years later.

Those rods were also early 77. Mid 77 went to even fire. The odd fire rods are available here. 6 pack and 2 singles.

http://www.standardcrankshaft.com/connectingrodcatalog.html?sid=4271