Rover 4.6 V8 Triage

[BlownMGB-V8]

Well Dave, you could still use your coated headers and EFI intake (have to use spacers though, and might not fit under the hood then). On the plus side you could use a 350 crank in it for 5.6-5.7L displacement. That flywheel might work with some machining and re-balancing but I expect that'd be possible without much difficulty. You need to thin it out some anyway I expect. And I'm guessing you are going with the Rover 5 speed?

But I do get it, you're in love with the light weight aluminum 4.6. It's clouding your judgement right now. Just consider that for what you are talking about spending to make it work, you can adapt your parts to the 300 (or sell and buy different parts) and possibly stroke the 300. And it will easily outlast the 4.6L Rover. I'd go with one of the 4bbl throttle body EFI's though myself. Simpler, easier, and looks better in my opinion. That doesn't help with your Rover transmission though, does it. Hmmm... What do those sell for these days?

It is basically a math problem on the face of it but with other factors. I'd definitely do the full cost comparison though before taking irreversible action.

Jim

[RDMG]

Hi Jim,

Your argument is compelling.

I spent yesterday morning in the local pick-a-part, hoping to find another RV8 that might be sound, but the only safe bet was in a Discovery with 180,000 miles on it.  Full rebuild territory. For $500.  No thanks.  

If a 300 Buick falls into my lap, I may shift focus.  I'm ready to think a bit harder about the options.

I can't seem to find the "recipe" here for stroking the 300 block.  Is there a parts list or a discussion thread anywhere?  

I already have a decent Camaro V8 T5 and a set of aluminum 300 heads (need work).

[mgb260]

Dave, 300 Stroker info:

https://www.mgexp.com/phorum/read.php?40,2598435

[7sand8s]

From BritishV8:
http://www.britishv8.org/Articles/MonsterMotor.htm

[88v8]

Perhaps you could ship a Turner top-hatted block over? A consolidator wouldn't charge you too much.
Maybe ask Real Steel; they use a consolidator, just in the opposite direction.

http://www.realsteel.co.uk/

Ivor

[BlownMGB-V8]

Dave, by now a few 300 strokers have been done, and much depends on your expected redline. To be completely honest, in an MGB a 350cid Buick does not need to exceed the factory limits unless you aim to race it somewhere. You can get an easy 375+ ft/lbs of torque out of it with the OEM build, and that's enough for great gobs of silliness. OTOH, a set of NASCAR take out rods and forged pistons are a relatively affordable route to 7500+ rpm speeds and ridiculous power levels.

So far there is not any one established formula. However if economy is the goal then the 340/350 crank main journals can be lathe turned to .030" oversized before going to the grinder. (1/2" overall reduction. Bear in mind that is like at least 10 complete full crank grinding jobs if the grinder does it all.) and then the 300 rods can be reused with suitable pistons of your choice. (Making sure to check the fit of the oil slinger in the 300 block.) The key to the entire thing is the rod and piston combination. The 300 uses a relatively long rod, the piston has a significantly larger than typical pin height, which only works due to the tall deck, and then the thing that makes the stroker work is that pin height. You can easily decrease that to accommodate the longer stroke without getting into the ring package.

So, for a performance build, start with the rods and plan on specifying custom forged pistons so you can get everything the way you want it, such as CR and squish area. This method allows you to minimize weight in the reciprocating assembly for a truly free-revving engine, and there is a LOT of room for reduction. The wrist pins themselves are 200 grams and that can be reduced by half.

For the near-stock build, use the 300 rods and either one of the pistons used in prior builds, any one that you find you like better, or custom. Note, piston crowns can be cut to modify deck offset, CR and dish plus there are a lot of things that can be done with piston pins if you feel like getting into that.

Bear in mind here that the difference between cast pistons off the shelf and fully spec'd out custom forgings is in the range of about $300-400 which may sound like a lot but you get a lot for that and spread over the life of the engine it is peanuts. Still, if I was being dollar conscious I would look very closely at the pistons that Chris used. That's been the latest development, and to my mind one of the most sensible. (Disregard Chris' whining, he's just a bit too much of a perfectionist. ;-) ) However we are yet to find the perfect rod/piston combo. Bear in mind also that early SBC rods with the large end narrowed are a valid rod choice and are available in forged rather than cast. This enlarges the piston options as well. The largest limitation to piston choices in fact is the 3.8" bore size, but expanding the search to non-American engines may prove fruitful. It takes a little math to get the pin height for the selected rod/piston combo but not that much. Deck height, stroke,rod length and then pin diameter to make sure you aren't into the ring package. You can use up to a 6.3" long rod with no worries. In fact I think it would be possible to squeeze in the longer 340 rods if the ring package was very compact.

So while it may sound complex, what you actually have is a great deal of flexibility. About 1/2" of leeway on rod length and the same on pin height. If you can't find a rod and piston that suits under those conditions either you just aren't trying or you are being too picky. Well, not you personally of course. There may even be some motorcycle pistons that would work just fine.

But again, for simplicity follow Chris' build. It's the easy recipe. Have your block sonic checked for core offset before you start (you can get an idea of core shift by looking at the cylinder roots at the crank end of the cylinders. If there is a great deal of visible variance it isn't a good sign.) and try to stay over 3/32" on the thrust side if you can, try to stay within .050" on the overbore and do the oiling mods. Since you already have the 300 heads set up an automatic search for a 300/4bbl aluminum intake and ask around. Any old iron block 300 will do the trick.

I currently have a 300 block on the engine stand with a turned but not ground 340 crank sitting in it. It'll be a slow build but my next step is to find the best rod I can at the best price. This engine will likely get Venolia forged pistons similar to my 340.

Jim

[RDMG]

Many thanks Jim, Jim, Ivor, and Dennis,

I clearly have a lot of reading to do!  

The 300 is a really neat idea, but I'll admit the level of effort described in the mgexp thread is a bit overwhelming!

Some beautiful custom pieces in that car.  Particularly the motor mounts.

Dave

[BlownMGB-V8]

It can be done very much like a straight up Rover swap. Except no liners to deal with. Doesn't have to be a stroker, plenty of power as a 5L.

Jim

[MGBV8]

Mike Moor gets just over 300 RWHP with his stock stroke 300.  So, one does not have to go to the trouble of stroking the 300 for it to be a very good engine.