Mopar 350 small block

[paolo_mangusta]

has anyone here had any experience of these?

http://www.speedomotive.com/mopar_318_t ... troker.htm

I'm thinking of ways to get round my broken-block-bought-on-ebay fiasco, and I was wondering if anyone has built one of these? The shipping makes it prohibitive, but I've got an article on how it's built in a Hot Rod book and the only bits I haven't got are the pistons? I know I'm not likely to find out what these are easily though

[Dave-R]

the only bits I haven't got are the pistons?

You have a stroker crank already? How come? Is the rod length the same as the stock rods you have?

[Dave-R]

Ah 6.123" is the stock small block length isn't it?

But what about the crank?

[Dave-R]

What about 390 inches?
http://www.hughesengines.com/crank_kits/390crankkit.asp

[Anonymous]

I think he's suggesting dropping a 360 crank in a 318 block to make an economical stroker and salvage something of what he's already spent. Seems like a plan to me... if it works... if it works without super duper expensive custom pistons...

[Dave-R]

What's the stroke on a 360 crank? Is the journal size the same?

I guess if the stock rod is too long to use with a 360 crank in a 318 block you would need to order custom pistons with the pin closer to the pistop top. Custom pistons are expensive but not impossibly so.

[DaveBishop]

REAL STEEL BUILT ONE OF THESE MOTORS A FEW YEARS BACK YOU HAVE TO HAVE THE 360 CRANK MAINS GROUND DOWN TO 318 SIZE AND HAVE THE PISTON TOPS GROUND. ONE OF THE BRITISH MAGS DONE A WRITE UP OF IT I THINK I STILL HAVE THE MAG SOMEWHERE. ALSO I THINK MANCINI DO SOME SPECIAL MAIN BEARINGS SO YOU DONT HAVE TO GRIND THE CRANK

[Dave-R]

That sounds simple enough then.

[paolo_mangusta]

sorry, had to go off and do some work

the build-up in the Hot Rod book uses standard 360 crank and rods, but some speed-pro 318 pistons with the top machined off them. I don't think they were anything fancy, but they only took 0.100 off the piston but it should logically be .250 (ish) higher, so the pin height must be different

The mains are ground down to 318 size and the whole lot has to be dynamically balanced because the 360 are external but the 318s internally balanced. Since my flywheel is from a 318 then I have to do some balancing anyway even if I build the 360

If Real Steel have done one in the past then maybe they'll be able to do it again

The cost is in comparison to sorting the very rusty 360 block that I've got and transferring all the innards from the broken block. Doing it this way doesn't rule out building a 360 in the future out of all the bits I've got left over, but would hopefully be a cheapish way of getting back on the road again. I think I'd only do it if I don't have to wait for bits from the States though.

If you find that magazine article Dave, that would be great

Cheers guys, I'll call Real Steel tomorrow...

[Anonymous]

don;t forget that 318 pistons sit a way down the hole as stock, so maybe thats why they only machined a bit off the top (ie to give a zero deck)

[paolo_mangusta]

Since the engine's in bits I'll have a look on Saturday to see how far down they sit - the article definitely says 318 pistons. They machined them to sit .020 inside the block and reckon that gives 8.8.1 CR. I reckon on 95 octane it should be ok to go a bit higher than that so maybe could go for zero deck height.

They used 360 heads, ported and polished. I've got 360 heads on the 318 already, but they're open chamber smog typre heads, so was going to skim them anyway, as it seems that if you put 360 heads on a 318 without skimming, then you get a rubbish CR. (stands to reason - start with a low-comp engine and increase the size of the combustion chamber and the cr goes down) It was pretty lifeless before, even though when I pulled it apart it was all in good nick.

I don't think all 360 cranks are shot-peened, but it would be better if it is - I'll try and find out what this would cost. they don't mention it in the article.

I'll still skim them a bit, I think, even with the larger swept volume, though that means more machining on the inlet manifold. The engine with the knackered block has got a crane cam in it as well, so I can put that in if I get stronger valve springs. It seems a lot of bother to end up with something that's not as good as a normal 360, but it should go faster on the cheap(ish) and will leave me with enough bits to build a 360 if I have the time and money to sort the rusty block out and if the '350' isn't fast enough. plus since I can't throw anything out that's got any life in it, it means I won't be tripping over a 318 short-block for the next twenty years. I'll be happy to see the back of the broken 360 block

I'll let you know what the verdict is from Real Steel

[Anonymous]

Pauolo,

http://www.nhra.com/tech_specs/engine/b ... HRY-76.rtf

These figures may help with your calculations
Courtesy of Dave from a previous thread

[Dave-R]

Word of warning about those NHRA specifications. I think they got them from the factory and what the factory was saying was not always what they were building....so don't trust those compression ratios stated.