Rebore or re-ring?

Anonymous · Post by **Anonymous** » Fri Sep 10, 04 8:59 pm

I've stripped my 360 and need to decide what to do next. Bores measure at .022" @ 2" down the bore which is slightly more than it should be. The engine came with free rings but, i'm tempted to rebore and put in Keith Black (107) pistons for approx 9.5 compression. Opinions please! Easy rebuild or spend the cash and hassle with rebore and run-in?

TrevD · Post by **TrevD** » Fri Sep 10, 04 11:11 pm

Miles , i had ICE automotive do my 440 and were verry helpfull , saving me loads of cash , thay are verry dedicated to the customer , give them a call and ask the question . if you throw it back together but need to do it again in a years time it is false economy .

Anonymous · Post by **Anonymous** » Sat Sep 11, 04 9:18 am

Trev, thanks for that, i havent had machine work (rebore/regrind) done for some years and was a bit suprised at the potential cost! Where do I find ICE automotive?

Pete · Post by **Pete** » Sat Sep 11, 04 9:34 am

Change the Pistons and you have to consider a re-balance; the cost starts to mount up....

You could always buy the motor out of my Sox Barracuda; that would perk you car up a bit

Anonymous · Post by **Anonymous** » Sat Sep 11, 04 3:45 pm

Pete, I suspect that your engine is worth more than my entire car (in fact, all of my cars!). I was going to balance the motor by using a B&M externally balanced flexplate.

Blue · Post by **Blue** » Sat Sep 11, 04 4:02 pm

Don't have an up to date no. for ICE, they advertise in Custom car so you should find it there. For balancing I can highly recommend Basset down balancing in Swindon , I called them the other day and they quoted me ?145+Vat for a full balance on a 440, they will do a same day service if they are not too busy, can't beat that!

Anonymous · Post by **Anonymous** » Sat Sep 11, 04 5:45 pm

thanks Blue. I could use a quick tutorial on external balancing for my 360. Am I wrong in suggesting that a externally balanced flexplate will do the job? At $75 dollars a go it seems reasonable.

Anonymous · Post by **Anonymous** » Sat Sep 11, 04 5:48 pm

Sorry Blue! I just checked an earlier post where you answered that question. However, does it still do the same (achieve balance ) if i have changed pistons & rods, I'm assuming that it would?

Pete · Post by **Pete** » Sat Sep 11, 04 8:18 pm

Nope.

340's and such like are internally balanced; 360's are externally balanced; but you still have to have the reciprocating mass balanced to cut out vibrations.

Changing the Pistons changes the weight and thus alters the relationship between the pistons and Crank assembly.

When I had my 440 built in th States with lighter Pistons and Rods, they had to take 140gms off each Journal. Worked though....

Or you could take a chance

Blue · Post by **Blue** » Sun Sep 12, 04 9:48 am

OK Miles, I'll try and explain whats happening here, but I think I'll have to start at the beginning. There are 2 types of balance, internal and external. an externally balanced engine is only in balance as long as the correct damper and flywheel or torque converter is in place because these are weighted to allow the engine to run smoothly with an unbalanced crank. An internally balanced engine has no need for external weights because the crank throws have been balanced to equal the weight of the rod and piston assembly. The problems arise when you want to change the torque convertor on an externally balanced engine, it has weights on it which the majority of convertors don't, so what you do is fit the correct B&M flexplate which will have this weight built in so that the engine remains in balance and you can fit any convertor you like. That's all that it does, instead of weight on the convertor you have the weight on the flexplate. If you were useing a weighted B&M flexplate with a stock 360 convertor then you would have to remove the weights from the convertor. Hope that explains that bit! Right, piston weight is a separate issue, when we are talking about balance, what we haven't mentioned are tolerances. Any mass produced item has to be made to a pretty wide tolerance to keep the cost down, lets say for instance a 360 piston is supposed to weigh 1lb and the engineers have decided that 50 grams light or heavy is acceptable, thats a tolerance of + 0r -50 grams, your new pistons might fall into that range and be fine or they might not, it is a risk. When I mentioned taking your components to be balanced, what happens is Basset down work to very fine, almost perfect tolerances, (taking out the manufacturers errors if you like) and a much smoother running engine results. So the bottom line is unless you get the engine balanced then it will be out, how much out and weather or not it will cause any problems is anyones guess, all I can tell you is that on stock type rebuilds most people don't bother about it. Sorry if that got a bit long winded but I couldn't think of an easier way to explain it!

Anonymous · Post by **Anonymous** » Sun Sep 12, 04 12:09 pm

Blue, Pete, that almost answers it! I was going to use the existing torque convertor with my 904 box + the BM balanced flex plate. Am I also wrong in thinking I can use my existing convertor (details unknown but, it works!). All of a sudden, 'dropping in' a 360 aint looking so easy now!
I,m trying to see where the hidden costs of this conversion are. e.g engine mounts (got them), correct manifolds(not yet), flexplate. Maybe i should go with Daves idea of using total seal rings on the existing pistons as my budget projections are staring to stretch :|

Anonymous · Post by **Anonymous** » Sun Sep 12, 04 12:18 pm

Blue, i just did it again

! I can use my convertor and BM flexplate ok but, if changing rods, pistons i need reciprocating mass balanced. Got it. Do appreciate the expertise chaps