Ol'Ron's book

[HCO41]

Got "Nostalgia" from Bill a few days ago and have gone through it cover to cover. EXCELLENT! Chances are I will have a competent builder do an engine for me but this book revives a lot of old memories and provides guidance when deciding how I want to go.
Lawson's book is great too, in that it demonstrates advantages and disadvantages to mods. on these engines. You can save a lot of money by following some tried and true applications performed by these two gentlemen.
One question, what's a 1CM engine, and why does Ron recommend it?

[Lawson Cox]

That'ld be John Lawson. lol

[51 MERC-CT]

Originally Posted by HCO41

One question, what's a 1CM engine, and why does Ron recommend it?

Probably because it's the Mercury version of the 8BA and has a 4" stroke crankshaft.

[Ol' Ron]

Yes, the 1CM/8CM have everything you need for a good street engine. If the rods, crank, valves oil pump and block are re-usable. the onluthing you'd have to buy are pistons, rings and brasrings. Have the block bake cleaned and magged, bore to 3 5/16. Cleasn and inspect the oil pump, knurl the guides. have the cam re ground reassemble with all the original nuts and bolts. Find a set of EAB (52/53) heads mill for .050" head clearance and you'll have one fine engine. No Need to re balance if the original crank assy is used. It's called the "Practical street engine"

[Ross F-1]

Did 1CM / 8CM have hardened seats or did they go to the rotator valves too?

[Ross6860]

Sponsored Links (Register now to hide all advertisements)

Ditto

It's Ron's fault I stayed up until midnight I also just got his book, along with two others recommended by folks here.

Great stuff.

I see the problems are always the same, decades apart:

Too much carburetor
Too much cam
Too much advance


Thanks for a great read...and all the real-world info.

[rotorwrench]

The early 8CM of 49 & early 50 had hard seats but the late 50 on have hard seats in the exhausts only. Most of the later 53 engines likely have no hard seats. The gas available was a lot better so they didn't use them.

[Walt Dupont--Me.]

Ron is right, on the perfect affordable street engine. BUT, if your not going to spend the money on balancing DON'T buy the 3 ring pistons. They are lighter than the 4 ring and really through out the crank shaft. If you use the 4 ring pistons there close to same weight as the stock pistons and you probably can get by without balancing a street engine. With the 3 ring piston you have to drill about 5-6 big holes in the big counter weights to lighten the crank. I have built a lot them in last 10 years and have most of them balanced and found that out about the 3 ring pistons. Walt

[Ol' Ron]

Unfortunately I disagree with Walt here. I always use the Egge 3 ring piston and have never balanced the crank assy. Had this discussion with an engine builder of NASCAR engines and he said that balancing is a black art and different builders use differen formulas. The piston weight is not critical, especially for engines that run less than 5000 rpms.. This is one reason it cost so much to build these engines, this isn't a piano. Yes I did balance the Bville engine. Is balancing better, yes. is it necessary, No.

[jr9162]

Every reciprocating aircraft engine is blueprinted and balanced during overhaul. That's because there aren't any parking lots 500 feet above the ground... Balancing, if done correctly, helps neutralize vibrations and premature engine failure.

[BILL WZOREK]

Ok What would a typical ( if Typical is possable ) cost to balance a Merc crank with 3 ring pistons?
If not Typical what can I expect to spend < HI $$ / LO $$ > on having this done???

Next is there any one in western Massachusetts that can do this???

[JWL]

I prefer to balance the engine. HOWEVER I, and many others, have built hundreds of engines through the early years with a piston change and no rebalancing. I do not have any memory of this being problematic even when done with a drag race engine.

[Walt Dupont--Me.]

I use EGGE pistons in 90 present of my engines. I build 8-10 flatheads every winter. I have 90% of them balanced. I use both 3 and 4 ring pistons. Every time I use a set of 3 ring pistons my balancer has to drill some big holes in the crank. A lot more holes than with the 4 ring piston. I don't know how that would effect the balance if we didn't balance the engine. I do know a friend had a 39 Merc original, he had the engine built at another shop, They didn't relies the engine had steel sleeves until they tried to bore it so they had the cyl honed .030 with a CK-!0 automatic cyl hone. The original pistons were cast iron and the replacement pistons were heavy aluminum. When they started the engine it had a vibration, They called me to see if I would come and look at it. It run good but had a vibration, I told them at that time to pull the flywheel and the rebuilt pressure plate and have the pressure plate balanced, I have see a lot of pressure plates way out of balance but this one wasn't bad so they stripped the engine and had it all balanced. The problem was the heavy pistons. It usually cost about $200.00 to have the pistons, rods, crank, flywheel, and pressure plate balanced. The stock flywheel is never our but a very little. The EGGE pistons are very close. the rods usually have to have the big end caressed, It's the weight of the piston, rings, and rod bearing, rods, the effect the bob weights. Walt

[Ol' Ron]

THe cost is 250 around here. At one time I could get a street balance for 100 bucks. They don't balance the rods or pistons just use them for the bob weights. Now when using a Merc stroker crank and 21A rods, you must balance it.

[Walt Dupont--Me.]

Originally Posted by Ol' Ron

THe cost is 250 around here. At one time I could get a street balance for 100 bucks. They don't balance the rods or pistons just use them for the bob weights. Now when using a Merc stroker crank and 21A rods, you must balance it.

Yea your right Ron. When you mix up all those parts, like most of my engine are they must be balanced. If you get a virgin engine and do a basic rebuild maybe bore .030 or so and grind the crank 10-20 there should be no need to balance. Walt

[rotorwrench]

Originally Posted by jr9162

Every reciprocating aircraft engine is blueprinted and balanced during overhaul. That's because there aren't any parking lots 500 feet above the ground... Balancing, if done correctly, helps neutralize vibrations and premature engine failure.

Our shop overhauls a fair amount of aircraft engines and we have never had to re-balance any of them. The cranks are balanced when new and the main & rod journals are never ground beyond .010" undersize so there is never any real reason to re-balance. We send the crankshafts out to another repair station to have them inspected, polished, or reground and for renitriding purposes and the con rods are generally checked only for dimensions & bend before magnaflux and bushing replacement. We rarely ever use a crank that has been ground past .006" under so that we don't have to worry about crankshaft breakage. We have only used one set of oversized bore con rods due to the cost of the oversized bearings. Aircraft engines are way overbuilt compared to any of the older engines of the automotive variety. The pistons are manufactured to a much tighter tolerance than automotive engines and you have to do an STC if you want to change to a different compression spec so there is never much of a change to pistons.

Some repair stations do re-balance but I doubt if they have to make much of a mass change during the process. Turbines are balanced every time you tear one down but that's a whole different technology.

[Conrad Rossi]

All,

What would be the price range to build a street a engine as you described compared to a basic rebuild? Thank you.

[dude]

My theory is at this point you have spent a few bucks to get where you're at. Balancing is kinda like good insurance.

[4tford]

up here in my part of Canada (Saskatchewan) a full rotating assembly balance runs about $450 Less if using Ross pistons as they are usually very close.

[Walt Dupont--Me.]

I was at my balancer this morning to pick up a flywheel he chopped 10# off and balanced the wheel and bolted on the Wayne Ind pressure plate, Wayne Indina Clutch -- pressure plate are always pretty close. I talked to him about the difference in weight between the 3 ring and the 4 ring piston and mentioned this thread on the barn this morning. He said the 3 ring is a lot lighter and will cause a vibration if not balanced. Walt