engine balance

Lawrie

Lawrie

Well-known member
I have an engine at the machine shop for balancing,it has never been apart before so no parts are mixed up.
I,m fitting new Egge pistons .
The Egge pistons are real close for weight at no more than 1.1 grams difference.
the rods are a little different ,with one 4.5 grams lighter than the rest on the small end,and another about 5 grams heavier on the rod end.
The shop wants to put a weight inside one of the wrist pins to get the weight up.
I,m VERY wary of this, any thoughts.
The rod end can be lightened by thinning the strengthening web on the cap,I,m OK with that.
How would 4.5 grams make a difference if I left the small end light.
Any thoughts
Lawrie
 
i balance a lot of engines, trust you guy it may sound funny but it will work if you are racing it that will be a big help or you can find a wirst pin that matches the weight let him do his thing
 
If there is going to be any difference the small end is the best place. It is very difficult to trim 4+ grams from the small end of other 7 rods so I won't suggest that. If this is a street engine you will never know about the 4 grams at the small end. Just put the heaviest pin and piston with that rod and drive on.
 
Lawrie said:
I have an engine at the machine shop for balancing,it has never been apart before so no parts are mixed up.
I,m fitting new Egge pistons .
The Egge pistons are real close for weight at no more than 1.1 grams difference.
the rods are a little different ,with one 4.5 grams lighter than the rest on the small end,and another about 5 grams heavier on the rod end.
The shop wants to put a weight inside one of the wrist pins to get the weight up.
I,m VERY wary of this, any thoughts.
The rod end can be lightened by thinning the strengthening web on the cap,I,m OK with that.
How would 4.5 grams make a difference if I left the small end light.
Any thoughts
Lawrie
Click to expand...


Hi Laurie, don't even bother "chasing" that amount, it will be a non-issue.

The running unit will not know the difference?

(Add) If it does bother you or the machinist that much, I would simply drill the center ends of the pins inside the lock area.

Thanks, Gary in N.Y.

P.S. The rods "look" flimsy and they are fairly lightweight as is, but they are reasonably strong considering their design. I wouldn't remove any of the strengthening ribs on the caps, not worth the risk. Those ribs help keep the "shape" of the large ends at higher RPM's.
 
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Thanks for the input guys,I,m off over to the machinist this morning with these replies,
Lawrie
 
For a stock engine I don't bother to balance them, especially if the only thing I change is the pistons. Race motors and strokers a different story.
 
Thanks Ron, This engine is a real find,it was a wartime generator and was like new inside,I have bored it to 3-3.16 and fitted new bearings,just thought as fitting new pistons that were a bit heavier than the cast iron ones I took out it would need a balance.
I will let you know how it runs
Lawrie
 
mate get the flywheel front pully and the clutch cover balanced at same time so that then is thew entire rotating assembly of another not ihad some balancing do by a reliable shop!!!!!!!!!! they took of the strenghing ridges on 6 of the caps i went balistic when i seen that be carefull mate
 
Trev ,I,ve just been down to the shop,I told them in no uncertain terms NOT to take any from the little end and NOT to take from the ribs,THEY know .
Hows things, wife just back from 2 weeks in waikanei.
Lawrie
 
Lawrie, l was told or read somewhere that the wartime generator set engines had a special camshaft fitted to get the best performance at the fixed constant speed that the generator ran at. They would not run too well in a vehicle without a cam change. Might pay you to check on that cam. Regards, Kevin.
 
Kevin, thanks for that,I was not using the cam in the engine ,BUT was going to keep it and the followers to use in another engine as they have no wear at all.
How will I find out about the cam,other than mapping it out.
Lawrie
 
Lawrie, there will be a part number on the cam at the gear end. What is the number? I can't really see Ford putting a different grind cam in for running at a single governed speed. maybe a variation on ign. timing or even valve timing, (by way of a "clocked " gear) but I doubt the need.
 
A 10 gram increase in the weight of 1 rod cost me 5 mph in top end speed on my model A ---nothing else was changed, the head, dist, manifold and carb were not touched ---only the pan was removed and the rod was put in from the bottom ---the spec on the A ford rod blueprint gives + - 1 gram for each end and total weight ---and the boxed sets of V8 rods I have found seem to carry this weight matching ---the boxed set of 21A rods I got at Hershey last year all were within 1/2 gram end for end and total.

For a wartime generator set that probably turned no more than 1800 rpm balance doesn't mean as much as making enough of them.
 
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