How tight is tight?
 

Hey Guys,
Just finished putting my B engine back together with the following new parts installed and adjusted to spec. New pistons, rings, rods and pins and ground crank. Valve springs also new.
It was getting really tight especially with the rods down to 001.5. My main concern is that I have little if any side to side clearance with the new rods at the journals. I don't want to put the thing back in the car until I at least get it to turn over with the starter (which I can't).

Thanks for any advice,
Pete

Re: How tight is tight?
 

There must be side clearance on rods. Now I have built many engines, but never an "A" engine. So I'm asking a general question. Can the rods be put in wrong? Meaning, most engines have a fillet on the crank where a chamfer rides. Is there anything like that in these engines? Could you have them turned around? Or is it a matter of just custom fitting every piece and you just need to plish the sides down enough for clearance? As a general rule, when putting together an engine, after every piston/rod assembly is installed, the engine should be spun around to check for problems. Did you do this? If so, was there one rod assembly that tightened everything up?

Re: How tight is tight?
 

Re: How tight is tight?
 

I've always gone by the following:

It should not take more then 35 foot pounds torque to turn the engine over at the crank bolt with everything assembled. If the head is on, perform this test with out the spark plugs in.

As long as all of the clearances are in spec.

If it is tighter then that, one by one loosen the rod bolts and perform the test. If you find that the assembly loosens up then that rod was the problem. If not, then keep going until it loosens up. If it is still tight then move to the main caps and do the same thing.

.

Re: How tight is tight?
 

I too have used the foil method with success. I have always been able to turn the engine over with a wrench on the pulley nut(testing at each assembly step,

Re: How tight is tight?
 

With the old oil splash systems, prior to aluminum foil & pastigage, millions upon millions of Babbitt bearings were adjusted on huge & small vintage industrial & steam boat steam engines & vintage internal combustion engines all over the World as follows:

1. Wipe off only the "excess" oil in Babbitt bearings & on crankshaft.
2. Adjust bearing clearance one at a time by carefully removing & installing shims from both sides.
3. Bearings are correctly adjusted when:

a) There is absolutely no up & down motion "felt"; &,
b) The crankshaft turns freely with extremely little or no binding; &,
c) There is easy movement from side to side between the crankshaft & the bearing with no binding when moved by hand.
4. Also, check each bearing by slowly rotating the crankshaft just in case the crank shaft is egg shaped -- if egg shaped, have crankshaft re-ground.
5. Provide final tightening on all bearings according to torque specs & check again to insure easy rotation, no up & down movement, but easy side movement by hand.

Out of curiosity, the last Model A engine I put together was the first one that I tried testing bearing clearance with "fresh" non-hardened Plastigage from an auto parts store -- both the mains & the connecting rods were "right-on".

I then threw away the Plastigae & will never try testing with same again.

Others may have different ideas & different methods, but through varied experience with vintage oil splashing system engines with Babbitt bearings, the above works.

WD-40 can remove Plastigage which is difficult to remove from Babbitt bearings.

Re: How tight is tight?
 

Thanks Guys,
That lack of clearance had been bothering me and the more I thought about it, the more I got to thinking I had metal against metal on those journals. I've used the tin foil method before but never had a new set of rods to play with. Les' book says .010 to .008 on the side clearance which makes good sense. I already have the pan back off to fix the situation. Hopefully I can take some babbitt off with a file so I won't have to pull everything apart.
Pete

Re: How tight is tight?
 

A Model B engine has a 2 inch crank, 1.500 thousandths is to tight for the mains. they should be 2.000 min., or 2.000-50 Max.

Plasti-Gauge works every time if the user knows how to use it correctly.

That is, Plasti-Gauge should always have oil on the cap, and the crank, to let the plastic strip spread out, with out drag interference, or it will always give you a false reading.

Plasti-Gauge was made for modern inserts, but they also should have oil.

On a Babbitt bearing, with out oil the Plasti-Gauge will embed it's self in the babbitt, like a small dent, and won't let the Plasti-Gauge spread out.

Never read the Babbitt bearing, but always read the shaft, the harder surface.

Your Rods are 1.873, and should be set to .001-80 Min., to .002-03.

Re: How tight is tight?
 

Thanks for the plastiguage tip. My read out on the crank looked exacially like the one in your pic. Any ideas about side clearance on the journals on the B since I think is where I'm ceased up? I think I can take some of the excess babbitt off with a file if I'm real careful.

Re: How tight is tight?
 

Your rod should be 1.617 wide on the Rod portion, below the web of the Rod.

Make sure you have your Rods are checked for Alignment, twist, Bend, and Off set, before you take any off, if any.

Never use a file to remove thrust Babbitt, use self stick No. 80, on a very flat surface. Then take the Rod and lay it flat, and go in circles

Re: How tight is tight?
 

Doesn't anyone use bluing anymore?
http://imageserver.grainger.com/is/i...productdetail$

Re: How tight is tight?
 

PeterJ, if journal clearance seems OK, then check to see if the rod is hanging up on the radius portion of the bearing and crank. Look for shiney spots on the bearing thrusts and radius that indicate tightness. Scrape the shiney (high) spots.
Also when tightening the rod, centralize the cap. Ted

Re: How tight is tight?
 

Thanks guys. Absolutely NO side clearance at the journals which I will start work on to get the recommended .008-.012. I'll probably use a sanding block rather than a file to sneak up on the correct measurements.

Pete

Re: How tight is tight?
 

Hi Pete,


What I did on my engine When it was on the engine stand was..I installed the rod so that it was backward's,,wrist pin hanging out the bottom of the engine..Then I adjusted the rod so it would "Fall" by it's own weight "with oil on the journel"


It's easier to do with the crank in a big vice,,,


Greg out West

Re: How tight is tight?
 

One Plastigage detail to remember:

"If" using Plastigage to check any of the bearings, do "not" try to rotate the crankshaft while the Plastigage strip is located in the bearing.

As per the mentioning of same in the very informative reply #8 above, unfortunately, it can get embedded in the Babbitt.

Re: How tight is tight?
 

I do like Greg, adjust the rods to the crank while the crank is on the bench or in a large vice. Then adjust the crank to the block and start the assembly. Make at least two full turns after each rod and piston is installed, to make sure it's fine.

Re: How tight is tight?
 

:pWhy?:confused:
Can't we just put the car in high gear and drag it around the block until the tight spots wear in?:confused::D:p

Re: How tight is tight?
 

.005" as an absolute minimum, as much as .020" for a race engine. If you have clearance when using a feeler gauge, check the radius area.

Re: How tight is tight?
 

Herm: What is self stick #80. I could not find anything on a google search except labels. Thanks

Re: How tight is tight?
 

80 grit self adhesive sandpaper