Did the Machine shop hose me on my Nailhead?

Originally Posted by BinderRod
That would also depend on the color of the CH

My understanding was that the standard measurement was that of the RCH (red). The BCH (black) is more common and is a bit thicker. I typically use the BLCH(blonde) as that is what is available here, the BLCH tends to be not as thick as the RCH. Sound right?

 

Plastigage it first. You just might "hose" yourself with the .002's

 

On a street deal I like to stay on the low side of clearances. Don't get me wrong, I mean the low side not tight! Why start out with worn out clearances to begin with! Mic's don't lie when used properly. Plastigage has been used forever and is fine to use. I'd take the crank back and let them mic it right there in front of me and let them explain their reasoning. JMO. Lippy

 

As far as taking it back, I would chalk it up to a learning experience. Anybody that I feel has less knowledge on a thechnical subject than I do, I write them off. I don't even want to remember I knew them. Things like motor tolerances, you shouldn't be the one that has to be educating the guy doing the machine work!!!

Did I say before that .004 is outside the tolerance expected on a main bearing?

 

The BLCH may not be as thick, but the actual BL will probably be 'thicker' than the R, hence all the BL jokes.

 

It gets so much more complicated real fast. When useing plastigage on rods for instance,you must have both rods on the appropriate journal. The reason for this is if you just put one on,the rod will **** to one side when torqueing. Thus the plastigage will smash more than it normally would giving a false reading. If you must use it put a feeler gauge beside the rods to take up all side clearance so it will stay straight when torqeing.
Too much clearance is also very bad as the amount of oil that goes thru the bearings and out the sides,wash the cylinder walls and overload the rings.It leads to possible oil consumption and less pressure and less volume for the rest of the engine.
Just take it back ,nicely explain your concerns and my guess is they will gladly help you get it straight.

 

COOL...I agree with PLASTIGAUGE, you realy can't get a mechinal gauge streight enough to measure crankshaft bearings. and i believe the measurements have to be spot on. yes 1 can open the cylinder bore a few thousands, for piston rings, especialy race engines. but you must have all crankshaft bearings spot on...POP.

 

I called Effingham regrind today to check on having the crank ground should I decide to go that way and they told me that the rod clearance should be no problem at .0027" and the mains can be .0036" and they said they wouldn't grind for a variance of .0005" beyond that on the mains? So now I am even more confused! they said they have done a number of Nailhead cranks. I am still trying to locate the .0001 and .0002 bearings. Brought home some plasigauge tonight and will check the main bores in the block also?

 

The rod clearance should be .002 on the high side and the mains should be .0025-.003...and I feel .003 is loose. There is no reason to build a hemmorage into the engine with loose clearances.

FYI your rod journals should be 2.2490 to 2.250 and the main journals should be 2.498 to 2.499.
The respective housing bores are:
Rods: 2.3740 to 2.3745
Mains: 2.687 to 2.688

You must be careful with undersize mains. If the main saddles are not in line, and believe me after 40+ years cast iron settles, you could easily have a rotation problem and scrub the mains. Each main could show adequate clearance but when all the caps are torqued down a bind can appear.

Have the rod and main housing bores been measured? I have no beef against Plastigage and in all honesty I do have the correct tools to measure everything so my point of view may be biased. A dial bore gauge and micrometer is far more accurate than Plastigage, of that there is no doubt.

Did you say You have a dial bore gage and a micrometer? If so you can accurately measure your clearances and put all conjecture to rest.

If you have a crank at or towards the low dimension and the housing bore at or towards the high there will be a lot of clearance... and a significant loss of oil pressure.

Another FYI, My 1965 Federal Mogul catalogue shows the rod bearings (P/N 2100AP) available in 1-2-10 on up to .060 and the main bearings (P/N 4217M) available in the same sizes up to .030.

If it was my nail head I would keep the RPM under 5,000, the rod clearance .0015-.0018, the mains .0022-.0025.

 

Well, STOP worrying until you do

 

I don't get the phobia with generous bearing clearance. The only reason manufacturers call for such tight numbers is to make sure everything stays super quiet downstairs. If I'm building a stock, driver type of engine, I keep everything within the manufacturers tolerances. If I'm building something that is going to get hammered on and spun to the sweet side of 6 grand with any frequency, I'll always add .001 to both the rods and mains. This type of engine gets a high volume oil pump anyway so any pressure loss is negated. When I build a fuel engine, I pull out all the stops. .0035 on the rods, .005 on the mains and .060 side clearance on the rods. Being the cheap ******* that I am, I will scotchbrite the rod bearings if they've got a little fuzz on them, and toss 'em back in. After a dozen runs or so, they're probably well over .004.
As for excess oil washing the cylinder walls, I don't buy that. The skirt will only allow so much oil to see the rings, and even with tight clearances, there's usually better than a quart wrapped around the reciprocating ***embly at any given time Stock rods even incorporate a "pisser" hole whose job is to squirt oil at the cylinder wall of the opposing piston.
Set the clearances any way you want, but I know from experience, a loose motor is a happy motor.

 

Pisser holes are to lubricate the wrist pins, cool the inside of the piston,and put lube on the camshaft ,not to lube the cyl. walls.

 

I stand corrected

 

Bingo. Good way to say it. Bearing clearance can be fudged a tad but side clearance on the rods will really get rid of oil pressure fast. I agree .002 is max on the rods for brng clearance. A street deal does not need a bunch of clearance. Especially with todays oils. I say .0015 to .002 is about right on the rods. .003 to .0035 is ok on the mains. I still say call the guys who did the work and politely ask them to verify clearances. We run .0045 on the rods and .004 on the mains on a 354 hemi with alum rods and 0ver 100lbs of oil pressure with 70wt oil on nitro. .004 on the street? I don't think so. Lippy

 

Well, like many things I think you really need a side-by-side comparison which will be hard top do since it would appear that the Brazilians have taken most of the supply. Another reason to go with "traditional".

As for the real discussion on measuring bearings, I find this very educational. A lot of knowledge here.

 

.000 to .002? Where did you find a spec like that? Are you measuring straight up and down, vertical with the cap? On the parting line you usually have more clearance. The bearing is crushed in the bore and tends to spread the cap making the parting line bigger.

With a 3" main I would run .003 for clearance and not even think twice. Be very carefull with the .001 or .002 under bearings. The journals don't wear flat and straight. Most of the time you get tight on the sides. Everyone is right about the plastigage. Make sure you install the bearings and leave them dry. If you have oil you will get a false reading.
Jeff

 

Using the shim clearance gauges I already mentioned eliminates the problems you mentioned.

 

Look here http://www.teambuick.com/reference/nailhead_engine_specs.php

 

I cleaned and checked all the caps and block, and ***embled everything with Plastigauge using the teqhneque most suggested above and as close as I can tell with the Plastigauge I have .003 to a max of .004 in some isolated locations. The problem now is everyone seems to have a differing opinion on what is acceptable??? As far as taking it back to the shop, after taking over two months for him to get it done the first time with him jumping me in front of jobs that had been in there since September I don't think so! I learned my lesson if you walk in a machine shop and there is a huge pile of blocks right inside the door and they tell you it will be done in a couple of weeks RUN! So here we go again am I good to build this with these clearances or do I need to drop another $375 in a grind and another set of bearings?

 

I'm a believer in measuring things before I'd go with Plastigage readings. Do you have someone that can measure up the crank, all journals, 4 places each to check for taper? It pays to have friends in machine shops. If you were local, I'd say, "bring everything on over".

I'd map the crank out first. Then have the rods checked with the bearings installed & the caps torqued. A Sunnen type gage or precision dial bore gage should get you within a repeatable .0001-.0002 range.

Then you have to have specs in front of you that you can trust. I use old Motors manuals myself, they have everything you need. From there, you can order up a set of .001 or .002 bearings. Someone else posted a source for you. For a borderline fit condition, err on the side of a little more clearance as opposed to less.

I really can't see grinding your crank .010 under since it seems to have been already polished and is in good condition.

Bob

 

Yes I do have the ability having worked as a machinist and even in a engine shop in my early years and I do have the tools. I have mapped the first two journals and crank and that is what started this thread! I am seeing the same thing with the Plastigauge I saw with my bore gauge and mic's. The problem is finding a consistant real world spec for the 401/425 Nailhead? Seems there are differing opinions.

 

Sometimes too much information can be a bad thing. You'll have to have to definitely know what you have there, have you tried the Buick forums? I know there is one for Nailheads.

I always fall back on what has helped me in the past, either by schooling or life experiences. I've often cracked open my 35 year old basic engine text books to gain a grasp on basics, such as clearances, fits.

I think you'll make the right choice shortly, just sort out the best advice and go with what's written in print to back it up. It was written down for a reason.

Bob

 

That's the good thing about Plastigage....you don't need specs. If this is your part-time Hot Rod, I'd run it just as-is. If it were a daily driver that gets a lot of miles, I'd be tempted to get it a little tighter, so it'll go the distance. With a part-time driven Hot Rod, it'll be YEARS before the clearance becomes excessive. But, if you can get .001 under bearings easily, do it. I wouldn't go .010

 

This is from an old Chilton's Manual

 

If it has too much clearance there is no way the journals are strait across, wear does not happen evenly, have the crank ground and be done with it. Get the line bore checked too!

Just a note; if you have the crank ground make sure your shop will put a radius in the journals. There is nothing wrong with an undersized crank even a .030 but if the fillit is not radiused you are asking for a crack. I think Buicks are rolled on the mains so it wont be a problem but the throws need it.

 

Still working on this one I called the machine shop and he asked that I measure the crank main bosses in the block with the caps torqued with no bearings to see if the caps are stretched. Does anyone have the spec for the main bosses in the block?

 

The respective housing bores are:

Rods: 2.3740 to 2.3745

Mains: 2.687 to 2.688

 

OK here is where I ended up, I torqued the main caps with no bearings and measured. 1 -3 were on the large end of the spec and 4 and 5 were right on. I then measured the crank 1 - 3 were on the small end of the spec and again 4 and 5 were good. when I figure the clearance 4 and 5 are .0025 and 1 thru 3 run .003 to .0035. Which to my estimation figures out given the measurments and stack up. I talked with the machine shop and since all of the Rods and rod mains are perfect and everything is within spec I am going to find a set of .001 bearings. Thanks for all the feedback and help!

 

See? I knew you'd come up with a solution. Lots of things come into play, the main bores, straightness of the crank, lots of tolerance build up that you may never think of. I think you'll be ok with the .001 under bearings, let us know how it runs.

Bob