Muckman

iTrader: (2)

I’m assembling my motor and trying to get the bearing clearances down and need a little advice. Block is a GSR Bensen 84mm sleeved with a balanced LS crank. Using CP pistons and Pauter rods.

I ordered a set of standard thickness ACL main and rod bearings. After plastigauging all the mains and rods this is what I got:

<u>Mains</u>
1.) between .0020 and .0015"
2.) .0020"
3.) .0020"
4.) .0015"
5.) .0015"

Now #3 is supposed to be looser than the others according to the shop manual. My goal is to for mains #1,2,4,5 to be .0015 and main #3 to be .0020. How does that sound? Or should I make them all the same?

Now obviously I need to fix at least mains 1 and 2 with some thicker bearings. This brings me to some bearing questions:

1.) Ive heard the standard thickness ACL bearings correspond to the "green" Honda bearing thickness. Is this true? I am basing all my other measurements off the "green" thickness. I don’t have a micrometer.

2.) In regards to main #2. Id need to use a bearing that is .0005" thicker than green. Honda does not make a bearing that thick. Honda Blue is the thickest at 0.0793”- 0.0791” which should give me a clearance of .0016 - .0017". I wont be able to get it down to .0015". Is this ok? What do I do?

<u>Rods</u>
1-4 are .0015"

Ive heard a few engine builders like to use .0017" on the rods, a little looser clearance for more oil. Do you think I should bother getting thinner Honda bearings to get .0002" more clearance? It seems petty to me, but this is going to be a 400+hp engine so what do you think?

RABHonda

your 1st and 5th main bearing are tighter than the rest, so you dont leak oil, plus they have added pull from the timing belt; flywheel. 2nd and 4th should be tighter than the rest to absorb any harmonics. 3rd main should be looser than 2/4, but tighter than 1/5.

run your rods with the extra clearance...its better to be loose than tight if youre not sure.

Muckman

iTrader: (2)

The rods are well within spec at .0015". The question is, is .0002" going to be worth buying 4 new set of rod bearings for? two ten thousandths of an inch.

PHiZ

Good thread.
-PHiZ

Muckman

iTrader: (2)

Earl do you wish to respond? What main and rod clearances do you use when blue printing an engine?

AVATAR

1) I'm pretty sure you are correct when saying that ACLs standard bearing is based off the Honda green.

2) Good ? about the being off just a tad. I woulnt think it would make that big a difference, but then again I dont professionally build engines I wonder if you could have that rod journal machined down and then rebalanced if you that concerned about it (which I would be also).

Let us know what you plan on doing. I've got a build similiar to yours and I will be building it myself as well so I wanna know the outcome

Muckman

iTrader: (2)

Heh machine the crank? I guess that could work too but you could also run a thinner Honda bearing and save yourself a ton of time and money. Thats really the goal and benefit of different sized bearings.

I talked with a few engine builders - Earl, Rocket, and Jeff Evans. Decided that the goal should be to end up with clearnances on the loose end of the Honda factory tolerances. But dont have to be super **** about it, realastically anything inside the tolerance is ok.

Straight from the Helms.
<u>GSR Main Clearances</u>
Mains 1,2,4,5: .0009 - .0017"
Main 3: .0012 - .0019"

<u>GSR Rod Clearances</u>
.0008 - .0015"

So I am going to leave my ACL rod bearings alone as they are in spec. And mains 4 and 5 are good too. I ordered a slightly thicker bearing than Green to bring the clearance of #3 down slightly. And ordered even thicker Honda bearings to get the clearances of 1 and 2 alot tighter.

AVATAR

LOL not the whole crank . . . just that one journal that you can't get into your "target clearance", then have it rebalanced. Jeez

Muckman

iTrader: (2)

I know what you meant but why would go through all that trouble when you could just run a thinner bearing and accomplish the exact same thing?

There are two ways to obtain the goal of more clearance, your way is much more involved thats all Im trying to say.

Muckman

iTrader: (2)

Update: Did some math using Earls bearing chart - https://honda-tech.com/zerothread?id=715490. Figure out what I needed to get the clearances I wanted. Then ordered 1 pair of Blue, Black and Brown Honda main bearings.

Main #1 got the black, #2 got the blue, and #3 got the brown. Plastigauged everything again and every main came out to be damn close to .015". Its not exactly on the "loose end" but its within spec and consistent so Im not going to sweat it. Now onto the rings.

Sliced Beard

this has always been my favored clearances and has never failed for me

**mains**
1-.0015"
2-.0015"
3-.0017"
4-.0015"
5-.0015"

**connecting rods**
1-4=.0017"

i like to run things a bit on the "loose" side of the spectrum, it allows the engine to be more efficient at making power

PTR1

where you guys buy plastigauge at anyway?

Muckman

iTrader: (2)

I agree with those specs. And I would have liked to get my clearances looser too but without the proper tools its very hard to accurately measure the clearance. My plastigauge only had .0015 and .0020. Nothing in between But realistically as long as your inside the specs your good to go. Im not gonna sweat it.

VIMPORT.COM - I had a hard time finding Plastigauges locally. I called every Autozone, Advanced Auto and Pepboys in town. Only found 2 stores that had them. All the others were like "huh plastic gauges? you mean like autometer?"

You can get them online from camp1320 or any local engine shop.