Rod bearings too tight

[HP2]

Going through my 360 for a refresh. Turned the crank down to .020/.020. Got it in the block, check the main clearances and they were all at .0020. Installed the pistons and rods, checked all these bearings and they are all coming in at .0015. I know specs tend to say .001-.003, but I've always thought looser being better for higher rpm use. Lacking a mic set, this is using plastigauge.

Now this isn't a dedicated race engine, its a street engine but it will see the occasional strip and track day effort. With the .0015 clearance, I could probably live with it and use a 5w-xx oil.  Would that be okay or would it be better to open these up a skosh?  I doubt I could find a .019 bearing so would it be be better to try to take .001 off the crank? If it goes too far, I see there are .021 bearings out there to close up the gap even more.

Thoughts? 

[RUNCHARGER]

I've used plastigauge for years but when I had my last Hemi crank turned, the plastigauge showed it tight as well. I discussed it with the guy that turned the crank as I miced the crank perfect. He said to check the bearings with a bore gauge so I bought a set of bore gauges (it's really easy to convince me to buy any kind of tool). Using the mic and bore gauge it measured perfect.
I would check it with a mic and bore gauge. Also if it is .0015 I wouldn't sweat it below 6000RPM.

[ek3]

i am not sure whats available for the 360 crank but as an example - if mine were loose  i bought a set of +001 bearings and used the tighter bearing only in the top half of the rod. i think you could do the same with a set with an extra .001" clearance and only use 1/2 of the bearing will give you an extra .005" of overall clearance which would put you about right.

[Flatdad]

Oh man, I might catch some flak for this one, but...

You can use Plastigauge on mains, but NOT rod journals. It will ALWAYS read tighter than the actual rod clearance.

[Chryco Psycho]

I would go with what you have take it easy during break in for 500 miles or so .

[HP2]

I've used plastigauge for years but when I had my last Hemi crank turned, the plastigauge showed it tight as well. I discussed it with the guy that turned the crank as I miced the crank perfect. He said to check the bearings with a bore gauge so I bought a set of bore gauges (it's really easy to convince me to buy any kind of tool). Using the mic and bore gauge it measured perfect.
I would check it with a mic and bore gauge. Also if it is .0015 I wouldn't sweat it below 6000RPM.

6000 is probably a safe rpm for this. In its previous life, I have turned it just shy of 7k, but I have stepped down the cam quite a bit, but I'd like to be more comfortable in case I zing it to 6500 on a missed shift.  To check it that close, I'd have to pick up a 2-3" mic and a bore set. I wouldn't want to go with Chicago branded units on this, but I suppose even a few hundred spent on decent mic is cheaper than a fragged engine. I might reach out to some friends and see if anyone has something they could loan or come by and check.

i am not sure whats available for the 360 crank but as an example - if mine were loose  i bought a set of +001 bearings and used the tighter bearing only in the top half of the rod. i think you could do the same with a set with an extra .001" clearance and only use 1/2 of the bearing will give you an extra .005" of overall clearance which would put you about right.

If my clearances were too loose, I could pick up a bearing set that is .021 (those are available) and try this trick. Since its too tight, that would make it even tighter.

Oh man, I might catch some flak for this one, but...

You can use Plastigauge on mains, but NOT rod journals. It will ALWAYS read tighter than the actual rod clearance.

Great, this is two opinions that plastigauge will read tight! How much tighter it's reading would be nice to know for my own peace of mind.

I would go with what you have take it easy during break in for 500 miles or so .

I'm sure it will live fine on the street. I've never used a 5w oil in a performance engine, so perhaps I'm just being paranoid and need to get with the times. 

[Strawdawg]

I would not hesitate a moment to run it as it is.  Modern machining quality and modern oils make all the difference when it comes to running tighter clearances than we used to and I suspect the engine will run better, longer than it would have 40-50 years ago.

[Ramman]

Agree 100% to what Strawdawg posted.

[MoparLeo]

Just a thought. Did you have the big end of the rods resized? If not they may not be round. This could also cause bad clearance readings. Make sure they are round and then use the proper sized bearings. You can only be wrong once...

[HP2]

Yes, rods were resized along with new rod bolts.

Modern oils...this is a flat tappet engine.  With tight rod bearing clearances and a flat tappet, what oils  would be recommended? In its previous iteration with loose clearances, it had a steady diet of Kendall GT1 racing oil in 20w50. When I used up my last bottle of it, the engine came out and has been on a stand waiting this refurb.

[Strawdawg]

Kendall!  Probably not a lot of us left that remember when it was about as good as you could get

I think you will have to try something and see what kind of pressures it gives you.  I tend to like Valvoline Racing.  Given the time of the year, you might start with the 10-30 and see what happens.  I tend to like 15-20 psi at hot idle (no load on the engine at idle so pressure is not very important_ and close to 70 psi at the top end-again with it fully warmed up.

When it gets hot outside, you might need 20-50 or a 15-50 in another brand.   Or you may not need that heavy. Without trying it and seeing what it does hot, it is really hard to predict.  Many of these heavy oils will trip the bypass when cold and you recirculate unfiltered oil.  Some filters don't trip it until closer to 20 psi of differential.  Baldwin and Fram Race filters (Fram Racing filters used to be built far better than their daily driver filters but I have not cut one open lately.

[HP_Cuda]

I personally like Valvoline VR1 and depending on the application/pressures either 20-50w or 10-30w.

Measure twice and cut once as the old adage goes. There is no second chances on this.

[Strawdawg]

I run 20-50 in one of my buicks...when I rebuilt it, the machinist thought it was a chevy and put loose clearances.  The other one runs 10-30 and has tighter factory clearances.

I tired some 5-30 Mobil 1 last year in the first one.  It was fine in the spring but when the temps started to get up there, one run under boost and the pressure started to drop.  I went back to 20-50 LOL...  It's been working on that for 20+ years.

[HP2]

Does Vr-1 have adequate zddp levels for a flat tappet cam?

[Brads70]

Does Vr-1 have adequate zddp levels for a flat tappet cam?

Quote
" Valvoline VR1 Racing Oil: Contains 75% higher zinc than SN or SM motor oil with a balanced additive package designed to work in both racing and traditional applications. Valvoline provides this product in both multi and mono viscosity grades: 20w50, straight 50, 10w30, straight 30, straight 40 and straight 60.
Longer-Lasting Zinc/Phosphorus: Valvoline uses an advanced zinc/phosphorus additive that keeps higher levels of phosphorus in the motor oil where it protects the engine instead of poisoning the catalytic converter. "

https://www.valvoline.com/about-us/faq/racing-oil-faq

Although I found this confusing?
Quote
" Which oil has more zinc/ZDDP: VR1 or Not Street Legal racing oil?

Valvoline VR1 Racing Oil contains .13 percent zinc and .12 percent phosphorus compared to the Valvoline "Not Street Legal" Racing Oil, which contains .14 percent zinc and .13 percent phosphorus."

I've used VR-1 with no issues in past engines, I've been using this now for years
https://penngrade1.com/

History... https://penngrade1.com/history/