[Haustkraft]

Hello to all, Ive been a long time reader-of-the-post, but this is my first post. First off, this is the best Nova site.

I have a 70 Nova SS original 396 from LA. Low Miles. Did a complete intertior resto(carpet, gauges, etc etc) A complete drivetrain build (build 12 bolt, TCI th400, TCI stall, and the motor) All suspension components replaced, etc (I will get pics up sooner or later)

OK, current motor is a 70's 454, cast oval heads, Edelbrock intake, Demon 850, hooker heads, MSD Distributor, 6AL box, timing control, etc.

I pulled the motor last year when I bought it, painted the block, did an oil pump, Milodon 7qt pan, and a few other things, ran mint for the summer and fall. Good Oil pressure and didnt have any problems. Got it going for the spring, while driving it, noticed oil pressure starting to get lower and lower (may have been the sending unit for the gauge, but prob not) I decided before anything got severe to pull the motor and tear it down. Tore is all apart, found gasket material in the pick up and the pump. Noticed the Cam lobes to look kinda discolored (Hydralic Flat) and a broken valve spring. I decided to go with a Comp Cam Hydralic Roller set up (11-430-8), new pump, and have the block and head tanked. Measured the crank and rod journals, nearly identical to stock specs (never machined)

I ordered a new set of Crank,Rod, and Cam bearings(stock replacements) Ive thought about it and doing a lot of reading here and online, do I even need to replace the bearings? The crank do not have almost any signs of oil lose, nor do the con rod journals. The bearings have a very uniform color, almost all gray, stil have part numbers on the back side (prob done recent before I bought it) The crank itseft only have a very small about of "glazing" I guess you call it (looks kinda like a glazed rotor) I dont want to open a bag of worms by replacing them to a non machined crank. Budget is getting smaller and I dont know what to do? Polish it with emery cloth?
Thank you in advance
Rob

 

[jlowery78]

Since you have bought the main and rod bearings, I would install them. Throw your old bearings in the trash, there is places where you can cut corners and the bottom end is not one of them. Take your crank to an automotive machine shop and have them polish the journals and see what size they are with a micrometer. This is not expensive. If I was building an engine for a demolition derby then yeah I would re-use the main and rod bearings, on a street car absolutely not.

 

[The Big Al]

Rob,
Take the crank to be checked for straight, also journals can wear egg shaped.
With no issue before this could be all OK. It's one of those things that if you don't check will bite you!

Having the crank turned by a quality machine shop is a good idea, nothing wrong with a .010/.010 crank, I would ask the grinder to keep the spec of the high side.

Spinning a bearing on a BBC can be major, as the piston will come in contact with the head in most cases.

Cam bearing play a BIG part of the oil pressure !!
Have them replaced. I would also opt for the BBC M77HV pump.

Unlike the forgiving SBC, the BBC can eat a bearing real fast when things are not right.

IMO
AL

IMO, thats a small roller!

 

[Paul Wright]

Not being meticulous the first time cost you money and grief. Don't make the same mistake or you'll be doing it again and again.

Here's some tips to help prevent more grief:

1. Make sure everything is cleaned in the engine and do it in a clean environment. Keep a clean plastic bag over the engine while it's apart or between build sessions. Large Contractor bags at Home Depot are the right size and thickness.

2. Measure the exact clearances (ten thousandth or 4 decimals) with the new bearings. For example .0025 might perceived to be .002 with less accurate measuring. Measure at least 2 spots, 90 degrees from each other.

3. I wouldn't polish the crank if the clearance is on the high side. It will only make the clearance worse.

4. New bearings are cheaper than doing the engine a third time, but if your clearances are high, you may need to get .001 under bearings to tighten it up without grinding. How? Use half shells to reduce clearance by .0005. Example: measured clearance is .0029.
Use one std. and one .001 shell to to get .0024

5. If the journal measure out of round (wider on X than Y), you'll need to grind the crank.

 

[Haustkraft]

ok thank you guys for your input, going to the machine shop it is then. I already planned on swapping the cam bearings. Al, I already had that oil pump before. I have always thought that have a Hydralic Roller cam needed less oil than a traditional flat tappet, right? In that case wouldnt I rather have a stock psi/stock volume pump to keep the majority of the oil in the bottom end? thank you for all your help guys!

 

[The Big Al]

Having the crank turned by a quality machine shop is a good idea, nothing wrong with a .010/.010 crank, I would ask the grinder to keep the spec of the high side.

Just a calcification! On my part!!!

When I say high side with the crank spec. If crank is turned.
I want the high side of the crank spec.
rod journal std spec is 2.199 - 2.200
if turned .010 I would want 2.1895 - 2.190

mains same thing
STK spec on mains. On a BBC crank they are different from journal to journal
1 & 2 spec is 2.7487-2.7496: I want 2.7491-2.7496
3 & 4 spec is 2.7481-2.7490: i want 2.7486-2.7490
#5 spec 2-7478-2.7488 : I want 2.7483-2.7488

Mains are very critical on a BBC

If you have it turned, ask to keep the spec on the High side of journal measurement.

3. I wouldn't polish the crank if the clearance is on the high side. It will only make the clearance worse.

Paul is talking about rod and main clearance.
STK spec rod .009-.0025
STK spec mains
#1 .0007 - .0019
#2,3,4 .0013 -.0025
#5 .0019-.0035

End play is ..006-.010


IMO if your maxed with clearance with new bearings then have the crank machined, new bearings you can add .0005 from break in.

 

[jlowery78]

My 454 has a hydraulic flat tappet cam, last year when I had the oil pan off doing some work, I replaced the oil pump with a melling M77 standard volume and pressure one. I run castrol gtx 30wt oil. When engine is cold and first started it has 60 psi oil pressure, it drops to 40 psi when warmed up. I wanted to run the high volume high pressure pump. The standard one has worked flawlessly in the past year I have been driving it.