Oil presure surging

[Mark Worthington]

Re: Oil pressure surging

Heh, no direct experience with flat-plane V8s here, my comment was simply me throwing my hat in the ring with a bet that Howard's pickup tube is loose. I bought a nifty little jig for drilling bolt heads and since then I've been actively looking for stuff to safety wire! /ubbthreads/images/graemlins/smile.gif

Jack, I would also like to know who you recommend for mirror balancing.

 

[Jac Mac]

Re: Oil pressure surging

Hello Howard & Mark,
The Balancing Machine is a "Sunnen DCB 750". I believe there are bigger and later model's in the industry now but this was the model mentioned to me. At the same time I should point out that there may be other makes out there that do an equally good job. The shop here in NZ ( ERS ChCh.NZ)that has one wont be of any use to you guy's (Unless you come down to our SFOS series and need to rebuild your motor's to keep up with Russ Noble), but with balancing the guy operating the machine and weighing the pistons and rod's to work out the bob-weight's is real important to the quality of the job. With mirror balancing you place the two flywheels on a mandrel, both flywheels must have their crankshaft flange side's to the same end of the mandrel. With reference to the staggered bolt pattern of the flywheel attachment bolts each flywheel must be 1/2 turn (180deg) from the other, now the two f/wheels & mandrel are placed on the balancer and checked. Material is removed/added to the unbalanced F/wheel to achieve a balanced state of the whole assy. (One Flywheel that you know has been correctly balanced for the motor in question, the other being the Flywheel that needs to be balanced), this can be done on a machine that spins up the whole assy or on a couple of knife edges.
Now this is where the Sunnen machine apparently shines, it operates at very low rpm and is very sensitive. With the above scenario we have two Fly wheels which on their own have an out of balance factor of either 50 or 28 oz.(You guy's with neutral balance can open another *fosters,bud,speights about now*). After you have balanced to a neutral state for the assy the two flywheels cancel one another out,BUT the out of balance individual flywheels are at different points along the mandrel, when spun at high rpm they try to whip the mandrel shaft which confuses the balancer. This has been a major factor with stroker crank's and longer heavier rod and piston combinations where with the old style high rpm balancers the crank would actually deflect/bend during the balancing process.Obviously if this was not detected at the time, when installed in the motor the crank tries to achieve its "bent balanced" state at high rpm much to the distress of the brg,s etc. With all the friction now being created a lot of power is lost for no good reason.
As you can probably gather Im not a big fan on "mirror" balancing for the above reasons, but given a good machine and operator it should be fine for Howards application/rpm range.
Howard I am not trying to ruin your day, and given an endless money jar we would all do things different. If your at all concerned after reading this pull the rear main cap while the pan is off, if there is no sign of movement on the cap/block mating faces its probably OK. Sorry to be so long winded about this but I realise some of you will have trouble understanding the process. Hopefully it's slightly clearer than mud!!

Regards Jack.

 

[Howard Jones]

Re: Oil pressure surging

I asked about how the "mirror" thing was done and the machine shop, Ashland Grinding in Hayward Calif., guy told me he waits until he has a SBF job with the correct imbalance, 50 or 28. He then completes the customers work resulting in a balanced crank, damper, flywheel on the machine. He then takes off the customers flywheel and puts on FW #1, in my case the SVO 5.0 flywheel, trues up the machine to zero and then puts on the FW# 2. This would be the V6 GTD wheel. He then balances fw#2 to the settings of FW# 1. Now FW#1 and FW#2 are the same. I don't know how the machine itself works so I'm not really sure what trued up means. He did say to me that I didn't have a balanced flywheel I just had two flywheels that were the same. No better, no worse.

By the way. Ashland has been in business for at least 40 years in the same location and have always been known to be the quality place to have cranks balanced around here in northern Calif..

Jack, Please tell me more about what to look for in relation to the rear main cap. I might just learn something yet! Thanks for your interest and help by the way.

 

[Jac Mac]

Re: Oil pressure surging

Hi Howard, When you remove the rear main cap take a note of the torque reqd to undo the bolt's( best way to check this is set the torque wrench to the spec , set up on the bolt being checked and note the position of the torque wrench in clockface terms relative to the engine block*ie-2 oclock etc*, now back off the bolt approx 1/2 turn then retorque to spec, if the torque wrench is now at say 3 or 4 oclock it is a fair indication that the bolts have relaxed their initial clamping force).
Now with the main cap removed (and with the aid of a magnifying glass if your as old as me) carefully examine the cap face that mates with the block. There should be no indications of movement of the cap to block- small shiny areas, fretting ,spalling, etc. Hopefully you wont find any of the above, find a simple solution to your original problem like a loose pickup tube, give Mark a chance to try out his loc-wire drill jig and kick back for some serious bench racing ( have a bud- coors whatever for me). Not until the pan is back on though and the motor running mind!!
Cheers Jack.

 

[Howard Jones]

Re: Oil pressure surging

So I'm looking for movement of the main cap as indicated by any deformity on the mating surfaces. OK thanks. Back in the day I used to cross drill EVERYTHING. I learned this from having a caliper mounting bolt back out on a TZ350 once. Big wake-up call on that one. Damn good thing I was in my 20s. I have the drill jig commin.

 

[Howard Jones]

Jack was right. Rear main bearing spun, crank trash, rebuilt with new crank, complete rotailing assembly ballance, line bored crank journals.

Note on crate motors. found that several rod bolts (4) torque setting at <10 ft/lbs. ring gap on at least one top ring at >30 thousands. This engine had 4,300 miles on it. The crank machinest said he believed that the bearing in question spun because the clearance on the journal was excessive.

Advice on crate motors, good sorce of parts. Take it ALL apart and ballance, line bore, and reasemble and completely plastic gauge ALL bearings. Check ring gaps.

This motor would not have stayed together for another hour. Got off cheap this time.

Thanks Jack.

 

[Howard Jones]

Jack was right. Rear main bearing spun, crank trash, rebuilt with new crank, complete rotating assembly ballance, line bored crank journals.

Note on crate motors. found that several rod bolts (4) torque setting at <10 ft/lbs. ring gap on at least one top ring at >30 thousands. This engine had 4,300 miles on it. The crank machinest said he believed that the bearing in question spun because the clearance on the journal was excessive.

Advice on crate motors, good sorce of parts. Take it ALL apart and ballance, line bore, and reasemble and completely plastic gauge ALL bearings. Check ring gaps.

This motor would not have stayed together for another hour. Got off cheap this time.

Thanks Jack.

 

[Jac Mac]

Hi Howard, While its not what you wanted to find Im sure you will be sleeping easier now. Hope the rebuild did not hurt the 40 fund too much. Ive heard similar stories about crate motors, but as you only hear about the ' bad ' ones its hard to tell how many dud's get thru. I tend to agree with you on the strip/balance/clearance check etc. The peace of mind would be worth every cent of the gasket set and balance work which is all it should cost you if the crate motor is new. Cheers Jack.

 

[Keith]

Hey Howard, sorry to hear of your spun bearing but glad you caught it. I too had a similar situation in a road race SBC and first noticed a fluctuation in oil pressure during a Donnington GT race. I thought the resulting excess oil temp was caused by rubber debris in the cooler at the time, but "dawdled" around to get a finish and pulled off the filter where I found a pile of bearing debris and a trashed rear main. As a matter of interest, did you check the oil filter before tear down and was there much debris present? I always check the filter as a first step whenever oil pressure problems surface.

I'm obliged to Jac for the balancing explanation - it would answer a lot of questions. I'm afraid we are not very V8 oriented here in terms of machining. The top facilities do exist but as Ron Earp mentioned on another thread, he was astounded at the prices we pay both in the UK and Oz for our stuff. The Sunnen machines, as you say, are considered to be the very best and we now always specify these as a minimum. Now, how to judge the operators ability?!?rockon

 

[flatchat(Chris)]

The old caneing of the street motor eh!
May be a bit of detonation there -- don't fully understand it but seen the results,like deformed ring grooves, scuffed bores and hammered bearings--clearences too tight for a race motor --just something else to keep in mind for the new mill.
Maybe Jack can explain it better ?

 

[Jac Mac]

Hi Fellas, Could do. Howard do you want it on this topic or would you prefer a fresh one? I will have a think about it today(7:30 in morning here) and post it tonite. Cheers Jack.

 

[Howard Jones]

After looking at the pistons I don't think it was a detonation issue. I did not look in the filter but the bottom of the pan was full of bearing particles. I spend nearly a day cleaning out the pan, oil lines, cooler etc. Several of the other mains (bearings) were damaged by debris from the first one. Interestingly the cam bearings looked like new (new ones installed never the less). The spun rear main was still at correct torque setting and showed no sign of movement. As I said before 4 of the rod bolts on three different rods were down to less than 10 ft/lb.


The rear main journal was scored about 28 thou deep. The balance shop man said he could fix but didn't want to. He would rather get me a good core instead and turn it 10 thou to true it up along with the other balance work. So that's what I did. I also had the block line bored to fix the minor damage to the journal and cap.

Go ahead and continue with this thread if you wish. It's not mine it's ours!

 

[JohnC]

Howard, you may want to consider replacing your oil cooler, rather than just cleaning it. At Caterpillar, we always replaced oil coolers on any engine that had a bottom end let go. These oil coolers were very expensive, large shell & tube units, but it was just too dodgy a proposition to try to clean them effectively and reliably, and chance ruining a fresh rebuild because of particles that were missed.

This may sound OTT, but I'd also try to flush the motor and oil galleries with an external pump & filter unit, and a lighter weight fluid such as diesel. If the motor has any blocked off oil ports on the block, it would be useful to remove the plugs and reverse flow through them. An external fuel pump can be used for this flushing, as they have high flow rates, and you want to keep the velocity of the flushing high, in order to "carry" any particles out.

Obviously, after the flushing, run fresh oil through the motor to "flush" the flush, then drain & refill before firing up for the first time.

John

 

[Keith]

Good advice I think. I did a complete tear down after the spun bearing too and started over. Hot tanked the block, removed cam gallery plugs etc etc. Still found some crap lurking in there despite all that. It's pot luck with the cooler - I blew it through with high pressure air and was pretty sure it got clean, (I had no more problems) but if you're picky - that's good (and expensive) advice also. But ask yourself - how much is a new motor?

Magnetic oil pan plug. Another vital accessory for telling you what's going on.

Rod bolts down to 10 lbs? Wow, that was too close for comfort.

 

[Dan Haynes]

replace the cooler

Most definitely. Or, ship it to Pacific oil coolers in CA. They can clean it up. They are the only certified place I know of. They cleaned my cooler a couple years ago. Wasn't cheap, but at 100 bucks was much cheaper than replacing my large oil cooler.

Definitely don't want to just run a hose through it and assume it is good to go. The bearing particles will stick inside the cooler. Someone on E-pay will buy it!

Dan

 

[Jac Mac]

Yeh ,probably a $$ starved Kiwi and with my luck It will end up in my shop to be fitted. Thanks for the warning. Jack.