Clearances and oil pressure

[Carolina_Mountain_Mustangs]

I know that this is splitting hairs but how all the gear heads around here do it.

We put the bearings in the rods and block and torque them to spec. The we measure the actual bearing with an inside micrometer and grind the crank to fit the bearing. We never just grind it .010" or .020" under standard dia. Yes it is usually only a few tenths of a thousandth but it is right. 

When we raced small engines in carts we set the clearance by using a roller burnisher and you could size the rods, wrist pin holes right to a .0001" easily. Roller burnisher for diameter of rods and crank mains would be expensive. 

Like you my short term memory is gone, lol. Didn't go back and read it all. Are you sure that you got all the oil passages spotless clean? A little bit of grit in there is a bad thing.

When they did the cash for clunkers deal they poured the crushed glass in the oil. Was talking with guy at local dealer he said most Japanese cars would seize in less than a minute. He had a Ford 300 6 cylinder run for 30 min. before it seized.

 

[OzCoupe72]

I know that this is splitting hairs but how all the gear heads around here do it.

We put the bearings in the rods and block and torque them to spec. The we measure the actual bearing with an inside micrometer and grind the crank to fit the bearing. We never just grind it .010" or .020" under standard dia. Yes it is usually only a few tenths of a thousandth but it is right. 

When we raced small engines in carts we set the clearance by using a roller burnisher and you could size the rods, wrist pin holes right to a .0001" easily. Roller burnisher for diameter of rods and crank mains would be expensive. 

Like you my short term memory is gone, lol. Didn't go back and read it all. Are you sure that you got all the oil passages spotless clean? A little bit of grit in there is a bad thing.

When they did the cash for clunkers deal they poured the crushed glass in the oil. Was talking with guy at local dealer he said most Japanese cars would seize in less than a minute. He had a Ford 300 6 cylinder run for 30 min. before it seized.

As the crank was brand new there was no need to grind it

The mains tunnels were align honed, block zero decked, fully balanced, new rods etc. Machinist supplied pistons, rings, bearings etc

Not sure exactly what the machinist measured but as I wanted to assemble the block myself I just used plasti-gauge to check it and unfortunately I must have used the OEM clearances.

If I had of gone with "performance" clearances then it would have been just a matter of purchasing ACL H series bearings which I think are .001 oversized then mix and match until acceptable clearances achieved

All good in hindsight to speculate, and boy oh boy have I done that, but the fact remains is I failed to get the right clearances from the start

The blocked was thoroughly cleaned including using rifle brushes to clean the oil galleries, flushed several times and blown out with compressed air

I can only hope it was just tight clearances that caused this but having no proof leaves me wondering, fingers will be crossed!

 

[c9zx]

"When they did the cash for clunkers deal they poured the crushed glass in the oil. Was talking with guy at local dealer he said most Japanese cars would seize in less than a minute. He had a Ford 300 6 cylinder run for 30 min. before it seized."  One of the most stupid things I've seen our somewhat mistake prone government do. How bored your friends have been to put ground glass in the engines to see how long they would run. Chuck

 

[Carolina_Mountain_Mustangs]

"When they did the cash for clunkers deal they poured the crushed glass in the oil. Was talking with guy at local dealer he said most Japanese cars would seize in less than a minute. He had a Ford 300 6 cylinder run for 30 min. before it seized."  One of the most stupid things I've seen our somewhat mistake prone government do. How bored your friends have been to put ground glass in the engines to see how long they would run. Chuck

That was not them being bored. That was the government requirement. When you traded a clunker in they kept the car for three days if memory is right. They spray painted C F K on the side of the car. The wise government idea was to boost car sales and get the clunkers off the road. 

The glass in the engine was required by the rules. None of the drive trains could be sold out of the salvage lots. It was so stupid. Killed the used car market for a couple years because there were no good used cars they all got crushed. They could sell some of the sheet metal but engines all had to be trashed. 

That was an Obama idea.

 

[Spike Morelli]

OzCoupe,

If you have the option with your assembler, don't shy away from the larger bearing clearances. In my Clevite books, which we use to enter bearing clearance windows to a build's paperwork, the window may very well read something like .0009"-.0029" for a given journal. That doesn't ever mean that just because the low number reads .0009" ( read that 9/10ths of a thousandth of an inch ), and it's technically "in the window", that anyone should EVER set, or allow a rod or bearing clearance to be so tight. Common SAE thinking is to give at least one thousandths oil clearance for every inch of journal diameter, as in .002" MIN for a 2" journal, again, this is a standard MINIMUM. There are lots of great running loose engines out there, but no great running tight engines, so go to the high side on your oil clearances, and you'll be happy.

The old jingle we all learned in basic auto shop for ring gap was "....Three to four ( thousandths) for inch of bore...", meaning for a 4 inch bore, you want MINIMUM .012 to .016" top and second compression ring gaps . This is, again, an SAE minimum, depending on ring manufacturer and ring materials used, they may very well have a ring gap information sheet calling out other gaps for an intended use ( I.E. stock, supercharged, alky, etc ), and using a Hypereautectic piston requires an even larger top ring gap, due to the rings's close proximity to the heat of combustion. Lots to know.

If you bought a Scat kit, crank, rods, pistons, bearings, you are likely in good shape. as Scat generally has the rod side clearances opened up as well, but you will still ( and always) need to check the ring gaps. And, not to beat this dead horse, always check the thrust ( crank endplay).

None of this is difficult, maybe scary for someone who doesn't do it all the time, but I hope you do great with your current build. Let us know how things work out.

 

[Don C]

As has been said on here many times, new does not mean good. Did you mike each journal twice, at 90°, to make sure they were all the correct size and round? Did you plasti-gauge every journal? Everything absolutely clean during assembly? It doesn't take a very big piece of debris under a bearing to wind up with zero bearing clearance. Main bearing caps on in the same position as when line honed?

There are so many variables that can cause an engine failure you may never know what caused it, if nothing obvious can be found.

Even something weird like a short oil pump drive shaft that drives the oil pump when bottomed out in the pump, but works it's way up into the distributor shaft and out of the oil pump might never be found. Not even sure this could happen, I would have to take some measurements.

 

[OzCoupe72]

Thanks guys, great to have your input and will take it on board once I get my engine back

I have raised it with the machinist several times to go to the larger end of the clearances and he seems to think .0020 - .0025 is fine

I will double check it with plasti-gauge though

He reckons the thrust(end play) will be about .007 - .009 which I'm okay with

Unfortunately I don't have expensive micrometers or bore gauges so just had to go with plasti-gauge, dial gauge and feeler gauges

Was pretty anal with being clean and everything turned over smoothly

The only thing we can point to is the clearances and unfortunately my memory doesn't serve me well as to how I determined what the clearance was

I don't doubt that I blew it in this regard but I do doubt that a tight bearing clearance would result in a sudden loss of oil pressure

It's been a long anxious wait and I just want to get my vehicle back on the road again

 

[Spike Morelli]

I'm always interested in what people are building and talk about on this 7173 site. I have a spare 351c engine in the garage, and I thought I'd build it up for future use for my own car. I have a daily driver, automatic, and not necessarily interested in a "racing' oriented build, however.....since I work at a performance engine shop, and can aquire various parts and services at cost, I thought I'd do a photo -journal style build up, showing shop proceedures, I.E. studding, bushing lifter bores, line bore, line hone, head work options,component choices, etc, with photos to accompany the story. I did this with my 406 Ford FE ski-boat engine build over on a boat site, and the entry got a lot of acclaim. One viewer said that he'd never built a Ford before but my article was so easy to understand, he might build one. So,...I think I'm gearing up to do this photo build up with tech. When I do, I'll post it here.

 

[tony-muscle]

I'm always interested in what people are building and talk about on this 7173 site. I have a spare 351c engine in the garage, and I thought I'd build it up for future use for my own car. I have a daily driver, automatic, and not necessarily interested in a "racing' oriented build, however.....since I work at a performance engine shop, and can aquire various parts and services at cost, I thought I'd do a photo -journal style build up, showing shop proceedures, I.E. studding, bushing lifter bores, line bore, line hone, head work options,component choices, etc, with photos to accompany the story. I did this with my 406 Ford FE ski-boat engine build over on a boat site, and the entry got a lot of acclaim. One viewer said that he'd never built a Ford before but my article was so easy to understand, he might build one. So,...I think I'm gearing up to do this photo build up with tech. When I do, I'll post it here.

Can you share the link to the boat engine post? Thanks.
Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[Spike Morelli]

Tony, The site was called "Performance Boats V-drives". I haven't actually been on that site in over a year. Something happened where, all of a sudden, everyone had to re-register ( maybe someone hacked in, I don't know ) , and I never could get my new identification to work, even sent messages to the mediator, so oh well. I just tried to find the blog but no success. I still have most of the photos on my computer.