Focus Fanatics Forum banner

1 - 16 of 16 Posts

·
Registered
Joined
·
361 Posts
Discussion Starter #1
OK , I blew a hole in my old motor so now I'm thinking I need to make sure my next one is built right. We are running a turbo and staying at factory Rev.. Can someone tell me what bearing clearances should be for 1. Rod bearings 2 crank main bearings 3. Piston clearances for forged slugs.
 

·
Registered
Joined
·
16,026 Posts
.002" on both journal types. Pistons it depends on the alloy used, they can vary, the piston maker will tell you. Go by that.

Don't use 5W-20 oil in it, will chew up bearings. Too thin.
 

·
Registered
Joined
·
16,026 Posts
If talking about oil minimum weight 30W. Anything less than 30 does not belong in any type of high performance motor in my view.

5W-20 oil is 5 weight oil modified to act like 20, when the additive wears out you are running 5 weight oil. Great for mileage but not for high loading of parts.
 

·
Registered
Joined
·
16,026 Posts
So...............what kind of statement is that? You realize hundred plus could mean 125 or 450 right? The inside of the engine does not run at ambient temperature and the turbo changes everything.

Stay with 30 if car lives on the street.
 

·
C2H5OH
Joined
·
11,867 Posts
If talking about oil minimum weight 30W or 20W-50. Anything less than 30 does not belong in any type of high performance motor in my view.

5W-20 oil is 5 weight oil modified to act like 20, when the additive wears out you are running 5 weight oil. Great for mileage but not for high loading of parts.


Not sure I've seen you make much more if an ignorant comment, ever.

I have over 200,000 miles on 5/20 and the vast majority is actually 0/20.


Oil technology has come along nicely since the last AMC rolled off the lines. Maybe you should get with the program gramps.
 

·
C2H5OH
Joined
·
11,867 Posts
Fleck,
Talk to the people doing your machine work and ask their recommendations.
 

·
Registered
Joined
·
16,026 Posts
'Not sure I've seen you make much more if an ignorant comment, ever.'

'5W-20 oil is 5 weight oil modified to act like 20'

Oh PULLEEZ, spare me...............

Somebody else has called me out over that in the past, I choked him to death with SAE material on the subject and I can you as well. It can be easily found if you simply LOOK. The additives alone are what make it 20 weight. ALL multi-vis is pretty much like that, the true starting oil base stock weight is generally the lower number. I knew that back in the '70s, where were you?

I've got MILLIONS of miles with 30 weight, gimme a break. And never mind all the 10,000-14,000 rpm engines in bikes I worked on that used the same. Name any that use 5W-20 weight oil, they know better.

And asking machine work people instead of the part makers themselves what clearances are needed???? Could be a real stupid move. That can burn your ass on pistons with all the alloys they have out there now. Machine work people only work the parts, they sometimes have NOT A CLUE as to what needs to be done there. I can't count the number of ones I've run across that blew engines up they did work on when the parts receiver did not check the work. Countless. Ask if you will for more rounded general knowledge but do NOT accept them as the final gods there. I know this from seeing many disappointments. We personally NEVER allowed them to set clearances on anything that came out of our garage and came behind them to remeasure the work and demand changes if they screwed up. I demanded a lot back then, too often they want the work done fast so they can go home. Some of the absolute garbage worst work I ever saw came from top rated super duper throwdown shops that were so full of their own bullsh-t. We had a couple here, the much vaunted Blue Max Racing Team shop (world famous funny car) and Reher-Morrison Race Engines (reknown Chevy pro stocker), both had kickass race cars but both did absolutely HORRIBLE machine work and engine assembly for others and their complete engines were always spotty. Reher-Morrison was known for radical fatblocks that repeatedly blew up in less than 5 runs, I saw it so many times I couldn't count. Blue Max? We rebuilt several of their twin fatblock Cigarette boats that all the car dealers around the DFW metroplex used on communal outings to the Bahamas, needless to say, their work was pretty damn bad and EASY to show them up so bad that we were choked with those boats for a good long while. Once one of those boats we had worked on stomped the others then those guys were coming into our shop left and right. The dealers there had a thing for racing those boats and dumped Blue Max so fast they called us up and cussed Dad out over their loss of bottomless pocket customers.

NO fleck, just trying to change some ideas in head about lightweight oils but 20-50 is a little too thick for stock rpm. I misspoke there and have corrected for it. Now if it was buzzing 8 grand yeah maybe. 10-30 or 30 or 10-40 summer and needs to be syn. Running 10-40 in one of mine now and no issues at all.
 

·
Registered
Joined
·
16,026 Posts
Forged pistons can have from .002" all the way to close to .010" depending on boresize and the type of aluminum. Stock type forged replacement pistons intended to replace cast ones can be .002", Hyper eutectic .003"-.004", after that the alloy used and percentage of silicon determines and many are .004"-.007". Smaller bore is tighter. Machine shop can't touch that unless they use that exact piston to know. Why you use the manufacturer above all things there. Forged pistons range much looser than cast ones do, they are tougher in hard use but they usually expand more with same heat. As well, some of them measure for that clearance in slightly different spots and again manufacturer knows where to measure. Some measure at bottom of skirt and some right even with the pin centerline depending on whether piston is barrel ground or not. So, see, you gotta find that stuff out.
 

·
FF Affiliate
Joined
·
30,611 Posts
I set Zetec bearings in the .0015-.0017 range , .002 would be the MAX I would go

And I would have to agree with iminhell that you need to talk to your builder and see what he sais to do , builders like my self are the end users , were the guys that see what works and what doesnt work , the manufacture makes recommendations but the builder is the guy that sees what those recommendations do and what needs to be adjusted to make them work the safest not the manufacture

Sorry iminhell but I think 20wt oil sucks , I know you have had good luck with it but I wont use it , I use Mobile full synthetic and use the 10-40 winter and the 15-50 I think it is summer

On the pistons because the builder never knows what the piston is made of on that I would go by what the manufacturer recommends and its one of the few things where I use the manufacturer recommendations and we tweek that a little depending on how much boost we know our customer is shooting for , Avg manufactures are for street boost not race boost on the pistons , NA , NOS , Boost all take different clearances

Tom
 

·
Registered
Joined
·
361 Posts
Discussion Starter #15
I imensley appreciate all the input. This is my first ever custom engine for a car. Tom we also broke some new ground on Tunning software with binary editor. If you ever want to peak at it let me know.

Sent from my XT1565 using Tapatalk
 

·
Registered
Joined
·
16,026 Posts
We didn't have synthetic oil in the old days but now, why wouldn't one combine both that AND a slightly heavier oil for severe use? It would be a combination of the best thinking. That 15-50 might be good stuff, I've never heard of it. Means nothing of course.
 
1 - 16 of 16 Posts
Top