Questions About Clearances for Internals on Modified Gen 2 Coyotes

[bhvnce]

Hey all,
So this will be my first time putting together an engine and I want to make sure I get all of this stuff right before I put it in the car and give it a go. After reading a bunch of forums and comments and watching a bunch of youtube videos about the topic, I've found that the clearances the shop manual calls for in regards to main and rod bearings may be a bit too tight for a boosted application like mine. On top of this, I've also seen that piston ring gaps might also need some adjustment because of the extra power output.

So I guess the questions is your recommendations for main bearing clearances, rod bearing clearances, and ring gaps for a boosted Gen 2. Before my pistons decided to fail on me it was running about 10lbs of boost and I was planning on bumping it up just slightly with the stronger internals. As I said before this is my first time putting together an engine and I am sort of learning as I go. So I have to ask exactly what is the method to adjusting your bearing gap or is it a "you get what you get" sort of situation?

Thanks to everyone who stops and reads and special thanks to anyone who drops some more knowledge in the replies! I appreciate you all.

Sponsored

 

[EFI]

So I have to ask exactly what is the method to adjusting your bearing gap or is it a "you get what you get" sort of situation?

This is usually left to the specific engine builder who is putting your block together based on the the expected usage you provide them.

All builders have different specifications for the intended use of the car and their past experience, along with what type and/or brand parts used. Different part manufacturers call for different clearances.

So have a talk with whoever is building your engine about it, let them set the specs as they are usually the ones who will provide warranty on the work.

 

[Jackson1320]

Order the main bearings std because they are fine. but the rods order the plus .001 clearance bearings and that will be enough
https://www.jpcracing.com/king-bear...-coyote-main-bearing-set-001-extra-clearance/

 

[bhvnce]

This is usually left to the specific engine builder who is putting your block together based on the the expected usage you provide them.

All builders have different specifications for the intended use of the car and their past experience, along with what type and/or brand parts used. Different part manufacturers call for different clearances.

So have a talk with whoever is building your engine about it, let them set the specs as they are usually the ones who will provide warranty on the work.

I’m building it myself! That’s the whole reason I’m asking is because I want to make sure I do it right the first time so I don’t have to tear this thing down again lol. Thanks for the reply!

 

[EFI]

I’m building it myself! That’s the whole reason I’m asking is because I want to make sure I do it right the first time so I don’t have to tear this thing down again lol. Thanks for the reply!

So you're building it all yourself and doing the machine work/blue printing?

Or are you having a shop do the machine work while you just do the final assembly?

I don't mean to be a downer, but if if it's the former and you're trying to do it all yourself, but have to ask this type of question on a forum then maybe this is not a good idea. It's not really financially feasible to learn how to blueprint your first engine on a boosted Coyote, but that's just me. I'd learn on a junkyard 90s engine.

 

[thelostotter]

Here is how my engine was built and it has given me 0 trouble on the road course. Rod bearing clearances are towards the upper limit, main bearing clearance is actually 0.0002" over max limit. If this engine ever needs to come apart I will be reducing main clearance to 0.0015".

Compression ring is gapped at 0.019" and second ring is gapped at 0.022". These might need to be opened slightly for a boosted application.

 

[Grimreaper]

are there preferred machine shops you guys would send a short block out too? im in DFW/north texas

whats the consensus on 8-12psi on 11:1 comp for ring gaps?

@thelostotter how were oil pressures with near max bearing clearances and are you running a heavier weight?

 

[WildHorse]

Since you didn't say, I'll assume supercharged.

For rings:
Top ring .007 x bore
Sec ring .006 x bore
oil ring stock

Bearings:
Stock.

To 'adjust' bearing clearances you:
cut the crank or line bore the mains, ditto with the con rod journals or the rods themselves.

 

[thelostotter]

are there preferred machine shops you guys would send a short block out too? im in DFW/north texas

whats the consensus on 8-12psi on 11:1 comp for ring gaps?

@thelostotter how were oil pressures with near max bearing clearances and are you running a heavier weight?

I originally ran 5w30 and 0w40 with a very efficient home built oil cooler and oil pressure was 80psi at WOT. It is worth noting I had to block off the piston squirters because I used Wiseco pistons. I also used low leak GT350R lash adjusters and cam phasers, I don't know how much affect these really have.

That oil cooler sprang a leak so I tried the Harrop kit which is way less efficient and now I need 5w50 to maintain 70psi at WOT hot. Not really that happy with this oil cooler but I know the loose mains are contributing so that’s why I’d shoot for tighter next time. I’d also use a piston which would let me maintain the piston squirters if possible.

 

[Jackson1320]

Since you didn't say, I'll assume supercharged.

For rings:
Top ring .007 x bore
Sec ring .006 x bore
oil ring stock

Bearings:
Stock.

To 'adjust' bearing clearances you:
cut the crank or line bore the mains, ditto with the con rod journals or the rods themselves.

Why would you run a tighter gap on your second ring?

 

[WildHorse]

Why would you run a tighter gap on your second ring?

Cause its doesn't get as hot.

 

[Strokerswild]

Since you didn't say, I'll assume supercharged.

For rings:
Top ring .007 x bore
Sec ring .006 x bore
oil ring stock

Bearings:
Stock.

To 'adjust' bearing clearances you:
cut the crank or line bore the mains, ditto with the con rod journals or the rods themselves.

Solid info for boosted.

The number that sticks in my head for the #2 ring is .0063" per inch of bore with #1 at the stated .007". As for bearing clearances, I always shoot for the loose side of spec.

 

[Jackson1320]

Because it doesn’t get as hot means that it does not close as much. Your information is backwards. The second ring should always have more gap than the top ring

 

[WildHorse]

Your information is backwards.

Been building engines forever sport. Most recent is my buddies 383 stroker with a 6-71 sitting on top. Every season he has me do a re-ring & bearings. Have yet to cut the crank, hone the mains, or bore the block. Never had a failure for what, 7 years now I think. SO I know what I'm doing. Dunno about you.

 

[thelostotter]

According to Wiseco, the bottom ring gap should be larger than the top ring to prevent ring flutter. The second ring in a Wiseco ring pack is not a compression ring.

Sponsored