itslogz

Got my ACL 0.25 oversize bearings today to go with my .0020" turned on main journals crank, heres the plastigauge results from tonight, torqued in sequence and all steps followed correctly.

#1 MainCap: .0014
#2 MainCap: .0015
#3 MainCap: .0016
#4 MainCap: .0016
#5 MainCap: .0015


The setup is going to be as follows, daily driven. Are those clearances sufficient for this setup to be daily driven, occasional track time?

B17A1 block/Head/Crank/Rods
ACL Main & rod bearings
CTR Pistons std 81mm
Blox tuner type-B cams
Skunk2 cam gears
RM titanium retainers
Blox dual valve springs
ARP headstuds and rod bolts
blox intake manifold
skunk2 70mm TB



Thanks for the opinions from people who know whatsup

racebum

looks great for plastigauge. slightly tight for a dial. many honda hot rodders i spoke with before i setup my bottom end seem to favor .0015 to .0020 on the rod and .0020-.0025 on the main measured with a dial. you're right in the ballpark though

Combustion Contraption

I would say .0025 on a main journal is a bit too lose for a street engine that wants to run for any length of time.

Having said that, to the OP, clearances look "OK" for what you are doing. A little on the tight side, but not factory "LS" tight.

itslogz

Yeah thats what I was thinking, maybe a tad tight than loose, i'd rather it be on the tight side if anything.


Thanks alot for the replies. Ill be checking the rod bearing clearances soon anough, got to get new arp bolts pressed in and the rods resized before I do all that.

racebum

you been setting up at .0020 on street NA builds? mine came out at like .022, i considered trying to fit them a hair tighter but like piston to wall i usually error on the loose side.

blackeg

the last motor i did had main tolerences of .0015-.0018 and its been going for 10k miles. 8700rev limit, 30 something track passes and about 15 dyno pulls.

as per the helms those clearances right in the middle to upper middle of the helms specs, i dont think you will have any problems with it especially for a "street" engine.

mar778c

iTrader: (1)

OP, those clearances are fine for a street car.

I tend to shoot for .002" on both the mains and rod bearings.

Search-first

It's a little tight, but you already knew that. The last B I built was all at .0015-.0019. I would think that you are just fine like everyone else has stated above, especially since you have had yours tinkered with and you aren't using factory bearings.

DonF

generally a .25 bearing (.010) thicker, with a .020 turned crank would have much larger clearance than you posted. Around .011-.012

racebum

is there any noticeable difference between setting up at .0017 to .0022? it's such a SMALL margin. i also wonder where they wear after 10k miles. has anyone measured the mains after running a year? any break in wear change the clearance?

Search-first

Well, I actually do wonder how much a motor that is built loose will last comparative to a tight motor as far as time is concerned.

Combustion Contraption

Noticeable to whom? A human? Probably not. To the parts spinning inside the engine at piston speeds above 4500fpm? Probably. Ask a precision machinist if .0017-.0022 is a small margin. I'll let you in on a secret. The tighter clearance you can run, the more HP you will make. No lie.

omniman

.0015 on the mains is the right place to be. also dotn forget aluminum expands when its heated so the clearance will actually grow several thousands at operating temp.

Why do people fight OEM spec bearing clearances so much lol its just plain stupidity. The clearances of a purpose built drag motor have no relavance to a street driven engine. failure to follow directions leads to failure.

mar778c

iTrader: (1)

Show your analysis and your test results. Looser clearances will net more whp and better bearing temps at higher rpms especially above 7800 rpms and that is no lie.

mar778c

iTrader: (1)

Yeah, if you plan to stay within stock limits. Most are trying for the ubiquitous 200 whp and 9000 redline.

Combustion Contraption

People only run the looser clearances on high perf. builds because its easier than buying a $3k crankshaft that is less than .0001" TIR.

b20vtech

been doing .0017 to .0020 on mains and rods forever now, no problem.
street motor on tighter end and race motor on looser end.

racebum

CC, if that's true why are endurance engines always setup loose?

Combustion Contraption

Do you know what they run in Sprint Cup right now? Ask DonF. You might be surprised.

racebum

i hope he comes on to post. i'd love to hear what he has to say. i'm even more curious what the clearances come out to be after a year of driving. the majority of b18c engines i've spoken to people about usually fail from a burned valve or detonated piston due to high oil consumption coating the exhaust valve so it fractures or getting in the ring lands and sooner or later lighting up. the one i just finished failed from a exhaust valve that came apart due to excessive oil consumption. the one clearance i think i may have a little too loose is the PW, it's those mahle power paks which are really similar to the wiseco. set them up at .0035 and suspect i could have went a hair tighter. that cold morning clatter is annoying.

racebum

okay, i couldn't help myself, i found a really neat page with specs of a nascar engine. they are running .0016-.0022 on the main. basically right in the same place as our performance builds. rods are at .0014-.0019, which again sounds like the well assembled vtec, the link below is a great read guys

http://209.85.173.132/search?q=cache...lnk&cd=2&gl=us

Combustion Contraption

Those are not actual specs for a NASCAR engine. Those are guesstimates by UTI students.

racebum

actually its an assembly guide. students actually assemble a working nascar engine. many of their grads go on to work in pit crews. that's probably the best engine building school in the country.

Combustion Contraption

They assemble a nascar SPEC engine. Trust me, those arent exact specs for engines being run in Sprint Cup right now. .0016-.0022 is a HUGE variance for he precision components in NASCAR.

And UTI is NOT that great. I have personally worked with 6 guys who have gone through the program, and they ALL agree they wish they could get their money back. Its like any other education program, where what you get out depends on what you put it, but they were no better off than me, with a regular college education, except that their pockets were much lighter.

racebum

tell me about it ! school is 100% what you put into it. i think the top end is where the secrecy comes in with nascar. i know cam lobes are a VERY tightly guarded secret. i wonder why the sprint guys are going tighter? could be using really thin oil since it's less windage and free HP. any ideas on the benefit? also, how long are the heats? i know an engine doing a 10 minute race could easily be set up tighter than something doing the rolex 24hr.