Main Bearing Clearance on N/A

[ek02]

I just dropped a forged 3.625 stroker crank in a 4.1. This crank has been in this engine with FEM-107M standard bearings. The clearance was .001-.0015 on those bearings when new. I put softer standard Sealed Power 7144-MA mains in this time. My clearance is now .00075-.001. Is this too tight for a mostly street engine with occasional trips to the strip with nitrous? The oil pressure should be real good with that clearance. The rods are .0015, same as with the old bearings. The main journals mike to 2.4995, same as a new crank. Anyone running the mains this tight?

 

[charlief1]

To keep it alive you really need to go with .0017 to .002. More or less than that you're looking for a problem. On NA you can go with more clearence but you will more likely be tearing it down sooner than you want.

 

[ek02]

I usually try for .0015-.002, but what I can't understand is why it's so tight with the Sealed Power bearings, but was fine with the FM's. Maybe because they are softer bearings, they make them a little thicker because they will wear faster than the hard FM's? I guess I need to have the crank polished to correct the clearance. A stock 231-252 has .0003-.0017 as the specification. That's really tight on the .0003. That's almost no clearance. The rods are perfect, just the mains are tight. I may try a different brand bearing before I have a perfect crank polished for clearance. Thanks.

 

[charlief1]

You might try getting another set of bearings and double checking the clearence. Polishing the crank may be the way you have to go but checking the bearings may show that the bearings are the problem.

 

[ek02]

The crank is on the floor and going to be polished tomorrow. As long as I use the same brand bearings, it should be ok for future rebuilds. Polishing the crank is the right way to go. If this was a stock crank and build, the clearance would propably be fine, but I do not want any problems at high RPM. Thanks for the input.

 

[usetaboost]

keep us updated. This will be a cool thread.

 

[ek02]

The Clevite Performance catalog has a PDF file that tells you anything you ever wanted to know about bearings. http://mahleclevite.com/pubs_detail.asp?c=1&id=108 Click on the PDF file. They make bearings with .001 more or less clearance for the rods on Buick V6's, but only a standard main set. Buick V6 bearings are on page 76. Polishing the crank is my only option. It's at the machine shop now. Once that problem is resolved, the rest of the parts are all ready for final assembly.

 

[usetaboost]

what are you putting this motor in? Can we get some details on your build?

 

[ek02]

It's been in a 1974 Toyota pickup. It went 7.60 in the 1/8th at 95 mph with a 150 shot of nitrous. I pulled it apart because of metal in the oil filter after the last time I ran it. It was mostly from the #3 TA cam bearing. I have a CAT 3.625 crank and H beam rods, JE custom pistons with file fit rings for a 9.75-1 compression ratio. It has a custom Comp roller cam 226 I-228 E, 108 LSA with 526 lift at the valve. Rollmaster chain, Comp 885 lifters, Champion GN1 heads with Scorpion 1.65 rockers, a Kenne Bell ported intake, and a 600 CFM Edelbrock carb. I built the headers after the old Kenne Bell 3 into 1 design. Jim Bell gave me the dimensions. MSD digital 6 ignition with a retard when the nitrous hits and a rev limiter, an NOS progressive nitrous controller, and a dedicated fuel system just for the fuel solenoid. The trans is a V8 Turbo 350 with JW clutches, TCI shift kit, and a JW 3400 stall converter. There is also a Gear Vendors overdrive on it. The rear end is a Ford Maverick 8" with 3.80 gears, a Detroit locker, and Curry axles. I run MT Street radials at the track and pretty much slip and slide. My 60 foot has never been under 2.00. I am afraid to run slicks with an 8" rear. I bought this truck new and swapped a 75 odd fire into it 2 years later. It's had 3, 3.8's in it, but this 4.1 stroker beats them all. I put a 3.8 back in it while I am rebuilding the stroker, and it feels like mush. Same cam grind but flat tappet, with ported heads, big intake valves and T&D rockers with a KB intake and 500 CFM Edelbrock carb. I can't wait to get the stroker back in it.

 

[charlief1]

I can help you get it to hook up better if you're interested. It's very simple but I won't post it on the board. Can't let everything out in the open after all. PM me your email if you're interested.

 

[mat231v6]

I can help you get it to hook up better if you're interested. It's very simple but I won't post it on the board. Can't let everything out in the open after all. PM me your email if you're interested.

i'm interested charlie:biggrin:

 

[charlief1]

i'm interested charlie:biggrin:

Sorry Matt, it will only work on a leaf spring rear.:redface:

 

[ek02]

PM sent.

 

[usetaboost]

better keep those leaf spring secrets. Soon all new car manufacturers and aftermarket companies will be stealing your ideas lol

 

[ek02]

I finally got my crank back today. The machinist said my 4340 forged crank was one of the hardest he has ever tried to polish. He got it from 2.4995 down to 2.4990. i dropped it in and checked the clearance with plastigage. # 2 & 4 have .0015. # 1 & 4 have .001. I ordered a set of King bearings tonight. There is something wrong with the Sealed Power bearing set. All the main journals mic the same. Unless my line bore is way off, the bearings have to be the problem. The line bore was good on the initial build 2 years ago. The crank turns easier now, but if I can't spin it easily by hand, it is not going together. The bearings should be here early next week. In the mean time, I am going fishing in the 10,000 islands of SW Fl.

 

[ek02]

I got the King bearings today and mocked up the crank in the block. I now have .0015 on # 1, .002 on # 2, and .0015 on 3 & 4 with Plastigage. I may check it with a bore guage just to compare it to the Plastigage. The end play is .008. The crank turns easily with a ratchet and GM EOS assembly lube on the bearings, and no rear seal. Tomorrow it will get a final cleaning and assembly with Red Line assembly lube. Red Line is really slick stuff. I will save the Sealed Power 3/4 groove bearings for a mint turbo crank I have if I ever build a stock stroke engine. Thanks for the input. Charlie, you never send me the leaf spring info. I also thought of disconnecting the sway bar to get more weight transfer.

 

[usetaboost]

I'd just ditch the front bar all together.

 

[ek02]

Yea. It is pretty big. The less weight on the front, the better. I may try some 90/10 drag shocks too. I have been using a TCS 2800 stall converter. I changed to the JW 3400 converter when I put the 3.8 in. I have never run it with the stroker, but it will probably need a little more traction off the line. I have a 15 gallon auxiliary fuel tank with 105 octane race gas in the back where the spare used to be. Filling it all the way up may help too. I usually run 10 gallons in it. I run 93 octane in the stock tank for the street. The bearing issue has stalled my progress, but now I can get it together.

 

[charlief1]

Well I finally got the online issues fixed but my system is a lot slower now. Fired off an email that should help you hook up better. If it doesn't make semse tell me and I'll try and explain it a little better.

 

[ek02]

Got it Charlie, thanks. I finished putting it together today. I did the head stud retorque recommended by Champion by letting it sit overnight after the initial torqueing, and backing off the nuts 1/8 to 1/4 turn and retorqueing. I marked the nuts and the heads with a Sharpie and sure enough, they went tighter. A couple of photos attached of the engine and the 3 into 1 headers I built a few years ago. I have a set of full length 1 1/2" headers I ran on my 3.8. These are 1 5/8" tubes and were run both on the 3.8 and the stroker. I really could not tell the difference on the street. According to Kenne Bell's testing years ago, the 3 into 1 headers were good for 12 more horsepower on a near stock engine. I want to build a set of full length 1 5/8" stepped up to 1/ 34" with a 3" collector to see if it makes a difference with a stroked 4.1 The engine is not as pretty as when it was new.