2G Rod style, Piston clearance, 2g block, 1g rod, 2JZ-GE piston

[1990TSIAWDTALON]

Those valve reliefs are DEEP, aren't they? I was going to mention it but he said he has to use what he has available. I don't have any JZ experience, but his service manual called for a MAXIMUM of .0047" clearance.

 

[RSS]

Have you checked you cylinder bores for size and then mic'd the pistons and done the math to determine your PTW clearance? That service manual is saying a maximum of .0047". I have ran with more but that should be the next thing for you to check and post back.

I have to bore the block to match piston size and clearance. It's 85.5 mm bore now, and pistons are 86 mm diameter.

 

[1990TSIAWDTALON]

Then your machinist will be able to give you a closer PTW since it will be a fresh cylinder at that point.

 

[RSS]

2jz is 86mm bore iirc so he's gonna have to bore/hone. 0.0047 would be pretty loose for a cast piston imo.

OP have you thought about valve reliefs?

2jz-ge manual,
standard oil clearance: 0.0029 - 0.0038 in. (0.073 - 0.096 mm)
maximum oil clearance: 0.0047 in. (0.12 mm).
What would be your choice?
I think valve reliefs are ok, people have used this combo.

 

[bastarddsm]

0.0030" would be my goal.

is your sohc 4v or 2v?

 

[RSS]

0.0030" would be my goal.

is your sohc 4v or 2v?

It's 4 valve soch

 

[bastarddsm]

It's 4 valve soch

OK in my mind it was 2v. Carry on!

 

[RSS]

Finally I bored the block, and piston to wall clearance is 0.07 mm, according to 2jz-ge manual.
Also, I narrowed 1g 6 bolt rods to use in 2g 7 bolt block. manual says 0.1 mm to 0.25 mm for rods big end std clearance and limit is 0.4 mm. When I measure narrowed rods side clearance, I got 0.2 mm to 0.25 mm for two of them (which is in specs) and 0.25 mm to 0.30 mm for two others, is there any problem in your opinion?

 

[bastarddsm]

Did you forget a zero in your big end clearance? Side clearance seems ok. long as the bores are parallel, and square to the sides, all is good.

 

[RSS]

Did you forget a zero in your big end clearance? Side clearance seems ok. long as the bores are parallel, and square to the sides, all is good.

As you no there is no perfect thing in the physical universe, A local experienced machinist did the boring, but I don't know how parallel are bores and about bores square to the side .

Pardon?
"Did you forget a zero in your big end clearance? "

 

[bastarddsm]

Nevermind, I thought you meant radial oil clearance in part of your post. I see now it was all side clearance.

 

[RSS]

Nevermind, I thought you meant radial oil clearance in part of your post. I see now it was all side clearance.

Tnx. Yes I was worry about side clearance

 

[RSS]

Is it bad idea to use 0.5 mm undersized crank for 250 hp engine (6500 max RPM)?

 

[1990TSIAWDTALON]

If clearances are good, it should be ok for your purposes. I have a 6 bolt in my shop that is cut .25mm on the mains and .5mm on the rods. The only issue is finding bearings for them. I believe all you can get is aluminum (soft) bearings when I checked for the man that dropped the short block off. I could not find a race bearing for a crank that was cut that much though. That engine appeared to be fine when I looked at a few journals for the customer. It just needed freshened up.....again.

 

[RSS]

If clearances are good, it should be ok for your purposes. I have a 6 bolt in my shop that is cut .25mm on the mains and .5mm on the rods. The only issue is finding bearings for them. I believe all you can get is aluminum (soft) bearings when I checked for the man that dropped the short block off. I could not find a race bearing for a crank that was cut that much though. That engine appeared to be fine when I looked at a few journals for the customer. It just needed freshened up.....again.

I found a pair of used std bearing I'm ganna measure clearance and check for crack.

 

[1990TSIAWDTALON]

Standard bearings on a cut crank will have WAY too much clearance.

 

[bastarddsm]

Hang the crank by a rope, and tap all of the counter weights with a hammer. Cracked crank will have a thud not a ring. Make sure you clean the crank really well. I use a piece of mig wire to get down into the end of the oil passage at the plug and dig around. I also use a curved straw on a can of brake cleaner to blast in there. Do it on a clean tray or something so you can see what comes out. Keep doing it till it stops. Usually takes 3-4 cans! Some like to remove the plugs but I have never figured a good way to re plug them.

 

[RSS]

Standard bearings on a cut crank will have WAY too much clearance.

I measured the crank with a micrometer. Main journals are 56.99 mm (2.2437 inch) and rod journals are 44.97 mm (1.7704 inch) next day I will buy std bearing (just DAIDO is available) and install them to get oil clearances.

 

[RSS]

Hang the crank by a rope, and tap all of the counter weights with a hammer. Cracked crank will have a thud not a ring. Make sure you clean the crank really well. I use a piece of mig wire to get down into the end of the oil passage at the plug and dig around. I also use a curved straw on a can of brake cleaner to blast in there. Do it on a clean tray or something so you can see what comes out. Keep doing it till it stops. Usually takes 3-4 cans! Some like to remove the plugs but I have never figured a good way to re plug them.

Yes, cleaning is very important. I like to remove plugs and using bolts instead of them.

 

[1990TSIAWDTALON]

The rod ends need tig welded back in if you remove the plugs, which I have never done either. I have used the same methods as @bastarddsm, which are good tips.

 

[RSS]

Unfortunately I got a new problem. When I was installing piston on conrod, I found out piston pins are very tight in piston pin hole, and pin stick to piston and do not rotate and slide. What should I do to solve this problem?