Optimus

Hello,

I'm in the middle of doing a headgasket job on my '95 4Runner 3.0L V6 and I want to chase the block threads. I do not remember the thread size, other than my chaser for 22RE's is too big (12mmx1.25pitch?). I went to the parts stores tonight, but they only had 10mm or 12mm. Of the tap and thread kits, only an 11mmx1.50 was offered. 10mm looks too small, and 12 mm is too big. I'm guessing it's an 11mmx1.25 (retarded size???), but I would like to get confirmation. The sad part is, I could of sworn I already had one but I can't find it. I have done one other 3.0L about 5 years ago, but if I had a tap back then, I have no idea what i did with it.

The threads are actually quite clean in the block, and I was able to run down an old bolt into each hole by hand the first try. I'm assuming the new head bolts I will be using will fit even nicer. However, I'm anal and will want to clean the threads just because. I guess worst case scenario I can just use one of the old bolts and cut a slot in it.

DudeBud

what i do is cut slots in the bolts with a die grinder works very good

Optimus

I ended up just using an old bolt. I didn't cut any slots though, on account the threads were already so smooth and clean there just wasn't much crud in there. I'm used to doing 22R/RE's which usually have nasty threads.

FishOutOfWater

Wish I would have seen this idea earlier. I purchased an M12x1.25 tap and chased the threads on one side (4 holes in a row). I then thought it realized it would have been a good idea to test one hole first with a bolt to see if everythin was ok. Sure enough, the hole is too big and the bolt is severly floppy. I ordered an M11x1.25 tap for the rest of the holes and chased them when it came in the mail. These holes are now also floppy, not as bad as the M12, but a little worse than the unchased holes. Are these bolts somewhere between M10 and M11 with 1.25 pitch? I am planning on drilling out and installing helicoils in the now M12 holes to get all holes back to M11, but should I be concerned with the extra floppyness of the new M11 holes?

TNRabbit

Those have to be a good, tight fit in order to meet your torque specs.

FishOutOfWater

So I guess I should start looking for head bolts that match the new M11 holes. Any suggestions? I have a bolt specification request sheet from ARB to see if they have anything in the size I will be needing. Has anyone ever used oversized diameter bolts or studs on the 3.0, and if so, what other headaches should I be looking forward to? Since I already have four holes at M12 I figure I might as well tap all four to that size, unless I am not thinking of something. This would probably require drilling larger headbolt holes in the heads. Ug....

TNRabbit

contact Ted @ www.engnbldr.com
he may be able to help you.

DaveInDenver

The holes in the heads would be sized for the right bolts, so yeah you'll have to bore them. I'd be careful not to make the walls too thin, there's going to be oil and water passages in the head and it would stink if one of them blew out because going up in size compromised the jacket. I'm not sure the thread size, but I am surprised it's not M10x1.25 or M12x1.25, Toyota is pretty good about avoiding oddball sizes. But since those are torque to yield, they are probably smaller bolts, like a 10mm or 11mm. When you ran the M12x1.25 tap in, didn't it seem like you were cutting? Should have been pretty hard to turn I would have thought.

FishOutOfWater

It was pretty hard to turn. I kept on looking at the material removed and thinking "Man there's a lot of crap in there..." and didn't think to check my diameters until I had tapped a complete row half way down. Idiot move... but I also assumed that the bolts would be M10 or M12. Turns out they are not even M11! Chalk this mistake #2 up to by first time building an engine and first time using taps. The M11 tap went in a little nicer, still more resistance than I expected, but less material removed, and I actually got to the bottom of the hole. Incidentally, mistake #1 was blowing up my first block about 30 minutes after I bought the car. DON'T TRY TO AVOID A TOW BILL WITH ROD KNOCK .

FishOutOfWater

My Block is back in the machine shop to have the head bolt holes tapped to M12x1.25. I will be contacting ARP today to see if they have head bolts or studs of the proper length with M12x1.25 on both ends, or at least one end if it is a bolt. I will post again when I have more info. I am also able to go to M14 on the block side if that is the only hardware they have. I would like to stay with the 1.25 thread pitch to avoid enlarging the holes too much, but I may only be able to find M14x1.5 for the block side.

FishOutOfWater

ARP has studs that I think I can make work. They are M12x1.25 on each end and 5.75" long tip to tip. By my calculations, the stud will stick out about 0.9 inches from the head bols counter bore surface if the stud is placed all the way at the bottom of the hole. This is good, because it gives me plenty of length to work with and still sits well below the cam inside the head. I will do a dry fit to make sure the washer and nut still fit inside the counter bore and that I can get to the nuts with a socket. The head bolt holes in the block will be tapped to M12x1.25, and the head bolt holes in the head will be enlarged to fit around the stud threads. Can anyone think of anything I might be missing? I also have part numbers of the studs, nuts and washers for anyone interested.

DaveInDenver

One thing is to make sure it will fit under the valve cover. If the studs are too tall sometimes that can keep valve covers from sitting right on the head, which causes oil leaks or can be noisy.

FishOutOfWater

I had't considered the valve covers. I guess I was so focused on clearing the cams. I'll check when I get home. Thanks for the tip Dave.

DaveInDenver

Yeah, are there studs (i.e., correct size, not the M12 that you are going to) that people normally use with the 3VZ? If so, you could compare their overall length to the set you are looking at, should tell ya something I'd think.

FishOutOfWater

The studs have arrived! There is plenty of clearance above the stud inside and outside the head. No interference from the head covers. The bolt holes in the head will need to be enlarged slightly, and block holes enlarged and threaded to the very bottom of the hole at M12x1.25. The closest fit point is where the nut screws on to the top of the stud. When everything is thightened down, the bottom of the washer will be even with the bottom of the threads on that end of the stud. This comes to about three threads. If things turn out to be a little closer I will simply add in an extra washer to ensure that I have plenty of thread left below the nut. There is additional clearance above the top of the studs, so if someone else wanted to do this mod, they could tap the block by hand and without a bottoming tap. With the stud at the bottom of the new hole, two washers should provide sufficient clearance above the bottom thread. I will update again when I get everything installed.

Any suggestions on torquing. The ARP directions say 80 ft.lbs using their lube. They also say this is 75% of the bolt's yield strength. What would the torque be on stock bolts?

FishOutOfWater

Everything is back from the machine shop. The block head bolt holes are not all uniform depth, so i may need to add an extra washer of two to several studs. Other than that, it looks like everything is still good to go. My machienist did not leave much clearance between the studs and the bolt holes in the head. This may make it a little more dificult to get the heads lined up properly, so they slikd nicely onto the block. If there is too much binding, i will send them back for a slightly larger hole diameter. A 1/2 inch diameter head bolt hole would be very close to the same clearance as the stock setup. The dowels are very tight, so they will keep everything from moving arround, and keep the headbolts from shearing off when the heads expand. I'll update again later.

FishOutOfWater

Heads are on and just about everything went wonderfully. I did need larger holes in the head for the head bolts to even get the heads on. I used a 1/2 inch hard metal bit and drilled by hand. The fit was still a little tight. If I ever do this again I will use a 33/64 inch bit to allow the heads to slide over the studs a little better.

I torqued the nuts to 80 ftlbs, but I also followed the torquing directions in the haynes manual for comparison. In incriments of about 10 ftlbs I worked up to 33, marked the nuts and kept on working up in incriments of 10. For the second head, after I marked at 33 I went to 40 then 60 then 80. So the Haynes directions said to rotate the bolts 90* twice after marking at 33 ftlbs. My method turned all the nuts a little farther than 45* I backed everything off, tried again, and still about 45* from the original 33ftlbs mark position. Everything felt smooth with no binding, and I re measured to make sure the nut was not bottoming against the end of the stud threads, so I am confident with the torque readings. Im just surprised how little rotation there was.

If everything runs well I will post a thread on the mods section with pictures. Keep your fingers crossed.