7 bolt rods and pistons in a 6 bolt

4135 Views 21 Replies 8 Participants Last post by 1fastgst, Dec 31, 2005

twisterad3

Discussion Starter · Nov 9, 2005

I know this is a dumb ass question, but if I had some 7 bolt crower rods, and weisco pistons, is there anyway to stick them in my 6bolt block? Or do I need to get a 7 bolt block and crankshaft from the junk yard and have them remachine. I have a 92tsi. And a stage 3 ported head for my block. Will the head even fit on a 7 bolt. Again, sorry for all the newbie questions. I'm trying to learn asap. Thanks guys/girls.

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green_bread

· #2 · Nov 9, 2005

well, my take on your questions is as follows:

you can put the pistons in the 6 bolt but you will have to use the 6 bolt rods. i havent looked in to it very much yet, but there is supposed to be a company who makes 1g rods that you can put the 2g pistons on without any modifications. if i talk to the guy i heard about it from, ill post the information up here later.

as far as the head, im thinking that the 7bolt head will fit on the 6 bolt block. there may be a couple of extra oil passages, though. someone please correct me if i am wrong here. I dont want to give mis-information!

ADAM

bryanwheat

· #3 · Nov 9, 2005

There is absolutly no reason to put a 7 bolt rod in a 6 bolt motor, it sounds like you have your stuff backwards. The 7 bolt engines blow, do not build one, you will regret it. The parts are not interchangable, the 1g rod is wider (big rod) why would you buy 7 bolt rods for a 6 bolt motor. Unless you are shooting for over 450 hp than i would go with some good 2g pistons with 1g rods and arp rpd bolts. You can get the nippon racing 2g 8.5-1 piston kit that doesn't require the rod to be narrowed for 125 bucks with pins and rings. They have even better reing land seperation than the normal 2g pistons. You will however still have to have the 1g rod bores out 1mm on the small side to accept the 2g pins. The 6 bolt head will fit on the 7 bolt block, but you will possibly have to get some shims for the head bolts. The 1g heads (6 and 7 bolt are the same head) have a 12mm bolt hole, and the 95+ have a 11 mm hole. Just build a 6 bolt. I would almost say for certain that if you build a 7 bolt that your thrust bearing will fail in the first couple thousand miles. Not worth it.

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twisterad3

Discussion Starter · #4 · Nov 9, 2005

I know that 6bolt motors are the way to go. But I have the 7 bolt crower rods and the wiseco pistons from a 93 talon. Since I enherited them, I just wanted to see if I could use them in the 92 6bolt. I know 7bolts are looked down upon, but i was just curious if there was any way to use them.

twisterad3

Discussion Starter · #5 · Nov 9, 2005

bryanwheat said:
You can get the nippon racing 2g 8.5-1 piston kit that doesn't require the rod to be narrowed for 125 bucks with pins and rings.

Where would I get these from for that price? The guy on ebay?

bryanwheat

· #6 · Nov 9, 2005

you can use a 92.5-94 7 bolt. They are alot better than the 95-99 7 bolts. Make sure you have the oul squirters welded shut though.

drcustom

· #7 · Nov 9, 2005

Ya the 7 bolts really aren't that bad...the early ones are really pretty good, and there's no reason not to use one if you've got those rods and pistons. They're still good stock to 350-400hp no problem, with those rods and pistons you'd have a hard time reaching that builds potential. The rods and pistons are the weakest point so I don't see why you coudln't use what you have. Actually, with lower rotating mass you should get more hp and faster revs with a 7 bolt.

To use the 7 bolt pistons on the 6 bolt rods you have to enlarge the bore for the wristpin and narrow the rod, it's not that big of a deal and most shops will do it pretty cheap. I don't know if there is any type of hardening on those rods though.

Also, you say you have a 92, did you check to see if it was a 6 bolt? As early as May of 92 they started using the 7 bolts.

All the heads are interchangeable. The most difficult thing to do is put the 2g head on the 1g block, but the only issue is making the holes a little bigger...and you can just hammer a stock bolt through for that. Any other combination just bolts right on.

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1fastgst

· #8 · Nov 30, 2005 (Edited)

drcustom said:
Ya the 7 bolts really aren't that bad...the early ones are really pretty good, and there's no reason not to use one if you've got those rods and pistons. They're still good stock to 350-400hp no problem, with those rods and pistons you'd have a hard time reaching that builds potential. The rods and pistons are the weakest point so I don't see why you coudln't use what you have. Actually, with lower rotating mass you should get more hp and faster revs with a 7 bolt.

To use the 7 bolt pistons on the 6 bolt rods you have to enlarge the bore for the wristpin and narrow the rod, it's not that big of a deal and most shops will do it pretty cheap. I don't know if there is any type of hardening on those rods though.

Also, you say you have a 92, did you check to see if it was a 6 bolt? As early as May of 92 they started using the 7 bolts.

All the heads are interchangeable. The most difficult thing to do is put the 2g head on the 1g block, but the only issue is making the holes a little bigger...and you can just hammer a stock bolt through for that. Any other combination just bolts right on.

I could not agree with you more. I have blown 6 bolts and 7 bolts. I went through a couple 6 bolts in my 1g, and 2 7 bolts in my 2g. I never crankwalked the motors though. There are people building very high hp 7bolts. Everyone is all scared about the crankwalk bullshit. My buddy's 95 mustang with a 5.0 crankwalked on him. I guess you should stay away from the 5.0 also. Shit can happen. Like I posted in another thread. I have a fully built 6-bolt 2g sitting in my yard. I cannot drive it. Guess why? Its crankwalked.

Also, I would recommend against hammering a 6bolt head bolt through a 7bolt head. Thats just nuts

drcustom

· #9 · Nov 30, 2005

1fastgst said:
Also, I would recommend against hammering a 6bolt head bolt through a 7bolt head. Thats just nuts

It's really not that bad, you're probably only taking off less than a mm. On my head most of the bolts went through without having to do anything, only a few needed opened up just a little bit. All it took was some light tapping.

twisterad3

Discussion Starter · #10 · Nov 30, 2005

So what are the acutal differance between the rods? Like bearing size? Or just the top part where it's 22mm insted of 21?

verticaljump1

· #11 · Dec 29, 2005

I hate it when people flame somebody for asking a question. He didn't buy the rods/pistons for the purpose of putting them in a 6-bolt motor, he's just asking if they can be used. The only difference in the rods is a little over 1/10th of an inch of width of the big end of the rod (1g is fatter), and the 1g wrist pin diameter is 21mm and the 2g diameter is 22mm. You cannot use 7-bolt rods in a 6-bolt motor because the 7-bolt rods won't sit flush against the crank "cheeks" causing too much clearance. That's what people say, however I contacted Polk Performance on three different occasions and they said that 7-bolt rods can be used on a 6-bolt crank as long as you use 6-bolt bearings. They said that they do it frequently to gain the advantage of having a bigger wrist pin. I have crower rods/wiseco pistons for a 2g. I'm going to be using a G4CS block/crank, so I'm not sure if I want to try the 2g crower rods on the G4CS crank of not (I know it's the same as the 6-bolt crank just a 100mm stroke). If Polk Performance said you could do it and they've done it I'd do it. Clearance should be a problem because the 1g bearings will seat flush against the crank "cheeks", and the notches in the bearings will line up with the 7-bolt rods, the rods won't slide side to side on the bearings, and the bearings won't float side to side on the crank journals. I'm not an expert on any of this, but hopefully that helps.

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1fastgst

· #12 · Dec 29, 2005

verticaljump1 said:
That's what people say, however I contacted Polk Performance on three different occasions and they said that 7-bolt rods can be used on a 6-bolt crank as long as you use 6-bolt bearings. They said that they do it frequently to gain the advantage of having a bigger wrist pin.

That is a very interesting piece of information. Has it been proven to be reliable?

EclipseRST

· #13 · Dec 29, 2005

drcustom said:
It's really not that bad, you're probably only taking off less than a mm. On my head most of the bolts went through without having to do anything, only a few needed opened up just a little bit. All it took was some light tapping.

OUCH! 1g head studs are 12mm... 2g head studs are 11mm. That is exactly 1mm difference. That is a lot!

Save yourself the hassle of cracking a head or fucking up your head studs and drill the head out! Who beats a head with a hammer to shove studs through them?!?! Damn.

1fastgst

· #14 · Dec 30, 2005

EclipseRST said:
OUCH! 1g head studs are 12mm... 2g head studs are 11mm. That is exactly 1mm difference. That is a lot!

Save yourself the hassle of cracking a head or fucking up your head studs and drill the head out! Who beats a head with a hammer to shove studs through them?!?! Damn.

I totally agree.

As for the 7bolt rods on the 6bolt crank. That really doesnt sound right. First off the bearings are smaller than the true width of the rod end. If you look at the rod end, you can see where the bearing ends, and a chamfer begins. That chamfer adds quite a bit of width over the actual rod bearing. Yes, the 1g rod bearing is going to be wider, but minus that 'chamfer area' I still think that you are going to have too much play. I am not saying that these people do not do this, but I do think that it should be checked out for reliability sake.

drcustom

· #15 · Dec 30, 2005 (Edited)

EclipseRST said:
OUCH! 1g head studs are 12mm... 2g head studs are 11mm. That is exactly 1mm difference. That is a lot!

Save yourself the hassle of cracking a head or fucking up your head studs and drill the head out! Who beats a head with a hammer to shove studs through them?!?! Damn.

It's obvious you have never seen this, and didn't read my article.

The BLOCK is 1mm larger, the heads just have ports for the bolts to go through...it's rumored that the 2g heads even came from the same casting as the 1g heads, and I've even had the same problem with 1g heads. You don't need to pound the studs through, you just need to clean the channels since there is only a very small amount of material being removed - only a very small fraction of a millimeter. All it takes is a few gentle taps, and that was only necessary on 4 of the holes - the other 6 went in with no restrictions. Really it was such a small amount of force I would have felt comfortable using the new studs, however I'm not as oblivious as you make me out to be...had you read the write up you'd have seen that I used an old stud.

Here is a pic that shows the tiny shards that were removed:

1fastgst

· #16 · Dec 30, 2005

ok

7 bolt rod rebuttal?

EclipseRST

· #17 · Dec 30, 2005

drcustom said:
It's obvious you have never seen this, and didn't read my article.

The BLOCK is 1mm larger, the heads just have ports for the bolts to go through...it's rumored that the 2g heads even came from the same casting as the 1g heads, and I've even had the same problem with 1g heads. You don't need to pound the studs through, you just need to clean the channels since there is only a very small amount of material being removed - only a very small fraction of a millimeter. All it takes is a few gentle taps, and that was only necessary on 4 of the holes - the other 6 went in with no restrictions. Really it was such a small amount of force I would have felt comfortable using the new studs, however I'm not as oblivious as you make me out to be...had you read the write up you'd have seen that I used an old stud.

Here is a pic that shows the tiny shards that were removed:

Are you stupid? I dont care what article you have, Hammering a head stud through a head is just plan rediculous. Building motors should have no "hammers" involved. If the head stud is 1mm over what it's suppose to be, then I am drilling the head.

I cant believe you think that hammering a stud through a head is a correct way of doing this. If anyone allows you to do this to their vehicle then they are just as dumb. Its not about whether its feasible or not. Its about doing whats right.

I'm pretty hammered right now and I can tell you 1 thing. You should not be around motors if you plan on installing heads like this!

I swear... Some peoples kids. Damn!

drcustom

· #18 · Dec 30, 2005

EclipseRST said:
Its about doing whats right.

I agree. Ask anyone who's seen my work and I'm sure they will agree. In fact, people hate coming to me because they know I'll tell them to do it right, even if it take more money and more time. Seems like you've got something against the way I make decisions...yet I don't think you've ever seen my work. What's up with that?

EclipseRST said:
I'm pretty hammered right now

Ah, well I don't feel so bad now. You've been on these forums for what, 4 months? Not that being here for any amount of time means much, but I just don't see anything that even suggests you have any idea what you're talking about. You think that what I did put more stress on a motor than drilling? No chance. Further, do you really think a head that can contain hundreds of high pressure explosions per second can't handle a few taps to clean out some guide holes?

EclipseRST said:
Hammering a head stud through a head is just plan rediculous.

Taking that statement for what it is, I agree. If anyone wants to attempt my method and the stud just doesn't want to go through with a few taps then by all means don't force it. I'd expect this would be common sense but apparently some people need these things spelled out. Additionally, if anyone is actually able to hammer a head stud directly through 3" of solid aluminum I'd be interested in seeing the pictures.

EclipseRST said:
Are you stupid?

This isn't my style, I'm done with this thread. I let a guy know that it's possible to use whatever head on whatever block and I get some opinionated kid who just wants to tell me that I don't know what I'm doing.

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twisterad3

Discussion Starter · #19 · Dec 30, 2005

it's okay. the question doesn't apply. I just sold the pistons and rods and got some other internals made for a 6bolt. It's too much hassle. Thanks guys

Spyder1gdsm

· #20 · Dec 30, 2005

I suppose me having to get my 1g 7-bolt head machined to accept 6-bolt headstuds for my G4CS block was a complete waste.

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