7-bolt rods on a 6-bolt

[belize1334]

Background: Manley makes a long rod (156mm) H-beam but only in the 7-bolt style. They also make a complimentary 2.4L long-rod piston designed for the 22mm pin.

So, the question is, can the 7-bolt big-end work with the wider 6-bolt journal. My understanding is that the actually journal size is the same between 6-bolt and 7-bolt. The only difference is that the 6-bolt crank is machined a bit wider to accommodate the extra material on the 6-bolt big end. But the side of the rod should never tough the side of the crank anyway right? So if the journal size matches and the width of the rod is "too small" does that matter?

 

[89Mirageman]

Yes, it still matters. There are service limits in the FSM that you check for rod to crank clearance with a feeler gauge.

 

[Spyke169]

I looked into this a while ago, from what I understand it is not an on the self item. Closest on the shelf item I was able to find is part # 14426-4. They are for a 6 bolt crank, but require that you use a 7 bolt (22MM wrist pin) piston.

I have heard of guys having 6 bolt pistons and crank with 156mm con rods made by Manley, but like I said, from what I understand they were custom made. If you don't already have pistons it shouldn't be an issue, buy the 14426-4 rods and some 7 bolt (23mm wrist pin) pistons. Some of the threads I read when researching this for my own build were a year or two old, so things may have changed. Your best bet is to give Manley a call (732) 905-3366

(Edited for grammar/punctuation)

 

[BogusSVO]

The difference in rod thickness between 6 bolt and 7 bolt is about .075 So it would not the best of ideas to bolt a 7 bolt rod on a 6 bolt crank.

Are you looking to play with the rod ratio? Want to build a long rod 6 bolt?

 

[belize1334]

That's the idea. I talked to manley. There just isn't enough demand to do a run of 6-bolt h-beam long-rods and my goals don't warrant stepping up to their turbo-tuff series.

 

[BogusSVO]

Well I found another option for you.

If you do not like the price of TT, doubt you will like this one any better.

click

You can pick your build specs as far as C2C, wrist pin dia and rod width.

click

156mm C2C, 22mm wrist pin, 6 bolt big end.

Just what you are wanting.

$799 and comes with rod bearings.