Cap/rod Guide Pins

[Ron Earp]

Okay, I have a basic question.

Do all cap and rod combinations have guide pins? You know, little locating pins either sticking out of the rod into holes on the rod cap, or visa versa?

What would happen if they weren't present? Would there be too much movement of the cap in relation to the rod that it would cause a failure of some sorts?

Ron

 

[Jac Mac]

Ron, The cap should have some form of alignment, I assume you are talking about the Jensen here where it has two small dowels. If the rod bolts are a snug fit in both rod& cap at the parting faces then the dowels could probably be removed. Most carrillo type rods use sleeve type dowels while production Ford/ Gm rely on the close fit shank of the rod bolt to align the cap&rod.

Jac Mac

 

[Ron Earp]

Jac Mac, you are right on as to why I am asking. I knew the Ford used the rod bolt, at least on the Ford's I've worked on, but wasn't sure about GM. It sounds like the rod bolts can do an adaquate job if properly sized.

I've got damaged pins that I think I can repair. But if I couldn't, the rod bolts on the design are shouldered 1/2 way down the length they protude into the cap. The clearance is probably around 0.0010" to 0.0015", they do fit tightly. And they probably fit tight enough to preclude the use of pins.

Thanks for the reply, you were one of the folks I had in mind who would probably know.

Ron

 

[CliffBeer]

The latest technology in this area is the "cracked" rod, meaning the rock and cap are pressure cast or forged and machined as one piece then the rod is "cracked" along a pre-determined break point. Once the crank is installed, the cracked (now) cap is re-fit - the cracking procedure produces very precise location and alignment by way of the irregular cracked faces. I believe the rods are cooled down to something like 100kelvin with liquid nitrogen for the cracking procedure. I think this technique is being used on new Ferraris and perhaps also Corvette.

I don't know if these rods are generally available in the after market yet for sbf/bbf but probably will be sometime soon if not available now. Good luck!

 

[Ron Earp]

The latest technology in this area is the "cracked" rod, meaning the rock and cap are pressure cast or forged and machined as one piece then the rod is "crack

Read about those, but, we're talking Lotus 907 motor here from 1972 so these are just machined surface rods/caps - nothing fancy!

Ron

 

[Sandy]

The latest technology in this area is the "cracked" rod, meaning the rock and cap are pressure cast or forged and machined as one piece then the rod is "cracked" along a pre-determined break point. Once the crank is installed, the cracked (now) cap is re-fit - the cracking procedure produces very precise location and alignment by way of the irregular cracked faces. I believe the rods are cooled down to something like 100kelvin with liquid nitrogen for the cracking procedure. I think this technique is being used on new Ferraris and perhaps also Corvette.

I don't know if these rods are generally available in the after market yet for sbf/bbf but probably will be sometime soon if not available now. Good luck!

I think Ford and BMW have been doing it for years now. They make the rods out of compressed metal powder then crack the big end. I think they even use them in some of the Ford Diesels but they don't have a reputation of being as strong as the older forged rods (some of the Diesels). I think they also get every rod to be the same weight since made out of a controlled amount of magic metal powder and saves some $$ in the engine cost since machining is reduced. Definitly an interesting way to make parts.

Sandy

 

[Jac Mac]

Ron, I went back to the pic's you posted on "I hate chevys". ( We have that in common ). The type of screen you have on the oil pickup tube needs a shroud or umbrella type cover over it so that oil is picked up from the very bottom of the pan. Without it air could easily enter the pickup with oil surge .

If that is a rod bolt on the block in one of the pics it doesnt appear to have a close tolerance shank in the reqd area that could replace the dowel's.

With regard to the 'cracked rod's', Mercury Marine have used this for many years and run a caged roller big end brg directly on the rod surface. (no inner/outer race). Have a friend who raced boats and I was amazed at the weight variation across a set of these when we balanced the pistons/rod's.
( It was not good when doing it on an end for end basis)

Jac Mac

 

[Ron Earp]

They fit mighty tight in the cap hole, that is for certain. They are not a Ford looking like design, but it probably doesn't matter anyhow as I've managed to do a pin repair. Now, if it'll just hold together.

That pickup thing crossed my mind as well. I think we'll pull it and weld a nice bottom feeder on there and I'm sure it'd help as you suggest.

R

 

[Howard Jones]

Ron, When you are done with your oil pickup mod could you post pictures of before and after. I love this kind of stuff.