Ever heard of Piston Guided Rods ?

SmokedTires · 01-16-2003, 05:02 PM

I just found out from my engine builder that my Carrillo rods are too narrow at .820 wide. Standard Chevy width is about .940 . He was figuring these must be for a Ford engine,

I called the place I bought them from and he says they are a piston guided connecting rod. :confused: He says that this is a trick that many Nascar teams use to get alittle extra HP (~8-10). I need to have pistons made with this option, but I need custom pistons anyhow so that's not a problem.

So have you ever heard of this before ? :cheers:

clem zahrobsky · 01-16-2003, 09:10 PM

with this much side clearance you will have so much oil thrown on the cylinder walls the rings will not be able to control the oil burning. SEND THEM BACK this BS!! :chevy

[Modified by clem zahrobsky, 8:12 PM 1/16/2003]

SmokedTires · 01-17-2003, 08:04 AM

Quote:

with this much side clearance you will have so much oil thrown on the cylinder walls the rings will not be able to control the oil burning. SEND THEM BACK this BS!! :chevy

This is my engine builders concern. He called Carrillo yesterday while I was there because he had never heard it either. They told him that Winston teams are doing this. They're going with thinner rods for the weight savings.

Instead of the large end having .020 clearance on the crank, they control the rod position with the pistons (.001 clearance per side on small end). Carrillo told him we shouldn't have a windage problem if the rods are centered over the oil journal holes. He's not totally convinced at this point & is looking further into it before we decide.

danno85 · 01-17-2003, 11:11 AM

I don't think you would have excessive oil loss and windage with that
much more rod side clearance. The clearance between the bearing and
crank journal is going to control how quickly (and how much) the oil flows out.

The thing that concerns me with the notion of the pin bosses holding
the rod in alignment is that, since the big end of the rod is heavier, that
as it still trys to move back and forth (front to back) that it would rock
the piston sideways in the bore (perpendicular to the skirts), which might
result in accelerated piston wear and potentially uneven bearing wear
as the rod "cocked" back and forth, especially if you had custom forged
pistons w/o any silicon content which would require .005" to .007" skirt
clearance. Remeber that the Winston cup and Nascar engines only have
to run 500 miles.

Would you have to trim the rod bearings to be more narrow also?

I wouldn't use them. Personally I think they are a little "too trick" for any
kind of street engine.

Dan

Twin_Turbo · 01-17-2003, 11:32 AM

with that much side clearance I think the oil will not squirt out in a nice spray pattern to properly lube the walls but it'll probably spray large squirts...

[Modified by Twin_Turbo, 9:54 AM 1/17/2003]

gkull · 01-17-2003, 12:11 PM

I don't think you would have excessive oil loss and windage with that
much more rod side clearance. The clearance between the bearing and
crank journal is going to control how quickly (and how much) the oil flows out.

I think this is a correct statement. I also think that NASCAR engine guys are thinking of every little thing to get the most power and longevity is not a factor. I would find out if those rods are for a restrictor type motor because less width gives less surface sq. inches. So the bearing loading goes up and longevity goes down.

[Modified by gkull, 11:34 AM 1/17/2003]

clem zahrobsky · 01-17-2003, 12:54 PM

that is why there is a spec on side clearance is to control how much oil is thrown out of the rods. we tried using wide side clearance on BBC to oil the wrist pins to prevent gauling and we had a oil control problem. JMHO

SmokedTires · 01-17-2003, 08:18 PM

Thanks everyone, there are some very good points here that I will certainly being taking to the vendor. I'm still undecided, but I'm starting to think these may not be the rods :rolleyes: .

Twin_Turbo · 01-18-2003, 03:07 PM

did you buy them from JR Motorsports? He's about the only one who frequently lists 6"2"rod .928 pin .82 width EDM Carrillo rods w/ 7/16"CARR bolts on ebay :) He does mention it in the auctions.

SmokedTires · 01-18-2003, 04:42 PM

Yes & Yes. It was listed on the auction when I bought them. I just didn't know any better. I am learning quite a bit with this new engine buildup though ;) .

Actually I just bought a set of fully ported Brodix heads from him when I called to question the narrow width on the rods :) .

[Modified by SmokedTires, 2:46 PM 1/18/2003]

Twin_Turbo · 01-18-2003, 06:11 PM

I'd contact him and ask im if you can trade them in on a set of 6.0 .927 .94 rods, he's got a whole bunch of carrillos and mabe you can work something out.

Marck

SmokedTires · 01-18-2003, 07:41 PM

That was discussed when I talked to him last. I'll probably end up doing that. He assured me that I'd make more power with these rods, & suggested I look into it before giving up on them. He may not be aware that they are for a street driven car though :) .

Twin_Turbo · 01-18-2003, 08:47 PM

Quote:

He may not be aware that they are for a street driven car though :) .

:yesnod: that's what i think too :)

clem zahrobsky · 01-19-2003, 10:08 PM

a lot of 2 stroke engines use piston located rods so the bottom end roller bearings get enought lube but they also have bronze thrust washers on each side of the rod on the wrist pin end. :chevy

Twin_Turbo · 01-20-2003, 12:08 AM

Mike,

I have Carrillo 6" .928 small end 2.125 big end .94 width rods w/ 7/16 SPS CARR bolts. They're identical to yours less the EDM and the difference in width. Keep searching, they're out there... wanna bet there will be a set on ebay soon. I think JR only has the .82 ones.

Marck