I need some help with selecting rods and pistons for my rebuild. I plan on using Scat 5.7 rods in a 350 and it will probably be around 375 h.p. I get the impression from Vizard's books that he favors pressed pins for street use, because of the wear involved. Any opinions from some motor builders. I would like to use the floating pins unless there is some real reason not to.
Thanks again in advance.

 

I'm looking at this same question for a big block. I know the 427 had some with floating pins but not any that I know of in the 454. Is the extra effort of going to floating pins worth it?

 

Firstly I would not use Scat rods due to their quality and lack of tolerance control. I've seen side clearances with new rods of .019" to .020"+. For a street car why not use the GMPP powdered metal rods or if your budget allows, invest in some Crower Sportsman rods.

Secondly, stick with pressed pins for the street. There is a reason they sell replacement bushings for those rods. In addition, the clearances are critical between the bushings and the pins and I don't trust many aftermarket rods to get it right. They are meant for ease of tear down after a race. Basically nothing can go wrong with a pressed pin rod and piston assembly, they are dead on reliable and that is what you want. There are no spirolocks or ring clips to fail and come apart.

I can tell you that I've organized two group buys on Crower rods on the forum with over 40 sets of rods being bought with a mix of small journal, large journal, stroker and big blocks, and not one set had floating pins.

 

Well, I gotta differ here a little bit.

First, I've seen excellent quality from SCAT stuff overall. GM uses it in their strokers, Mopar uses it in lots of their stroker stuff and Ford uses it in their strokers. Many of the big name builders who's name is on the line trust it to perform at insane HP levels.

I have a set of SCAT rods in my 540 and they were dead on on clearances all the way down the line.

Eagle stuff and all much of the *house brand* stuff all comes from the same foundry....it just depends on how close they watch machining.

Now *CAT* brand is a whole 'nuther deal. Very low attention to detail and just plain sloppy to me.

That said, Crower always makes excellent products...you can trust them. Many of their parts ar emade by Schneider and it's good stuff.

Lunati is also a good source.

But back to original question....pressed pins are primarily cheaper, plain and simple. That's their claim ot fame. It costs more to use floating pins, but Mopar and Ford did it for years and years on a lot of normal run of the mill motors. GM did it on the top of the line stuff. Medium and big bore diesels have always done it. Wear on bushings isn't a big deal to me....you will very seldom ever see a worn one.

The two advantages of floating is *maybe* easier to disassemble...but have you ever tried to get double spirolocks out? It can take a few minutes without the lock buster tool and you could press them off faster.

To me the big advantage is there is one more surface for everything to pivot on. I've seen piston pin bores start to gall and if it hadn't been for the ability of the rod to pivot on the pin, it would have surely come apart. Again, this is extreme stuff..but it does show that it works. NASCAR guys throw everything in the trash after one race, yet they still have floating pins. If the pressed were more stable and reliable, you can guarantee they would be in there.

But for a 375 Hp small block..there is no real need for it. If the kit you buy has them, then there is absolutely no reason not to use them. Just that much more added insurance.


JIM

 

Well there you go, now you have two opposite sides of the spectrum that should make for an easy decision

Jim, I must say they have been around for years but they must have good batches and bad batches. As an example, the weight of their rods can vary as much as 20 grams per set for the same P/N. I don't get that at all. I know when I order a Crower P/N, that set of rods will be within two or three grams of any other set with the same P/N.

Maybe you caught the post by Jackson a few weeks back about the large end of a set of Eagles being torqued incorrectly for machining or something to that effect.

 

My race engines are full floating and have never had a bad rod or piston due to extremes. Donovan, Chrysler, and Chevys included. And to be a winner there is only one way to use them.

Small chevys, didn`t the 302Z`s have full floating pins?

 

I know if you get an Eagle forged kit it comes with floating pins. Don't know about their cast kits.

 

Yeah I know..it makes it tough. No doubt Crower makes good stuff. here lately we just got a set of Eagle 6.535 BBC rods and they were fine..no big deal on balance. I've also seen stacks of LS-1 Eagle rods and they have also been very close. Now they are a lot looser on side clearance since you have a piston guided rod, but balance in the sets has been easily close enough to deal with. The builder is doing LOTS of motors for export and doesn't have time to fix a lot of bad stuff, but they HAVE to be perfect when they leave. He has been very happy lately.So maybe it's as you said..good and bad batches.

And to add onto all of this, I wouldn't even put a set of Carillo's in without checking them. I don't trust ANYONE!!


Again for the Hp range he's talking about here, you could throw stock whatever GM rods in it and be fine.

JIM

 

Thanks again for all of the information.

 

Yes, GM used full floating pins for 302's in Z/28's. They were used with some very expensive (babbit plated small end - no bushings) rods that were exclusive to 302's. This made the floating pins and special rods eligible for SCCA road racing. They wanted to beat the snot out of the Mustangs and they did. The 302's got all the good stuff.

I am running Eagle full floaters in my 302 but side with pressed pins for street cars. The NASCAR boys DO toss everything after a race. The street guys will run them for years and have a whole different set of issues to deal with over time. Maintenance and real world operating conditions are not the same. Not that it makes that much difference but I would not hesitate to run pressed pins on a street engine especialy if I did not expect to tear it down again in the near future. Just the fact that we can debate it this much means it probably does not have a clearly definative answer.

If you expect to tear it down in the future, you might like having the floaters. You can do those yourself.

-Mark.

-Mark.

 

You don't need floaters in a street motor ... no real advantage. Since it's a 350 ... you won't be clearancing lower end ... so having the ability to quickly pop pistons on-off rods won't be needed.

The ONLY floater advantage I can see in this app (350/375hp) is that floater pistons aren't exposed to the stress that happens when a pin is pressed through & into rod.

Floaters do help in a motor that routinely gets its pistons removed from rods (race).

Spirolox are a PITA.

Several pistons on market today that use a different lock to hold a floater. Mahle performance/race have nice wirelok ring with a digout notch in piston boss that makes it rather easy to remove wirelok. Many SpeedPro use a lock that pops right out with needlenose pliers. Others can use a conventional internal snapring. Again, you don't need floaters in a street motor.

 

GM puts full floaters in their bread and butter 3800 motors.