alternate connecting rods for 401?

[FordsRiv]

Was reading the R&C article on "Building A Better Buick' and they state that there are 3 different lengths of connecting rods. What lengths are they?
They also state that there are Poncho rods that can be used, that are longer. But these require machining to make fit. Anyone have any info on these? Length? What they originally came from? p/n's?
Any info/help would be greatly appreciated.

[rcull]

Here' s a start on your answere:
'53 are one of a kind, #1343144
'54 - '56 264, 322 they are the same, will fit '53 motors with '54 -'56 piston pins #1162050 (press fit type)
'57 - '60 364 57 -58 #1173217 59 - 60 #1186538
'59 - '66 401, 425 casting #1185487

I think

[telriv]

Your question can only best be answered when we know what you have in mind. As the deck heights increased the rods got longer to compensate. '53-'56/264/322 one length. '57-'61/364 another length. '59-'66/401/425 another length at 6.219-6.220. You can use 364 rods to stroke a 401/425 .125" but will need custom pistons. You can use Pontiac at 6.625" but will also need custom pistons. For that matter any different length rod will need a custom made piston. Everything that deviates from stock will need custom machining & parts. This all costs $$$$$$. How many are willing to spend the $$$$ nec. to find out if the combo they are planning to use will work or not. If it does, GREAT!!!!!! If it doesn't alot of $$$$$ was thrown out the door. Using a 364 to stroke a 401/425 will throw off the sin degrees at 1/2 of the crank/stroke rotation. As a matter of fact the max degrees that are liked to be are 17*. A stock 401/425 is 17* approx. 30 seconds. The shorter 364 rod in a 401/425 would throw these ratios off. You have to take into account rod length stroke ratio also. There were two engines that had the correct rod length, stroke ratio & degrees of sin. The best engine designed for this was the 302 SBC & the 331 Hemi. The SBC was designed, I'm sure, the 331 was just a lucky guess in the way it turned out as I'm sure they didn't know as much about degrees back then as today. I could type for days & with one finger would take me days. So I suggest you do some research.

Tom T.

[FordsRiv]

Thanks for the info.
Wow, that's a lot to think about.
I really wasn't thinking that much about the rod/stroke ratio. I've seen a lot of successful engines that weren't exactly perfect in that regard. Actually a lot that were far from perfect.
I was just thinking of getting the piston to dwell at TDC a little longer. (Since these engines are already undervalved, any extra time I can make for additional cylinder filling is good. And the lower sideloads on the ring pack will make for longevity in a street engine.)
And to reduce the compression height so I can get custom pistons made for it.
What are the actual lengths?
Are the big ends of the non-stock 401 rods bigger? Or the Pontiac rods? Possibly there has to be some machining in the pan rails to clear them?
What about the small ends? Are they wider or thicker(bigger in Ø)? I'm thinking of clearance between the pin bosses of the piston. And the undercrown. I could trim them if they're too wide. I doubt that the inertial loads will be high enough at the engine speeds expected, to cause undue pin ovalization or bending.
It's nice that Buick forged all of the internals. They sure built them like tanks.
Initially this would be for a NA build. I'll add forced induction later. For a given hole size(inlet valve), if you reach a limit getting it in by sucking, blow it in!
Has anyone done that lately? I've seen pics of blowers on nailhead drag cars in the 60's.

[5GScars]

A stock 425 piston w/pin is almost 1000grams! The pin alone is a half pound(225gms.) and that is an area to take weight off the rotating assembly which on a nail is very important if you want to spin it beyond 5500rpm safely IMHO.
Turbo would be much easier to force air into the motor as you could use the stock intake/modified.
I had planned this way back when Accell came out with a kit for SBC's back in the 70's and even had 8.5 compression pistons by Jahns(?) made up by KenneBell. The hot side fab work would be the most difficult running one side of the exhaust to the other and fabbing a mount for the turbo of choice. I have to ask some guys with turbo Mustangs why they use such large turbo's that are not even close to their sweet spot for efficiency. Could be that at 5-9 psi they keep the intake temps down and that would make that end easier and spool would make power quickly. Good Luck!

[FordsRiv]

Spooling up turbos with the limited (even with lightweight recips) RPM range would be difficult, even with 2. I'm thinking of a procharger running thru a sheet metal intake, with EFI. I've made a lot more, with a lot less c.i. (sport compacts), so this is a relatively restrained plan.