Making a 350 out of a 327 (3892657)....

[Tom P.]

Re: Making a 350 out of a 327 (3892657)....

Good information from Clem above.
I do this kind of build quite similar to Clem's above process. Something that I do differently is the rod/piston assembly. Years ago, I had my machine shop grind a tiny amount of material from the OD of a wrist pin (both for a BB and a SB) that is just barely a slip into the small end of a rod. This permits doing trial fitting and clearancing as Clem mentions above. Once ALLLLLLLLLLLLLL the fitting and clearancing is done, as Clem points out, then take everything back to the machine shop for final balancing.
I do this with each individual rod and piston and then number them so that they go back into the hole where they were trial fitted (I use number punches on the rods and a black Magic Marker on the head of the piston).
This method was especially helpful when I built a 420SB. Each piston had to have a few thousandths milled from the piston tops and they needed to go back into the respective holes where I had done trial fits.
The 420 was built by boring a 400 block .030 over and having the rod journals of the crank offset ground down to small journal size (2.10 down to 2.00) which produced an additional .100in stroke. I used a set of resized 66-67 style 327 rods and new ARP Wavloc bolts. Hasn't come unglued yet!

[Clem Z.]

Re: Making a 350 out of a 327 (3892657)....

Good information from Clem above.
I do this kind of build quite similar to Clem's above process. Something that I do differently is the rod/piston assembly. Years ago, I had my machine shop grind a tiny amount of material from the OD of a wrist pin (both for a BB and a SB) that is just barely a slip into the small end of a rod. This permits doing trial fitting and clearancing as Clem mentions above. Once ALLLLLLLLLLLLLL the fitting and clearancing is done, as Clem points out, then take everything back to the machine shop for final balancing.
I do this with each individual rod and piston and then number them so that they go back into the hole where they were trial fitted (I use number punches on the rods and a black Magic Marker on the head of the piston).
This method was especially helpful when I built a 420SB. Each piston had to have a few thousandths milled from the piston tops and they needed to go back into the respective holes where I had done trial fits.
The 420 was built by boring a 400 block .030 over and having the rod journals of the crank offset ground down to small journal size (2.10 down to 2.00) which produced an additional .100in stroke. I used a set of resized 66-67 style 327 rods and new ARP Wavloc bolts. Hasn't come unglued yet!

did the same had a SBC and a BBC wrist pin centerless ground for a slip fit into a press fit rod for easy checking of the set up.

[Thomas H.]

Re: Making a 350 out of a 327 (3892657)....

Thanks for all the great information.

What about the 5.7 rod versus the 6.0 rod?
I was told that the 6.0 rod motor would be easier to internally balance.
On a 383 6.0 rod motor the wrist pin is up in the oil ring on the piston.
Which rod is better?
Thanks again for all your help
Tom

[Clem Z.]

Re: Making a 350 out of a 327 (3892657)....

Thanks for all the great information.

What about the 5.7 rod versus the 6.0 rod?
I was told that the 6.0 rod motor would be easier to internally balance.
On a 383 6.0 rod motor the wrist pin is up in the oil ring on the piston.
Which rod is better?
Thanks again for all your help
Tom

with a 6" rod you will have a shorter lighter piston with a spacer ring in the oil ring groove. i have used this setup on race engines with no problems.

[Tom P.]

Re: Making a 350 out of a 327 (3892657)....

Thanks for all the great information.

What about the 5.7 rod versus the 6.0 rod?
I was told that the 6.0 rod motor would be easier to internally balance.
On a 383 6.0 rod motor the wrist pin is up in the oil ring on the piston.
Which rod is better?
Thanks again for all your help
Tom

Ummmmmmmmmmmmmmm, depends.
First, if it is a street performance type 350, you will be just fine with the longer 6in rod. No issues. Yes, the piston will be a little shorter, the rod angle will be less (which is a good thing), so you will be fine.

BUUUUUUUUUUUUUT, when building a 383 or 400, then there are issues on both the pro and the con side for a 6in rod.
First, again, a 6in rod will reduce the rod angle (which will be considerably less than the stock 5.565in stock 400 rod). That will be good. And, depending on your point of view as well as the way the car will be used, there is a down side to a 6in rod in a 383-400. As Clem mentioned, the piston will be somewhat lighter, which is OK for reciprocating weight reduction. BUUUUUUUT, because it is a shorter piston, with rather short skirts, there will be a greater tendency for the piston to rock in the cylinder, and as also mentioned, the wrist pin hole will also be into the oil ring groove. I personally do NOT LIKE this in a street performance engine. For a more or less pure race or competition engine, it would be fine.
I am no longer in the hard core race engine scene, soooooooooooo, my personal preference for a rod choice in a 383-400 is the 5.7in (350) style rod. The piston manufacturers make pistons for a 383-400 with a 5.7 rod and the price per piston really is not much more than a normal 350 piston. With a 5.7in rod in a 383-400, you get a longer piston (ya, it's a tiny bit heavier, but no biggie), but you also reduce the piston rock in the cylinder and the wrist pin hole is NOT in the oil ring groove.

Here's a .030 over piston for a SB400 with a 5.7in rod (from my 420). You can see how close the wrist pin hole is to the oil ring groove (ya, it's got a busted skirt, that's what happens when you get lake water in a cylinder----along with a bent rod ).
This is a Federal-Mogul hypereutectic piston which had a larger dish before it was milled down for the increased stroke of .100in