343 or 360 Crankshaft

kegler343

Hey, I have been browsing through your guys' threads, and have decided that you collectively could give me some guidence. I had my 343 mildly built by Haps Racing in Ames, IA and now have had no luck keeping a Borg Warner auto trans behind it. The combo is in a 69 Rebel with 2.73 rear end, with 32" tall rear tires. Funny, never have spun those?!?! So, here's my question. I have a junkyard salvaged 360 motor. Would it be better, ie cheaper and easier, to get the adapter kit to go to a 727 tranny or mabye use the 360 crank in the block? By the way, the crank is out of the motor and needs polished, and the flexplate for the 343 has come up missing but do have a new 360 flexplate. In the rebuild, the block was decked .0040 (had to go that far to straighten the warp), and the heads were planned .0020. That sums up to a serious question as to what will the longer stroke do in that block! I don't know how far, performance wise, that I will go with this ride. Currently, I just want it back on the road. This is a list of what I know is in it; Engle 5020H cam, 496 lift, 226 @ .050 duration, 110 lobe centers Pioneer SBC valve springs(outers only) w/125 lbs seat preasure Badger replacement 360 2bbl pistons, 30 over Stock 390 intake Holley 600 vaccum secondary carb 1 5/8 Hedman dogleg headers. Any and all advise is GREATLY APPRECIATED Thanx, Pete

FuzzFace2

I could be wrong here but the 343 and 360 have a different stroke, but same bore. Now the crank will bolt in the block but I don‚Äôt know what rods, pistons you could use as the deck height & piston pins are different between the 343 & 360 also. Any one know? 343 bore + 360 crank = 360 cid You know one of the venders makes an adaptor to use the 68-71 cranks with the TF or TH400 tranys. One is a bolt in the other you need to machine the crank. Dave ----

AMX69PHATTY

The 360 Crank should yield 0.000 nominal deck clearance in the 343 block with those pistons that should have a 1.580 nominal compression height. Stock 343 had 1.600 Comp Ht and .060 deck clearance so those 1.580 Comp Ht pistons should be .080 down in the hole. 360 stroke 3.44 minus 343 stroke 3.28 = .160 / 2 = .080 ! =D> So the difference in throw, .080, should equal the current nominal deck clearance. :-| This ups CR, C.I.'s, and give an excellent 0.000 Deck & .045 Quench. This combo works like a charm is great ! :t: It's what I've been running in my 343 for 15+ years :wink: Be sure it's a '73 & up 304/360 Crank made for the TorqueFlites. Should have Rotating Assembly re-balaced, use a 360 Dampener. I'd bet it'll spin the tires after this.

FuzzFace2

AMX your saying to use the Badger pistons, the 360 rods & crank in the 343 block? You running dog leg heads on your combo? If so did you drill & tap the block for them and are they small or big chamber heads? Dave ----

AMX69PHATTY

Yes, they're actually Zollner Pistons I have, $100 from Maddog Racing.
Previous build were discontinued TRW's Part #9047P.
Pretty sure these, Badgers, and Sealed Power's are all the same 1.580 nominal Comp Ht.
ZOLLNER Part #Z9398, equivalents listed on Zollner Box
Badger #P891, Federal Mogul #362P, SilvoLite #2225

The available Egge 343 pistons are also 1.580 Comp Ht.
The rods for 343 and 360 are the same, also 290 & 304, all 5.875, .9309 Dia Pins.

Yes, I have a 9.175 343 block, 1.580 Zollners, stock 5.875 Rods,
and 304/360 Crank that's 3.44 stroke stock, but
had the crank offset ground .010 for a 3.460 stroke
so pistons are .007 above the deck because the Rods
were re-conditioned which makes'em a little, .003, shorter.

Heads are dogleg '70 304 closed chamber fitted with 2.02/1.68 11/32 stem valves
ported and milled about .060 for a 48cc chamber volume.
The dished pistons have a big _27cc or so dish volume.

Nope, left the '69 343 block with stock 7/16 head bolt taps but
did buy new ARP 7/16 head bolts that come with heavy washers.
( had to grind the header flange to clear'em too )

Right about 10.0:1 Static CR if my calculations are right :-|
and about 8.2:1 Dynamic CR per KB SilvoLite calculator.

But one must watch piston to valve clearance, clay to be sure.
Cam is .525 lift 290 deg advertised and it's at the ~.100 min. clearance :shock:
( he he he - that smiley kinda looks like valves in a chamber )

yeah, slow gettin' it together and back in the car, but I'm close :oops:

kegler343

Wow. Nice to find someone willing to give up what they have learned in the AMC arena. I have run on entirely too many that claim they are willing to help a fellow AMCer, but when you get technical, they clam up. After building the 343 (and smoking two trannys in the break in period), I had the car in my cousin's race shop next to his late model with a Ford 351 Windsor/Cleveland alcohol burner. With the exhaust dropped of the AMC motor, you could not tell a noticable difference between the two. Same noticable lope and instant throttle response. His buddy is a Ford die hard, or at least was until he had to pick his jaw up off the floor. The next weekend, the winsor/cleveland grenaded a piston and cuz never had the heart to go it again. So, the AMC kills another of the big three while up on stands!!! By the way, has anyone used the disk brake conversions offered by scarebird on ebay. He claims to have a bolt on plate that uses Ranger rotors and S-10 calipers. Sounds sensible to me, but I have been wrong before. Pete