I've been reading the series in Mopar Action by Bob Tarozzi as he helped with the AAR 'Cudas run by Dan Gurney in the Trans-Am. Got me wondering, how would the GRM minions go about building such a thing these days, just in case you wanted to?
I've been reading the series in Mopar Action by Bob Tarozzi as he helped with the AAR 'Cudas run by Dan Gurney in the Trans-Am. Got me wondering, how would the GRM minions go about building such a thing these days, just in case you wanted to?
305, either bore out a 273, or de-stroke a 340 or 360?
I've crunched some numbers on this one. The "easiest" way would be a .030 273 with a 360 crank. That will get you to 301. Would require either cutting down the mains on a cast 360 crank to the 273/318/340 mains size or getting an aftermarket forged crank that has the 360 stroke on the smaller mains.
Now that combo gives you a weird 3.66" bore and a 3.58" stroke. You won't fit any good sized vales in that bore without clearancing the cylinder walls.
The Trans Am motors used a custom Keith Black crank. I think it was a really short stroke like a 2.95" in a stock 340 bore (4.04) Stock 273/318/340 stroke is 3.31"
Other combinations based on factory parts I've thought of require diving into earlier and more obscure A-engines and using combinations of them and LA motors. It requires an odd combination of parts that would be difficult to locate and may not even work together.
A destroked 318 would probably make the most sense. Would have to round up a forged crank then weld up and offset grind the throws down something like .18-20" to get it around 305 CID/5.0 Liters.
Rob_Mopar, why not use the 340 crank and heads on a bored 273 block? You end up with a shorter stroke than by using the 360 crank. I have no idea if you can bore the 273 out enough, or if there are appropriate pistons available though.
273, 318, 340 all had the same crank.
I still say custom 3" crank in a 360. 4"x3" worked well for ford and chevy.
340 uses the same stroke as a 273, no real advantage there. Some restored 340's are out there running 273 forged cranks in 'em.
Any 273 pistons are slim pickings, but any of these combos would require custom pistons.
The early 340's came with 2.02" intake valves. The 273 & 318 came with 1.78 intakes. The 2.02's won't clear the cylinder walls of a 273. I don't think the 1.88" intake valves from the late 340's and the LA 360s will clear either. The bore can be clearanced for a larger valve, but I can't remember how far before hitting water. And even then the shrouding is really bad for a motor that would need to be wound up.
318's have a bigger bore than the 273 so you can fit some bigger valves in them. The 318s were in production a whole lot longer so there's more of them to mess with. And they are usually cheap.
neon4891 wrote: 273, 318, 340 all had the same crank. I still say custom 3" crank in a 360. 4"x3" worked well for ford and chevy.
That thought has crossed my mind a few times. Would be curious to see what something like that would cost. Just won't want to pay for it. 
Rob_Mopar wrote:neon4891 wrote: 273, 318, 340 all had the same crank. I still say custom 3" crank in a 360. 4"x3" worked well for ford and chevy.That thought has crossed my mind a few times. Would be curious to see what something like that would cost. Just won't want to pay for it.
Yeah, I've thought about this a lot (actually plan to build a 3.655"x3.58" 273 at some point; have the crank rods and block, but need greater solvency).
I''ve got a set of ported 273 heads with 1.88/1.6 valves in them, I'm pretty sure they'll clear a 0.030" over bore. After all (0.100/2) - (0.030/2) = 0.035" is only less bore to valve clearance than stock. At 10.5:1 it should make for one torquey 5 leter!
I've thought atbout the whole de-stroking thing. For road racing I'd want to start with a billit crank and resto 340 block (basicly a stock machined R3 block). For running in SVRA that would be the way to go to run with the Fords and Chevys that are spinning to 8,500. But A) that's $5K BEFORE you get to the machine shop; and B) HSR mandates and VRG encurages a 6800 RPM limit; for that a steel cranked 318 makes a lot more sense. When I penned the '64-'66 Valiant, Barracuda, and Dart supplimental preparation rules for SVRA http://svra.com/SVRA/SVRAHome.nsf/attachmentweb/EJEN-7ZS4YK/$file/Chrysler+Corp-MoPar+(64-66).pdf?OpenElement I negotiated the following engine/weight break down:
273 Nom-Cid = 2700# /w driver
318 Nom-Cid = 2800# /w driver
Alt Bore & Stroke under 4999 cc = 2800# /w driver
My Dart has a 0.040" over 318 (324 Cid) and weights 3411 with about 10 gollons of 93 octane and me in it. No way is the Dart getting much under 3300#. SVRA allows up to a 0.060" over bore (about 327 Cid on a 318).
Dave
Is this the engine combination that someone ran at Daytona in 1971 when the wing cars were limited to 5.0 liters?
Quick search found this.
I heard stories that on the back stretch that the tach was pushing 10,500....
In reply to BoostedBrandon:
Oh, to hear that noise.
BoostedBrandon wrote: Is this the engine combination that someone ran at Daytona in 1971 when the wing cars were limited to 5.0 liters?
Almost certainly. Given the limited lead time it was very likely a direct copy or loen of one of the KB TransAm motors.
I was doing some F5000 research (per the Aluminum Monocoque thread) and found that the Shadow team from 1975/76 were using Dodge engines, which made me think of THIS thread--hence the Zombie. 
I did a bit of digging and the information that I could find indicated Lee Muir moved from McLaren to Shadow and was building the Shadow engines based on the NASCAR Mopar engine. Muir (with assistance from Chrysler) used the 340 block with a different crank to give the required displacement. Apparently the engine was significantly heavier than the Chevrolet but did offer more horsepower. The only win for Shadow with the Mopar engine in F5000 was at Road America (and I was there watching but don't remember seeing the Dodge reference in the picture above) so it makes sense that RA was the only track where the HP advantage offset the weight penalty. There was a reference to Shadow using the same "induction system" as used by NASCAR but that makes no sense as NASCAR was using carbs, not fuel injection. If anyone is really interested let me know and I'll see if I can recover the links I found.
BTW, they were claiming 540hp.
You'll need to log in to post.
