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View Full Version : 340... 4 bolt mains?


aspen514
06-14-2007, 11:40 AM
Anyone know what years or what smallblocks come with a 4 bolt main. Im interested in making a stroker motor and was told I'd need a 4 bolt main to handle added horsepower?

1973Swinger
06-14-2007, 12:32 PM
Im not completely sure, but I dont think any mopar smallblocks came stock with 4 bolt mains, but the 340 T/A blocks had thicker webbing on the bottom end that allowed the installation of 4 bolt mains (good luck finding one of those hahaha). If you are building something under 500hp, then dont worry about it, a 2 bolt main is fine, get it sonic checked and install a main stud girdle. If you plan on 500+, then use a R3 block.

greasydonkey
06-14-2007, 02:31 PM
he is correct, they never produced one in passenger production. 2 bolt main is fine for anything but all-out serious racing. mopar performance makes a main cap kit where you can have a machine shop drill and tap your block for 4 bolt when its in for machine work anyway. even then, all the caps arent 4 bolt, the rear cap is still 2 bolt. come to think of it, the front one might be too. but it makes the middle three 4 bolt for sure. use those and a girdle and youre set for serious power.

aspen514
06-14-2007, 05:55 PM
ok thanks for the info guys. I wanna take a 340 or a 360 and stroke it out to atleast 400 ci and go with a hotter cam than last motor. I don't think it would go to 500 horses but I wanna try to get around 450 with upgrades. Is this obtainable and will just a 68-70 340 block work for it?

pcrmike
06-14-2007, 06:13 PM
Perfectly fine. The material in a Mopar engine and the difference in geometry in the bottom end (read: rod ratio or rod lean angle) makes the Mopar handle a lot more in the bottom end than a Chebby or Furd with two bolt mains. Also, a stronger factory crank. If you ever machined one, you would notice the Chubby has as-cast counterweights, while the Mopar has a factory, fully machined crank. It has fewer stress risers and is more perfectly balanced. You will find it to be superior in many ways. Yes, I am a Mopar fan, but I build GM, Ford, AMC and especially Mopar engines. I like the engineering involved with the Mopars. All have their strengths, but they seem to have the most balanced, capable package. Easy to make power with too. :-)PCRMike

DanL
06-14-2007, 08:03 PM
Grab the July 07 issue of Hot Rod Magazine. They put a 4" crank in a 340 block, took it out to 414 CI; it put out just over 500HP. Sounded pretty easy.

rumblefish360
06-14-2007, 11:53 PM
The stock block will take 500 easy without mods. Hard blok and adding main bolts and girdles can all be done to band aid it up to perform higher, but after 500+ hp and living long, I'd look for a race block and do it up well.

aspen514
06-15-2007, 05:09 PM
cool thanks guys thats what i needed to know. And as for the hot rod magazine i'll definately grab one that seems like exactly what i want to do.

Tarrbabe
06-16-2007, 01:14 AM
.:smoking:Stock S/B's come with 2 bolt mains and stand up to 400-450 hp forever almost. There are many different substitutes that many have gotten good service from at higher hp ratings ( cast iron, steel, 2 bolt, 4 bolt and now I understand they use aluminum main cap on the ultra egnines and swap the caps out instead of the crank or block. The stress will always be there but it comes down to what you want to take the stress. Stock and Mildly modified engines can do with the stock set-up. The question is where do you require more? I believe that between 450-500 hp you should go to steel caps. This places more stress on the block. Then when you get above 600 hp aluminum caps should be used and replaced often. There are differences between BB & SB engines so you have to make your choice according to the strength of the blocks and main caps. Where do you make your choice? If you make the right choice you save money overall. If not, you spend much more. This comes back to the old saying. How fast do you want to depends on how much money can you spend?
Yes, I recommend building the bottom end to the VERY BEST you can. It will save you money overall.


Just thinking out loud

sanborn
06-16-2007, 08:12 AM
The application of Torque to the block is what kills them, not horsepower. Short stroke, high horsepower combinations can live in a stock(well prepped) block.

The longer the stroke, the more torque an engine can generate---the harder the torque is on a block.

And the more often maximum torque is applied to a block, the quicker the block will fail.

If you are building an engine with 500HP and producing torque 450 Ft/Lbs. or less, a stock block will work fine for moderate use. If torque is higher, the life of a block becomes a time clock---How long will it last.

Just make sure there is no pre-detonation present. That plus torque will kill a block quick!

Tarrbabe
06-16-2007, 07:42 PM
I am a mere student compared to the knowledge he has come by in his exploits on the round track. If you can get an engine to stay together for lap after lap after lap ( you get the idea ) then building a street/strip engine should be a snap.

sanborn
06-16-2007, 10:46 PM
Now Tarrbabe, I was just trying to say the same thing you said---only a slightly different way!

Tarrbabe
06-17-2007, 04:15 AM
but I should have addressed torque instead of horsepower. Torque is what is the true enemy of engines. I rememYes I understand...............

but I should have addressed torque instead of horsepower. Torque is what is the true enemy of engines. I remember 301 Chevy’s turning 10,000 rpm every weekend at 292 or 301 cid every week at the drags with the 3.00 stroke. If those engines failed, everyone thought they had bad parts. I remember a 3.02 camera ( Little Stinker ) that launched at 6000 plus and shifted at 10500 according to the driver. Damn, that was wild. That was at Buffalo Valley Drag strip.


Torque is what tears an engine apart, Not horse power. Horsepower does come into the figure but only after the torque is in prospective. I helped Eddie Kanter, ( The original Fast Eddie ) from the Detroit Area. He was a designer for GM in the early 60,s and ran Pontiac then. Then he moved to Cookeville and opened a Speed Shop. I learned a lot from him and although, I didn't have a lot to do with his Dirt Track car ( Atomic Speedway )Oak Ridge Tennessee. I learned a lot from him. Back then, we ran a 55 Chevy chassis with a 72 Vega body. We started out with a 350 engine that soon came to problems. Then we de-stroked it to 3.00 and it screamed. Right up till it put a rod through the block while we were leading the race. A 200 lap feature that I have regretted to this day. Our driver quit after that and Eddie sold the car due to his wife threatening Divorce if he drove it. He was in his 50's at that time and his wife was less forgiving.

P.S. I told him something was wrong just before the engine blew up. I saw sparks coming for the headers. I am sure it was the rings and pistons giving up the ghost.
bur 301 Chevy’s turning 10,000 rpm every weekend at 292 or 301 cid every week at the drags with the 3.00 stroke. If those engines failed, everyone thought they had bad parts. I remember a 3.02 camera ( Little Stinker ) that launched at 6000 plus and shifted at 10500 according to the driver. Damn, that was wild. That was at Buffalo Valley Drag strip.


Torque is what tears an engine apart, Not horse power. Horsepower does come into the figure but only after the torque is in prospective. I helped Eddie Kanter, ( The original Fast Eddie ) from the Detroit Area. He was a designer for GM in the early 60,s and ran Pontiac then. Then he moved to Cookeville and opened a Speed Shop. I learned a lot from him and although, I didn't have a lot to do with his Dirt Track car ( Atomic Speedway )Oak Ridge Tennessee. I learned a lot from him. Back then, we ran a 55 Chevy chassis with a 72 Vega body. We started out with a 350 engine that soon came to problems. Then we de-stroked it to 3.00 and it screamed. Right up till it put a rod through the block while we were leading the race. A 200 lap feature that I have regretted to this day. Our driver quit after that and Eddie sold the car due to his wife threatening Divorce if he drove it. He was in his 50's at that time and his wife was less forgiving.

P.S. I told him something was wrong just before the the engine blew up. I saw sparks comming for the headers. I am sure it was the rings and pistons giving up the ghost.

sanborn
06-17-2007, 10:04 AM
Did you ever run at the Smithville Dragstrip?

Tarrbabe
06-17-2007, 05:22 PM
but never raced there.

sanborn
06-17-2007, 07:55 PM
Since you and I are probably the only ones still alive(or active) that remember the track---let me pass along this true story.

I had been racing around Nashville since 1960, bought a rail chassis in 63, put a flathead in and raced that year. In 64, installed a SB GM and ran B/D. The car was fairly nice(for that era), engine was OK(297", 6 Stromberg 97s, Herbert roller, vertex, etc.). Anyway, we raced all around TN, KY, AL. I was in school in Cookeville---so the car went with me to Cookeville when fall classes started. Four of us rented a house, just off the square, just down the street from Loftis Auto Parts. The house had a nice drive-in basement. That was the rail's home for a couple of years.

Back to the Smithville track. I think it was early 65 when the guy that owned Smithville contacted me to see if I would do some exhibition runs at the track. Seems as though they had never seen a "real" rail at Smithville. The track ran on Sunday afternoons so it wouldn't conflict with any other races.

I had an old set of Bruce recap 7" slicks(hard as a rock), I oiled them up, ran the pressure up and could literally spin them at will all the way down the track. I looked like Don Garlits with tire smoke(about 12 minute ET). The crowd went wild, the owner was happy and he paid me $50(I think)---which wasn't bad in 1965.

I ran there twice---until a few wised up to what was going on.

Oh, those were the "good ole days".

PS, I pulled the rail with a 1954 Ford four door sedan, 6 cylinder with the rear seat removed to carry extra parts, tools, fuel, etc. The trailer was a single axle, unsprung and used a 1 3/4" ball on a bumper hitch.

Tarrbabe
06-25-2007, 05:04 PM
Souuds right for the times too.
Sorry I took so long to answer. Been gone for a week. Has a Disk removed from my back last week and I'm home now, doing better.:)

sanborn
06-25-2007, 06:25 PM
Hope you are doing OK!!!!!