Destroked Small Block?

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Bonneville is another place with cu in classes
and it is a high altitude long drag race
where an all top end car may not be able to get up to speed
I'm guilty of saying "Bonneville" when someone proposes toobig a cylinder head and or cam for their application
but it really does not work that way- even with a push start
the gears are too tall and the gear spreads have always been big until the newer multi speed trans arrived
 
The biggest issue with destroking a 340 is the very tall deck height. A 340 already has a 1.850 compression height. As you destroke the engine that compression distance gets taller and that's bad. It means a heavier piston, and generally ring seal that can be marginal at best.

You can correct some of that by using a longer rod. I always wanted to do a .400 long BBC rod but back in the day it was tough to even get a rod manufacturer to discuss it with you.

Now, with billet rods out there you can get just about anything you want and it may be worth looking into.

The other option is finding an R block with a shorter deck...say a 9.000 deck block. I've seen a few here on FABO. That way you can use a 6.123 rod (I use 6.125 Chevy rods instead and turn the rod throws to 2.100 or if you are even more die hard turn them down to 2.000) and still keep the piston weight somewhat light and with the pin not over 2 inches down from the deck.
 
yellow rose said:
The biggest issue with destroking a 340 is the very tall deck height. A 340 already has a 1.850 compression height. As you destroke the engine that compression distance gets taller and that's bad. It means a heavier piston, and generally ring seal that can be marginal at best.

You can correct some of that by using a longer rod. I always wanted to do a .400 long BBC rod but back in the day it was tough to even get a rod manufacturer to discuss it with you.

Now, with billet rods out there you can get just about anything you want and it may be worth looking into.

The other option is finding an R block with a shorter deck...say a 9.000 deck block. I've seen a few here on FABO. That way you can use a 6.123 rod (I use 6.125 Chevy rods instead and turn the rod throws to 2.100 or if you are even more die hard turn them down to 2.000) and still keep the piston weight somewhat light and with the pin not over 2 inches down from the deck.
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Im selling off my 340 stuff going to 318 platform or engines Im trying to hort up some blocks as we speak.
 
1Badcolt said:
Im selling off my 340 stuff going to 318 platform or engines Im trying to hort up some blocks as we speak.
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Why in the hell would you do that? The 340 bore size will make more power in a identical build then the 318. Also the 340 has larger main caps for strength
 
We used a big block chevy forged rod, I think the C to C was 6.442, which enabled us to use a lighter piston with less comp. height. We also ground the crank down to a chevy size, I think the rod ratio was almost 2 to 1. The motor really liked to rev quick , it was built about 30 years ago and still running strong.
 
light reciprocating/ piston/ rod weight is the key to a quick revving motor rethink the 340 even then use a longer rod
 
replicaracer43 said:
Why in the hell would you do that? The 340 bore size will make more power in a identical build then the 318. Also the 340 has larger main caps for strength
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Wyrmrider said:
light reciprocating/ piston/ rod weight is the key to a quick revving motor rethink the 340 even then use a longer rod
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Cubic inch to weight rule.
Hence the questions on stroking up and down.
A smaller engine gives him a weight break.
A larger engine could earn a weight penalty BUT with the ability to add weight where you want it.

It’s a game fellas, read your rules carefully.
 
rumblefish360 said:
Cubic inch to weight rule.
Hence the questions on stroking up and down.
A smaller engine gives him a weight break.
A larger engine could earn a weight penalty BUT with the ability to add weight where you want it.

It’s a game fellas, read your rules carefully.
Click to expand...

A - Gas 6 Lbs per cubic inch
B - Gas 8 Lbs per cubic inch
 
Umm yeah, the 305 Dick Brooks was running was a SMALL BLOCK and not a Hemi. I think they culled a Keith Black Trans Am series unit for that effort. I have a Bryant billet 3.25" 340 configuration crank that I'd like to try in a 318 or 340 block, but it has a generic (Chevy) flange on the back. Also have a 3.25" 383/400 Moldex crank that might be interesting (396" long rod 400 B). I even had a friend grind me a 3.5" 383 steel crank out of a smoked but not bent forging. Have all the stuff to build a 422" (destroked 451-lol) out of it, just haven't found the perfect (light!) chassis for it yet...
 
rumblefish360 said:
Cubic inch to weight rule.
Hence the questions on stroking up and down.
A smaller engine gives him a weight break.
A larger engine could earn a weight penalty BUT with the ability to add weight where you want it.

It’s a game fellas, read your rules carefully.
Click to expand...
Right....and my thoughts were if he's destroking a engine, it would make sense to use a larger bore, and shorter stroke to achieve his desired CID. Interesting discussion, would be better if we knew what cubic inches he's shooting for
 
replicaracer43 said:
Right....and my thoughts were if he's destroking a engine, it would make sense to use a larger bore, and shorter stroke to achieve his desired CID. Interesting discussion, would be better if we knew what cubic inches he's shooting for
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Havent done nothing yet
 
I just looked at those A gas rules, I'd probably keep it simple, build a 340, with W2 heads, with a tunnel ram. Would need to weigh 2040 lbs, and I think I saw a weight break for removable plenum, maybe was 25 lbs
 
replicaracer43 said:
Right....and my thoughts were if he's destroking a engine, it would make sense to use a larger bore, and shorter stroke to achieve his desired CID. Interesting discussion, would be better if we knew what cubic inches he's shooting for
Click to expand...

YES YES YES!

I certainly would use the biggest bore possible to take advantage of the beauty! I agree that makes sense. And best power.

The only thing I’m missing is the cars weight. This I think is an unknown. And we are a bit aways from finding out since he has to still do a cage and etc.... work on the car.

Generally, I don’t see the 318 blocks limited bore size as an advantage BUT wise and crafty work could yield interesting results.

Once the cars weight is estimated or known, then the cubic inch chase begins. How it is finalized, maybe a single or multi factor advantage or hindering.
 
I guess it becomes a matter of how light can the car be built, I'm not sure on that, but 2040 is pretty light, not sure how much lighter is possible on his gasser build
 
replicaracer43 said:
I guess it becomes a matter of how light can the car be built, I'm not sure on that, but 2040 is pretty light, not sure how much lighter is possible on his gasser build
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Exactly!

Or, he builds the biggest honkin monster he can and adds weight over the rear axle.
 
replicaracer43 said:
I just looked at those A gas rules, I'd probably keep it simple, build a 340, with W2 heads, with a tunnel ram. Would need to weigh 2040 lbs, and I think I saw a weight break for removable plenum, maybe was 25 lbs
Click to expand...
Tunnel rams and single 4 intakes get a weight break if they are old school type like the ones I have in photo
TR5 tunnel ram
Tm5 single 4
And others also

20180803_235350.jpg
 
rumblefish360 said:
YES YES YES!

I certainly would use the biggest bore possible to take advantage of the beauty! I agree that makes sense. And best power.

The only thing I’m missing is the cars weight. This I think is an unknown. And we are a bit aways from finding out since he has to still do a cage and etc.... work on the car.

Generally, I don’t see the 318 blocks limited bore size as an advantage BUT wise and crafty work could yield interesting results.

Once the cars weight is estimated or known, then the cubic inch chase begins. How it is finalized, maybe a single or multi factor advantage or hindering.
Click to expand...
Here is a current competitor within our group running a Henry J with a 38+ inch chebby motor !!!
Ok this should get some minds to thinking?

Screenshot_2018-08-14-11-36-37.png
 
smaller motor should (that's should) make more HP per cu in if you can spin it up
so lighter works better
for the same cu in larger bore shorter stroke wins
you can use a long rod with correct cam
throw your car on a scale and lets see what it might weigh
lots of motor size choices once you know the weight
Ted Cyr (Cyr & Hooper) built a blown sbc three wheeler with drop to go jack stands he had two HUGE batteries back of the Axle to make weight
I think the class was some BB/A or BD/A fiat body Long Beach cold night fortified with a little flask- sound really ripped
slipper tires B4 slipper clutch short wheelbase Scotty Fenn style what fun
opening the exhaust early can really make some noise
1800 for a 305 would be tough even for Sneaky Peet Robinson
 
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