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That's a lot of power for a street driver....most guys i know can only afford gas for 1 cruz nite per week at those power levels. That engine will out rev most 408's and seems more like a race prepped engine to me.I don't know why the 372 isn't more popular? As for drivability i think most guys...

I don't actually know but have "read" long duration cams have very poor cylinder filling and mixing, are inefficient and make very little power at lo rpm. That broken idle that most guys love is actually raw gas burning and exploding in the exhaust system. Maybe it's not the torque number but...

maybe it was explained a little yonkey. I think he is saying losses on an automatic leave .80 at the rear wheels losses for a manual leave .85 at the rear wheels.

I agree, it's the duration. As OldRick suggests, strong acceleration from lower speeds...even at part throttle.

Cruising around town 1400 -1600 is where i noticed throttle response was lazy. Compare the 256 with the 268. and the 256 wouldn't make as much torque as a stock cam below 2000. The graph doesn't show the diifference below that but it is even greater. I did have a stock 340 with the generic...

When driveability is discussed concerning longer duration cams it is the the low rpm power that is questioned. I've often mentioned that when i ran the mopar performance .474 or comps XE268 low rpm torque was not strong. if i hit it when driving slow, acceleration was lazy until higher rpms...

Tx for all the good info guys. My questions have all been answered and then some.

And i have to agree with you. My Dynamic 9 1/2" drove normal for the most part. However i did find it difficult in that it would maintain a lazy attitude or blow the tires out completely. Also as I mentioned earlier it was uncomfortable driving through the converter or out of it going down...

Very good point, bigger cams can add hp between 2500 and 4500 rpm. My XE 268 had strong mid range from 3000 up on the occasion i got on it leaving the village to well past highway speeds.The power in that range seemed limitless! It still needed a converter to make power from idle up and that was...

I agree...we spend all our time driving under 3000 so that's were you want power. I have also used the old .474 purple shaft with about .238 duration and like all big cams it was a dud on the street. Those cams make power at high rpm and are a necessity for 12 seconds at the strip, but require...

Yup..gears and converter will fix the lo end but now you're heading to more of a race build and the all around driver is sacrificed to some degree. I ran a warm 340 with a .230 duration cam and it was lazy. A 9 1/2" Dynamic converter solved the lo rpm power but the novelty wore off driving...

Could make a good discussion. But if the stock heads stall out around .480 lift can you get 425-450 with a big cam and stock heads? Long duration would surely help but it would have a tough time at lo rpm. Hang on from 3000 up!

J heads will flow 400 hp and really 325-350 is plenty for a nice all around driver. To push 400 hp you'll need a bigger cam and aluminum or ported stock heads.Then you'll have more expense and a "dud" on the street.

Wow..lots of good info guys. It seems a rebuilt set of J heads would be a better choice for most builds.

Tx...as i suspected.

So i was lookin' through the Summit catalogue today and priced them at around $1000. Is that for a pair...looks like just 1?

yup...just googled it. T bird, Torino and Trucks!

what was it available in...I never knew that?

Now...here's one. Has any manufacturer ever built a square engine i.e. same size bore and stroke? There is a reason the engineers pick certain dimensions.

You didn't understand the point that was illustrated. It was comparing two engines with the same displacement, cam heads and specs except for the stroke.

AJ, that stock 70 340 Swinger would have pulled hard to well past highway speeds and break the tires loose easily. A lot of fun to drive and I'm betting it would be enough for 95% of the guys on this site. Of the membership i often wonder how many actually race their cars. In my area I know...

I agree. A 408 revs nicely to 6000. Many warm 340 / 360's shift at 7800-8000. A long stroke engine cannot physically rev as fast as a short stroke engine with the same displacement if they are similarly built. It's physics.

Looks like i've ruffled more than a few feathers. The only point i was trying to make was a shorter stroke engine will rev quicker in engines similarly prepped with the same cubic inch and to a point will accelerate faster in a street driven vehicle.

I'm sure you could make changes to either one to "one up the other" He just said they had identical cams, same compression and were built with nearly identical specs. I think he was pretty disappointed...he is a Mopar guy. It would never matter to me because i don't race. As i said earlier i...

Be careful what you wish for. The 408 may not be what you think you want. I have a friend with a 396 camaro and a 408 dart. Both engines are very similarly prepped and geared. Now he raced his cars numerous times against each other and said the Dart always beats the Camaro off the line but by 80...

Something that hasn't been mentioned is the return someday if you decide to sell.

I'll say it again...340 guys take a lot of heat. I have seen a lot of 360 a bodies much nicer and faster than any of my builds have ever been, but because i prefer a 340 in my clones or 340 cars i now have an attitude. My builds are not fast enough to win a race or nice enough to win a car show.

I wouldn't build a 68 - 73 A body or a 70 - 73 small block E body with anything but a 340, not even a clone. That was the performance small block they were available with. Don't care if your 360 cost half as much and has 100 more hp...just not interested. 340 guys take a lot of heat?

You would be limited to the cam size for either head. I think stock X or J heads flow stalls out around .490 valve lift. Those TV guys can get 400 hp with a cam, headers and carb swap, but you and i can't.

Stock 1.88 valve j heads will support 400 hp. You will need to do a lot to the motor to gain anything with x heads. The J heads may have better acceleration on the street to well past highway speeds, but you will win all the parking lot races with the x heads.