Comp cam XE262 in a 340

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The difference between the 262 and 268 is so small that you probably wouldn't know or notice the difference. Not like you're moving duration 20* one direction or the other.
 
Specs on the 10200703 are
268/276/110/.44/.513 and 226/234@050
In at 106,this will net an ICA of 60*, and drop your your Dcr to 7.8/155@sealevel, too low for me. But not too low for a hi-stall and bigger gears as already mentioned. But faster lobes are out there.
 
AJ/FormS said:
Specs on the 10200703 are
268/276/110/.44/.513 and 226/234@050
In at 106,this will net an ICA of 60*, and drop your your Dcr to 7.8/155@sealevel, too low for me. But not too low for a hi-stall and bigger gears as already mentioned. But faster lobes are out there.
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o.k. you're suggesting the 703 would be better suited to 10:1 and up 340 w / 3.23 and a stock converter?
..how might the 703 work in a 9.1:1 372 or 383 still w / 323 and 2400 converter.Would the extra cubes help?
 
Generally speaking, extra cubes equal extra torque which makes the converter stall higher and the cam seem smaller.
The loss of 1 point in compression is a small thing I would ignore. I would actually consider it to be a better running and working ratio to start with.

It should work a little better.
 
In this case, the extra cubes amount to 3.3% and 6.3%
I wouldn't expect the 372 to run much different. But the 383, if it is a BB with it's shorter stroke, might be even worse.
Personally, while I can live with a soggy bottom end,a big TC, and race gears, I don't like it.I much prefer dumping the clutch at like 1200 and motoring away. And while 4.30s are fun on the street,on weekends; I found them a royal PITA in my clutched DD.
Personally, I like running the compression on the edge of detonation but not yet into it. The engine response is immediate without bog or hesitation from well below 1800rpm; taking full throttle with a 750DP and with a 10.7 starter gear to perhaps as low as 1500 rpm.I like lighting up 295s like it was a BB. I like getting fantastic fuel mileage. I like being able to jump in and drive a 1000 miles on a weekend,not having to have saved up for months, to be able to afford the trip. I like putting the hammer down at 30mph in second gear, not having to downshift to blow some punk off.I like being able so slide through a turn, feathering the throttle to maintain control, not having the engine revved up to the moon. I like running a small cam, and letting the heads and compression do all the work;INSTEAD of a 2-sizes bigger cam and a 3500TC and 4.30s.

I challenge any SBM streeter that is currently running their Dcr compression in the basement,a 3500TC,big gears,and a ferocious cam, which is sortof a pretty good combo; to back up the bus. Rebuild it with a 223 to 232 at most cam. Reset the Dcr to the max. Pull that 3500 in favor of a 2400/2800. Pull that 3.91 x 2.45=9.58 gear in favor of a 2.74 x 3.55=9.73starter And install some matching heads.
Now go out and tell me how much more you like the new combo.
And when gas goes to 8.49 a gallon,try to remember what a pig your old combo was on gas.

Some guys do not put much emphasis on compression, and rightly so for a drag racer. The difference in ultimate power is not that significant, from the torque peak to the power peak and up to trap rpm.
But we streeters don't spend a lot of time up there. And from idle to the torque peak which is where we DO spend most of our time,the difference from a Dcr of 7 to a Dcr of 9 is a HUGE difference in torque and thus a very significant difference in power, and the fuel useage in steady-state cruising I have proven to be up to 100% increased. For an SBM streeter, and especially for a streeter that is gonna spend some significant time on the hiway, IMO, compression is a very big deal.
If you are putting pistons in anyway, IMO, it behooves you to pay very close attention to your FINAL Dcr, and run it as high as you dare.It costs very little more and pays back bigtime.
Consider even what the auto industry is doing. Are they still running low Scrs? No! We are seeing Scrs now that are mostly higher than they ever were in the glory days of the 60s and 70s. Do you think they might be on to something?

In truth setting the Dcr up to the max, might actually cost less, depending on your combo;by the time you add up the installed cost of the big TC and the rear gears.
My 367 is running; Scr 10.9/Dcr 8.6/175psi/aluminum heads/87E10 .
A few braver-than-me fellows here, report that they are successfully running Dcrs with their aluminum heads into the 9s, and pressures over200psi. I think I recall one fellow successfully running 9.2Dcr on 91 gas. If I ever get a do-over, I am definitely gonna pump mine up higher. The throttle response and fuel-mileage alone are worth it to me.
Notice throughout this post, I refer to IMO.This is cuz these are the things I have experienced with my three iterations alone; the 292/508/108, the 270/280/110, and the 276/286/110 cams, and various Scrs from 11.3 to 10.9; over a period of over 14 years and a distance of over 100,000 miles.
To me, a 9.5 engine is not worth building,from scratch, for a SBM streeter. To me if I was stuck with one, I would not slide much cam into it. If I was broke and couldn't afford to pump it up, I would drive it with the factory cam in it, and save up for pistons.
I'm not saying there is anything wrong with a 9.5 engine! I am saying if I have to rebuild it, the proper pistons are chump-change more, and will very substantially improve your first gear performance, and most especially your fuel-mileage, and your off-idle to about 2400 rpm torque, and throttle response.
See SBMs are cubic inch handicapped, for a muscle type car. So you really have to squeeze them to come alive. A 9.5Scr 440, well that is a beast. Sure Dynos have have shown even 8.5 engines making plenty of power, Again, from the torque peak to the power peak. For a Streeter I say SO WHAT! We don't spend a lot of time up there! But every time you start off, you are passing from idle to about 3500 rpm. What sense is there in having 400/450 horsepower at 5800, and you need a 3500TC/3.91s to drive through the hole you just created from idle to 2000rpm? No, friends, FAR better it is to have more modest small-block power, and gobs of torque to pull 3.55s and a 2400TC. So what if it takes a few milliseconds longer to hit 50/60 mph.The tires are gonna be spinning most, to all, the way there anyway.So what indeed.
For you guys with Desk-top Dynos and similar programs, I'm afraid they won't report this stuff. So don't waste your time trying to prove it. These programs are great at what they do, but by and large they are very focused. And not on daily driving,lol.I shelfed my early version in 2004, and haven't revisited it since.

So anyway, that is my opinion.
 
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This is so funny.

I'll leave this to the "war and peace" bookwriter, baffle them with BS, as to whether such a small change in camshaft from a xe262h to xe268h would be noticeable. Going from top fuel to lawnmower with that cam change! It's not, but I digress. What a waste of time. Not worth the time or effort to say anything in here anymore with the horsecrap that gets beat to death.

My scientific calculator broke so I can't comment. LOL

You want a 320-360hp 340? Run either camshaft, getting timing right and put a decent intake/exhaust on it. Anything else is making mountains out of molehills...
 
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Don't get to caught up in compression. Use it as a tool for the combo. I know this is a street car but I have drag raced for 25 years and I can tell you 1 number of compression does almost nothing but make you run race gas. They say 1 number = 4% power increase. So going from 9.5 to 10 to 1 on a 400 hp engine nets you 8 hp not worth to me. Airflow trumps compression every time.
 
ir3333 said:
we nearly hit $7.00 / gallon in Canada before oil fell.
it will eventually be there again...but when?
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2.29 a gal in USA.... at least where I am. I did reach a hair over 4 bucks, though, a while ago.
 
i don't think there are any topics more controversial than "which camshaft"?
or which is better a 340 or a 360? ( of course we all know it's a 340)
 
ir3333 said:
i don't think there are any topics more controversial than "which camshaft"?
or which is better a 340 or a 360? ( of course we all know it's a 340)
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Sez you! 360!!!
LMAO!!!!

I gave up 1/2 through AJ's ultra long winded post. It was a record for me to read that far.

The difference in 1 point of compression are minimal and not noticeable by you in the drivers seat. But you will notice it when you have a engine pinging away. Be careful with compression and pump gas.
 
Well AJ might have exaggerated a bit here and there but i think his point is a stock high compression 340 with the small stock or rv style cam will plant you in that bucket seat from idle up to 4500 - 5000rpm in 3 gears.
.. the later 8:1 with a big cam...not so good until you get moving.
 
ir3333 said:
.. the later 8:1 with a big cam...not so good until you get moving.
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This has what exactly to do with the OP's question? Carry on with the blovation!

The ignore function is getting a workout early this year. :) Not you ir3333
 
That's Ok you won't hurt my feelings. I've done it both ways,and lots of in-between ways, and to me there is no substitute for plenty of compression ON THE STREET.
And in Go-cart racing Too!
 
  • Not disagreeing with AJ I just play it safe because I don't have the tuning savvy to make it all work. But then again I might learn to if gas was $7.00 a gallon. I'm spoiled 91 is 2.60 a gal. here. By the way. What was the original question. LOL
 
bill340S said:
I'm looking for feed back on the Comp Cams XE262 as compared to the popular XE268 in a 340. If your trying to torgue up a 340 the XE262 seems a better choice to me based on spec's and comp cams free online dyno graph. My engine is 9.5 compression with stage one X heads. Anyone used this cam?
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I have a 40 over 340 with the XE262H 8.1 dynamic CR, old TRW forged slugs .018 above deck, ported 202/160 j heads 66cc, fel pro 1008 .039 head gasket. All sharp edges are removed from the piston tops and head chambers were smoothed (not polished). I'm at sea level and 93 octane is readily available. I carried a wrench to back off timing from 34* in case I got a bad tank of fuel. Car was a 4 speed OD with 3.91 gear and 26.5" rear tire. 3 row radiator, 160* thermostat, and clutch fan to keep things cool. Also sealed hood scoop for cold air intake. You'll need to have a good tune, no lean spots in the fuel curve, etc. I chose the 262 due to the OD tranny. Cam was making good power past 6k and still could pull a pass on the interstate without lugging at cruise 2250 rpm. Motor was built as a fun driver. A simple cam and spring upgrade is all that is needed to race. Gave the car to my son with a 318 and the 340 motor is now my spare if the Magnum 360 I race ever fails.
If you go with a Comp Cam don't use their lifters. I had two collapse after a few hundred miles of easy driving. Took them apart and they were clean, no debris. Bought a set of Johnson lifters and tossed the Comps.
 
Are those slugs flat-tops with eyebrows? Cuz I keep coming up with a 10.33 Scr. My math works out to 66head+8.9gasket+5eyebrows-3.9deckht=76cc total chamber volume. And at 4.08 bore by 3.31 stroke, I get 709.15 swept.
 
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There he goes, Splitting hairs.

Next time I'm in Melbourne I'm calling you up MD.
 
Great reading boysssssssssss.Keep it going.I still learn someting every day.Now if I could teach my cat to SHUT up at 3 in the morning.
 
IR3333
Pay attention to post #46, While this combo is quite different from yours, it is similar enough in some ways. Notice he has 3.91s, and a 3.09 first gear, for a 12.08 starter gear. This is a very light load, for the 340.
And he has a fairly high compression, ratio. To this he adds that it has lots of torque to pass at hiway speeds in overdrive at 2250rpm, and that the cam pulls to over 6000. Notice also that he has fresh cold air and a minimum water temp of 160, and that he has a powerful cooling system,namely the clutch fan and 26 in rad. And What else? You guessed it he says "good tune and no lean spots" .
His engine is a 340, so the Scr/Dcr in your 372 will need to be carefully set. The point is this;the Voodoo702, 262* cam will be very nice, in your combo.
 
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