high revs with a short cam?

[Anonymous]

what would happen if you spun an engine with a 194 d cam up to 5000 + rpm ?

 

[Anonymous]

Im not sure but woow 5000 plus RPM is extremely fast i dont even think it would be heathly for a built up 6 to take that much spinning

 

[Anonymous]

A short cam spun at higher rpm would suffer from inadequate breathing, and the HP curve would be declining from some rpm point. The valves are not open long enough to get much volume into the cylinder. Performance would go flat and it would not pull hard up to 5000 rpm.
Is that what you are asking?
Doug

 

[Anonymous]

yes, if I put in a cam for 3500 rpm max and carb it high for 5000 rpm

 

[ski4evr]

I have 3.50 gears, a c4 and an essentially stock 200. I also have the stock 13" wheels with the goofy hub caps. The only thing for performance that I've done so far is the addition of a pertronix II and flamethrower coil. At 80 miles an hour on the highway, I'm hitting 5000 rpm (installed a small tach on the steering column). The engine sounds fine... I just don't want to take it faster until I restore the suspension and brakes. I'm confident the engine can do more... it just can't breath with stock carb, exhaust and the stock '66 log head.

ski

 

[Anonymous]

At 80 miles an hour on the highway, I'm hitting 5000 rpm (installed a small tach on the steering column).

Either your tach is not set to the 6 cyl setting, your tranny isn´t going into 3rd gear, or you have much steeper gears than 3.50s.

 

[JOHN G]

NOT TO MENTION,5000 R'S FOR AN EXTENDED TIME CAN'T BE GOOD. THE INLINE IS VERY PRONE TO CRANK HARMONICS SINCE THE ENGINE FIRES EVERY 120 DEGREES VS. EVERY 90 DEGREES FOR A V.UNLESS YOU'VE GOT BIG RODS AND SUCH, IT WOULD TEAR THINGS APART.

 

[Anonymous]

A larger carb may meet the air requirements, but the stock intake and the short valve duration would limit the ability of the engine to ingest the air.

So far, my car is basically stock except for the Weber 32/36, non-Loadamatic distributor, MSD and a T-5 trans. At 4000 - 4500 rpm, it starts feeling like a Star Trek episode, with Scottie yelling "I'm giving it all she has got and she can't take much more of it Captain".
Doug

 

[wsa111]

Huntersbo, the only thing you could do with such short a camshaft would be to retard the camshaft 2 degrees, or 4 degrees. this will give you more top end by allowing the intake valve to close later, but at the expence of low speed torque. You will need an adjustable timing gear set from mike to do this or use an off set dowel pin. You can try it, but the best bet would be more camshaft. Let us know. william

 

[Asa]

NOT TO MENTION,5000 R'S FOR AN EXTENDED TIME CAN'T BE GOOD. THE INLINE IS VERY PRONE TO CRANK HARMONICS SINCE THE ENGINE FIRES EVERY 120 DEGREES VS. EVERY 90 DEGREES FOR A V.UNLESS YOU'VE GOT BIG RODS AND SUCH, IT WOULD TEAR THINGS APART.

???
i was under the impression that one of the things that was so good about the I6 when compared to the V engines was that because of it's design, it has virtually no vibration
or are you speaking of something else?
source

What about vertical / transverse forces? like 3-cylinder engines, the vertical and transverse forces generated by individual cylinders, no matter first order or second order, are completely balanced by one another. The resultant vibration is nearly zero, thus inline-6 is virtually a perfect configuration.

BMW's M3 with the I6 revs up to 8000 with no problems
so i'm a little confused

 

[Anonymous]

I think that I would rather go with a biger cam, 204 with 3.73 or 230 with stock 4.27 and 31" tires. Np435 with 6.69 first gear

 

[Anonymous]

how long will the rods need to be if I cam it to 5000?
and will I be able to run .700"lift on this 250 with a 2v head?

 

[Lazy JW]

NOT TO MENTION,5000 R'S FOR AN EXTENDED TIME CAN'T BE GOOD. THE INLINE IS VERY PRONE TO CRANK HARMONICS SINCE THE ENGINE FIRES EVERY 120 DEGREES VS. EVERY 90 DEGREES FOR A V.UNLESS YOU'VE GOT BIG RODS AND SUCH, IT WOULD TEAR THINGS APART.

???
i was under the impression that one of the things that was so good about the I6 when compared to the V engines was that because of it's design, it has virtually no vibration
or are you speaking of something else?
source

What about vertical / transverse forces? like 3-cylinder engines, the vertical and transverse forces generated by individual cylinders, no matter first order or second order, are completely balanced by one another. The resultant vibration is nearly zero, thus inline-6 is virtually a perfect configuration.

BMW's M3 with the I6 revs up to 8000 with no problems
so i'm a little confused

I'm no engineer but I have always heard that the inline six configuration is inherently smooth BECAUSE of the 120 deg intervals. Kinda hard to get those nasty harmonics going when the intervals are staggered like that. The bent 8, however, can do some ugly things, and the inline four is the worst of all. The 2.5 liter GM four in our 89 Buick had a reverse rotating counterbalance inside that turned at double crankshaft speed to try to compensate for all those vibrations. Just isn't necessary with the straight six And the Ford sixes DO have big rods and seven mains. If anything can turn five grand it should be one of these.
Joe

 

[xctasy]

John G, what you have rightly said is that six cylinder cranks can suffer whip and torsional problems when compared to other designs. However correctly sizing the main bearings adds lots of deadening mass which raises the torsional period to an RPM level where you won't run into it. Small in-liners have small bearings, larger ones get larger bearings. Huge in-liners get huge bearings. In the begining, all ohv 144-250 sixes ran 10 bob weights and were not fully balanced like the later 1996 up Aussie cranks were. They got 12 bob weights. Holden sixes, which form 1980 had 12 bob weights, had tiny 1.9" rod bearings and 2.5" mains, yet can run to 7500 rpm without breaking. They are only cast nodular iron



The modified 144 Falcon engines, run by forum member Randy Wold (HydroRacer), had three 42 mmmDellorto carbs, and could run to 8600 rpm with the stock four bearing crank, 2.5" stroke, 2.126" crank pins, and 2.3" mains. The only way you'd break one of those is if you dropped it on a cement floor before putting it in the block!

I've turned my 144 cu in motor over 8600 rpms in my hydroplane with stock rods with no failures. However, they were drilled and fitted with 3/8 396 Chevy rod bolts. Balancing, forged pistons and proper clearences are a must. No short cuts or you waste your time and money.

The stock nodular iron seven bearing 200 crank can hack 400 to 500 hp installations, as witnessed by drag-200stang's amazing device from the late 70's early 80's.

{Regarding Nitrous}So you're talking 150 hp plus 180 - that's 330 hp. No problem. For a full 1/4 mile loosen the end gaps on the rings. I have never had a crank shaft break and I have abused it severly. The rods will bend - but not break. You're fine with these horsepower levels. .030 would be better than .040.

In Australia, the 250 Falcon x-flow crank, inferior to the US 250 crank becasue it has a smaller 200 crank snout, can cope with 6000 rpms flights behind turbo engines with over 600 hp. It does have a torsional vibration period, but it's not an issue when you have 2.4" mains, even with a 3.91" stroke, and one third of the crank overlap a 144 crank has.

Ford cranks are over 30 inches long, and if there is a problem, then the latest 250 based 400 lb-ft Falcon F6 Typhoon will find it at its 6000 rpm red line. Oh, it has 2.65" main bearings.


44 years of cast iron Falcon cranks, not breaking.

Huntersbo. The cam is the heartbeat and packmaker!

The choice of duration at 50 thou and full lash defines the rev range. The valve lift is related to duration. You can't get any more than 700 thou unless you have a lot of duration. The worst case for load is a short duration cam with high lift. The ramps on the cam and the rate of lift makes huge loads on the lifter, and will result in failure.

Taken simply, just adding better breathing or carburation won't raise the point at which maximum power is arrived at by much. If your 200 or 250 gives maximum power at 3600 rpm, then with the best carb, it will make power at 3800 to 4200 rpm still. The result is less loss of power ath high rpm, but no real change in peak power speed. The increasing of lift won't make much difference.

 

[Anonymous]

THanks everybody, so with a small cam it will not rev high.

I think I got it...

I think with a small six I migh as well take advantage of the crank designe and go with a big cam especially since a scout comes with 4.27 gears.

oin 4th gear that would put me 75 mph at 3500 rpm and have 3000 rpm after an up shift.