8000+ rpm motors

[jflem3]

alot of the of the oval track motors are 4.155 bore (.030 over 400) with a 3.30 stroke to get to the 358 cuin. limit. they run lightweight 6.1" rods with 45mm rod journals and (believe it or not , (honda rod bearings)) with light weight pistons to cut down drag and reciprocating mass. the top of the motors consist of shaft mounted and girdled rocker arms to keep everything lined up a 9500 rpm. titanium valves,and keeper and oil sqirters to keep the springs cool(very important for high rpm longevity.
It would be possible to build a streetable 8000+ rpm motor. 4.125-4.155 bore, 3.0 stroke 6.0 rods lightweight pistons use a roller cam, 11.0:1 or better compression( the big cam would bleed of compression down low) you would have to spend some money on the valve train and cylinder heads (2.05 -2.08 intake valves). Fuel Injection would make driveabilty worlds better.
You would definitely have to back it with a t-56 or something of the sort to keep the gear changes tight as it would be a rather peaky motor for a truck.
4.56-5.53 gear depending on tire size and it would rip through the gears and and cruise on the the highway with the .50 6th gear of the t-56

sounds like fun just bring your water cooled checkbook!!

hell, you could even start a new trend a blend of nascar street racer NASTREET.

[Sinister]

cool, factual info...
thanks, where did you learn all that?

[Cheyenne Super]

build a stout street motor. just dress it up like a nascar engine. also theses engine idle at about 2grand. even with fuel injection and a really low rear gear the rod stroke ratio along with the cam porfile makes getting off of low rpms a struggle unless you drop the clutch. just my .02

[jflem3]

I work at GM, and have always been a motor freak. (have a road race vw scirocco,8000 rpm motor, built a couple for people,haven't grenaded one yet. but its the almost the opposite of the setup we talked about it has 3.28" bore and 3.65"stroke ,big solid cam and lots of compression 13.6:1) and Individual runner FI. the V8 stuff- couple of my friends crew and prep a couple of the hooters pro-cup cars. (chevy and Mopar) the guy they get their motors from builds for alot of people in SE michiganand I've spent some time talking setups with him.

A 1400-1500 rpm idle would be easily attainable. the short stroke and low recipricating mass, has the greatest effect on the low end torque. the long rod improves the torque transfer to the crank from the piston. the physics isn't hard its the breathing ability and valvetrain harmonics of a pushrod motor that makes it more difficult.

[Durney]

Our Super Stock engines with big heavy steel rods and fairly heavy (403gm) pistons with NO titanium valves leave the line @ 8600 rpm....

I have a customer with an "old" 327 with the original crank (yes it was tweaked for longevity) and heavily modified 461X heads that has turned 8000+ for the last 5 years.....

Piston speed is the critical factor with these type of engines ( not the roundy round stuff) and valvetrain harmonics are ...well... accepted losses. If you really want to turn some RPM then you simply must eliminate the camshaft ... can you say pneumatically controlled valve timing .

Ask David Reher (the late Buddy Morrison and I were often chewing this very cud) about rod length (or any one else that has done the testing...I have over 300hrs on this) and you will hear that rod length is NOT as critical as you think.... (Buddy once said it dont mean Sh#@.....)

Our NMRA shootout ford stuff runs SHORTER than stock rods....


As far as not having grenaded one yet....well either you havent been doing it long enough or you just need to try harder.
Bill J. said it best to me 10 years ago...THEY ALL BREAK!

The VW combo sounds like fun to sort out.....have you tried welding the chambers closed and making custom dished slugs for it yet ??? (my best friend used to drag race those things and win LOTSA cash from the v-8 guys...terrible sounding but scary power/ci.

[Cheyenne Super]

the why do nearly all "torque" engines have 1.75 or less rod stroke ratio and nearly all high rpm "horsepower" engines have 1.75 or higher rod stroke ratio. I agree that valvetrain reliability is a concern, but the parts are avaliable for a fully reliable high rpm valve train.

why do you have to eliminate the cam for high rpms? the overhead cammers can turn 14000+ all day long.

maybe i'm wrong. that's just what i am seeing from my side.

[Durney]

Ok at the risk of opening a can of worms......

You say the word "all".... I can give you instances,many in fact that contradict the long/hp short/torque theories,

One of the best texts (if you want to start studying for your degree in internal combustion engineering) is Heywoods ICE fundamentals. It is a key text that has fallen under extreme scrutiny relating to ongoing research in the field of wave analysis and in particular how r/s and b/s ratios affect efficiency.

The fact is one of the key proponents of the long rod was the Late Smokey Yunic himself but after listening him speak at the SF conference the year before his death he was echoing the short rod sentiment regarding HP production.

KEY things to remember folks:

1 - Long rods were used to minimize side loading in production/early race pieces that didnt have the strenght we use today

2- Long rods were then found to have an added effect of optimizing the factory (or mediocre quality race) heads in use then.That was because as the piston initially moves away from TDC at a slower rate with the LR's then picks up speed it offered increased cylinder filling/VE with a compromised port configuration
This is VERY simplified but you get the picture

You mention 14000 rpm with OHC's what are you referring to? Aurora's (nope), F1's (nope), Honda oval piston (close @ 13000)

If you have spent any time at all with a Spintron you will see that the camshaft by nature imparts violent harmonics and starts doing things like "loft" and "t-bounce"

I'll say it again....pneumatically controlled valves (Just ask Warren J, J. Roush, E.Ferrari, etc.) but then you start pushing the envelope of ring sealing........

hope this helps - Scott @ GMS

[jflem3]

I was watching the F1~ race this weekend and the announcers were talking about the ferrari F1 motor It was spinning 17,000 RPM. hydro-pnuematic valvetrain and unlimited budget.
the vw motor is set up with the chameber milled down to 26cc, the piston pops up .018 w/ .055 gasket for .o37 squish and -7cc dish in the top of the piston.

[Durney]

Inyeresting,

They banned the L01 (Ferrari) engines in 1999 (pneumatically controlled) I guess they found a way to handicap them. Dont follow it too close as there are just too many lap tops for my taste.

Notice in my previous post I mentioned asking Ferrari about this method..... they (in conjunction with BMW) pioneered this technology.

Yup sounds like one of those ear-ache VW's

A friend works for Pro-Car (VW race castings) and his Ghia (i think thats right) will click off 10.20's OFF the bottle. Nasty little creature.

[Cheyenne Super]

your right we shouldn't open a can of worms...