roller camshaft opinions please.

[Clem Z.]

these new corvettes will not pull top top speed

in 6 th gear and max top speed is achieved in 5th. i am not sure if this is true about the new ZO-6. this why a lot of the owner change the rear gear because they do not need or want 190 MPH top speed as 160/170 is plenty. the fastest i have had my 05 LS-2 is 154 MPH but it was still pulling at that speed. mine is a 4 speed auto with the optional 3.15 rear gear in place of the std 2.76 and this corvettes get about 1-2 MPG less than the others with the std rear gear BUT the kick in the ass you get is worth the cost in MPG. 80 to 130 comes up so quick it makes your head spin. at my age 72 i am not sure my reflexes are good enought to get a ZO-6 BUT as soon as they start discounting them i am sure as hell going to give it a shot.

[Michael H.]

Re: that is why drag racers use electric water pum

Also of interest is, if you've ever shut off the oil supply valve to a dry sump system on a running racing engine that has an "accu-sump" for back up pressure, the engine idle RPM suddenly jumps from 1200 to about 1400. That gives us some idea of how much energy is going into that pump even at a slow RPM. Just thinkk of the energy at 7000 RPM!

This is another reason why distributor bushing wear is accelerated by a factor of about 20 in an old racing engine that has a ultra high press/vol pump.

[Michael H.]

HP Required To Turn A Racing Engine

Smoky (Yunick) once concluded that a full race small block consumed roughly 100 HP just to spin at 7000 RPM. He came up with a great big electric motor that stood about three or four feet high, connected it to the engine, and somehow calculated the amount of HP. (I think it was most likely Ralph Johnson who did the math) I think his dyno was somehow involved too but I have no idea how. That's a lot of HP to give away.

[Duke W.]

Re: HP Required To Turn A Racing Engine

I did such a test when I was an undergrad at Washington. We had a Ford Falcon inline six on an electric dyno. I think it was 144 CID, but we were limited to running it at about 3000 max revs.

An electric dyno can be set up to "motor" the engine. You do it after the engine is fully warmed up, usually after some high rev power runs - shut off the fuel, open the throttle then spin it up to various revs and read the wattmeter on the motor. That's the friction power - the internal parasitic loss. And one minus FHP/BHP equals mechanical efficiency. It's also noteworthy that friction power increases approximately with the square of speed.

If you have a cylinder pressue indicator, which we did, then you can calculate indicated horsepower and IHP-FHP = BHP should hold if you did the tests properly, and mechanical efficiency can also be expressed as BHP/IHP

EA shows about 150 FHP for a good mechanical lifter 327 SHP engine at 6500, and things can be done to reduce parasitic loss on a race engine - looser piston and bearing clearnace, dry sump, and low flow rate pumps, so a good racing engine should have better mechanical efficiency that a typical production engine, but production engines are getting pretty good because better mechanical efficiency means lower fuel consumption.

Duke

[Duke W.]

Re: that is why drag racers use electric water pum

I thinks it's a new BMW engine that has an electric coolant pump contolled by the engine control electoncs. It only runs fast enough to provide adequate cooling or cabin heating as required.

Duke

[Duke W.]

Re: these new corvettes will not pull top top spee

Those engines have such broad torque bandwidth that only five speeds are really needed for best performance, and they're traction limited in first gear. Sixth is strictly a cruise gear on all Corvette models including Z06, who's quoted 198 MPH top speed is achieved in fifth right at the power peak.

The new six speed auto accomplishes the same thing - a gear for every purpose, and it eliminates the need for an optional axle ratio.

Duke

[Clem Z.]

i was at katech last week and the were

running a 4 cylinder race engine in the test stand power by a electric motor checking for the losses. the NASCAR restrictor plate engines use narrowed main bearings,roller cam bearings and honda size rod bearings to cut down on the loses. these engines also use the "beehive" shaped valve springs because of the ability to turn the RPMs without heavy tension. GM submitted a new engine design to NASCAR last week but i have not heard if it was accepted. they are going for a raised cam to use shorter push rods for more stable valve train at the RPMs they are now running. chevy engine design is the oldest in NASCAR but they keep winning the championships so NASCAR says "quit complaining"

[Terry F.]

Re: The whole point of a roller cam

Thanks for the engine prescription. I will take your recommendations and apply them. I might be asking questions later. I really want to try and figure out the compression ration accurately and see if the right side and left side are off a bit. I like the challenge of trying to make it as nice as possible. Thanks again, Terry

[Patrick H.]

Re: these new corvettes will not pull top top spee

Clem,

You and I both know where you can try a Z-06 for free and see if you like it.

Patrick

[John H.]

Re: that is why drag racers use electric water pum

Yup, and it must be a helluva pump (computer-controlled variable-speed); the service replacement BMW pump is $2800.00!

[John H.]

Re: these new corvettes will not pull top top spee

Viper is the same way - top speed (192mph) is 6000 in 5th gear (0.75 overdrive with a 3.07 axle); shift into sixth (0.5 overdrive) and it drops to 182mph - can't pull the equivalent of a 1.53 rear axle). The Viper is a "torque-monster"; has 440 ft-lbs. of torque at 1600 rpm, 540 ft-lbs. at 4500, and only drops off to 495 at 6000 (fuel cutoff is at 6200). It's all about TORQUE.

[Duke W.]

Re: that is why drag racers use electric water pum

That's reason number 137 why there's NO WAY I'd buy a new BMW!!!

Duke

[Michael H.]

Re: The whole point of a roller cam

Terry,

I agree with all of Dukes advice. There is an easier way to measure the actual comp ratio of your engine than measuring all of the components. If you purchase a CC burrett, (pharmacy supply) you can measure the actual volume of a combustion chamber in CC's while the cyl head is attached to the engine. On disassembly, remove the heads and, using a dial indicator, rotate the crankshaft until a piston is at exact top center. Fill the area between the piston and cyl wall, above the top piston ring, with light grease to create a seal. Reinstall the cyl head with the original used gasket and run the head bolts down to about 20 ft lbs. Roll the engine on the engine stand until that cyl spark plug hole is facing straight up. Using something like automatic transmission fluid in the burrett, fill the chamber through the spark plug hole until the fluid is at the bottom of the threads. This will give you the actual volume and you will be able to compute the ratio of volume at TDC to that volume plus the cyl total volume. (convert cu in to CC for the cyl volume)

Because big block pistons have domes and valve relief's, it's not possible to mathetically compute a CR unless you have the exact piston top volume, which may be a negative number because of the dome. Using the fluid measurement method eliminates this problem and gives you a very accurate CR measurement.

When the valves and valve seats are machined, especially if the seats are opened up to the outer edge of the valve diameter, they will likely sink slightly in the chamber which will increase the total volume of the chamber and decrease the CR. As Duke mentioned, if the engine didn't have a pinging problem before rebuild, it would likely have even less after rebuild because the CR has been lowered. This will allow you to use the correct original steel OEM style head gaskets. (don't forget a light coat of aluminum spray on both sides of the gaskets)

If the cyl heads have to be machined (hope not) this will increase the CR. If that's the case, you may then have to use a slightly thicker gasket.

Hopefully, your machinist has an automatic feed precision hone machine. Without it, it's not possible to create an acceptible cyl wall finish or dimension. Many engine builders that don't have this expensive equipment will argue this point but in my opinion, there's no other way to properly prepare a cyl. Improperly honed cyl's is probably the number one cause of failed engine overhauls. One more deluxe option is honing with deck plates installed. I never build an engine without it. It adds to the cost of the project but maybe you can use the money you saved on the roller cam and rocker arms. Keep us posted.

[Terry F.]

Re: The whole point of a roller cam

It sounds as though I will be calculating the compression ratio on each cylinder. What do you do if you have a cylinder head valve that is lapped in a bit and you have a difference in compression from one cylinder to the next? What is an acceptable difference between cylinders?

Thanks, Terry

[Michael H.]

Re: The whole point of a roller cam

Terry,

If you're shooting for absolute perfection, you definitely have a lot of work to do. There are a number of ways to equalize the CR in cyl's but some of these methods involves assembling and disassembling most of the engine several times. If you have new pistons in new oversize bores, you can swap these around from cyl to cyl as long as they haven't been final fitted to a specific cyl. The actual deck height and dome measurement between pistons will vary slightly and produce different volumes.

Many commercial engine builders grind a very small amount out of selected areas of the combustion chamber to equalize all of the chamber volumes but that doesn't include or correct the possible difference in piston dome/deck volume. More than likely, you will find that all of your cyl CR's are within an acceptible range. Piston deck measurements on old big blocks usually come out surprisingly close from front to back and side to side. Also, the combustion chamber volumes are usually within a reasonable range.

I would probably select/check the end cyl's on each bank and if all are close, (1/2 cc) I wouldn't be concerned with trying to get things any closer unless you have too much spare time. (is there such a thing?)

Big blocks, by their very nature, have lean and rich cyl's that cause one or two cyl's to ping before the rest, even if all the CR's and volumes are dead on accurate.