Valve lifters…solid/hydraulic/roller tappet/flat tappet?

[zrayr]

Originally Posted by blykins

That's a pretty common misconception....a longer stroked engine can pull the rpms just like a short stroke engine. I have 4.100" stroke 445W's pulling over 6500, as well as 4.300" stroke Boss 9 engines pulling 6500 rpms.

I have a customer that runs the 7.50 1/8th mile class. The 347 that I did for him gets shifted at 7000.

in the narrow scope of this discussion, using stroked SBF engines as examples, you are essentially correct. As you say, a 289 stroked to 331, etc, will rev to 7,000 or more. Bit I still maintain that shorter stoke engines will hit the red line quicker if the overall displacement is more or less equal.

In the long run, long stroke engines just can't compete with over-square engines in a maximum rpm context. Valve size is the one major limitation in small bore/long stroke engines, but excessive piston speed (measured in ft traved per minute at maximum rpm) cannot be ignored.

That said, for example I am much more happy riding the long stroke 650cc Triumph vs. the short stroke 650cc BSA.

Z.

[blykins]

Originally Posted by zrayr

to the degree we are talking about, stroked SBF engines, you are correct. However long stroke engines just can't compete with over-square engines. Valve size is the one major limitation in small bore engines, but excessive piston speed (measured in ft traved per minute at maximum rpm) cannot be ignored.

Z.

Try to explain that to the pulling truck guys running 557ci BBF's (4.420" bore, 4.500" stroke) turning 8000 rpms....

There are lots of spoken generalities with engines that are not always the case.

[zrayr]

Originally Posted by blykins

Try to explain that to the pulling truck guys running 557ci BBF's (4.420" bore, 4.500" stroke) turning 8000 rpms....

There are lots of spoken generalities with engines that are not always the case.

I just edited my last post to include, "...That said, for example I am much more happy riding the long stroke 650cc Triumph vs. the short stroke 650cc BSA..."

which is exactly the same as the example you provided. ha ha. Especially on the dirt track , the long stroke, high torque Triumphs ruled. Lower torque, higher rpm machines consistently ate their dust & finished out of the running

Z.

[DAVID GAGNARD]

Thanks David, for more of the real world comments.
Can you tell me why you decided on flat tappets?
Cheers,

Because back in the mid 90's when I built this engine, it was to be a street cruiser/show car/sunday driver and I was dirt poor and the camshaft with lifters from SUMMIT at that time was about $79.00!!!!!!!!!!!!!!

Every street engine I've built for myself since has gotten a hydraulic roller camshaft....
My race engine uses a solid lifter,roller camshaft.......

The hydraulic roller camshafts just have so much more to offer,it's a no-brainer for me...

David

[xb-60]

Originally Posted by zrayr

to the degree we are talking about, stroked SBF engines, you are correct. However long stroke engines just can't compete with over-square engines. Valve size is the one major limitation in small bore engines, but excessive piston speed (measured in ft traved per minute at maximum rpm) cannot be ignored.

Z.

Yes, surely the maximum piston speed on a 347 with a ....3.4"? ...stroke must be a lot higher than a 2.7" or 3" stroke engine? That's got to make a difference in the cost of the bottom end
Cheers,
Glen

[Gaz64]

Originally Posted by xb-60

Yes, surely the maximum piston speed on a 347 with a ....3.4"? ...stroke must be a lot higher than a 2.7" or 3" stroke engine? That's got to make a difference in the cost of the bottom end
Cheers,
Glen

Very true Glen, and yes you do have to spend money the larger you go, but there are engines out there with 5 1/4 inch strokes or more that spin to 8000 rpm.
For example: John Kaase Racing Engines.

As others have said, if you have a choice, go for a milder package with more cubes, much better combination.