I've been wondering for awhile about how high certain or all straight 6s can rev to if built to withstand it. Like in one magazine theres a car with a Pontiac OHC straight 6 and for one of the pros it says "shifts at 7200rpm" but then when reading in the racing here it says one member is going back from a 292 to a 250 becuase he liked the high revs. I know it should be safer to do this in a later block becuase of the 7 main bearing. But really what I want to know is what engines can rev easily to 7000rpm?
Or is it only the Pontiac OHC could go that high becuase it had to push rods and nothing floated at high rpm. Just read the article again and its not 7200rpm its 7000rpm shifts.
You need to talk with Ken @ Custom Design on this issue.
I shift my 300 bracket motor as high as 7200. My 240 shifted at 7800. My friends 300 race motor shifts at 8600. and Charlie Stewart revs his 4.2 Vortec to 9600.
How would I get ahold of Ken @ Custom Design? By the height of your shift points Flyer I hope Chevys are the same or close.
Mr. Ken Carlsom c/o, CUSTOM DESIGN PERFORMANCE, 860.228.3449 (east coast time).
Remember, these engines were a hundred horsepower from GM. To get speeds like 'French town' gets takes a lot of time & money in re-design.
Good luck.
All I really want to know is if I take say a 292 bore it over 30 or 60, maybe get newer rods and pistons, port the crap out of the heads and then run like roller rockers and all new valve train would it have no problem with going to 7000rpm. I think it should but wondered if others had advise. This project will most likely have a turbo on it becuase I like how they have 7 main bearing and think they would hold some serious power. Any suggestions are welcome.
Ok, here's my suggestions to rev a boosted 292 to 7000+:
Keep the overbore to a minimum and fill the water passages with HardBlok to stabilize the cylinders which will assuredly want to distort when you pour the coals to 'er.
Grind the crank journals with a big cheek radius and heat treat and balance the crank.
Do a search on what people have done to keep the flywheels from shaking loose and harmonic balancers together.
Use lightweight aftermarket rods and forged or hypereutectic pistons.
You don't want an engine that will rev to 7000 - you want an engine that will rev to 7000 REPEATEDLY.
Good Luck. Post pictures of your progress.
AMEN.
For what it is worth, I use 6600 for the shift point on my 292. The balance stays put, but the flexplate does come loose about every 20 passes. It will be torn down this winter for a different flexplate and a rebalance.
My God. Frenchtown said that his friend can rev a Vortec in 9600!!!
That is a lot RPM.
Here, in Brazil, we use the 250 much more than the 292, but when we rev 7500, we got on our knees and pray all day long.
I´ve never thinked that a sausage crank like the 6 inline could hang up so many RPM.
Frenchtown, do you know the cam grind your Vortec Friend uses?
Nope, don't know the man personally. Remember that engine uses a 4-valve double overhead cam head, giving it lots of rev potential. I'm sure the cams are steel billet roller variety.
There is no need to rev a turbo engine to the point of destruction. Adjust the boost to reach the max desired at a reasonable RPM the engine can live with, use an intercooler and enjoy your engine. Read Corky Bell's books
Ed Pruss
Longmont, CO
In Australia we used to have a kind of mini-stovebolt 6 in the Holdens... four main bearings, six cylinders that were just about square in the region of three and a tad inches of bore and stroke.
They had the inevitable side plate to cover the valve gear, it had the dreadful cork gasket that went over the joint of the head and block, it had siamesed inlet ports and four of the exhaust ports too.
At 2.16 litres, it was a neat little engine, improved over the old Chev by having pressure fed big ends.
In time, because it became the most readily available engine in the country (over a million made, IIRC, between 1949 and 1962), it was hot-rodded by everyone from boat racers to drag racers to road racers in sedans and in race cars. At the speedways they droned around in droves behind the few Offies that made it here.
Enter Des West.
Des was one mean driver, he rallied with distinction, he built a neat early model Holden for racing on the road circuits.
And he revved it for all it was worth! Max Stahl raced against Des, he reckons he'd have Des beside him going up the straight, he'd change to third (top) gear and Des would keep on going in second. For a short time.
I don't remember the actual figures, but it was something like nine crankshafts in ten racing miles. They just didn't like going over 8 grand.
And the point of the story? It's better to have the engine come out alive at the end of the day.
Hi there, guys!
I´m form Brazil, And I´m making a Chevy 250cid Twin Turbo to rev above 8.200 rpm with roller cam, and a all Aluminum 12 port head by Sissel Automotive. I just expend a lot of money in a Main Girdle plate do keep in place the main caps, block and Crankshaft.
The engine is not finished yet, but I thing it will work in the middle of the year!
Do you have any pictures of the main girdle plate?
Thanks
Hank