thank you for sharing your information , i enjoy reading about getting more performance out of the old str8 8 s Bravo
If it costs an arm, count me in. If it costs an arm and a leg, I need more time to consider. My bet is that more than 10 guys would scream to get those, right away!Originally Posted by 36 Century
Junior Member
thank you for sharing your information , i enjoy reading about getting more performance out of the old str8 8 s Bravo
It never crossed my mind to uncork my headers, but you just made me wish I would have! And I sure will...
Member
After about an hour on the cam software I have a prototype ready to be machined on the mill, then I will trial fit. I am deciding weather or not to use a bronze bushing, or a torrington roller. The bronze bushing will work perfect on the stock rocker shaft, the torington roller will require a harder shaft. I will engineer them to use the stock pivots and adjusters. So basicly you just insert your adjusters and jam nuts, and insert them on the shaft and you will be set. I can make them in different ratios, anywhere from 1.5-1.7. The first set will be 1.5, just like stock. If I had to estimate a cost, I would say somewhere around 500.00 a set.The main thing that is bad for making them, is there is actually three different rockers on the shaft. Straights, rights and lefts. The straights are the EX, and offsets to the left and right are the intakes, so for production, it gets more involved.
Last edited by 36 Century; 10-30-2008 at 05:58 PM. Reason: Content
I give my vote for bronze bushing and 1.6 ratio. I remember someone claiming the stock ratio would be 1.35, but he was talking about the smaller engine. And we are now talking about the 320, right? I'm not convinced that the torrington bearing is such a major improvement in a shaft mount system. It sure is an improvement over a single stud and pivot ball system (like SBC). But this is only my vote! Keep us updated on the progress.
Senior Member
Roller bearings are designed to rotate 360 degrees continuously as are ball bearings and the like. Reciprocal (spelling?) motion is best handled with a bushing. Plus, without shaft seals the rollers won't stay lubed as they should and won't hold oil pressure nearly as well as a close-fitting bushing.
Senior Member
Thought I'd weigh in here with my 2 cents worth. Are any of you guys breaking the stock rockers? 36 Century, are you having problems keeping the stock rockers alive in your drag car? I see very little benefit for anyone not doing an all out race engine. Except making your now much lighter wallet easier to carry around. The stock 320 rocker measures out to be a 1.5 ratio. Going to a 1.6 might give you about .020 extra valve lift. On a hot small block Chevy at 6500+ rpm this equates to about 5 horsepower. Just about the edge of what a dyno can measure. Roller rockers are mostly for reliability when using really stout valve springs. The Torrington design is also a real friction benefit on an engine like the Chevy and they have a fairly long ( with proper lubrication ) service life. Roller tips by themselves are of zero benefit. You only need a rocker strong enough for the valve springs that you are running. Which is a function of valve weight and rpm. I do believe what I've read about the straight 8 being limited in the crank speed dept. Even with valves of the stock weight it doesn't take a lot of spring pressure to run to 5000 rpm. How many of you guys out there are running your straight 8's this high? I don't think a stock 320 will pull this rpm with a stock cam and single carb. It might rev this high with no load. But a Roadmaster with a dynaflow? I think Alleycat had good info on this in the other straight 8 performance thread. When I talked to Bob Opperman at Bonneville years ago, ( my pictures of his straight 8 car are in the race pictures on this site) he was turning about 5500 rpm because of the crank harmonics problems that are inherent to these engines. As you can see in the pictures he ran with the stock rockers and he said that he never had a problem with them. He also said that he was only running as much spring pressure as the cam grinder said was necessary to prevent valve float ot the speeds he was turning. As long as you don't have valve train separation i.e. "valve float" a stock rocker will take a lot of rpm. The drag boys can get away with a little higher crank speed because of the short duration of the race (10 seconds or so) and the fact that the engine rpm is constantly changing. Which doesn't give the crank much of a chance to get too bent out of shape. I kinda looked into making rockers myself awhile back. I too figured out that 3 different rockers kinda sucks. Along with every used shaft I've seen has a fair amount of wear on it. Not to mention the lack of a lot of room in the stock valve cover. The deal breaker for me was how to lubricate the pushrod cup / adjuster ball interface. This is going to require some engineering and some complicated drilling. To do this right and have any real benefit I'd use the Torrington bearing but I'd get a bigger one and put an inner race in it and then slide it over the stock shaft. This would negate the need for a hardened replacement shaft and helping with the oil hemorrhaging ( leaking for our foreign buddies) problems. All of this can be overcome, but at what cost and benefit? The guys at Wayne Manufacturing Co. repop the Wayne 12 port Chevy and GMC 6 heads and they offer a roller rocker setup. But it's priced at something like $1,500 and has 4 less rockers. If your serious about making Buick rockers I'd call them and see how they designed theirs as I believe that the GMC's oil the top end similar to the Buick. I think $500 is way too low for a cost estimate. If your doing it for yourself it doesn't matter but if your going into production, even very small runs, I think you'll lose your butt on every set at this price. I think the Wayne price is more realistic. The Waynes might even be adaptable to the Buick, who knows? I think there is a lot more bang for your buck to be had for this money. Head milling, getting your cam reground a little hotter, ignition and exhaust upgrades etc. Hell not much more money and you could probably engineer a belt driven centrifugal supercharger for it ( like the Kaiser ) and really feel what you spent your money on. 36 Century I really respect and admire what you guys have done, and I wouldn't dream of telling you haw to spend your spare time, but I think is gonna be a tough nut to crack. I'd rather see you and that wonderful machinery making us a set of permanent molds so we can cast some pistons with some domes on 'em! As ever sorry for the rant.
Senior Member
the main thing about RPM,s on any inline engine is CRANKSPEED. That long crank starts getting oscillations, that can,t be stopped. They can be limited with heavy duty crank dampners and more main bearings, etc. but its very difficult to control completely. Case in point, the Bugatti straight 8 race car from the ancient days. They took the crank drive from the middle of the engine block! In essence 2 four cylinders in each direction was all that had to be controlled. So more breathing,more valves, big valves, hevy duty valve train is a moot point on them old straight 8,s. 6 grand is about it, as far as rev,s are concerned. So all that hi revving stuff has to be limited and build them for torq not as much for hi rpm,s
BigRivy, you definitely have some thougth there. However, I wouldn't call roller tips a zero benefit. First of all, the roller tip eliminates the side loading of valve stem, and it does reduce friction. There's considerable shear between the valve tip and rocker, as on my 90,000 mile 320, some rockers were worn out.
For reasons discussed on previous threads, we don't want a lot of duration and overlap. Instead, we want to increase the "area under the curve", that is, faster valve acceleration for any given duration, just like the idea of a roller cam. A higher-lift rocker would give us just that, and now that I'm thinking about it, it oughta be 1.65 ratio. My buddies have seen much more substantial gains in SBC than 5 HP, using high-lift roller-tip rockers (not even full-roller rockers)
I'm glad you addressed the oiling. It's an important issue.
I don't think we need a mold for cast pistons. Everyone out there has a different need for a dome and bore size. And I think Venolia, Ross, Arias, and similar mfg's are able to make anything you like.
I would like to hear from anyone who had his cam ground, if Howard, Isky, Herbert, or any other company are able to manufature a completely new cam, or do they all require you to supply your own core to regrind?
You see, sending my existing cam overseas for a regrind and back, would have some risks, costs, and downtime, as compared to ordering a new cam.
I still would like to hear from 36 Century, why he wants to use a non-stock lifter, aside from being expensive and hard to find?
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