C2 small block intake flow rates

[Michael H.]

Re: C2 small block intake flow rates

Mike,

If yer talking about the old black/gold Camaro, the complete front end was still at Yunick's shop as of about two years ago. I don't think the hood was with it but the entire front clip was "out back" behind one of the buildings. No idea what happened to the rest of the car.

A lot of the high RPM numbers on the tach telltale were recorded during downshifts, not upshifts. I know Yunick's motors had a little more on top than most of us but not likely they were making power at 9500 RPM. As I'm sure you remember, at that time stock valve train was required, including the stamped steel rocker arms and they wouldn't take 9500 on the way up but a short blip of the throttle while downshifting seemed to be acceptable. I rarely went over 7800 under power with mine and it was built almost exactly the same as Yunicks. My telltale often showed near 9000 but, again, this would have been from down shifting a little too aggressively. I'm sure you've been here also.

Michael

[Mike Cobine]

Re: C2 small block intake flow rates

Downshift aggressively? Never.

Actually, I was surprisingly good at not using any engine braking when downshifting. Engine braking was a good way to stretch rods and rod bolts, and stretched rods tend to become bent rods and well, we know where that goes.

I learned real fast not to do that after a "eventful" downshift on a bike once. Still have those scars.

No, the Corvette was gold/black once, and I didn't know of any Corvette he had ever done. Camaro, Chevelle, etc, but never a Corvette. However, he might have because he took a rather keen interest and asked a lot of questions about it, but he plays his cards too close to his chest to find out if there was one in his past.

[Michael H.]

Re: C2 small block intake flow rates

Sorry Mike, thought you were talking about SY's Camaro. I wasn't paying attention and didn't read the entire string of posts.

At Road America, and several other long tracks, you really can't rely on brakes alone. Some of those hard 90 deg turns are at the end of long downhill straights and even the good metallic lining will fizzle after a few deep 165 MPH charges. I really shouldn't be talking about road racing because it makes me want to do it again. Tooooo much money tho....

[Dick W.]

Re: C2 small block intake flow rates

We ran our engine anywhere from 8,500 to 9,200. We were getting the total valve train from Smokey at that time. I believe that the springs actually had 50 or so pounds more pressure at full opening than the stock did. I do remember after each race we replaced rockers, springs, retainers, locks, and valves as a standard practice.

[Michael H.]

Re: C2 small block intake flow rates

Dick,

Were you using the red/rust colored springs? These would be the 142's that went with the 140 cam? GM sold these (and still does) and I think I remember them giving roughly 300 pounds open pressure with the lift of the 140 cam. Great spring but as you mentioned, their life span was short, especially at high RPM. If I remember correctly, we had to use a GM part numbered spring, rocker arm and push rod for SCCA.

Were you road racing that Camaro or drag racing?

[Mike Cobine]

Re: C2 small block intake flow rates

At Road America, and several other long tracks, you really can't rely on brakes alone. Some of those hard 90 deg turns are at the end of long downhill straights and even the good metallic lining will fizzle after a few deep 165 MPH charges.

You need better brakes. That is why about 1981, the new GT classes allowed to fit any brake that would work, rather than just production brakes.

I ran production brakes, but with Motul fluid, insulators on the pistons, Ferrodo pads, and a whole ton of ducting, not just to the rotor, but the caliper, too. It would have been nicer and easier with the aluminum Wilwood or JFZ though. The Chevy metallic pads just transfer too much heat to the pistons and the fluid to be really effective. That is why the first design calipers had insulators.

Under the walk over bridge at Sebring, I was in the 165 mph range, just before the hairpin. At Daytona, I was in the 185 mph range, just before Turn 1 into the infield. So it could be done. Watkins Glen I never had the car at full potential so the brakes weren't an issue. At Bridgehampton, you wanted to be going foot to the floor through Turn 1 anyway, not braking.

And you would never downshift brake a formula car. Of course, the brakes on one would pull your teeth right out of your mouth anyway.

I really shouldn't be talking about road racing because it makes me want to do it again. Tooooo much money tho....

I can fully relate.

[Michael H.]

Re: C2 small block intake flow rates

Mike,

The last thing I raced was a big block 67 at the historic races in 1990 and at that time I believe the group 6 cars had to have correct original configuration brakes. I originally interpreted this to mean caliper/rotor and was hoping to be able to use Wilwood's but I was told this was not allowed. I can't remember if it was VSCDA or SVRA so maybe one of the two organizations did allow aftermarket brakes. I do know that at least one car had Wilwood's that weekend but at that time it was a little easier to sneak these things through tech. I know everyone had something other than OE brakes by the early 80's but these organizations are trying to duplicate the original 60's/70's configuration.

Besides, it's period correct, right down to the sound the cars make when coming into turns. They're supposed to downshift, just like in the old days. Wish I knew how to send video's through email because I have the entire race on tape, from inside the car.

[Mike Cobine]

Re: C2 small block intake flow rates

We were lucky in that we didn't have to run the stock valve train parts. I picked up lightened .100 longer pushrods and roller rockers from Angus Racing Products in Miami. In person, cash in hand was good for a discount.

Phil took each spring and went through a bunch to find 16 that matched. He went through and matched each rocker, pushrod, retainer, and valve for weight before they were assembled. I have no idea of the hours he put in on all of this.

[Mike Cobine]

Re: C2 small block intake flow rates

That is about the time Jack Boxstrom approached me about getting my dual pin calipers for his Greenwood Stars & Stripes car. He said that SVRA was after them to get period stuff on and he needed soemthing that would haul that monster down. The deal started off very good with him getting the Corvette calipers and me getting a set of Wilwoods but the deal ended not going through when all was said and done.

You don't want to send video through the email. It is usually huge for very little time. Through work, I do a lot of IPTV stuff and the feed is constantly running, even with a 1.5 MBps download.

This is the type of stuff to have at a party somewhere.

[Mike Cobine]

This is NCRS, right?

National Corvette Racers Society?

[Michael H.]

Re: To Be Continued........

Mike,

You and I need to continue this discussion at the winter NCRS meet. The guys that were discussing the original question about intake manifolds are probably getting a little miffed because I managed to somehow totally change the subject. Again. Sorry guys, it's just that I really love racing these cars and enjoy talking to others that have.

[Michael H.]

Re: This is NCRS, right?

I think we're on the wrong page.

[Dick W.]

Re: C2 small block intake flow rates

We ran the Camaro in NASCAR's short lived Grand American Series. Mustangs, Camaros, Cuda's/Challanger's. My feeble memory is suffering from NCRS (never can remember squat) disease on the color of the valve springs. Coming from Smokey who could be sure of what you got. I remember he was always shorting us something, fifteen springs or lifters or whatever. In 68 he was the only source during the early part of the season.

[Mike Cobine]

If you didn't replace the valve train

If the link works, you'll see the picture. If not, go here

or go to

and down to "BANG! What happens to a 1966 Corvette when a valve drops at 7500 rpm ..."

[Michael H.]

Re: Smokey Yunick

Smokey sure did have the market cornered on parts. GM sent him at least 10 sets of everything to start with and that was just the begining. I have a lot of pictures of the inside of those buildings and the parts volume was incredible. He had the largest selection of piston rings I've ever seen. Looked like a picture taken at some ring mfg or warehouse.

Smokey was a bit tricky to deal with on parts. He didn't often come out on the short end of a deal.