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Techin’ In With Fletch - Tech Questions - June 2013

Dan Fletcher Dec 16, 2013

Is It Blow-By?
I am a new subscriber, but have enjoyed your magazine for years and look forward to receiving it every month. I own a 1970 Chevy Chevelle SS396/350 HP clone, with matching numbers. So when I had a problem with the engine some time ago, I had it rebuilt to original specs with a new rebuilt carb. It runs great and I put over 2,000 miles on it this past summer. The problem is that it accumulates oil in the air filter pan. I have cleaned it out many times, generally once every 250 miles. It is enough oil that it will pour out at first, probably an ounce. We have checked the PCV valve and it is sucking copious amounts of air and is never clogged. The builder thinks it is fine. Others say it is blow by. The exhaust always looks fine. I would like your opinion.

Edward Tarquinio
Rutland, Massachusetts

While blow-by certainly could be, and most likely is, a contributing factor, I'm afraid your scenario is simply one that is somewhat inherent to a street-car-type big-block Chevy application. There's just so much piston going up and down that it creates a ton of backpressure. That big rotating slug does have a downside, ya know. I would ensure proper baffling, and would also entertain the idea of multiple breathers. And although the PCV isn't doing anything for you at wide-open throttle, I would still consider adding a second one for benefit at partial throttle. If the car has headers, I'd recommend a vac-u-pan-type set up. That's pretty cheap and easy to install, and while it won't totally resolve your issue, it will definitely help the situation.

Get Shorty
I'm a long time subscriber and a first time question asker. I have a '69 Camaro with a stock cowl hood that I'm having a 496 standard deck engine built for. I have all of the correct engine mounts. The engine builder wants to use a Team G intake, which I have found will absolutely not fit the hood I have (which is already painted). My question is which single plane intake will fit? I know an Edelbrock Victor Jr. is not as tall. Should I look for an old Torker? Thanks for any help Super Chevy can provide. I didn't know who else to turn to.

Bob Patton
Richboro, Pennsylvania

You say a “stock cowl” hood, so I'm assuming you mean the ZL2 option cowl hood. That's the same hood I used when I ran a 396/375 Super Stock motor in my '69 Camaro. I also had the stock frame mounts, but used Moroso solid engine mounts, but I can't see any potential impact created by their use for the purpose of this discussion. Back at the time, my engine builder used a Dart intake on this particular combo, but he has since moved on to using the Victor Jr. He builds the standard deck motor with that intake manifold for your exact application, so you're good to go there in regards to clearance. Additionally, he uses it because he feels it makes the more power on my combo, and that's always a good thing.

And if I'm somehow managing to misunderstand things and you're using a flat hood, there's good news: the Victor Jr. will still clear with a Holley 3310. I don't think you'd get much in the way of spacer under it, but it will definitely clear, as I know for a fact of people running them in the NHRA.

Quiet Down!
To start with, I love your magazine. I have a ZZ4 crate motor with Air Flow Research cylinder heads, GM hot cam, roller lifters, and roller rocker arms. My question is this: the valvetrain is very noisy, and everything has been checked out more than once. The engine runs fine. Is this a normal thing with roller parts? Is there some way to quiet it down? Would stiffer springs help? I hope you can shed some light on this and help me understand what's going on. Thank you for any help you can offer.

Harold Larsen
Andover, Minnesota

It is completely normal to hear valvetrain noise with a roller set up. If we assume a normal roller lash of 0.020- or 0.030-inch, although it may not sound like much, it's enough to create a pretty good tap. Drag race engines with very aggressive cam profiles do typically run extremely stout valve springs. The NHRA Competition Eliminator car I drive has an open spring pressure of nearly 400 pounds, but it also sees in excess of 10,000 rpm, so it's pretty much required to keep the thing in one piece, lol. But remember, it also has a 55mm billet camshaft that's designed to absorb that kind of load.

To your question, I absolutely would not run greater spring pressure to quiet down the valvetrain noise. It is inherent to the design. If you really want to quiet it down, my only thought would be to perhaps tighten the lash. With that said, you would obviously be sacrificing power by doing so, assuming you're currently running at the manufacturer's specification.

Have It Bronzed
I have a 1968 Camaro that has been in the family since 1969, and it has a paint code of 00. The research that I have found says that it is a special paint color called Corvette Bronze. I have only seen one other Camaro painted this color. My question is can you tell me how many '68s were painted this color? Thanks for the help.
Bob Mauldi
Crosby, Texas

My research indicates that Corvette Bronze was actually a relatively popular color for the '68 Camaro. While I can't tell you exactly how many were painted that color, I can tell you Camaro Research Group, a respected website, puts that choice at 7-percent of production. The most common shade in '68 was Matador Red, while the least popular was Fathom Blue.

My father purchased the '69 Z/28 Camaro that I campaign in NHRA Super Stock Eliminator brand-new. It was born Hugger Orange, and I once thought that was a somewhat unusual color choice. Not so much. At 12-percent, Hugger Orange was the most common color offered from the factory in 1969. Regardless, I still think it's sexy. For your perusal, I've included a link to the page of the CRG website that details exterior color production codes and percentages:

Fletch Questions Himself
It's time once again for me to offer another of my own questions (and answer it). This one was one of the most confusing scenarios that I've encountered in my long racing career. It's about our Chevelle, below, a perplexing power problem, and how we cured it.

Got a restoration question that's been puzzling you? Send it to:
[ m ] Super Chevy, Fletch, 9036 Brittany Way, Tampa, FL 33619.
[ e ]
[ f ] 813/675-3557



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