Camshaft Shopping

"Rusty Vandura - www.tinyurl.com/keepoppo" (rustyvandura) 02/22/2018 at 12:41 • Filed to: None

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The Offenhauser intake manifold bolts to a stock exhaust manifold to allow for heat from the exhaust manifold.

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And exhaust manifold for a 292.

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More than 350 CFM is overkill; the 250 can only breathe about 300 CFM at 5000 rpm. Max.

Demon-Xanth knows how to operate a street. > Rusty Vandura - www.tinyurl.com/keepoppo 02/22/2018 at 13:33

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Most centermount Corvair owners end up running a 390 4bbl for the same reason. A 2.7L engine only can suck in so much without boost.

crowmolly > Rusty Vandura - www.tinyurl.com/keepoppo 02/22/2018 at 16:29

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That’s a 4bbl intake with a 2bbl carb, just FYI.

What rear axle ratio do you have?

Rusty Vandura - www.tinyurl.com/keepoppo > crowmolly 02/22/2018 at 16:34

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To the first point, yes.

To the second point, I don’t really have any idea. My plan is to do the rear end last, give it two legs, and gear it so that I’m turning 3000 rpm at 77 mph in 5th gear. (T-5 transmission...)

crowmolly > Rusty Vandura - www.tinyurl.com/keepoppo 02/22/2018 at 16:45

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Looks like 3.90 gears with a 27" tire and a T5. Might be able to go with the 268H then.

Rusty Vandura - www.tinyurl.com/keepoppo > crowmolly 02/22/2018 at 16:54

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Yes, that’s the cam. I thought I posted a link to it. But that’s the one. That’s a shorter gear than I would have guessed, but I am far from any sort of expert.

crowmolly > Rusty Vandura - www.tinyurl.com/keepoppo 02/22/2018 at 16:56

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You did post a link. Don’t know where it went, but it was to a 260H. Not saying this thing needs to be a hot rod, but with a manual trans and short rear gears it will tolerate a more radical cam.

Rusty Vandura - www.tinyurl.com/keepoppo > crowmolly 02/22/2018 at 18:01

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You’re right. I got my duration numbers mixed up. The old guy I’m consulting with on this said the following:

There’s also a 268H cam, but it has a pretty noticeable idle lope and it requires some machining on the valve guides to accommodate the higher valve lift. Either one would work well with the 307 pistons, but I’d recommend doing some cylinder head milling for a little more compression to offset the longer cam duration.

It’s a lot to learn.

crowmolly > Rusty Vandura - www.tinyurl.com/keepoppo 02/22/2018 at 18:38

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That’s good advice. Are you trying to run it on pump regular? Or is pump premium OK?

Rusty Vandura - www.tinyurl.com/keepoppo > crowmolly 02/22/2018 at 20:52

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Regular. And 307 pistons to increase the compression by about a number.

RacinBob > Rusty Vandura - www.tinyurl.com/keepoppo 02/22/2018 at 21:36

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No disagreement on cam or carb. It’s better to be too little than too much cam as big cams really can kill torque. Do you plan to take it to a dyno guy for setup?

Rusty Vandura - www.tinyurl.com/keepoppo > RacinBob 02/22/2018 at 22:29

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I would definitely be curious to see what it’s pulling... How much does that sort of thing cost?

RacinBob > Rusty Vandura - www.tinyurl.com/keepoppo 02/23/2018 at 00:19

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150 bucks maybe for an hour. The real payback is the dyno test allows you to set the jetting and timing properly.

Our breadvan busted a set of pistons due to a lean condition in the last race. We had the carb rebuilt and they found out it had way too small of jets. SO the guy who rebuilt it put correct jets and we assumed we were good right.....

Well we went to do our dyno test and discovered the problem was still there. The tuner did one pull and shut it down. We hope we found it and assume there were other problems with the carb that a re-clean dealt with. If we hadn’t done the dyno test, we would have taken it to the track and would have busted the motor all over again.

Engines run forever if you don’t run them too lean and/or too much advance. A dyno test is cheap way to prove everything is ok while maximizing HP. This was at Don’s Machine Shop, Kenosha Wi. (PS we run a Holley 350 like yours)