L29 454 Improving Airflow

TimEldridge74

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Ill describe the situation I'm in first, as I'm between a rock and a hard place.

I'm going to be building an L29 454 (96-00). I plan on making this a top to bottom build, making a 496 stroker. I have the 2.1L Whipple Supercharger that was made for this engine, bolts directly to the factory intake. So, to use this supercharger, I have to use the factory intake, which includes the lower intake manifold.

Unfortunately, one of the biggest restrictions of airflow are the intake ports on the factory heads. They're an improvement from the 91-95 heads, but its still a big restriction. To improve, an easy way would be swapping to rectangle ported heads, can double/triple the airflow from factory. However, I'd need a lower intake manifold with matching rectangle ports that still bolts up to the rest of the factory intake. I have searched with no luck. The way the lower intake from the factory was made, there (looks like at least) isn't enough material on the ports to have them drilled and matched to the rectangular ported heads.

Obviously, I'll be adding power with the Whipple, but there's just so much I'm missing out on power-wise with the factory port-style heads and lower intake manifold.

Looking for recommendations. Is there an aftermarket lower intake out there that has rectangle ports AND still fits with the factory intake? Or, do I ditch the intake entirely and go to an EFI setup and plumb a custom intake to where the Supercharger sits? it would solve my airflow issue hands down, its just I've never seen it done before with that specific Whipple setup. Any advice is greatly apricated, curious what anyone has to say.
 

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TimEldridge74

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It's just such a huge improvement going rectangle. plus, even if you went with heads w/ bigger ovals you'd have to port the lower intake manifold, which doesn't look possible. Looks like there just isn't enough material around the ports to do it, you'd have an awfully thin area making contact to the gasket no?
 

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Supercharged111

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It's just such a huge improvement going rectangle. plus, even if you went with heads w/ bigger ovals you'd have to port the lower intake manifold, which doesn't look possible. Looks like there just isn't enough material around the ports to do it, you'd have an awfully thin area making contact to the gasket no?

It's obvious that the rectangles are too big, aren't L29 heads midsized ovals? I don't know how much bigger big ovals are, but I figured they might be close enough to be able to port the intake? There is a motor build thread on here with some intake porting info.
 

Schurkey

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Rectangle ports on a truck engine are an undesirable waste of time, money, effort, and enthusiasm.

Decent oval-port heads (probably aftermarket) would be better than rectangle-ports. Downside with most GM iron oval ports is that the chamber is too enormous for most applications. However, they might be "just right" for a boosted, stroked Big Block. The L29 heads have a decent chamber shape and size, but the ski-jump in the intake port like the SBC swirl-port TBI heads. I guess some folks have had good results porting the OEM L29 heads; I can't say that I'm enthusiastic about that. I guess it's an option.

There are some old, open-chamber oval-port iron heads; they breathe OK and they burn OK, but they're not up to aftermarket standards. (Example: The "049" castings) The aftermarket is the way to go. Modern chamber, reasonable ports, the only downside is the expense. Available in iron or aluminum; with or without raised exhaust ports.

I'd strongly consider using the OEM intake, with better, aftermarket oval-port heads.

Be sure the pistons have enough valve relief for the bigger intake/exhaust valves, especially since you'll be milling the block decks for proper quench.

And--since this engine is boosted AND stroked--figuring out your desired compression ratio may lead you to heads with a larger chamber so you don't need dished pistons. Kinda depends on the boost level that Whipple provides.
 
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GoToGuy

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This is a little confusing. You said your doing a top to bottom build? Air filter to oil pan right? Thats generally what that means right. So if thats the plan, and your intention is the most available power potential. Why are agonizing over the heads, get good aftermarket that fit your needs.
Your gonna push alot more air, what about exhaust? Still got cats, oe mufflers.
Is the the power generated between the two different intake and head combinations like Nascar huge gains ( 1 or 2 horsepower). Or gains like 350 / 5.7 in my truck versus 350 in '69 Nova SS ?
If its 10 or 20 horse are you really going to know? Good luck, have fun.
 

Schurkey

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Supercharged AND stroked, I'd expect somewhere around a hundred ft/lbs increase in torque. Maybe more. And a very broad torque curve.

A lot of that will depend on computer tuning to suit the additional 40 cubes and huge increase in manifold pressure; not to mention cam and ignition timing changes.
 

yevgenievich

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Good oval port aftermarket heads would support enough for that supercharger. A bit of porting and the lower intake should be enough for it.
 
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