[mad hooker]

i just got my hands on a pair of 305 58cc heads, and was wondering if i put in bigger bigger intake valves, say standard 1.94 valves in the 305 heads instead of the wheezy 1.84 valve how much power i would gain besides the compression bump? if i use these they will go on a mostly stock "mexico'' 350. they are the better 14014416 heads, i belive they are 165cc chamber.

 

[RB69SS396Conv]

Stock, the larger valves by themselves won't do much, because the throat of the port is pinched off.

With port work however, they flow similarly to alot of the old double-humps. They also need the chambers unshrouded, especially on the intake side.

They'll end up probably around 62cc or so with the necessary work.

Altogether better than the smoggers that come on most of those "hecho en Mexico" units; usually 76cc 993s.

Your CR will end up probably somewhere in the low-mid 9s; 9.3-9.5 or thereabouts.

That motor probably came with a 929 cam. I'd strongly recommend an improvement in that are as well. The Comp XE262 is known to work well with that combo; most likely the small Voodoo that's of similar size would do well too.

 

[Guest]

Fine if you work w/ them.

More like 58 to maybe 60 cc chambers w/ maybe 160 cc intake ports.

(I'm trying to pull up Chevytech.net to check but not having any luck??)..

You really need to cc them so that you will know for sure.

And fwiw, 305HO, -601's are down around 52 to maybe 58 cc's so again, you need to cc them. I mention them b/c, imho, their chamber is a lot better than the -416's.

The -601's are bathtub chamber shaped and double-quenched like the original -461 fuelie double-hump heads instead of squared off like the -416 smog heads are.

My pair of -601's cc'd at 53 and 55 cc's and 160 cc ports!!

pdq67

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[mad hooker]

yeah with a little bit of work, and say a cam with around .450 lift with 1 5/8 headers what do you guys think it will put out?

 

[RB69SS396Conv]

Depends on the cam.

There's alot more to a cam than just a peak lift number. There's some REAL FINE cams with about that lift, and some REAL GARBAGE too.

Those heads, like most typical stock heads when used on a 350 or larger, will benefit from a larger exhaust lobe than intake. And of course like any motor, it'll run better with a modern, SOTA cam, than it will with the old cams like the Summit grinds or the "Performer RPM" (which you could get cheaper as one of the Summit ones) or old stock ones like the crappy -151 or some such. Since as we all know, seems like cars go a bit faster every year; one of the reasons is the cam improvements that people keep coming up with. Hard to overcome a built-in disadvantage by reaching back 40 years into the past; no matter how good it ran back then, the reason there's new ones now, is because they run better.

The Comp XE cams, or the Lunati Voodoo, are known to be real good with that combo. Don't go too wild; the XE262 or XE268, or the Voodoo products in that same general range (60102 and 60103 I believe they are), would be about perfect. Get the right springs to go with whatever cam you pick, and make sure they're installed at the right height.

1-5/8" headers should be fine. A 650-750 Holley DP and a Performer RPM manifold would work well with it.

You should be able to get into the mid 300 HP range without too much trouble, given good port work; maybe 350 or so, give or take about 10 or 15.