hartsmike

New question here: On older 350 SB, with basic rebuild, say bored .30 over, what kind of HP increase would one expect with Flat top pistons and an RV cam?

sofakingdom

iTrader: (1)

Depends on what it started out as.

Might even be a net loss.

But compared to a typical 70s 350 w 882 or 624 heads, 929 copy, and 12cc dish pistons .045" in the hole, it'd be a net gain for sure. Probably a good 25%... IOW about 35 HP. More if the block was zero-decked.

hartsmike

Don't know much about engine I have now except it was "supposedly" a rebuilt engine with some "added pep". But, this thing is a complete dog! Builder said rebuild with RV cam and flat top pistons. Said may have to run on mid-grade gas because compression will be higher. I asked him if it would get me a 300 HP engine and he said would be close.

hartsmike

By the way, I've got a weiland intake and Holley 600 double pump carb on it.

sofakingdom

iTrader: (1)

Well without knowing what's ACTUALLY IN IT, it's impossible to guess what it should do. You'd have to open it up and look at the parts and measurements yourself, to know what he did, what he put in it, or whether he's just pumping your anus full of sunshine, or what. But if it's altogether gutless, I'd guess it's "rebuilder" pistons with the extra .025" of deck clearance (whether flat-top or whatever other configuration), the cheeeeeeeeeeeepest crappiest most commonplace heads he had on hand (882 or 624, or TBI garbage such as 193), the least amount of machine work he could get away with, and who knows what cam.

Weiand (now a division of Holley, since the early 80s) sells ALL KINDS of intakes; from basically stock replacement, to full race. Just the brand by itself doesn't tell much about it, other than, it's not an Edelbrock or whatever else. Won't have much bearing on the matter at hand either way though, in most cases.

hartsmike

Is it difficult to get 300-350 HP out of the older Chevy 350 blocks? I've researched and read where heads are important and even where people are using the old 305 heads bolted onto the 350 block to increase compression.

hartsmike

Another quick question for you engine guys: Does the RV cam have a "lope"?

sofakingdom

iTrader: (1)

Given that the factory got more than that out of em at times, and LOTS of people have got upwards of 600 out of em, I'd say, no.

The block isn't the limiting factor to HP anyway. All of em have equal power producing potential.

Power comes from FLOW: getting air/fuel mixture INTO and BACK OUT of the cylinders. The block isn't involved in that. Heads, cam, & exhaust are the main things.

No "The RV Cam" doesn't have a lope. Lope comes from reversion into the intake from the int valve opening while there's still pressure in the cylinders, which in turn comes from long int valve duration, which is one of the ways to optimize an engine for high-RPM power (FLOW) at the expense of low-RPM efficiency which is what a RV situation (huuuujjjje heavy vehicle, small motor) needs. "The RV Cam" idles smoother than some stock cams.

hartsmike

Typical pre 86 350, bored .30 over, flat top pistons, RV cam, headers, straight pipe-no converter or muffler and moderate head work with (and I'm not sure which Weiland intake I have-I'll have to look) and Holley 600 double pump carb, any guestimate on how much HP possibility?

thanks so much for the replies and the thought behind the replies guys!

sofakingdom

iTrader: (1)

Depends on what pistons (whether they have the added "rebuilder" deck clearance), what heads (the SINGLE MOST CRITICAL thing to HP potential), and what machine work and attention to detail it was given.

But most likely, somewhere between 225 and 300 HP.

Incidentally, Weiand doesn't have a "l" in it. https://www.holley.com/products/intakes/

hartsmike

Thanks for the reply! Does shaving the heads take from bottom end?

sofakingdom

iTrader: (1)

Not generally.

On most smogger heads, the change in compression from "shaving" them, is negligible.

Gotta dive into the details to do anything more specific than just guess in generalities. What head casting #? What piston part #? What's the MEASURED as-installed deck clearance?