355 help

[Yellow76]

I have a mild 355 it was originaly going to smog but now it doesnt matter it has a mild cam (not sure what) hi comp pistons doug thorley headers and Edelbrock performer intake with a quadrajet on top of it. My question is what do you guys think i should do to get more power for my buck? I was thinking the intake/carb set up but im not sure. Thanks

[ripdog28]

What kind of heads are on it? Cam/Carb/Intake would be the cheapest and easiest but Cylinder heads make the biggest difference. Even just some after market Vortech ones at $3-400 each.

[Yellow76]

I believe they are 194s but again im not sure my uncle gave me the motor so im not positive i did notice that they had square exhaust ports though not really sure what that means

[ripdog28]

I would replace the heads before anything else. Change cam while at it. You can find After market heads on Ebay for cheap $2-300 a set. Or if you dont mind spending a little more, get some from RHS/Dart. IMO, i would not waste the $$ changing a cam/intake with those stock heads. I would not even waste the $$ getting them ported.

[Yellow76]

ttt

[Yellow76]

so i just looked at my heads and the I.D number on them is 462624 and i looked them up and i guess these arent good at all is this true? And if so what should i replace them with? Thanks

[mongoose]

like an 882... the everything head of the era.. pretty much junk...

what is your budget?

[Yellow76]

I really wouldnt want to spend more than 700

[ripdog28]

If buying new, something like the SR torquer I think youll be able to find something on Ebay.

[Yellow76]

First of all thanks for all the help. with the bare heads what all else do i need to buy for it. Can i put the springs and stuff from my old heads (witch are new) on different heads other than the valves or do i need all new stuff?

[ripdog28]

Im sorry, didnt realize they were bare. Here are some assembled. Summit products are often produced by Dart/World Products other big name companies just cast the Summit logo into it and sell at discounted priced. Again, check Ebay or Racingjunk.com always cheaper.

[Ticker]

S/R ("Stock/Replacement") heads are really made for racing classes that require a "factory" type head - the flow isn't all that much better than the old-skool factory heads, although they do have additional "meat" for porting.

The cam is probably the first place to look for more power - depending on what the current cam is, even a mild upgrade can produce decent power with even lo-po heads.

Next up would be a set of Vortec heads, but you would need an intake swap for a Vortec intake - best case, a Performer RPM. You'd definitely want a different cam to match...but we're getting up around $1200 for a Vortec top.

[Yellow76]

Ok i always wondered about the vortec heads are they all the same or is there sertain things i should look for in it?

[Ticker]

The best deal are new GMPP ones available via Summit, SDPC and lots of other vendors. Part number is 12558060.

IMHO the "upgraded" Vortecs with better valve springs aren't a great buy - the stock Vortecs are limited to .475 lift (more practically, around .460 lift) and as long as you're not going beyond that (which you don't need to as they won't flow) then you're golden.

The stock, stamped-steel rockers (P/N 12495490) are fine as well - roller/roller-tip rockers aren't needed at this power level.

Remember that you do need to check the valvetrain geometry...

[Yellow76]

Alight i dont want to be a pest by asking all these questions but i want to be able to make about 425 hp are the vortecs good for that amount of hp?

[Ticker]

Without knowing more detail on the shorblock it's hard to say for sure, but I'd be pretty confident you wouldn't get there. 350-375 HP is a more likely target.

If you're looking to make 425 HP from 355 CID (1.2 HP/CID) you're going to need to step up to some 2nd tier heads...which is way, way over your budget.

AFR 180's would get you into that territory, as would some 195s/200's from other vendors. You're looking at $1500+ for heads before you even start talking about rockers, cam, etc.

You can estimate HP from realistic flow numbers with the following formula; note that you do need to adjust for the intake; about 20% or more for a dual-plane low-rise, then less from there.

Peak_HP = Flow_CFM * .26 * Number_of_Cylinders

Applying this to Vortecs with a low-rise dual plane:

235 x .8 = 188

188 * .26 * 8 = 391 HP gross.

Money makes power.

[Yellow76]

Alright sounds good what do you think about these heads on ebey?
http://cgi.ebay.com/ebaymotors/NEW-C...Q5fAccessories

[Ticker]

Originally Posted by Yellow76

Alright sounds good what do you think about these heads on ebey?
http://cgi.ebay.com/ebaymotors/NEW-C...Q5fAccessories

I have no idea. I can't imagine buying a "new aftermarket" casting of indeterminate origin...

[team39763]

I've heard good things about the Dart Iron Eagle heads. They're not too expensive on ebay. I know there was one guy that was selling "fixed" iron eagles for a really good price...I think it was $500 for the set, but I can't remember if it was bare or assembled.

[Ticker]

The best way to objectively evaluate heads is to compare the flow, runner size and intake/exhaust flow ratios.

For flow, we're looking not just at peak flow but flow throughout the lift range - and numbers that match the power levels we're trying to make. Heads that have crappy flow until very high lift numbers are a sure sign of hogged out ports that make great flow bench numbers...but don't work well in the real world.

For runners, we're looking for the smallest runners consistent with our flow goals. A 185cc runner that flows the same as a 195 or 200cc runner in another head means we'll get higher intake velocity with the smaller runner...and more power.

I/E ratio is simple - the higher, the better SBC heads all have weak exhaust ports to some extent, so anything over 75% or so is excellent.

[Rodms]

882s can be made for good torque,just who does it?