Which vortec heads for 383 build

[38special]

I see different vortec style heads new with different sized valves and runners. Some are advertised to out flow the stock vortec heads. Some have the 170 and 185cc runners with 2.02 and 1.60 valves. Would these heads be OK for a 383 build? I plan on running stock exhaust system and my outdrive is a sx cobra volvo penta. Is 350+H.P. with no drop off until 5,000 to 5,500 rpm's with good torque doable? Most of the threads i've read here had stock vortecs or aluminum heads used. It all most looks like i would be money ahead to buy new with mods already done than go with used vortecs.

 

[38special]

Re: Which vortec heads for 383 build

Something i found on another forum

its been my experience that standard vortecs become a restriction above about 4500rpm compared to several options, and are not the best selection if your trying to exceed 430hp

you don,t build an engine combo by selecting just heads, first and then matching the other components to that head flow rates, you select a hp/torque/rpm power band as a goal and then select the necessary components to slightly exceed that hp/torque/rpm power bands requirements knowing all parts NEVER work at 100% of the potential when matched in a combo.
http://forum.grumpysperformance.com/viewtopic.php?...

Obviously i don't need 430 hp but 350 + would be nice. I also read the stock vortec runners are 170cc. Would 2.02 valves in a stock vortec head let you get away with less cam lift for more hp and torque?

 

[Bondo]

Re: Which vortec heads for 383 build

you don,t build an engine combo by selecting just heads, first and then matching the other components to that head flow rates,

Ayuh,... Stock exhaust is restrictive...
Unless yer gonna throw the cash for water cooled Headers,...
The stock Vortec heads are more than sufficient...

 

[38special]

Re: Which vortec heads for 383 build

Ayuh,... Stock exhaust is restrictive...
Unless yer gonna throw the cash for water cooled Headers,...
The stock Vortec heads are more than sufficient...

Bondo could the after market aluminum manifolds for the 5.7 mercruiser be retrofitted onto a 5.7 volvo penta? They advertise them to have a better flowing exhaust. I like the idea of less weight and a little bit better exhaust flow. A loud exhaust is out of the question for my boat.

 

[Bondo]

Re: Which vortec heads for 383 build

Ayuh,... Those are still manifolds, 'n Not Headers...

 

[38special]

Re: Which vortec heads for 383 build

Ayuh,... Those are still manifolds, 'n Not Headers...

Granted but if for no reason other than weight savings? The volvo penta manifolds that came with my boat are center rise. Could the aluminum mercrusier manifolds be made to work? I'm not going to put headers on to gain more hp.

 

[Bondo]

Re: Which vortec heads for 383 build

Ayuh,... I don't know, but I'd guess there'll be bolt holes ya need for mountin' stuff, that won't be there...
And,...
The outlets may, or may not line up, 'n be the same size...

 

[John_S]

Re: Which vortec heads for 383 build

Stock iron vortecs, but you want them modified for more lift, valve springs to match cam, and possibly screw-in or pinned rocker studs.

 

[38special]

Re: Which vortec heads for 383 build

Ayuh,... I don't know, but I'd guess there'll be bolt holes ya need for mountin' stuff, that won't be there...
And,...
The outlets may, or may not line up, 'n be the same size...

Sounds tempting. I'm a welder by trade. Both the mercruiser and volvo penta manifolds have inlets for water and dump out the exhaust?

 

[Tail_Gunner]

Re: Which vortec heads for 383 build

I see different vortec style heads new with different sized valves and runners. Some are advertised to out flow the stock vortec heads. Some have the 170 and 185cc runners with 2.02 and 1.60 valves. Would these heads be OK for a 383 build? I plan on running stock exhaust system and my outdrive is a sx cobra volvo penta. Is 350+H.P. with no drop off until 5,000 to 5,500 rpm's with good torque doable? Most of the threads i've read here had stock vortecs or aluminum heads used. It all most looks like i would be money ahead to buy new with mods already done than go with used vortecs.

Not really modifying vortec heads is a very simple process...I believe you could put state of the art rockers.. springs...rods...retainers and flowed for the price of alumin heads there about a 1000 if memory serves me

 

[greg82255]

Re: Which vortec heads for 383 build

I'm using a set of stock vortecs, 906 castings, for my 383 build (see my signature). I have been told by the builder I'm working with that these heads matched with the cam (Comp Cams XM270HR .495/.503 218/226@.050, 112 LSA) will make 400+ hp. In order to have them work, the valve guides need to be machined to accommodate the extra lift and the also springs need to be upgraded. Depending on your cam, the pressed-in studs may need to be pulled and the bosses would need to be tapped for threaded studs. I'm also using 1.6 rockers, and to use those the push rod holes need to be widened to 1/2". Stainless valves are also a plus for marine use.

If you need any assistance building your 383, my thread is very informative on a lot of topics. I'm building a vortec 383 and I've asked a ton of questions and a lot of experts have answered.

 

[greg82255]

Re: Which vortec heads for 383 build

Sounds tempting. I'm a welder by trade. Both the mercruiser and volvo penta manifolds have inlets for water and dump out the exhaust?

I think that Bondo's point is that regardless of which company makes the manifolds, they're still stock manifolds. One is not less restrictive than the other, and they're all very restrictive. The only difference is that the Merc manifolds may not have the bolt holes needed for OMC or volvo, or the other way around. The aluminum manifolds are something like 40 pounds lighter per pair but are not more free flowing. If you want a less restrictive exhaust you can go with IMCO powerflow, CMI headers, Stainless Marine, Hi-Tek Exhaust, and a few others that are out there. Check out http://www.cpperformance.com/c-9-exhaust-systems.aspx

They're all going to cost in the ball park of $2000.