383 heads?

mtnrat · Sep 11, 2007

I am building a 383 for the boat this winter. Will be built for torque, max rpm 5000. Any recommendations for cylinder heads? I want to keep the compression to about 9:1.

reelfishin · Sep 11, 2007

Re: 383 heads?

mtnrat said:
I am building a 383 for the boat this winter. Will be built for torque, max rpm 5000. Any recommendations for cylinder heads? I want to keep the compression to about 9:1.

I've used both OEM GM heads as well as Edelbrock Performer heads for this application. Since your main concern is torque, much like in a truck or tractor pull motor, you won't need a huge set of heads. Your main concern will be your cam grind. Keep the duration down and concentrate on intake lift. Keep in mind that a boat also doesn't coast, so the cam grind really must begin to work at idle.

wire2 · Sep 11, 2007

Re: 383 heads?

Easy/cheap way to increase lift in a SBC is switch to 1.6:1 roller rockers. (OEM is 1.5:1 stamped steel).

I got a name brand set for $125, had them in & adjusted (by myself, no ongoing arguments for 48 hours

) in about 2 hours.

They work well with my ss headers.

Bondo · Sep 12, 2007

Re: 383 heads?

Get yourself a set of Vortecs,...............

180shabah · Sep 12, 2007

Re: 383 heads?

Second vote for a set of vortecs, Low price and great flow.

John_S · Sep 12, 2007

Re: 383 heads?

Merc uses Vortec heads in their 383 and 377. GM crate HT383, does as well. Just have to use all the right parts such that the compression doesn't go too high.

blh1972 · Sep 12, 2007

Re: 383 heads?

vortecs.....

mtnrat · Sep 12, 2007

Re: 383 heads?

If I use vortecs (which i do have a set of small port bowtie vortecs in my basement), I would need a fairly dished piston to get down to the 9:1 compression that I am looking for. I also want to get the squish to about .040. Where can I get a D dish piston that will accomplish this. Seems I would need about -24???? A -22 could give about 9.2:1?
Calculations using:
bore size 4.030
stroke 3.75
quench .040
combustion chamber volume 65cc
One of the main reasons I am asking is that an engine builder I spoke to yesterday (who may be doing my machining), told me that the vortec bowties have too small a chamber to get the compression ratio that I want.
He is currently building a 383 for his own boat that is using world product heads and flat top pistons.

John_S · Sep 12, 2007

Re: 383 heads?

I am not up on aftermarket pistons, but a -22cc would seem to be a challenge. Per your requirements, I believe your builder is correct, it would force you into 76cc chamber heads. Aftermarket cast-irons, would probably be better than the GM ones in this catagory.

There are a few experienced stroker builders that hang out here, so they would be able to give you more insight in your choices.

BTW: Merc and GM make that compression ratio by not worrying about quench.

mtnrat · Sep 12, 2007

Re: 383 heads?

imported_John_S said:
BTW: Merc and GM make that compression ratio by not worrying about quench.

Hmmm, from what I have researched getting the proper quench is important in getting maximum efficiency.

Looks like I can get a Dart or World Product heads in a 72 cc combustion chamber. The Dart has 180cc runners and the World Products has 200cc runners

John_S · Sep 12, 2007

Re: 383 heads?

Yes it is a good thing, just won't find it in any production marine engine. With the aftermarket heads, make sure you don't have any exhaust manifold/sparkplug location space issue.

Vortecs are 170cc, so the 180's would be prefered vs 200, for the rpm band you want.

mtnrat · Sep 14, 2007

Re: 383 heads?

I am leaning toward using the small port vortec bowtie heads that I have. They are 65cc combustion chambers, 175cc intake and 65cc exhaust ports, 2.00 intake and 1.55 exhaust valves, and can tke up to .530 lift.
I have found some D dish pistons that will meet my needs with a 28cc D dish. (JEP 170817-8) http://store.summitracing.com/partdetail.asp?part=JEP-170817-8&autoview=sku
This will give me about 8.8:1 compretion ratio, With the quench being .040. Just what I am looking for I do believe.

John_S · Sep 14, 2007

Re: 383 heads?

It would have been nice to have it at 9:1 or little higher, but I know how hard you have been looking. Just about every forum I went on, had some discussion going on.

You are at the same static compression ratio that I calculated for a stock merc 350 vortec. That was using info from DM book, for a stock 0.051 head gasket. Just make sure your dynamic compression ratio doesn't drop too far with your cam selection. Please keep us updated as you make your other key selections, cam, intake, carb, etc.

gregr1971 · Sep 14, 2007

Re: 383 heads?

what are you meaning when you say "small port" vortec head??
if you use true "vortec" heads, you will have to use an intake designed specially for votec heads, the other gen 1 sbc intakes WILL NOT WORK.
'96 and later were the vortec heads

gregr1971 · Sep 14, 2007

Re: 383 heads?

i have a nice set of world products motown heads with manley extreme duty exaust valves, and manley severe duty 2.08 intake valves, isky tool room 1.55 springs, 72cc chambers, ready to go, make you a heck of a good deal on them.

180shabah · Sep 14, 2007

Re: 383 heads?

--------------------------------------------------------------------------------

what are you meaning when you say "small port" vortec head??
if you use true "vortec" heads, you will have to use an intake designed specially for votec heads, the other gen 1 sbc intakes WILL NOT WORK.
'96 and later were the vortec heads

he has a set of bowtie vortecs (from the gm performance catalog) they are better than the standard vortecs used on production engines.

gregr1971 · Sep 14, 2007

Re: 383 heads?

i see now.........

mtnrat · Sep 14, 2007

Re: 383 heads?

I will keep looking for something that will get me a little more compression. Having the proper quench should allow me to go a little higher than 9:1.
I am not married to the heads so I am still looking at all options. I am just removing the engine from the boat this weekend and will disassemble it. I will then take it to the machine shop to have it checked and measured. That will really tell me where I am at and give me more research time
imported_John_S, You have seen that I am getting opinions from everywhere, including local engine builders. Nothing like a little research to do it right the first time.

383 heads?

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