Building a 383 Stroker

[John_S]

Re: Building a 383 Stroker

I'm not 100% sure which cam is in the 350hp Black Scorpion, but believe it is this:

12370846 - Hydraulic Roller Design
This hydraulic roller design contains eccentric for mechanical fuel pump. It is for off-road use only. The duration at .050" tappet lift (intake/exhaust) is 222/230; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 509/528. Valve lash is zero/zero and lobe centerline is 112 degrees.


The lift matches the SM anyway.

 

[greg82255]

Re: Building a 383 Stroker

I'm not 100% sure which cam is in the 350hp Black Scorpion, but believe it is this:

12370846 - Hydraulic Roller Design
This hydraulic roller design contains eccentric for mechanical fuel pump. It is for off-road use only. The duration at .050" tappet lift (intake/exhaust) is 222/230; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 509/528. Valve lash is zero/zero and lobe centerline is 112 degrees.

Alright, I obviously have some research to do. All I know for sure is that I want to get to 350-375 horsepower. I'm bringing the block to the machine shop tomorrow and we're going to go over some of his recommendations for parts. When I get back, I'll post what he says and see what you guys think.

 

[joewithaboat]

Re: Building a 383 Stroker

375 now your getting greedy your o/p said goal of 350 hp right. Im just funnin with yea but 1 hp per ci is pretty doable past that you start having to spend $$$
Good luck, take a pen and paper with you when you go dont try to remember it all.
Have fun thats part of it!

 

[John_S]

Re: Building a 383 Stroker

With any engine, once you get to a certain point, to increase HP means moving the powerband up in rpms, and low rpm torque will start to suffer.

I think you are starting to fixate too much on a certain HP point. If your goal is all out speed, and you are willing to take your alpha over 5K rpms, thats much different from a basic 383 near stock engine. Is your hp goals crank or prop? That makes a big difference. 375HP at the prop means over 400 at crank. I think you were headed toward a 350hp crank / 320 prop, which would be more like a stock engine.

Common SB HP at Prop:
350 standard head 2brl alpha: 210
350 standard head 4brl alpha: 250
350 Mag standard head 4brl alpha: 250
350 vortec head 2brl alpha: 250
350 vortec head 4brl or efi alpha: 280
350 Mag vortec head MPI usually bravo: 300
383 Reman vortec head MPI bravo: 320
6.2L MPI vortec head bravo: 320
6.2L Black Scorpion vortec head bravo: 350

You need to select the rpm/power band you want, and sellect all the components to complement each other to work well at that powerband.

 

[joewithaboat]

Re: Building a 383 Stroker

With any engine, once you get to a certain point, to increase HP means moving the powerband up in rpms, and low rpm torque will start to suffer.

I think you are starting to fixate too much on a certain HP point. If your goal is all out speed, and you are willing to take your alpha over 5K rpms, thats much different from a basic 383 near stock engine. Is your hp goals crank or prop? That makes a big difference. 375HP at the prop means over 400 at crank. I think you were headed toward a 350hp crank / 320 prop, which would be more like a stock engine.

Common SB HP at Prop:
350 standard head 2brl alpha: 210
350 standard head 4brl alpha: 250
350 Mag standard head 4brl alpha: 250
350 vortec head 2brl alpha: 250
350 vortec head 4brl or efi alpha: 280
350 Mag vortec head MPI usually bravo: 300
383 Reman vortec head MPI bravo: 320
6.2L MPI vortec head bravo: 320
6.2L Black Scorpion vortec head bravo: 350

You need to select the rpm/power band you want, and sellect all the components to complement each other to work well at that powerband.

great summary John S !!!

 

[greg82255]

Re: Building a 383 Stroker

speed is my goal, but I'd rather not lose much torque either because I do pull tubes and skiers from time to time. I'm okay with spinning slightly over 5k (maybe 5500?). I'm scared anymore will kill the alpha. I'd like to see 350 at the prop.

 

[RogersJetboat454]

Re: Building a 383 Stroker

Greg,
If you really want to know the HP after the build, you could always bring the completed engine back to Chad for break in/tune/run on the dyno. Of course dyno time ain't cheap!

What did he say today?

 

[John_S]

Re: Building a 383 Stroker

Be upfront with your builder/machinest. Tell him that is your goal (about 375hp at crank) with max rpms of 5500, and you need a decent idle without sucking water back in.

Your target is something close to the Black Scorpion. It has MPI, and you are going with rpm intake/750cfm carb. You are down to about 335@prop with a similiar build otherwise. If the BS is using Mercs standard exhaust (have to check), you are probably gaining back 10HP with a mild perf exhaust. Now, if I have the correct cam, the BS may not idle well with carb, don't know. You can try more cam, or start other work on the vortec heads. Maybe, going to larger valves. Given that HP requirement, don't bother with the assembled vortecs. Start with bare heads, or good cores, and go from there. For the extra lift, you don't have to machine the valve guides, you could choose beehive springs. They are more expensive than standard heavier springs, but you can weigh that against the machining cost. At those rpms, you probably want stronger push rods, full roller rockers, and screw in studs. The valve train must hold together at those rpms and not float.

You are also going to need a marine ignition system so you can adjust your initial advance seperate from wot advance. Probably adjust the advance curves as well. The T4 restricts your flexibility there.

 

[greg82255]

Re: Building a 383 Stroker

Greg,
If you really want to know the HP after the build, you could always bring the completed engine back to Chad for break in/tune/run on the dyno. Of course dyno time ain't cheap!

What did he say today?

I actually didn't see Chad today. He was out for the afternoon and I spoke with his partner George. He was really nice and showed me around the place (the shop is very clean) and tagged my block and such. Chad said he was going to call me tomorrow morning once he takes a look at the block. We're going to go over all of his recommendations again and hopefully arrive at a final list of specs and a cost.

Be upfront with your builder/machinest. Tell him that is your goal (about 375hp at crank) with max rpms of 5500, and you need a decent idle without sucking water back in.

Your target is something close to the Black Scorpion. It has MPI, and you are going with rpm intake/750cfm carb. You are down to about 335@prop with a similiar build otherwise. If the BS is using Mercs standard exhaust (have to check), you are probably gaining back 10HP with a mild perf exhaust. Now, if I have the correct cam, the BS may not idle well with carb, don't know. You can try more cam, or start other work on the vortec heads. Maybe, going to larger valves. Given that HP requirement, don't bother with the assembled vortecs. Start with bare heads, or good cores, and go from there. For the extra lift, you don't have to machine the valve guides, you could choose beehive springs. They are more expensive than standard heavier springs, but you can weigh that against the machining cost. At those rpms, you probably want stronger push rods, full roller rockers, and screw in studs. The valve train must hold together at those rpms and not float.

You are also going to need a marine ignition system so you can adjust your initial advance seperate from wot advance. Probably adjust the advance curves as well. The T4 restricts your flexibility there.

He also told me that the block isn't going to work with roller lifters unless I get one of those retrofit kits. There are kits on CP Performance for $950 that include a cam, lifters, push rods and springs. If I get a set of bare vortec heads, or cores, maybe I could put them together myself.

I replaced the Thunderbolt IV this summer with a Delco Voyager ignition system. Was planning to reuse it with the new engine. Will this system work?

 

[John_S]

Re: Building a 383 Stroker

Let the machinist assemble the heads otherwise no warrantee. Not going to save much on the assembly either.

It doesn't look like that ignition has adjustable timing curves. You will have to see how it runs and go from there.

 

[greg82255]

Re: Building a 383 Stroker

All of the Merc 383's are using the Thunderbolt V ignition from what I see online. The 350's are using the Delco Voyager like I have. I suppose I'll address that issue when I get there. Still waiting for the machine shop to call me and go over their recommendations. Should be some time today so I'll post it when he calls.

 

[John_S]

Re: Building a 383 Stroker

That would be a surprise to me that the 383's were running T5. They were all MPI, and thought only carb engines were using T5 anymore. As far as I know all 5.0L and 5.7L carbed units have used T4 from when it came out and transitioned to T5 around '95. While there are only 2brl carbed now, I believe they are still T5. To change a T5 advance curve you have to buy a new ICM ($400-$500).

If you were staying with a more basic build, the ignition would probably be fine (like Merc's Reman 383). Given the HP you are shooting for and the cam that you will need for that, your timing curve will probably need to change. You would probably run more initial advance, but still cap the wot total advance.

Do you have the advance curve for your ignition? I didn't see it on the quick search I did.

 

[greg82255]

Re: Building a 383 Stroker

That would be a surprise to me that the 383's were running T5. They were all MPI, and thought only carb engines were using T5 anymore. As far as I know all 5.0L and 5.7L carbed units have used T4 from when it came out and transitioned to T5 around '95. While there are only 2brl carbed now, I believe they are still T5. To change a T5 advance curve you have to buy a new ICM ($400-$500).

If you were staying with a more basic build, the ignition would probably be fine (like Merc's Reman 383). Given the HP you are shooting for and the cam that you will need for that, your timing curve will probably need to change. You would probably run more initial advance, but still cap the wot total advance.

Do you have the advance curve for your ignition? I didn't see it on the quick search I did.

Oops - I was only looking at the carbed engines, not sure what ignitions the 383 MPI engines run. I'm not sure what the advance curve is for my ignition. All I know is it came with a timing shunt to set base timing, which was supposed to be 8 degrees BTDC. I'll check the manual and see if the advance curve is in there. It's an EST if that helps?

 

[greg82255]

Re: Building a 383 Stroker

Alright, so the machinist has not called me back yet. I'll be going up there on Friday to bring them my flywheel so I'll talk to him then. As of now he wants $600 to rebuild a set of heads, and it looks like a good set of cores cost around $2-300. If I have to spend that much on heads, I figure I might as well get a good set of new performance aluminum heads. I've heard good things about AFR (but they're expensive) and bad things about Edelbrock's performer heads. What would be a good set for this 383 that is somewhere under $1000? Any suggestions?

 

[Bondo]

Re: Building a 383 Stroker

Alright, so the machinist has not called me back yet. I'll be going up there on Friday to bring them my flywheel so I'll talk to him then. As of now he wants $600 to rebuild a set of heads, and it looks like a good set of cores cost around $2-300. If I have to spend that much on heads, I figure I might as well get a good set of new performance aluminum heads. I've heard good things about AFR (but they're expensive) and bad things about Edelbrock's performer heads. What would be a good set for this 383 that is somewhere under $1000? Any suggestions?

Ayuh,.... The 170cc Edlebrock E-tecs...
Their pretty much aluminum Vortecs...

 

[greg82255]

Re: Building a 383 Stroker

Is there a difference in performance between the aluminum and iron?

 

[Scott Danforth]

Re: Building a 383 Stroker

AFR has precision matched combustion chambers. however a new set of vortec's can be had for about $550

 

[mhouse40]

Re: Building a 383 Stroker

Also aluminum is lighter than cast,, however if you over heat aluminum it warps/fails. I have heard alot of great things myself on AFR heads,,,,,, Would be worth a shot to try and locate a slighty used pair on ebay to help with the budget , dart and brodix also makes some fine head's. When I do my engine rebuild , I plan on going with afr.

 

[greg82255]

Re: Building a 383 Stroker

AFR has precision matched combustion chambers. however a new set of vortec's can be had for about $550

I agree on the $550, but the machinist (and several posters on this thread) say I will most likely have to change out the springs to match the cam that I choose (haven't chosen one yet). I'll look for a set of slightly used AFR heads to recondition. Assuming everything else is the same, how much power can I actually add using AFR heads over a standard set of GM Vortecs?

 

[joewithaboat]

Re: Building a 383 Stroker

I think at the power level you are talking about (350 to 375 at the Crank) alum heads would be a luxury not a necessity. The best thing about them would probably be that you could get away with a higher compression ratio compared to the same set up with iron heads. Then of course the weight savings. I think this has already been mentioned earlier in the thread. I have used Brodix track I with great success on small blocks, a friend has afr 220's and makes great power. They both cost double what you are talking about though. Vortec iron heads are hard to beat for the money.
The edelbrock heads mentioned above are prob the most cost effective head assembled and ready to bolt on. Prob $1,300.00 to your door.