Black04Vert

I am going to stroke out my 74 L82 to a 383. I need a bunch of help with figuring out the bottom end. (approx 500HP, 9.4:1 CR, 4 speed, street only, 3.55 rear end)

If I am sleeving does this matter as long as the final bore is still around 4.03?
Forged or cast components? Does a manual necessitate forged?
Deviate from flat head pistons only to reach compression ratio goals?
Any recommendations on a bundled crank/rods/piston kit?
My 2 piece rear main seal leaks now. What 's should I look for in a replacement?
I estimated a .025 deck clearance. Does it end up being that in practice?
Good brand for cam and crank bearings?
What paint should I use on the outside of the block?

TimAT

I'd go with forged stuff. Build for any future upgrades. I just built my 496- Eagle forged crank and rods, ARP bolts/studs. All Clevite bearings. Comp solid roller cam with a cast distributor gear..

jim2527

Would it be more economical to buy a completed short block?

Black04Vert

Maybe. The block is original so I'd kinda like to keep it. Also, the cheapest short block on Summit with forged internals was $3800. I see forged full rotating balanced assemblies from Lunati and Scat for $2700 but I'm not sure how those would relate to a pre-built block from Summit.

Black04Vert

That's what I was figuring. If I wanted to go with bigger heads or change the cam (tougher) later, I can always swap it out with the engine in the car ... the bottom end I can't.

I was going to go with AFR 75cc 195 Street heads, Comp 268 XFI retro roller hyd. cam with a Holley Sniper EFI.

cardo0

500hp is very optimistic for a 383" stroker sbc. But 450 I think would be more reasonable for a first time effort. If you do have a original block once you deck the surface no one will ever be able to determine that once the stamp pad is cut down.

You need to find a auto machine shop you can work with. Your going to need block cleaning, boring/honing, decking, alignhoning, cam bearing replacement, maybe balance too.

But once the block is ready then I choose pistons with the dish I want for the compression I want. Then buy the heads I want with the chamber size for the compression I want. Next I measure the above piston volume and head chamber volumes to accurately determine the actual compression ratio. Finally I select a cam to work the best with that compression ratio.

Good luck and let us know what you measure for those volumes.

Black04Vert

I wasn't planning on decking the block. The machine shop said they could level the sleeves with minimal if any decking.

I have one but I don't know anything about the parts that they use. I don't want to dish out several thousand unless I know exactly what is going into the bottom end.

I want a torquey streetable engine with a lopey but reliable idle. My calculations for 500HP were:

AFR 75cc 195 Street Heads
Comp Cams 268XFI retro roller hyd cams
Dur:218/224 @.050 Lift:.570/.565 RAR:1.6:1 LSA:113
Holley Sniper EFI 800cfm
Dual plane intake ... I haven't decided on brand
Headers ... I haven't decided on primaries or collectors widths yet

9.4:1 compression ratio assuming:
75cc heads
0.025" piston deck clearance
4.03" bore
0.04" gasket thickness
Flat top piston with 5cc valve relief

Using Comp Cams CamQuest software (I know it's not super accurate) it calculated:
503 ft/lb of torque at 4000
502 HP at 6000 (This isn't accurate as the cams are only rated to 5800)

0GolenEngineService

We build quite a few of the 383ci Chevys that make 500hp on our Superflow engine dyno and here is the combo that you will want to run to make that power.

Your 2pc block will work fine for this level of power but you will need 4-bolt mains and I would recommend an ARP main stud upgrade, these are only $100 and well worth the money. Deck the block as close to zero as possible to keep the quench around .040".

Camshaft we run is the Comp Cams XFI 280 which has a 230/236 Duration @ .050" with roughly a .575"/.575" Lift on a 113 LSA, this cam will give you a good sounding idle but nothing over radical. 10.5:1 compression which will run on 91 octane plus fuel when running 38 degrees of total timing with the AFR 195cc CNC ported street head. You best bet is the Mahle Motorsports forged piston running a -5cc flat top and the best crank for the money is the Scat 9000 series which is cast steel and obviously the 4340 forged version will be stronger if your budget allows. We run the Scat 4340 forged steel I-Beam rods 6" long and they are always rock solid with no problems to speak of.

On the AFR heads you best bet it to customer order them from an AFR dealer such as ourselves and then you can have them made with the 70cc chamber and I would upgrade to the ARP 7/16 rocker studs for an extra $30 and upgrade to the AFR # 8019 valve springs for an extra $60, these two options are a must in building a long lasting and reliable small block chevy that makes 500hp.

Run the Edelbrock Performer RPM if you have the hood clearance and the Holley Sniper EFI has been great, we have used at least 10 of them on the dyno with no issues and easy tuning. Holley offers a distributor that allows you to connect it with the Sniper EFI and control timing, this is a must if you want to have the best control of both fuel and timing.

Headers you will need a 1 3/4 long tube and at least a 2 1/2 exhaust with a free flowing muffler.


Let me know if you have any other questions or need any advice at all.

Chad Golen

GOSFAST

If you choose to go retro-hyd-roller (highly recommended) I would set up your early block to accept a later style thrust plate (photo below). This eliminates the need for any cam buttons OR "chasing" end-play.

It also makes no difference with this setup which timing cover you use, there is no more cam button needed.

Thanks, Gary in N.Y.

P.S. Have dynoed a bunch of these units with the thrust plate setup with excellent results. Makes assembling the build a "walk-in-the-park" so to speak. Have sold numerous sets of tooling to modify these early blocks! Also like the Comp's cams mentioned above, EFI cams but with a carb!!

Black04Vert

That's a cool gadget.

I first looked up a thrust button when I saw that the notes for Comp Cams retro roller kit requires a thrust button and wear plate. My understanding is that the flat tappet cams actually had a slight taper which pushed the cam towards the distributor. Since roller cams don't have that taper it requires a spacer that wears against a wear plate (unless you get the roller button) to keep the cam in the correct location.

How does that thrust plate keep the cam in place? Does it have any component on it that wears like the thrust button?

Black04Vert

I believe my L82 block came with a 4 bolt main so I should be good there. The ARP stud upgrade is for the bolts holding the main caps?

I don't want to deck the block to the point that the VIN numbers get ground off the block. If my compression ratio is too low I'm assuming I can swap to the 65cc chambered AFR heads instead of the 75cc. Or is there a benefit other than total compression area to reducing quench?

I designed for a 9.x:1 compression ratio just using the conservative rule of 10 octane for every point of compression. I take it the 10.5:1 is doable due to the increased duration of the 280XFI cam vs the 268XFI that I was planning on?

CheezMoe

I used a scat9000 Crank, Scat I Beam rods Diamond CNC Pistons (Flattop-5cc) and a Howards Roller retrofit cam. I went high $$$ on the pistons and total seal rings and the leakdown is <3%. Came out at 10:1 static and 8.2:1 dynamic. Internally balanced it all. No regrets! Good luck!

bluegtp

My build was pretty cheap considering it was a stroker motor. It was a street car and it was a very fun motor with tons of torque. I speak in past tense because after 10 years of my 383 running strong I pulled and sold it to do an ls3 swap. The scat cast kit I used was $540 about 10 years ago, brodix ik200 aluminum heads were right at 1k. Comp cams extreme energy I think had about a .510 lift similarly on intake/exhaust. Not as large as golen specified. Edelbrock performer rpm intake with holley 650. I ran some 1.6 roller rocker arms. Engine was an l48 and I left it a 2 bolt main motor.

Most setups I saw that were putting out decent power when researching stroker motors had a compression ratio higher than 10 (aluminum heads too). Mine was around 10.4:1 and no problems with detonation as long as I ran the higher octane fuel.

I agree to go with the roller valve train while your there. I didn't and always wished I had. I think some kits are clearanced for it but make sure to check clearances between rods and cam and rods to block. I had to take some off the block and some off the rods to clear full rotation.

gkull

I agree with Chad. With enough cam 10.5 cr will achieve near your goals. Yes the l82 is a 4 bolt. I fully studded my 383

It will require some block clearancing on the front cylinder pan rails when using bigger rods. I also recommend the 8 quart stroker oil pans

GOSFAST

It's possible to mill the decks as much as desired without ever touching the OEM block numbers, we do it all the time whenever necessary.

We could take as much as .100" off and still leave the numbers!!

(Add) We are making above 500 HP with under 10:1 on the 383" platform. Am NOT a big fan of Dart's heads but the SHP's (127422's) will hit 500 "from-the-boxes" @ 5800 with 9.75:1. With 11:1 we can do over 550! Also, stay with a 2.020"/.1600" valve layout on the 4.000" bore build, you'll hit over 480# Torque

Thanks, Gary in N.Y.

P.S. That .100" mentioned above is an example ONLY, obviously no one would mill that much off, but with the CNC it's very easy to "save" the numbers!

cv67

Right on Gary, bust those myths about decking

Spending thousands on a new motor and cheaping out on a lousy deck, line hone etc makes no sense at all. It is totally worth it

Compression is where its at

Buccaneer

I want a torquey streetable engine with a lopey but reliable idle. My calculations for 500HP were:

AFR 75cc 195 Street Heads
Comp Cams 268XFI retro roller hyd cams
Dur:218/224 @.050 Lift:.570/.565 RAR:1.6:1 LSA:113
Holley Sniper EFI 800cfm
Dual plane intake ... I haven't decided on brand
Headers ... I haven't decided on primaries or collectors widths yet

9.4:1 compression ratio assuming:
75cc heads
0.025" piston deck clearance
4.03" bore
0.04" gasket thickness
Flat top piston with 5cc valve relief

Using Comp Cams CamQuest software (I know it's not super accurate) it calculated:
503 ft/lb of torque at 4000
502 HP at 6000 (This isn't accurate as the cams are only rated to 5800)

I ran the Comp 268 XFI HFT cam for about 12 years with no issues in my 383, but the HR 268 would be a better choice if that's the cam you really want. Stay with a roller, no matter what cam you choose. A custom cam may be a better choice depending how much you want to spend, they are a bit more pricey though.

Also, since you want to make power at or around 500hp, I would NEVER put anything cast in that motor, it just doesn't make sense no matter how you look at it. You want to build for strength and quality, not just HP. A cheap parts 500hp motor is just that...a cheap parts 500hp motor that won't last making that much power for very long. Spend a few more duckets and put good forged parts in the motor...crank, rods and pistons.

Black04Vert

I should have been more specific. I was looking at using the 268XFI HR13

Any brand suggestions for crank, rods and pistons?

I see that Scat, Eagle and Lunati Voodoo all have non-twist forged 4340 cranks for $600-700. What's a good package price?

PS That Crossfire looks like a piece of art

Metalhead140

You want a tight quench for detonation resistance. You can have low compression and still suffer detonation if your quench is too large. I'm running 11.1:1 compression with no pinging on pump fuel (bigger cam than you're discussing, but similar power level), with a .037" quench. A lot of people like it even a bit tighter, but I'd definitely shoot for no more than around .040".

NewbVetteGuy

If you can still get a quench of 0.040" with a stock block and piston height using a Felpro 0.015" gasket, what benefit exactly is there to decking the block?

I understand that you want the deck perfectly square and flat, but what benefit is there to blocking the deck all the way down to 0.000" if you can still get proper quench without it?


Adam