Thread: 383 400 rwhp build

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first of all my goal is 400 hp at the wheels on pump gas. looking for a good build sheet. need some help i am so lost right now. lol right now i am looking at dart heads 180cc with a 72combustion chamber, rotating assembly is a scat 9000 crank probe forged -12cc rods are I beam with bolts cut for cam clearance moly rings and king main bearing. all balanced. my motor is 4 bolt 350 bore is 4.040. cam i am looking at is comp cam 280 magnum hyd, holley 750cfm, compression ratio around 9.5:1 any help with this would be great and very appreciated. or change my whole build sheet. i know 400 hp or pretty close can be had a million ways. please dont say afr heads i know they are the best but i buy them and well there goes almost all the money i have for the build... would love to have a set though!! this is just a start to my build and i am not actually starting my build until next spring when it warms up a bit. hopefully by then i have a good build sheet laid out before then. oh and before i forget its going in a 1982 c10 swb 12 bolt read end and 373's motor will be matched with a monster in a box th350. would like to build this at a reasonable price. would like to keep it under 2,000.00 on motor if possible.

Any,short of a new SHP or new block like it,needs to the machine shop to have the bores checked for roundness.It is kind of rare to find a block that just needs a hone and you can run it at 4.00.
Now a 4.00 x 3.75 stroke doesn't make a 383.That would be a 377.A 383 is a bore that is .030 over. While I talk about bores,the machine shop should have the pistons in hand while boring or honing for the final size.So don't allow them to bore or hone anything until you have the pistons to give to them.And the deck should be checked too for flatness.Where you set the deck height will make a difference in the SCR.(static compression ratio)At the end of the day the DCR(dynamic compression ratio) the takes into account all the factors of SCR which includes the deck height,type of piston,head chamber cc,and what kind of cam choice you made for the cam timing,really shouldn't be set any higher than 8.5 for pump gas.In this link(s) are some formulas to get you started on the SCR and DCR.

AutomotiveCalculators and Converters

Wallace Racing - Automotive Calculators

Welcome to CHR from a UofA Razorback now in Kansas. You pointed out that your block is already 0.040 over, so it's clear you're talking nominal numbers as opposed to specifics on your cubic inches, which is perfectly OK - nothing to get hung up on. With the TH350 you're looking at something in the 500HP range at the crank to yield 400RWHP (~20% losses through the gears), which is a pretty healthy build. Several guys on here can get into the specifics of a SBC build with you. If Tech (TechInspector1) had his super computer out of storage he's got the Dynosim software to run tons of variables to get you where you want to be, and the knowledge to plug & play it right. In fact he can probably get you there from memory, and explain the "why's" along with the "how's". Good luck on your build.

Assuming that Roger's 20% rule is acceptable (it probably is close), go to this site
Ryan's Small Block Chevy Stroker Engine Combo Page
and scope out the different build parameters....you can search for 500 hp to see what
it takes. IF YOU CHANGE ANY ITEM, all bets are off. You can dork up a combination with
a simple cam change......500hp isnt easy, especially with a single 4bbl. The $2000 budget
is probably acheivable if you take the $2000 to Vegas, bet it, and win 10X at the crap table.
Have fun in Vegas.

Yepper I missed the part about your block being .040 over for it to end up being a 384.Still the DCR formula you want to apply to end up no more than 8.5 for pump gas.
The Ryan's web page for 108 SBC builds is dated now.

Richard "Techinspector 1" does have some very good advise. Two resident engine builders on here is Pat and Jerry.

I like the choice of a 180cc intake runner for low end grunt,but your are going to find it has it's limits for top end HP. With 383's you can go to the 195 to 200 CC heads.

To to clarify,have you started this build yet or any part of it??. Is your 350 a roller block from a truck L31 1996 to 2000 yr.

You didn't say or I didn't see anything about decking the block.

Got to run for now,I'll check back later.

BTW-if you haven't started anything yet,you might want to see what Pat could do for you in a short block.

Originally Posted by jamesnelizabeth

first of all my goal is 400 hp at the wheels on pump gas. looking for a good build sheet. need some help i am so lost right now. lol right now i am looking at dart heads 180cc with a 72combustion chamber, rotating assembly is a scat 9000 crank probe forged -12cc rods are I beam with bolts cut for cam clearance moly rings and king main bearing. all balanced. my motor is 4 bolt 350 bore is 4.040. cam i am looking at is comp cam 280 magnum hyd, holley 750cfm, compression ratio around 9.5:1 any help with this would be great and very appreciated. or change my whole build sheet. i know 400 hp or pretty close can be had a million ways. please dont say afr heads i know they are the best but i buy them and well there goes almost all the money i have for the build... would love to have a set though!! this is just a start to my build and i am not actually starting my build until next spring when it warms up a bit. hopefully by then i have a good build sheet laid out before then. oh and before i forget its going in a 1982 c10 swb 12 bolt read end and 373's motor will be matched with a monster in a box th350. would like to build this at a reasonable price. would like to keep it under 2,000.00 on motor if possible.

I saw another young man on another forum asking how to build a 350 with 400 hp at the flywheel motor for $1500, now here you come looking for a 383 with 400 at the tires for $2000. I want some of whatever you guys are smokin'.

but Tech, he CAN do that.....just follow my instructions.....take $2000 to Vegas and invest it in a few rolls at the crap table....stop at $20K in winnings or keep playing for a few more rolls to build an even stronger motor.

Seriously, I cant even build a stocker correctly for that money.

Never said I only had 2000 dollars just said I like to keep it a bottom dollar. Kind of a penny pincher. I have 6500 top dollar mark. Don't want to spend no where near that much. That is crazy when you can buy a crate at that price. But crates take the fun out of the build. People who buy crate motors have no idea what is actually in the motor unless they pull it apart. Now back to the block. I did leave out decking. 0 decked. 9.5:1 compression ratio. Is what I was looking for. By pump gas I mean premium.

I asked for help with this not sarcasm. Sarcasm isn't showing your intelligence just your lacking of topic. Thanks. Also 20% would be around 480 fwhp and this I am aware of. Making right around 400 rwhp.

Originally Posted by jamesnelizabeth

I asked for help with this not sarcasm. Sarcasm isn't showing your intelligence just your lacking of topic. Thanks. Also 20% would be around 480 fwhp and this I am aware of. Making right around 400 rwhp.

No sarcasm. A 20% loss is subtracting 20% from the flywheel number, not adding 20% to the rear wheel number. If you're looking for 400RWHP then 400 = 0.8 x Crank Horsepower, which says you need ~500HP at the crank to yield 400 at the rear wheels, assuming 20% losses through the tranny and rear gears, which is a pretty good conservative estimate. With 480 at the crank you'll have ~385 at the wheels, again assuming 20% losses.

As for the costs, your initial post is pretty clear,

...would like to keep it under $2,000.00 on motor if possible.

Tech is simply telling you that your stated budget is unrealistic. Lots of knowledge here, if you take time to communicate clearly and don't blow smoke.

Welcome James (and Elizabeth?) to CHR:

You can certainly make (or come real close) to the horsepower you’re seeking with a stroker motor however; I’m a bit confused with your post and would like to ask a few questions.
1. Have you already bought or are you planning on a Scat 9000 cast crankshaft?
2. Are you referencing “forged” piston with a – 12 cc?
3. Are you buying a Scat rotating assembly that includes .040 over pistons and Scat rods?
4. As to clearances: # 1, 2, 5 and 6 are the ones that can hit. The Scat “I” and “H” rods are manufactured to clear the camshaft. If you are going to use stock GM rods, you need to remove about .050 - .060 from the top of the rod bolt. This is vital (sounds like you may already know this).

I’ve used variations of this combination for a lot of years. It’s proven and should net you well over 450 horsepower and 460 plus foot pounds of torque. As a side note: I’d go with a 2500RPM stall converter.

First and foremost – find a good machine shop where you can talk to the technician who will be doing the work. The prep on your block is critical. The stroker motor can be a screamer if built correctly, but heaven help you if clearances are not correct as the whole thing will come apart and you’ll have one very expensive door stop! Make sure that the technician has built many 383 motors. I know everyone has to learn somewhere – but you don’t want it to be your engine.

That said – have the block cleaned and tested – no need to build a block that has cracks or cannot be squared. Make sure that the machine shop understands that you’ll be building a screamer so you want to have the crank journals align bored. You said a “0” on the deck however; if you have not already cut the block, I’d recommend deck be cut to 9.003” – this is an important measurement!! Have the machine shop install new cam bearings and new brass freeze plugs. Also have the machinist go over the location of all the galley plugs with you so you know where they are and that they have been properly installed. When you get the block back from the machine shop make sure you really scrub that baby down with hot soapy water. I like Dawn dish washing liquid and water straight from the bottom of the water heater. Put the block on the engine stand and dry with compressed air really well. Paint the inside of the engine with Glyptal. Its $50 a quart from Eastwood – buy the brush on and a quart will do the job real nice. Also paint the exterior at this time too. Let everything dry real well – at least 48 hours.

Rotating assemblies are really your choice. I’ve used a lot of Eagle cranks and had good success – some here think they’re junk and will tell you so. If you’re set with Scat, that’s fine too. The nice thing about a kit from a top tier company is that you can get the crank, bearings, rod, bolts (and pistons and rings) in one package that should increase the likelihood of everything fitting nicely together. Again, some will differ – but I have used the kits from Eagle, some from Scat and years ago, from PAW (their “in-house” kit) and had good luck. I still mic everything and check clearances but in a “whole-lotta-builds” I’ve rarely had to return anything. I have had Summit send me replacement bolts for free one time when I had an issue. I find if I ask nicely when I have had issues (again, very few) I usually get good support and service.

Back to build – I’ve used a -7cc flat top and with the above deck height (remember that 9.003” measurement?) and that keeps things in the 10-10.5:1 compression ratio with a .041 head gasket (see below for part number). A -12 piston will certainly lower your compression ratio into the 9’s, but IMO - this could cost you some horsepower. As Gary mentioned, have your machine shop match final hone/size to pistons and press the pistons and rods together – it’s a bit tricky if you’ve not done it a lot and you need a press.

You didn’t mention an oil pan assembly. You can go stock, but need to be mindful of clearances here as well. I like the Milodon 30901 as it holds 7 quarts and fits stroker motors – might need a bit of adjustment with Eagle or Scat rods so be sure and check. Use Milodon 18750 oil pump with the 18314 pickup. Use Milodon 23050 oil pump drive shaft and 41000 one piece gasket. Milodon 81300 is an oil pan stud bolt kit – worth the $20 for ease of assembly.

Top the engine off with the components listed below:
I really do like AFR heads and think they may be good for +/- 25-50 HP – but you seem to want the Dart 127122 heads. I understand the cost (twice as much for the AFR’s – yikes!)
Double roller timing set - Summit is fine
Comp Cams 7972-16 chrome moly 5/16-inch pushrods
Comp Cams 812-16 lifters
Comp Cams 1305-16 Pro Magnum Roller rockers 1.60
I’d go with the Comp Cams 12-250-3 Xtreme Energy hydraulic cam XE284H
Demon 5402010 Mighty Demon 850 Carburetor (I have not yet used one, but like the looks and tech specs of the new Quick Fuel carbs, but they are expensive ($6-700).
Edelbrock 2975 Victor Jr. intake manifold – proven success and available used on eBay
Fel-Pro 1205 intake manifold gasket
Fel-Pro 1003 head gasket
HEI Ignition - stock Chevy is a good unit - pair with a MSD ignition (stay away from Accel anything – I’ve never had good luck with Accell and they’re no cheaper than MSD which has always been good to me.)

You may be able to do some eBay Craig’s list shopping to find some bargains but I agree with others here that $2K for 400HP to the rear wheels is just not realistic. I’d be surprised if you could do this for less than $3-3,500, but hey, I’ve been surprised before!

Good Luck,
Glenn

Thank you Glenn!

And every one else for your help. I know to play you gotta pay. But I was hoping for another's input if I may have missed a better option this I may have miss. The build I came up with is around 3800. With out block decked cleaned honed cam bearing and freeze plugs. Just was looking for some one else's input for some help with it. 375-400 rwhp. Is just around what I am looking for. Thanks a lot and If any one else has any other opinions just let me know please. And glen what compression ration would be good for this on premium pump gas?

Originally Posted by jamesnelizabeth

....what compression ration would be good for this on premium pump gas?

James,
Something to consider, "premium" pump gas varies from place to place, so if you're planning on this being a driver any distance from home you might want to dial back the compression to something that supports say 89 octane. Around here there are only a handful of stations that sell premium ethanol free, and they may disappear soon. The octane of the premium ethanol blends varies from 91 to 93, which is a pretty wide range as it affects timing.

I'll butt out now, and let you get the answers you want.

Also glen these are just parts I am planning on purchasing. Dished pistons are forged. Rotating assemble is a complete assembly from damper to flywheel to crank to piston. Supposed to be ready to put into block. Rods I am not sure if try are scat but its I beams and crank is scat 9000 I am guessing is cast. It is all internally balanced. I have carb already. Just snagged today. Brand new as well as a radiator both for 80.00. Carb I get was edelbrock 750 cfm. I have I Chevy 302 I am building currently and may use for this build. Got lucky on this motor. Truck I bought I paid 300 for whole truck. No rust and drive able. Truck when I got home I started running number guy told me it was a 350. But I pulled it and found out it was actually a 283 from 1958 vette. Measured the bore and it was and 4" bore. Ran numbers on crank and came back to a forged 302 crank. Four inch bore 3 inch stroke 302!! Truck has 12 bolt rear end 373's true dual 40 series flowmaster exhaust. Anyways I was very happy. But so far only purchases I have made. Got the 350 four bolt main block and a new engine stand! It had a th350 so I got the th350 monster in a box from monster transmissions. It's rated at 500 hp/torque so you are right. Sorry to sound rude just crappy day. No need to take it out on everyone. Lost a friend last night.