Building a 383. Need alittle Advice

[OrangeAnimal]

I will start with the basics. I am using a 4 bolt main block it will be bored .060 over. I was told that the bore being that much won't matter.

I am using a Eagle Internally balanced rotating assm. 10.7 to 1 comp ratio.

I am using a set of Dart Iron Eagle heads. I know there are better ones out there but this is what I have. IIRC they are 200cc runners and have 2.02 int. and 1.60 exh. Angle plug.

I am going to use a performer eps intake and a BG Mighty Demon 750cfm carb.

Still unsure about the cam and the carb though. I don't want to get too crazy with the cam even though it's a 4 speed. Need something that can be driven and streetable.

I was thinking something like 220* duration @ .050 and about 480-500 lift.

Hoping to produce a solid 400hp.

What is the deal with a small base circle cam? I can't even find any noting that.

Thanks for the help.

[shortbed70]

Ok as for your compression..too high for the street
as for the cam 480.500 wouldnt be bad for that compression ratio but you could run a larger cam with 10.7 and the heads beeing 200 cc runners will be kind of doggy down low but will wake up quick. I would run the thickest gasket you can and find a cam with more duration to bleed off some low rpm compression and listen very closly for detonation.

[Rodms]

look at a 250 60 cam advertise and the single plane intake will wake it up if your not going to drive everyday

What your talking about in your post is a race motor!!

[OrangeAnimal]

Well yeah this is a friends setup we are working on for his 81 stepside on bags. He just wants a 383 I told him he would have to tone it down. I am guessing it would run better with 9 to 1 compression.

[Hottrucks]

9:1 is ok for the street and your 750 is more than you need

alot of people tend to think a bigger carb is better but if the motr can't flow it then its wa ste

[mongoose]

what cc heads? the 64 or the 72? if they are the 72 i think you'll get it down the 9.8-10:1 with the bigger chamber.. unless that's your math... or they're not using a 64 cc head for the measurements.


for a cam.. you can run something like 230 @ 50... .500" lift. should match a combo like that well.

[OrangeAnimal]

The heads are 64cc.

As far as the heads and carb they are ones from the previous engine that was built way too hot on stock rods. He also has a Victor Jr intake but I advised against it.

I really think he is looking for something more streetable and more reliable even though it's not daily driven. He can't take it to the track cause it is on air ride.

He goes to drive in shows locally and tows to events like Heat Wave and so on.

Back on topic though I was thinking that 650 would be enough carb for the 383.

My idea for the engine is this. 650 Holley, Performer EPS, 9:1 compression, With the heads mentioned and As for the cam something with 480 lift and 220 @ .050 Duration.

[ProStreet71]

With that much compression on pump gas you will need a cam in the 240 @ .50 range to help bleed off cylinder pressure. Call your favorite cam company and let them spec a cam for you. As for running a thicker head gasket, it will have minimal effect on lowering your compression, could even promote detonation due to the increased quench area. The 750 carb would be rite at home on your engine. I would run the Performer RPM air-gap or the Vic Jr you already have. And of course you will need to run a stall converter. OR you could buy you a diff set of heads with 72cc chambers and lower your compression and proceed with the original plan.

[ProStreet71]

Oh and as for the small base circle cam, you have to run one of these in a stroker motor to clear the rods.

[OrangeAnimal]

Thanks prostreet71.

It has a manual trans in it so the stall converter isn't something we have to worry about. We are going to research some more on the cam. I think a call to Comp Cams is in order.

[Marv D]

Not going to say anything about the head choice other than,, 200cc runner and only a 2.02 valve, is pretty counter productive... BUT,, you have what you have. You would be MUCH better off with a smaller runner on the street, but... you have what you have. It ain't gonna be that bad and you can make up for port velocity in cam timing.

My suggestions would be...

Intake:
Edelbrock RPM air gap intake. It will match the combination and the heads. Vic Jr is intended for 4000 to 7500... is that where he's driving on the street????? nuff said.

Do NOT put a double pumper carb on this thing if you want street manners. That big runner is going to have a poor low speed velocity to begin with,, why kill throttle response with a mechanical secondary. A 650 or 750cfm (max) VACUUM SECONDARY box stock Holley will fit the combination much better. I run,, very far, and very fast when anyone says they want a BG anything. I've never seen such overpriced fad/hype based, 'trick of the week' junk in my life. Few people winning races run the BG junk. Unless this is 'just' a show piece and he just wants to 'show' he spent too much money on a POJ Deamon..... Proform Holleys with it's anodized metering blocks 'look' just fine and actually WORK without having to be rebuilt before using. (rant mode: off , I should not bring personal issues to the board, sorry)


Block:
I would have to disagree with whomever told you +.60 is OK. Unless they have sonic checked the particular block you are going to use,, I would STRONGLY disagree. The cylinder walls are thin enough at 4.00 I have seen very few blocks that deserve a second chance at the boring bar after +.040,,, which is what it takes to true up and clean up the used bore. I've seen a LOT of power go through a 2bolt block with main studs. 4 bolt mains are better without a doubt, but finding a suitable 4bolt block that will clean up at +.030 or +.040 is getting harder and harder to find. An option is a new GMPP 4bolt production block is right around $700-$750 now. (there is reason I bring that up)


Cam:
Now were going to spend some money. Oil quality is in the crapper to support a flat tappet cam. I'd start looking for a late model roller cam block (86 and up had factory rollers available in some motors, 96 and up MOST were factory hydraulic rollers). Lots of those around some in 4bolt, and they will be easier to find than the 2piece old style block. OR that GMPP 4bolt block I mentioned up there. (see there was a reason)

The factory roller block will save you a buttload not having to buy the retro-fit lifters. The GM OEM hydraulic rollers are plenty cheap and easy. Get the spider and all the hardware to go with the block.

Today’s cam technology is to have MASSIVE lift, and short duration, set the intake valve opening and closing events to match the combination of parts. You really can't do that until EVERY part of the combination is set in stone. Then a cam can be designed to fit.

Doesn't matter what final static compression you end up with (within reason that is,,, 11:1 ain't gonna work well on the street) the cam designer will set the intake timing to build the 'right' cylinder pressure, for the fuel, and the intended. use. Yes,,,, you know where I'm going . A CUSTOM grind, hydraulic roller. You can get one for about $300. The GMPP OEM hydraulic rollers will bring the price to roughly $500 for cam and lifters. Compare that to $250+ for a flat tappet cam, and the risk of loosing the cam on break-in, or more likely loosing the cam at startup after it's been sitting for a couple of weeks. Cam goes away, trash is circulated through the motor, now you get to replace the cam AND bearings, polish the crank, and a complete teardown and rebuild. That $500 roller cam looking more enticing yet????? Call Jay Allen at caminnovations.com with the FINAL combination of parts and he will fix you up. Be aware, Jay can be quite difficult to deal with in e-mail / internet communication only. You really need to call and talk to him. A very nice guy BUT, do not expect him to quote any cam specs over the phone, or invest hours of design until you have paid for his service. He gets right around $300 to design the cam, have it ground, cam-doctored for final as-ground report of specs, and shipping. He does not give out info or ideas for free,, unlike the big cam company phone jockeys that will spout off which of their shelf stock cam specs (that they feel at the moment) will fit you application. If they don't ask more questions than you have answers for, they are GUESSING. (ooops, again: rant off)

So,, you need to set the combination in stone before you even think about cam. You bleed the block decision, because you don't have a deck height, don't have the piston cc volume, haven’t cut them for valve to piston clearance, and that means you can not calculate compression yet.

Logical steps to get started here... have the heads checked (you said they were on the last motor) if there clean and flat, cc them so you know what they REALLY are.

Decide on a block, have it sonic checked, bored, decked if necessary and get those final dimensions so: ONE. you can pick the correct piston for the bore, TWO. so you can start making some assumptions and calculation to get TRUE compression ratio. Believe me, a advertised 10.7:1 compression listed with a piston is a WAG at best. There are too many variations that will DRAMATICALLY effect final compression ratio.

For example:
a 383 (4.030" bore) with a 9.025" deck (average 'normal' production sbc deck height) , a 0.039" Felpro gasket, 6cc for valve relief’s, assuming a head with exactly 64cc chambers, will be exactly 10.32:1 compression

Let's take all of that exactly the same and deck the block to 9.000" for a zero deck. Compression now is 10.94:1. All we did was cut 0.025" off the deck for a tighter quench and raised compression .7 points and out of the realm of 'acceptable' pump fuel performance.

If those iron heads are a little 'irregular' on the deck and you have to make a couple of passes to true them up,, now your at a 62cc chamber,, and guess what.. compression just jumped to 11.20:1

See where I'm going,,, VERY SMALL measurements make VERY big changes in compression. You put a cam in here with a real early intake valve closing and your going to build cylinder pressure that will detonate on 94 octane! Remember, with iron heads on a sbc you want to keep static compression to no more than 9:1 for today’s pump fuels. (9.7:1 or so with aluminum heads)

In the end...
You can play with cam timing to band-aid a poor combination, but you have a clean slate here. I'd suggest you work slowly and methodically to build a great combination. And first things first, you have to select block (dictated by the choice of flat tappet, 2piece rear seal,,,, or late model one piece seal, factory roller)
Then IS THE BLOCK SERVICABLE at the bore your looking at.


my 2cents,, maybe worth 1/2 that because.....

You need to realize, there are engine assemblers, Engine builders, and engine designers. 99% of us fall in the catagory of 'assemblers' as we don't have the machinery necessary to make, mill, bore and 'fit' components together in the package. Then there are the guys with the expertise to actually 'design' components for the 'builders' to make, for us assemblers to bolt together. If you go to the expert for each step, you will have the the better end product IMO

[Green Machine]

Small base circle cam depends on the connecting rods used. If the rods are clearanced on the bolt heads or you use capscrew "stroker" rods then a standard base circle cam should work. But it also depends on the cam lift. That is one thing that has to be checked during assembly. Rods need to clear everything by at least .060.

[jgh64pkup]

here is what you need
summit link
jegs is cheaper i think they are around 275
the site is down for routine maintenece or some bullcrap i will post the jegs link later

[OrangeAnimal]

Well we got the Eagle rotating kit. Internally balanced with SIR rods. The stuff looks stout. He went with a Comp Cam XE262H-10 .462 intake lift and .469 exhaust lift. Duration at .050 intake 218 and exhaust 224 with a 110* lobe separation. I think it will have a nice smooth idle with that cam. I doubt he is getting all he could out of the heads. He had what would basically be considered a race engine before and was trying to drive it on the street and well that didn't work so good. LOL. I think this combination should be good for about 350hp maybe more. I don't know alot about the heads other than what i listed earlier. If anyone else has some insight into this I would love to hear it. Oh the comp ratio is 10:1.