oil pan 4

I was looking around to day and saw some headmen headers for my camaro for $200.
They were step up full length headers.
They go 1 1/2 primarys turn to 1 5/8 primarys into 3'' colecters.
plain is while I'm over seas( up to 3 years @ ramstine AFB ) I'll leave the car home and keep sending back $ and have it worked on. I was going to have a stroked 350 ( 3.850 crank ) vortec headed camed from 238' to 244' and lifted to .510'' with 1.6 rockers put in ( the list goes on). @ 6500rpm it will inhale 808 cfm it will need at least a 850-900+ cfm carb.
That over 100 cfm per cylinder of burned expanded 12.5:1 A/F air going out, I think it will consume .6 gallons of fuel @ wot per minute.(car will pass every thing on the road but gas station).
I still want to make some power down low and want it to peak under 6500 rpms so do you think 1.5>1.625>3 is to small?
Pay the $300 or $400 for the 1 and 5/8's to 3?

OldSStroker

Some thoughts:

I ran your combo thru Engine Analyzer Pro, a very good engine simulator, with the following results:

WELL PORTED Vortec heads will support about 500 hp around a 6000 rpm power peak on your 393 inch engine, and about 500 lb-ft around 5000.

Actual max cfm for that hp level is under 650 cfm which would indicate a 750 or maybe a vacuum secondary 850 carb.

With a BSFC of .47 that is about .6 gal/min IF you could run the engine at full load at 6000 for any length of time. Unless you are on the autobahn and geared for max speed in the 300 kph range, or on the dyno, or at Bonneville, you won't be able to sustain that 4.9 miles per gallon burn rate.

Your header primaries sound a llittle small for 500 flywheel hp. I used 1-3/4 primaries and 3 inch secondaries and 3 inch true duals through virtually zero restriction mufflers like Dynomax Ultraflo welded 3 inchers. There were substantial gains above 5000, and no real losses below.

Using 1-5/8 dia. primaries cost a few hp and pushed the torque peak below 5000, compared to the 1-3/4 but it was still better than the 1-1/2 to 1-5/8 stepped. Now if you aren't using well ported Vortec heads, with 250 cfm (@28 in. H2O) at .500 lift, your power will be down a bunch and 1-5/8 would be just about right. Just make sure the rest of the exhaust system is up to the task.

My $.02

oil pan 4

500 and 500 is a little much.
I was going for 450+hp and around 500 ftlb of torque.
I have an automatic so I'll keep the duration to 238' with .500'' plus lift.
If the car gets done early I might have it sent over to germany, I would have to pay for it tho.

OldSStroker

For those numbers, you might consider a different cam.
238 is a ton of duration for only .500 lift; it's 'lazy' compared to an aggressive roller.

IMO, it's not the max torque, but the average torque in the operating range of the engine that gets the job done. Let's say 2800 (stall) to 5800(shift). You could use a cam that made maximum average torque in that range that would idle like a stocker and still rip your head off. It might need to be a hydraulic roller to get the aggressive lift rate, but it works.

I wondered why you want a 3.85 stroke? That sounds non-standard. There are good packages for 383 with 3.75 strokes which include all the bits for a good price. I'd use one of these and spend a little more of my budget on the valvetrain (hydraulic roller, good rockers and springs).

Just some thoughts.

oil pan 4

Well what ever the normal lift of a 238' cam + 1.6 rockers.
I picked a 3.850 crank to go with 6'' rods to use cheap, light, and strong 1.000'' compression hight pistons with a thin .003 head gasket and a 9.000 deck for a C/R of 9.6:1 with plenty of piston deck clearance.

OldSStroker

I'm confused:

I get .075 from the top of the piston to the deck. With a .003 thick gasket (that's a typo, right?) you put yourself right in the "squish' height that PROMOTES detonaton. Why would you want to do this? Get a zero deck, a .040 gasket and 10:1+ on the same 92 gas. I've seen 11.75:1 on a dyno engine with 92 octane, and .035 total 'squish' height, without detonation from 2500 to 6500. It did have aluminum heads.

1.000 compression height is just about the minimum the good piston guys will make for a SBC. At this compression height, you need oil ring supports, as the oil ring goes thru the piston pin bore.

"cheap and light"? I'm familiar with a 1.025 compression height forged piston from JE recently purchased for a 550-600 hp SBC mentioned above. They were 390 gms light but almost 4 figures of "cheap".

Keith Black KB-164's for 3.75 stroke and 6 inch rods with 1.13 compression height are $250-$275 (for 8) and will easily support 450 hp. They are about .005 out of the hole with a 9.000 deck.

Obviously we come at this from different points of view.

Good luck with your engine.

SStrokerAce

Well that also had 35 deg of timing in it at 3000rpm too! Detonation was slightly there I know I heard it! but the 400+ ft lbs at 2500 was why it was there.

Really don't try to screw around with all of this b.s.
You're caught in the big trap in engine building, I have seen it before. Don't spend that amount fo money on a bottom end that has no top end to make the power to some close to breaking it.

You are talking about under or around 500hp, unless you plan to N2O this bad boy later do not go this far. All you need is $2000 total bottom end, nothing more.

Spend the money on the heads, and the VALVETRAIN!

I'm sorry, but the Vortecs are great heads! spend the money to make them work better! Get a good cam that will allow you to drive this car anywhere and make stupid power! The reason he is suggesting a larger set of headers is because that along with the smaller cam with less duration and overlap will be a better cam for a street car.

Here is another story for you......... It fits what I feel you are trying to do.

Another engine builder who was building an identical engine to my 365 had his engine in the shop and a customer 406. The customer had to have a "magic" hp number of 550hp. Well the smaller engine that he was building made more low end TQ and more HP and absolutely spanked the 406 on the dyno everywhere! So what happened? the guy wanted the 365 because that's what he really needed! It got it's *** kicked by 40 less cubes! Just because he had to have an certain number!

Give the engine what it needs, not what you want it to have to get a certain number.

Bret

oil pan 4

I was a little off I re ran the #'s.
The .003'' head gasket is right felpro makes super thin gaskets every thing else has compression vol's like 10-12+ cc's the .003 gaskets have comp. vol's of around 2cc's.
That was with a 9.015 deck and flat top pistons.
The pistons are .075 in the hole but there is all most no head gasket to realy speek of that's all most normal head clearnce.
That gives me a 9.71:1 C/R perfectly where I want to be.
And you mentioned nitrous oxide use on this engine, How did you figer out that one?
Am I that predictable?
Like the .003 thick head gasket perfectly made for use with nitrous ( very little blow out aera ). The .003 thick head gasket and nitrous go together like stink and ****.
The forged 1.000 pistons are common I don't want to fork over 2X the $ for custom pistons.
A .040 head gasket has blow out writen all over it .

SStrokerAce

hmmmmm....... N2O how did I know? Belive me it's easy.....


First the .078 is wrong. You want the piston to be in the whole .035 and then put the .003 gasket on. You will be able to run more compression safely, in fact it will work better than the .078 BY A TON! If you don't listen to me on anything else PLEASE PLEASE PLEASE run that! Trust me, after you get this together and you end up with a problem going smaller on the quench area (.035-.040) will keep detionation at bay!

If you are dead set on the 1.000 comp height pistons make the rest of the engine fit them. Deak the block more (.040) and end up with a deck height of 8.960 if you want to run that combo.

BTW how much N2O? if it's going to be under 550hp or just a 150 shot you can run the Scat cast crank (3.75) and save your self a ton of money.

We have all seen this before. I'm 24 and I know what youthfull exuberence can do to an engine! You have that stamped on your face (or posts, whatever)

BTW this is one of the first engines you have built.

Bret

Bret

oil pan 4

The crank is an 3.875 I dont know where I got 3.850 from.
Last time I checked Lunaiti and iron eagle and a (very) few others made them
I wanted a duel plane intake manifold so that limets me to a 175-200 shot.
First of all useing a 200 wet shot on a car that I migh be driving to work the next day in is insane.
I was thinking 3 stage 125 or 150 third stage.
I have all most fnished a 3 stage (extreamly varible) controal module schematic. Part of the circuits are on paper and part of them are on paint in my computer. about the only thin I heven't writen in is the ignition retard for each stage. I don't think 1 page of paint will hold it all.
Then I'll have to right the wireing diagram, that's going to be a b*ich, the wire # and size of each wire drawn up as they will some what look in real life when its fnished, there will be about 900 changes to that before I'm done.
It is made with about $200 of MSD rev controal boxes NOS and NX micro swithces and $20 worth of radio shack relays, switches and fuses.
Maybe I could sell them for fun and profit also.
I looked at NOS controal boxes and they were $400+.
I redid the engine #'s and got better deck clearance near stock to flush with the deck with some 1.062'' -10 to -20cc dished pistons with combos going from C/R of 9.6 to 10.2.
What I want the engine to have is the long *** 3.875 stroke 6'' forged H beams 64cc chambers 1.00 to 1.1 and maybe even 1.125 inch pistons and thin as hell head gaskets.
And I found some summit 1 5/8 primary to 3'' headers for $75 ,
I was thinking slap them in with 2 or 3 bolts to hold them on for a few hours and drive them around open and burn off all the paint, take em back out and put the steel wool and high temp paint to them.
After helping to rebuild a few stock engines and seeing the same old lame cams go back in them with a timing chaine flat taped lifters and stamped steel rockers, crappy heads and big heavy 1.25''+ pistons makes you want to do insane things to one of those blocks. 305 and 350's living lame 220-270 or 280 hp lives is boring to me.