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backyardracer 03-30-2012 12:46 AM

283 hp predictions
 
here are the spec of my build

283 block .030 over
stock forged crank ground 10m 10r
looks to be completely reworked stock rods maybe after market don't really see any marking on them
forged trw pistons with 4cc domes
lunati 00010 230 @ .050 lobe sep 109 with my 1.6-1 roller rockers it will have close to .512 lift
looks to be well ported fully rebuilt 601 heads probably would for about 230cfm at .500 lift with proper valve springs
near 10.8-1 compression
jr victor intake
holley 750 dp carb
and full headers

i would like hp and tq predictions my guess was around 380hp 340tq

my87Z 03-30-2012 01:26 PM

i think your predictions may be a tad high, but if i had to guess i would say 340ish hp/ 310ish tq. is this going to be a street motor or a race motor. considering the parts it will likely have such a narrow power curve that it will not be all that fun to drive. the heads may be ported but just because a head can flow a higher peak flow, that is not really what you should be looking for, you should be looking for flow from .300-.500". i would guess that these heads have had ton of material taken out of the runners, which causes bad lower rpm velocity within the runner. the whole idea behind the intake runners on a heads it to be able to flow as much as possible at all lifts while keeping the runner cross-sectional area as small as possible, this is what creates velocity and rams that air into the cylinders. add the poor heads with the single plane intake and a larger 750 carb and you have your self a motor that wont even get out of it's way until it hits 3500-4000rpm.

backyardracer 03-30-2012 01:39 PM

the heads havent had tons of metal removed for the the runner but more around the valve guide and the bowl with the 1.94 in take valve installed they have been ported properly with a good 3 angle valve job and the valves have all been back cut they should maintain there velocity

it going to be a hot street engine some times track its going in a 914 porsche with 4.6 gears and the car is very light to begin with around 2400 pounds with me in it

backyardracer 03-30-2012 10:33 PM

thanks ya i think i'm done getting opinions on what it will put out. I think it should`do well. I also have a edelbrock rpm intake that I can try

Bowtie man 03-31-2012 06:58 AM

Let us know what it does should be a fun ride.

Blazin72 03-31-2012 03:57 PM

Quote:

Originally Posted by backyardracer
looks to be well ported fully rebuilt 601 heads probably would for about 230cfm at .500 lift with proper valve springs

I didn't know you could tell airflow numbers just by looking at the ports?

LATECH 03-31-2012 04:09 PM

I was thinking 275 horse, maybe 300 if lucky. Thats better than 1 horse per cubic inch on naturally aspirated engine. Those numbers seem real. JMO
Still pretty spicey for a 283

backyardracer 03-31-2012 10:37 PM

lets say you were to put all those parts on a 350 forged crank reworked lighten stock rod forged piston nicely done rebuilt and ported heads with a 230 duration @ .05 advertised duration is 292 lift would be about 512 with my 1.6 roller rockers and 11-1 compression nice dull plane intake or maybe open could go either way 1 5/8 header nice free flowing exhaust and a good carb

so with all that a 350 should only put out 350hp that sound kinda funny

my87Z 03-31-2012 11:10 PM

Okay so you can understand this better, 601 and 416 heads were both factory 305 heads the 416's are the better performing more coveted pair. I just looked up on Stan Weiss cylinder head flow chart and a pair of 416's with a mild port job only put out 180cfm @ .500" if the person who did the work did a good job then you may see 200cfm @ .500". This flow is what is hindering you do much. My estimate of 330-340hp is likely a push but you may be able to push this out. Remember these heads from the factory were used on an engine that was putting out less than 200hp. Is this seriously the head you want to try and make "good power" out of.

And yes, a 350 with a mildly ported set of .601 heads, a .230 degree cam... Would only make around 340-360hp. A motor is only as good as its heads. A motor could have a poor combination but a good set of heads and still make pretty decent power. But a motor with a well planned combination of parts with a mediocre set of heads will only make as much power as those heads will allow it to make. Never skimp out on you heads, on a decent motor it can literally be the difference of 100hp.

backyardracer 04-01-2012 03:11 AM

not one of those heads had the 1.94 intake valve installed and i have both sets i have the 416 and the 601 mine both came with the 1.84 valves they came off a ho 305 motor yes they only put out 190hp and like 240tq stock any how the only differences i really see in them would have been the valve shrouding but they have been let open a bit to help deshroud the intake valve every set of ported 416 and 601 heads with the 1.94in valve put in i have seen flow tested flowed around 225-240cfm at .500 look up F-BIRD'88 ported heads and mine look very similar to his i know there is know way to know for sure what mine flow but i would say no less than 220 for sure

LATECH 04-01-2012 07:53 AM

Quote:

Originally Posted by backyardracer
lets say you were to put all those parts on a 350 forged crank reworked lighten stock rod forged piston nicely done rebuilt and ported heads with a 230 duration @ .05 advertised duration is 292 lift would be about 512 with my 1.6 roller rockers and 11-1 compression nice dull plane intake or maybe open could go either way 1 5/8 header nice free flowing exhaust and a good carb

so with all that a 350 should only put out 350hp that sound kinda funny

The 350 has a longer stroke. It would make more horses per cube because of that alone , due to the fact that the longer stroke would make more torque.

my87Z 04-01-2012 08:01 AM

Okay buddy, can't no one tell you anything.

First off when people flow test heads the usually use a rather large bore plate (4.125-4.200) as to inflate the numbers. Head manufactures have been doing this for years, as well as head shops do they can make their work look better. But since you are using a 3.875 (3.905 @ .030) then those flow numbers decrease much more than you think. When you see a pair of heads from a manufacturer that have been flow tested out to say 250cfm at .500" (4.200 bore plate), I've seen these re-flow tested for a 350 with a 4.030 bore plate and only make around 235cfm. With that much loss going from 4.200-4.030, imagine how much more loss there would be to 3.875.

Your cylinder bore makes a big difference because it is what is creating the vaccum to suck the air down into, obviously a 4.200 bore will create more vaccum than a 3.875. Increasing the valve size from 1.84-1.94 will help some but not that much, I would bet my car that your 601 heads flow tested with a 3.875 bore plate wouldn't make over say maybe 205-210 MAX at .500"

You came on this forum and asked the questions so don't get angrey because you are getting answers you don't like from people who know what they are talking about. I've seen it a hundred times, when peoples bubble gets deflated.

backyardracer 04-01-2012 04:52 PM

i dont know any more i just feel that you are giving me enough credit as a builder these heads were flow with 1.84in valve and a 4" bore

Chevy 416 Ported Meaux Racing SS Iron N/A 1.84/1.50
4.00 bore
99/98 .200
153/136 .300
197/170 .400
225/183 .500
231/188 .600
they are the 416 head but the 601 have the same runners

and i might just take you up on that but the bore size will be 3.905

I realize i asked the dumb question but i did want more onions on it and i really do have to use the 305 head because of the small combustion chambers

my87Z 04-01-2012 05:45 PM

I know that you can get these kind of numbers out of a set of 416 heads but did you happen to see who did the head work on the ones you posted. Meaux Racing ain't no joke, they would be in the top 5% of head porters. You won't likely get the same kind of numbers out of the average performance shop. Then take into account the extra 5ish% you will loose going from a 4.00 bore plate to a 3.905" bore plate. 225cfm at 500" - 5% would equal 213cfm at .500". When I gave you the estimate of 205-210cfm @ .500" that is an extremely realistic number.

These heads from the factory are only pushing around 170-180cfm @ .500" and when you do a mold port/ valve job you can expect to gain about 8-12% in flow. Given these numbers a mild port/ valve job on these heads would get you about 190-200cfm. With the 3.905 bore you should be mildly happy with around 205-210 @.500".

It takes a lot to make good power out of a small bore motor, this is why you don't see many people using these old 265, 283, 305, and 307's. If someone has used them it is usually just for a stock rebuild or for a very mild performance build. I still think that you may make around 320 maybe 330 hp and making that out of a 283 ain't bad at all

1971BB427 04-01-2012 06:06 PM

I think whatever HP your 283 build makes will be way up there near 6500-7,000 with the cam and heads you are using. There's really an issue with flowing the kind of numbers you're quoting, and I wont argue if they flow that, but if they do it's going to be at very high end.
I'd be very surprised if it makes much over 300 hp also. I built a very similar 283 long ago for my '55 Chevy gasser, and used the old 1.94/1.60 "fueler" heads with some extra porting, and it was pushing around 308 hp at the crank.
Your lower gears in the rear will help, as will a stick tranny, but it will be pretty void of HP or torque up to around 3500 rpm's. Might have to launch around 4,000 rpm's and try to keep it in the 4,000 plus range. Not exactly a well mannered street engine when it doesn't make good midrange torque or power.


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