Thread: HP guess?

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heh guys, I realize it will be a guess but can yall give me an idea of what kind of power my little SBC is making? I plan on doing alittle bracket racing this spring and just kinda curious where I stand. I know she accelerates VERY good and I can take most of my buddies off the line. Also, yall think my lower end can handle a 100hp shot of NOS for alittle more top end power?

1966 Impala 2dr hardtop
283 block
327 forged crank
.030" overbore (312ci)
mild RV cam
flat top pistons (10.1 comp.)
powerpak heads
Weiand Stealth dual plane intake
Carter 750 cfm 4bbl
MSD HEI igntion
full length headers
2 1/4" dual exhaust with 18" glasspacks
TH350 with shift kit and 2,000 stall converter
4.10 gears

Thanks,

Bowedup

When You say power pack heads are you reffering to the heads that would have come on a 283 --4bbl carb or are you reffering to the 462 heads that would have come on a 66 --275hp--327 .Why not pull a valve cover and get a part# and build date off the head. This will help to arrive at a much more accurate estimate of horsepower.If its the 462 they will have double humps on the front of the head. A 750 sounds like too much carb. either way. It would proberly run better and faster with a smaller carb.600 cfm maybe.

the heads are the ones which came on the motor, they have the rectangle casting with a triangle on top of it on the front of the head. As far as the 750cfm carb, I too wonder if its too big but I don't get any bog off of idle and it runs very well (pulls very strong through the midrange). Thanks,

Bowedup

O.K. I'll play, 240-280 hp, 320-340 tq , probley feels like more due to the 4.10's, and as long as it's in good shape (ie, no smoking or knocking) the 100hp hit should'nt be a problem.

Vikings guess should be right on target. I do think the 240 is closer than the 280. The head you have ,or something very close to that would have would have come on 283---- 220hp and 327---250hp. Neither are close to being as good as the 462 heads on a 66---327---275 hp. CARBURATORS ! If a 1965 Corvette with a 327---350 hp. had a Holley carb. with less than 600 cfm. then its hard to believe that a 750 could possibly help your motor.What do You think?

I have a good set of 462 heads at the house that cam off of my 327 which thrashed the crank last week, ya think they increase the power of my backup engine (the one we are discussing) enough to make it worth the trouble of swapping them over?

Thanks for the input guys!

Bowedup

It sounds like your car may have come with 275hp--327. Why not put a crank or turn the crank in the 327? Have any of these heads had a valve job and had hardened seats put in? They were designed for leaded gas and more octaine. To answer your question the 462s should help you overall but they will hurt you on the bottom end . They have bigger valves, 194/150 compared to172/150.The small valve will give you more torque off idle to maybe 3500rpm . Above that the bigger valve and better head will make right much power. I have a round to it car that I may never get round to Its a 66 Impala 4 dr,275hp 327 I did put 2&1/2 exhaust,turbos and ralley wheels on it . It ran pretty good but is now sitting out back going down hill fast.

the car did come with a 327, but like I said it bit the dust last week. This car has been bracket raced off and on for about 4 years now. I started hearing a rattling sound in the lower end of the 327 a couple weeks ago, dropped the oil pan last weekend to see what the problem was, turned out I had a main cap broken in two, and the other caps were now egg-shaped and the bearing shells no longer snap into them, they actually have nearly 1/4" of play in the caps! Surprisingly there was no knocking or loss of oil pressure, but the crank is scarred up pretty good. We were trying to get the car ready to play this spring but we ended up going to my backup motor for the time being (the stroked 283). Anyways, thanks for the help!

Bowedup

first off what kind of pistons do you have cast, forged if you have cast pistons I wouldn't recomend nitros. If you do run nitros retard your timing 4 degrees for every 100hp. your best bet for more power is a better cyl head the old double hump heads are great but the are collecter items now and exsensive to find and exspensive to rebuild for unleaded gas. I recommend finding some 882 castings these are unleaded heads cheap to find and cheap to rebuild and the flow about the same as 462. You will lose about half a point on compression but will make up for it on performance. 441, 487 or 041 heads are also a good choice but have same problem of not being unleaded. the cost to make them unleaded will be anywhere from $75 and up depending on machine shop. 041 heads are the same as 462 but they have accessory holes in heads.

I have a 283 that I use an I'll list it's spec and you can go from there....
66 283 (stock bore) steel crank
flat top pistons 462 "cammel backs"
495 lift , 230@ .050 duration ( cam dynamics)
1.5 rollers .headman longtube headers

this engine dyno'd with 320h.p and about 335tq.

best run to date 12.91@111mph in an 83 camaro with 4:10 gears and a 3800stall coverter ....no juice but it,s in the future....I cross the traps @ 7,800rpm in drive

I'd also recommend the 305/58cc head on these motors... as it will bump compression and the ports are NOT restrictive on these peanut motor.... I have a set being done now for spring...

Protopline makes 220cc (runner) 58cc chamber heads and may be a added feature

as far as your carb questions if it works leave it alone.....the only thing you'll gain by going to a small carb is very bottom throttle response ( which is optimum for light to light driving)

I use a heavily reworked Q-jet (795cfm to 825cfm) that is very sensitive to changes...

There is really no such thing as "to big" when it comes to carbs the engine will only takes what it needs...with the "right" jets and so on any carb will work

we tested this theory on a 434sm bl... with a sheetmetal intake and 1100 dominator.... added the second 1100 dominator and picked up 50+hp....final hp after tunning 1,152@8,500rpm