Bbc hp est
 

454 .040 over kb hyp pistons 11:1 Chevy 781 heads 2.19 in 1.72 ex bowls blended 629 lift solid flat tappet cam eagle forged crank stock rods all balanced Holley single plane intake and a demon 850

im gonna say 550-600ish

Re: Bbc hp est
 

-what's rest of the cam specs? duration, lobe sep?

duration 306 @.050 260 lobe sep 110*

bbc hp estimate
 

I had a similar (but a stroker) set up, slightly less cam (both lift and duration), 489 inches
(4.25 stroke .030)with a 1050 dominator made 578 hp with a very nice flat torgue curve. It was a roller cam and rect port GM heads, and 10.4 to 1 compression.
good luck !
My guess is 540 ish

It don't matter! You really don't care . .

"Horsepower" is one of two things. A measurement determined by testing the actual output with a Dynometer, or a term used at the Bar when trying to impress people who don't know any better . .

If you're a racer (or engine Builder) and build an engine for a specific purpose (Like Quarter Mile Drag racing, for lack of a better one) then ET is (or should be) your primary concern.

Doesn't matter whether you're racing heads up or Brackets, it's ET or the potential to get to that ET that you're concerned with . .

And, based upon both experience of yourself, or those who are relatively successful at the type of racing you're doing, ascertaining the build and it's potential results should be, literally, empirical . . .

The "Fine Tuning" for good results and engine longevity belong to the user . . . and still have little to do with the spoken word "Horsepower" . . .

Jus' sayin'

x2! very true. build an efficient, reliable engine for your application and let the HP number fall where it falls

i think differently ... no self respecting car nut is gonna be ok with saying... well its 300hp but it runs consistent.... lol I'll take the ponies and tune it to be consistent :wink:

Well it's not a drag motor and will never be consistant, its in a pulling truck and every track is different and the sled can be weighted differently as can the gearing it the weight box. So i was just asking to have a clue where i stand withe the other 600-625hp trucks out there. Sorry if this thread bothers some of you.

Are you in a class that limits what head or camshaft you can run?

Stock heads but I can run a roller cam, which I will do next year.

That would help and some GM rectangle port iron heads would help too.
I'm assuming the 781's are oval port.

yes they are ovl ports but with some work they will be fine builder was think they would have more torque at the end of the track so it wont fall on its face

The 781 oval ports will give you more torque and lower end power. Put some bigger valves and some port work and i think these heads will work better than the 990 heads. Good luck ejm and have some fun.

well got her going and wont really idle right and went down the track great but header glow at end of track any ideas

check your exhaust gas temps
check the timing it maybe running rich and the timing may be too far retarded most common cause is not enough timing and too much fuel

I had total timing set at 30* think I should go higher?

I would start at 36* and work from there in 2* increments up or down.

maybe thats why when it "dogged" down at the end it flat out almost died under 3000 rpm (dist not locked)

How do you leave the line when pulling? Do you foot brake and at what rpm?

dual disc clutch around 4000 4500 ease into it four speed im gonna give a link to video

http://www.youtube.com/watch?v=W8EthyUDKZk&feature=plcp
this is the video not the best quality!

Just guessing, but I think I'd lock out the advance and start at about 36°, based on the comp ratio and combustion chamber size . . If he's got the right MSD smart box, he might leave at around 38° and bump it down to 34° or so at the end of the pull.

I'd think, because of the demand on the engine and the increasing weight of the sled as he gets into the run, you'd want to increase torque at the end of the run. It's kind of inverted way of racing. We gain momentum as we increase the run time, he's trying to get all the momentum at the start and needs brute torque to end the run. I think. ejm, correct me if I'm wrong . .

But it's still just a SWAG because I don't know the type of fuel (maybe I missed it here) or the kind of air he's running in . . . either . .


On th' HP thing . . Not being a wiseass here, We're getting mid 9.20's @ 150 with an iron '67 Camaro (582 BBC & 2800#) at 4850' msl (8700' corrected) and we don't know, or care . . Because it really doesn't matter, well, at least unless you're ordering a new converter . . (Tongue in cheek there)

The race track is the most honest dyno ever created! . .

Road kill you are exactly right if u think I should lock it I will no prob
110 oct msd 6al pro billet dist

Not enough timeing, 38-39 total, and leaveing too soft, at least 5-5500, what kind of rpm's are you seeing at the end of the pull?

first pull on this motor not really wanting to turn more than7500 but it pulled it all the way down at the end

defiantly more timming

Based on what I know about "Truck Pulling", which is almost exactly nothing, I'm gonna say you're pretty close to doing what you wanted to do . . Based on the video and the quoted post. Looks like tuning is what you're after . .

On the timing thing. Locking out your mechanical advance and running a set timing number is to maintain a specific ignition tme when you narrow the power band and run the engine within a specific parameter . . If you need a specific timing curve, again, I'd recommend a MSD 735A (If I remember the model number correctly) where you can adjust your timing curves up and down during a run . . and they're exact.

If your EGT is above about 1250, y'might fatten it up a little and definitely, if you choose to bump the timing you should fatten it up. (Advance leans the engine out)

On the glowing headers . . back in the day, if you had a Fuel car with Zoomies, when the glow was down to where the curl started, it was "just Right", as the baby bear said . . . any farther out and you were either heating the engine too long or it was too lean . . . What's your engine temp when you get to the end of the run?

Dunno about leaving harder. I've found with our car, we can leave a lot softer (4750plus/minus) and get really hard leaves that're a lot easier on drive lines than the old 5500 rpm launches. And we "Throttle into" the launch rather than hammer the driveline and tires . . (1.35 60' times) and we use all the tire with no spin, even on late day or greasy track conditions . . But we're drag racing, not pulling . . There's a difference, I'm sure . .

And we're still 'spearmintin' so I'm certainly not the last word . .

Well only one more pull next weekend. It got up to 220 which I didn't care for the carb came off of a 509 originally so I figure it wouldn't be lean. But if you say advancing would lean it out wouldn't that glow the headers then?

For sure on rejetting the carb, with advanced timeing, but you still need to keep the rpm up on the leave as not to lug the engine, it's not like drag racing, in that the load gets heavier as you move away from the starting line, ease into it as always, but at a higher rpm, bout 75ft out drop the hammer. :wink:

was the last pull of the year and pulled great at 36* coolant temp only went up to 210 when last time it was at 225 but still header glow??