Hot Rod Forum banner
1 - 18 of 18 Posts

·
Registered
Joined
·
331 Posts
Discussion Starter · #1 ·
A friend of a friend has a 496 BBC in his Chevelle. He bought the motor from a guy that used to race it and it supposedly came with a dyno sheet stating it made around 700 h.p. This guy says it comes alive around 3,000 RPMs and flat out hauls. Here's the issue: I got to see the "build sheet" on this engine and I call B.S. It has Dart Pro 1 310cc heads with 119cc chambers, an extreme energy 294 hydraulic flat tappet cam, scat crank, eagle rods and, get this, J.E FLAT TOP pistons. Papers said 8.7 to 1 compression. Dart single plain intake too. When I told him there was no way his engine made 700 hp he got mad and referred to the dyno sheet (which I never saw) as proof.

Then he started saying things that were just dumb. Said he broke three starters due to high compression.
Is able to spin the motor to 8 grand (with that hydraulic flat tappet)
The car the engine came out of did 6 second quarter miles.

This guy is either completely clueless, and got suckered, or just spouts stuff to seem cool.

At any rate, I'm not an expert on 496s, but can this engine come anywhere near 700 hp without nitrous? Again, I call B.S.
 

·
Registered
Joined
·
15,300 Posts
Sounds like it was built as a blower motor, I‘d say with something pumping air into it 700 is reasonable otherwise just breathing air like you and me figure 200 to 300 hp less. The lacking compression on a decently large cam would kill power at the low and high rev ranges. It is harder to make big power numbers on a big block simply because of the needed breathing, you gotta go really big on compression, cam, porting, valves, and carb on these big motors.

Sir Harry Ricardo the guy who invented the combustion chamber GM calls the Vortec or Fast Burn way back before WW-2 felt that poppet valves could not be made big enough to feed really big displacement cylinders, hence the development of sleeve valve engines with their marvelous and complicated gear trains that rock a cylinder liner sleeve to uncover and cover intake and exhaust ports thus eliminating the dimension limits of poppet valves being tied to cylinder diameter. American engineers Pratt & Whitney and Wright added cylinders and higher boost supercharging which while add complications in their own right is a much simpler solution to that of sleeve valving on a Bristol Centaurus. But nonetheless the Centaurus is beautiful, mechanical artwork and it makes power.

So it is with Big Block Chevies and Fords in that without a pump blowing lots of air into the intake, getting big power numbers takes a pile of attention to the details of moving mixture in and hot dirty fumes out.

Bogie
 

·
Registered
Joined
·
5,224 Posts
one would wonder; is this a nitrous engine for sandbag racing? Perhaps the reason he broke starters has more to do with some sort of timing issue and less to do with compression? Or, these idiotic fits-all starters that require shims and a few shots of rye to get through the excercise
 

·
Hates: Liver. Loves: Diesel
Joined
·
6,303 Posts
With that cam and compression, he is making at least 290 hp and has to suffer through the first 3000 rpms with about 200 lb-ft of torque.
And an 8000-rpm big block costs somewhere north of $30,000. If you spend less than that, you can still hit 8000 rpms.... once. Then it's PIECES of a big block.
 

·
Race it, Don't rice it!
Joined
·
8,819 Posts
That's only 1.4hp/CI
The same hp/CI on a 350 is 490hp.
It's possible.....
More often than not those who brag are exaggerating but I'm more impressed with time slips and lap times that dyno numbers anyway.
 

·
Registered
Joined
·
331 Posts
Discussion Starter · #11 ·
The old street racer, snick, act like a tool with no clue, then clean house.
Unless you have seen receipts of the parts in THAT engine. It might be "told" that way for a reason.
Or he is just out there.
I did see the receipts along with the build sheet. It was all in a binder that came with the engine when he bought it.
 

·
Registered
Joined
·
331 Posts
Discussion Starter · #12 ·
Sounds like it was built as a blower motor, I‘d say with something pumping air into it 700 is reasonable otherwise just breathing air like you and me figure 200 to 300 hp less. The lacking compression on a decently large cam would kill power at the low and high rev ranges. It is harder to make big power numbers on a big block simply because of the needed breathing, you gotta go really big on compression, cam, porting, valves, and carb on these big motors.

Sir Harry Ricardo the guy who invented the combustion chamber GM calls the Vortec or Fast Burn way back before WW-2 felt that poppet valves could not be made big enough to feed really big displacement cylinders, hence the development of sleeve valve engines with their marvelous and complicated gear trains that rock a cylinder liner sleeve to uncover and cover intake and exhaust ports thus eliminating the dimension limits of poppet valves being tied to cylinder diameter. American engineers Pratt & Whitney and Wright added cylinders and higher boost supercharging which while add complications in their own right is a much simpler solution to that of sleeve valving on a Bristol Centaurus. But nonetheless the Centaurus is beautiful, mechanical artwork and it makes power.

So it is with Big Block Chevies and Fords in that without a pump blowing lots of air into the intake, getting big power numbers takes a pile of attention to the details of moving mixture in and hot dirty fumes out.

Bogie
Bogie, I'm in a real pickle with this. I have not been in the car to see how it runs out, but flat tops, open chambers and a lot of cam spell turd in my book but he and my friend say it really hauls. This leaves me in a bad spot because he wants me to build a 496 for a truck project he's working on. He wants "500 horses" and "wants to do burnouts". I know, walk away. Now, I can easily build a legit 500 horse engine with dump truck torque for a pickup, but what if it smokes his Chevelle? Or worse, his car is that fast and he thinks the engine I built is a turd?
 

·
Registered
Joined
·
331 Posts
Discussion Starter · #13 ·
one would wonder; is this a nitrous engine for sandbag racing? Perhaps the reason he broke starters has more to do with some sort of timing issue and less to do with compression? Or, these idiotic fits-all starters that require shims and a few shots of rye to get through the excercise
This guy bought the engine for too much money, put it in his Chevelle and thinks it's crazy fast. That's why I wanted to see the dyno sheet. I wanted to look for the tell tale spike from the nitrous if it was used. I just don't buy 700 hp from an 8.7 to 1 engine.
 

·
Registered
Joined
·
331 Posts
Discussion Starter · #14 ·
I was just thinking.... that build sheet is a huge mismatch.... unless it has about 9 psi worth of snail-shaped heat converters on it.
I agree. Those pistons with that cam is just dumb. Can you imagine how impressed that guy would be if the pistons were changed to get 10 to 1 with that cam? He has plenty of head on it.
 

·
Registered
Joined
·
489 Posts
I trolled the forum with a similar flat top .090"+ piston/head 355 build years ago, here's a link to that thread...
What do you guys think of this sbc street/strip combo?

Current engine is pretty much the same as the one in that thread, just uses better parts and more nitrous. 700 NA out of a 496 is roughly equivalent to 500 NA out of my 355, but my 355 is solid roller and can spin well past 8k. Not sure a hyd cam'd bbc could do the same without a lot of attention to detail.

Grant
 

·
Registered
Joined
·
331 Posts
Discussion Starter · #17 ·
why assume the build sheet is correct?

a 6 second quarter mile car must have been a rail.
Oh no, he claimed it was in another person's '68 Chevelle with that 496. Laughable at best! I assume the build sheet is legit because of all the receipts that back it up. Idk, something just isn't right about any of this....
 
1 - 18 of 18 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top