WENT TO TRACK TONIGHT

[LS1GN]

I think Holley's have a bad reputation for driveability because people often put too big a carb on.

I intentionally bought a smallish carb (670 cfm on a 6.0) for 1. nice manners around town, 2. because I am at WOT about 1% of the time and 3. because I researched the cfm requirements and VE of a typical performance V8.

You want an eye opener? Google cfm calculation for engine displacement. Most 5 liters (stock 302 or 305) would do fine with a little 390 cfm 4 barrel !!!!!!
Oh, and while I'm on this soapbox, Super Chevy did a carburetor test on a 383 SBC stroker. When they went from a 650 Holley to a 750 Holley they gained 1 horsepower!

Look at my signature - at the track I am beating LOTS of guys with 750 double pumpers!

 

[olds307 and 403]

670 is tiny for a 6L motor with 10 to 1 with a decent cam. I know a guy that put that carb on an Olds 350 with 9 to 1, 210/216 cam, had increase the jetting 2 sizes to get the best time. I don't whether the inefficient heads is the reason that Olds like so much carb. Again, very impressive. Out of the box carb? It should help mileage and response running the smaller carb.

 

[dogsht]

Holley's got a bad reputation for driveability because its got a bad crude design for driveability. No air speed / poor part throttle response or transient response among other things. Squarebore carbs are built for wot. Useing a small carb for the motor is somewhat of a band aid but it really helps for the street. With the right jetting the 670s not hurting his wot performance hardly at all. Its what I would do to make one work on the street better.

 

[LS1GN]

Don't fall into the trap - thinking that we all need big, BIG carburetors! I spent months reading and researching carburetors before deciding. Bottom line is your engine's displacement and RPM. Volumetric efficiency plays a minor role. Unless you spin 8,000 rpm and have an engine with 125% VE you don't need an oversized carb.

A 670 seems small because we have been conditioned by so many people with 302s and 305s sporting Holley 750s. If my engine is producing approx.gross 400 horse/400 tq (which is my guesstimate) a 670 is more than sufficient, actually too big.

At the dragstrip, my little 670 is running quicker than some people with 750s, 850s etc. etc.

 

[dogsht]

LS1GN I don't disagree with anything you are saying although I want to add something. Not just dyno operators but tuners be it on a roller dyno or motor dyno tune and select carb sizing primarily via vacuum. If the motor is drawing too much vacuum or drawing too hard ie has to suck to pull the air & fuel in their is power on the table and the motor would benefit or more power would be found with a larger carb. The displacement horespower rpm volumetric efficiency carb sizing formulas are a typical situational ballpark guide. Some engines depending at least in part by head design typically benefit from a larger cfm carb then what a chart or simple formula would suggest. The Buick 455 is one of these motors as they almost always benefit from a larger carb than what these formulas would suggest.

 

[mechanic58]

No one makes a kit for the Olds small block yet.

Yet? I admire your optimism. LMFAO!!!

(there's a good reason why no one ever made any kits for engines that haven't been in production in more than 20 years)

 

[olds307 and 403]

I know and a 403 kit will never happen. A 350 Olds kit with a 3.75" or 4" stroke would be nice. Supposedly, there are cranks coming out. That is the beauty of the Quadrajet, basically a variable cfm carb. For a square bore carb manifold, I would be tempted to try the new Street Demon based off the Thermoquad. That on a new LS motor should get awesome economy and decent power with it. Plus you can go aluminum or polymer main body on them.

 

[mechanic58]

Yeah, there is no doubt in my mind that the LS series of engines are far supreme to any of the other pushrod motors that GM built in the past. I was very tempted to put one in my Regal, however I have always wanted do one up with a very nicely done 455 Buick. Perhaps my next project will include an LS motor.

 

[LS1GN]

455

I had an empty engine compartment during the planning stages for this car. I also had a bunch of free time. I narrowed my engines choices to three: a stroker SBC, an LS1, or a Buick 455 and then began to research.

Although I liked the idea of keeping it all Buick with a 455, I couldn't because:
1. I would need to find an early one (pre smog) the later ones are crap
2. The oiling system would have needed immediate attention - even if only spinning to 4000 or so
3. There was a lot of core shift in the Buick block casting process and boring these out can be hit or miss. I read one guy's post who had five blocks to choose from and all five were bad! He had to go with the "least worst"
4. The LS motors just crank out massive amounts of power - my long block is absolutely stock and I am shocked at how hard it pulls!

 

[mechanic58]

I can certainly relate to your logic on that - I may have defaulted in the same direction except I just happened to run across a complete 1970 455 with a TH400 for $275. The combo was low miles and in good shape. I was also aware of the casting issues they had with the 455s, especially the earlier ones, however after a close inspection of this one I decided to go with it. The machinist I use all the time also agreed that it was a very nice specimen. I got lucky. The worst thing that I had to deal with was broken exhaust manifold bolts (in the cylinder heads), but they all came out without issue. I have owned an LS1 and several LS2s, they are fantastic engines. Its almost hard to believe how tough they are. The one I had in my '05 GTO had an APS TT setup on it - it was making just under 650hp at the wheels - through a slushbox with a 3000stall converter. It was SICK. Except for the turbos and bigger injectors, that motor was bone stock. I was running around 11psi of boost on it.