Slow....

I'd have to dig out the time slips from New years day. I'm thinking only around 70+ mph. Ya, cause I run 3000 rpm on the highway and it's just hovering around 70 mph.


Larry

 

Original67, just a point of curiousity about 2bbl vs 4bbl and their affect on Desktop Dyno software. I've heard in enough places from knowlegable sources that I believe it, that CFM ratings on 2bbls and 4bbls are like apples and oranges in that 2bbls are rated at 3" of vacuum and 4bbls at 1.5".

As I understand it, back in the 50's when 4bbl carbs were first designed the flow machines of the day would only pull 1.5" on a 4bbl, and they've been rated that way ever since.

Another reason I bring this up is because the butterfly's in the 500 Holley are real close to the same size as some models of the stock carb. No doubt the Holley has a much more performance oriented design, the open boosters for one thing, but butterfly wise they ain't that much different. Whether the peformance features of a Holley over stock could account for a 15 HP increase I couldn't say, but I'd be suspicious!

I've done a lot of 4cyl racing and while the Holley 500 is the carb of choice, a lot of guys get by and run pretty fast with the Autolite/Motorcraft 2bbl like we find on our trucks. I think the 181 model or something like that has the biggest butterfly's.

That being said, a 600 cfm 4bbl must flow way more than a 500 CFM 2bbl and I wonder how the Desktop Dyno takes that into account.

 

desktop dyno has a seting for different mercurys.

 

A 500cfm 2bbl won't flow as much as a 500cfm 4bbl. They are rated different. The difference in flow between the two isn't real big though. Even though the 2bbl is tested at twice the pressure drop it. The difference maybe like 20%. I can't remember what the formula was someone threw out there.

 

I did take the pressure drop difference into account when I ran it. I ran the 500cfm 2-barrel at 3.0"Hg pressure drop, and the 600cfm 4-barrel at 1.5"Hg pressure drop. This is the standard way they are rated, has been for years. 2-barrels get 3.0"Hg pressure drop ratings, 4-barrels get 1.5"Hg.

Ratsmoker, I believe this is a good opportunity to compare DD2k to DD2k3, would you mind running the numbers for the above mentioned engine so we can compare?

 

what kind of power kits are taliking about im might try it for a hundered bucks

 

what do you guys think my truck will run in the 1/4: 1975 f150 ranger regular cab long box, 2wd. 3:25 gears. stock C6. 390 bored .060 over, polished stock 4v intake. holley 750 carb. 2in carb spacer,polished stock heads, stock valve size. electronic ignition, 40,000 volt coil, equal length headers, true duals with glass packs, desktop dyno says about 372hp/4500rpm and 460ft/3500, ive got the moterjust about ready to go in the truck so it will be a couple weeks before ill get to the track.

 

You have the 941 cam right? I would say high 15s with ease on stock tires.

 

It's anybodys guess (and I'll say mid 15's) and you will always be wondering - until you take it to the track and find out for sure. That little slip of paper in your hands is the root of all evils

--Mike

 

I was hoping for mid 15s when I built mine. The first time I redlined it my buddy couldn't keep up in his 14.8 second WRX. We were both amazed. You never really know until you take it to the track.

 

Well that shows how much I know about Desktop Dyno and it sure sounds like it has all the bases covered.

 

I've got a small fortune invested in my project. It was never meant to be a drag racer, but it's always been in the back of my mind. OK, maybe I did want it to be dual purpose. Unfortunately, I've set myself up for dissapointment, since my stock drive-train daily driver runs low 13s...Maybe I should just give up on the boat puller and make it a dragster. A little juice and some sticky tires out back...maybe I could see 13s?? Then, what would it need to get 30MPG as well?

 

Like Rusty said, cheap headers =$100, stock 4 bbl manifold = $25 and a junkyard 4bbl= $35-$45. You will probably still bust your budget in gaskets, rebuild kit, etc. To bad you didn't race him in the eigth mile instead of the quarter.

 

well mid 15's dont sound to bad, i wonder what it will be like up against my friends 84 camaro with a 305, he wants to race me when im done, but if im figureing mid 15's or around there maybe i have a chance cuz i know his car is bone stock.

 

Shouldn't be a problem. Those mid 80s 305 Camaros were heavy and underpowered in my opinion. He's still got you on aerodynamics. But, I think that 80's 305 stock was in the 150 HP range.