Hey guys I just bought a 89 RS with t-tops. It was originally fuel injected but it was changed over to a carburated 350. the engine has a 750 holley and i was wondering if it was too big for my setup.
350
9.5:1 compression
Not sure what kind of heads, but they have been shaved and have had $400 worth of work done to them (3angle valave job)
edlebrock RPM intake
Headers
Dynomax exhaust
is this carb to big?
should a go with a 650?
thanks
Tom

i forgot to mention that it has 1.6 rockers (not sure if they are rooler or not)


[This message has been edited by Zio (edited May 02, 2001).]

A 550 is much closer. I'm running a 750 on a pretty modified big block.

People don't seem to understand what cfm an engine really needs. Unless you're running a NA small block above 7500 rpm's, a 600 cfm carb will be plenty.

Do yourself a favor and get a copy of desktop dyno 2000. It will show you exactly where the gains stop with increasing carb size.

The same people run the 1100 cfm double pumper holleys that run the 2-1/4" headers on street BB's and wonder why they don't run right. Yeah, it gets 5 mpg. That's because it has such a high power motor. Suuuuuuuuuuure.

;-)

Todd

no the 750 is not too big for your engine at all. Learn to tune your Holley so that it runs like you want.

Some squarebore carbs suffer from weak signal on the primaries which hurts throttle response, low RPM torque, and gas mileage. There are several ways to fix or avoid this problem. Many people simply use spreadbore carbs, but another thing you can do is install annular discharge boosters on the primary side of your Holley. I pick up these boosters pretty cheap at swapmeets as they came in some factory Holley 600vs carbs.
If you have a good dualplane intake and a 4-hole carb spacer, the 750 will work great with the annular discharge boosters.
You could also go with the Holley Economizer boosters for increased signal on the primaries, but they are rather restrictive with airflow.
ODB




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*I do custom performance mods on Edlebrock Performer carburetors (dualplane intake mods in the works),
White 1986 Irocz, 305 with iron #416 heads,
383 with aluminum TFS heads,
Edlebrock Performer-RPM intake and Performer #1407 carburetor, +110hp shot of crack, 700R-4 tranny, Vigilante 2400 lockup converter, 3.25:1 Ford 9" rear, Mcreary Road-Stars, SLP-stainless 1.75" shortie headers & Y-pipe, single 3" Borla exhaust, Linginfelter-TPI camshaft part number 74216 pulls 17" vacuum solid. Cam specs 213/219 @.050 114-LSA, sometimes advertised at 216/219 @.050 112-LSA .462/.470 lift @1.5:1 ratio. Using Harland Sharp 1.65:1 roller rockers. MSD-6AL, billet distributor, multi-retard, blaster-3 coil, and RPM switch. SouthSide machine subframe connectors, SSM lift-bars, Moroso 4" underdrive crank pulley.

N/A runs 10.9 @124,
Crack-runs 10.3 @135
haven't run at track since Oct-99
* vizit miy homepayge * http://www.geocities.com/trailerparkpage/

It does have a space but i do not know what kind. I am going to have my uncle help me tune it because he has worked on them before.
What size yets should I have in the primaries and secondaries. and how do i know what i have in there now? (aren't they different colors?) I want more throttle response than top end. this is going to be a daily driver.
Thanks
Tom

I say 750 as well. it is not too big. Hell I even know a guy running a 750 on a 305, it's a little soggy down low but not that bad. It's mostly in the tuning.

There was also a guy on here not long ago that went from a 650 to a 750 on his 350, and was extreamly happy about how much better it felt.

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"American made baby. 100% American iron. The muscle among the masses. My hero. Yep, you can take your ergonomically designed, space age, computer controlled, 4 door, cup holding map lighted split double wishbone split fold down retractable cargo covered moon roof piece of transportation and keep it. For I have felt the thunder. And I know the difference!"
JSP Motorsports
ICON Motorsports

Af far as jets go , it's a matter of trying on jets until you get the best performance. So u can more or less get an idea I currently have 64 jets primaries on my 383, the secondaries are #86's. I get great trottle response .

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Big 454 72 Chevy Nova
383 86 Camaro Z28
10.5:1compression 186 casting Heads,234dur.488lift exh&int,Edelbrock performer intake, Holley750 vac.sec 400 crank,flat top pistons,edelbrock valve springs and lifters,tranny shift kit,2500 stall converter. Will install 3.73's later on and might go with a more aggresive cam.As of 4/01 added Hooker Headers,2.5inchpipes with 40 s. Flowmasters.Ignition upgrade include: MSD Coil and MSD module.

[This message has been edited by Big454blockchevy (edited May 02, 2001).]

I tried bigger jets on primaries but I did not like my how my engine responded off idle. It was actually kind of sluggish with #68. You really need to try on different sizes till u get the right ones.

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Big 454 72 Chevy Nova
383 86 Camaro Z28
10.5:1compression 186 casting Heads,234dur.488lift exh&int,Edelbrock performer intake, Holley750 vac.sec 400 crank,flat top pistons,edelbrock valve springs and lifters,tranny shift kit,2500 stall converter. Will install 3.73's later on and might go with a more aggresive cam.As of 4/01 added Hooker Headers,2.5inchpipes with 40 s. Flowmasters.Ignition upgrade include: MSD Coil and MSD module.

I have a Holley 750 dual bowl vacuum secondary on my 350. They q-jet I took off was rated around 850 I believe.

I moved down from 72 primaries to 68, and think I need to go lower because I am running a tad on the rich side of my A/F gauge.

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

what are the gas millages like with the 750 cfm carbs on a 305? im thinkin bout getiin 1.

SOOOO many things contribute to gas milage. I get about 20+mpg depending on temperature, my right foot, traffic, road, tires, time of year, rain/sun, wind direction, semi in front or not, etc. that have nothing to do with the carb tuning/size/engine.

I would suggest that unless your 305 is a monster, or you get a killer deal (ie-free) on a 750, then you might want to go with something smaller.


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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock with the exception of the Holley 750vac... all the suspension stuff... 9-bolt posi disk is in...

-=ICON Motorsports=-

yeah dude i would'nt put a 750 on my 305 even if it was a good deal.You have to have a damn good built 305 for a 750.Also zio is that a double pumper or vacuum secondary?And also what gears do you have and what rpm do you shift at?

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85 iroc with 305 weind single plane intake 650 double pumper msd crap bad *** cam 350 turbo tranny 2400 stall soon to be 3000 and 125 horse shot of nos and alot of other stuff

Right now i only have 2.73 gears and it the carb has vacuum secondaries. I have come to the conclusion that I am going to go with a 650 holley. my bottom end response is no where near where it should be. Plus it will probably be a little better on gas. If i was going to race all the time I would leave the 750 on it, but this is my daily driver. Now all I have to do i find a 650 sale and rebuild it.
thanks Guys
Tom

Thats cool but go with a 650 vacuum secondary.The double pumper would give you better throttle response but would'nt be good on gas.And since you what gas mileage go with the vacuum secondary.It would work better with those gears anyway

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85 iroc with 305 weind single plane intake 650 double pumper msd crap bad *** cam 350 turbo tranny 2400 stall soon to be 3000 and 125 horse shot of nos and alot of other stuff

thanks guys for all the help. i am going to make the swap as soon as i can find a 650.
Tom