Yet Another Holley Carburetor Thread - 74 350 1/2 Ton Manual Trans Stock

[Gregski]

I would like to replace my Rochester Quadrajet four barrel carb with one that does not have all the extra SMOG Emission control dodads.

I am thinking Weiand 8120 Street Warrior aluminum intake.

I will be also putting on long tube headers with dual 2 1/4 turbo mufflers exhaust straight out the back on my otherwise stock engine and removing all emission systems, for a nice simple and clean engine bay.

The goal is a healthy street vehicle good idle with a bit of oomph hopefully making more than the advertised 160 horse power back in the day.

So I would like a Holley. You guys have a plain canvas, please learn me on what I need.

CFM?
Model?
Choke?


Bonus Question: Will my distributor be happy in the new configuration or do I need to replace the Holly Trilogy, Carb/Intake, Headers/Exhaust, and Distributor?

----------------------------
1974 GMC 15 Hundred
All Stock
350 Rochester Four Barrel Quadrajet
4 Speed Manual

[Gregski]

Summit Racing website recommends a Holley 4160 Part #0-80450 Emissions Replacement - Stock Replacement

Barrels 4
Booster Straight
Brand Holley
CFM 600
Choke Electric
Finish Gold Dichromate
Fuel Gasoline
Fuel Inlet Single
Material Zinc
Model 4160
Secondaries Vacuum
Throttle Bore 1.563 inch

Replace your old carburetor with original Holley performance 4160 carburetors. Budget-minded enthusiasts, like you, will be rewarded with maximum performance from your stock or mildly-modified engine. These Holley 4160 adjustable float carburetors are easier to tune than full race carburetors with temperamental secondary metering blocks and dual pumps. Plus, they're available in your choice of universal or direct fit OE replacement versions with all emission provisions. Bolt-on installation and improved performance; no wonder when car guys think of carburetors, they think of Holley 4160 carburetors!

Not a big fan of that "with all emission provisions" part

[donut]

Sacramento, I would assume California? If so, then you may be limited to what they say you need for emissions. (don't know what they demand.)

Have you tried tuning what you have first?
If it makes you feel better you can add about 100 hp by just saying so. (net vs. gross hp) Won't change how it runs though.

What do you have now for emissions that you want gone? How about some history? Are we dealing with a 150k engine and original carb? Has anything been done to the engine?

[Gregski]

All good points/questions, let me address them one by one

Originally Posted by donut

Sacramento, I would assume California? If so, then you may be limited to what they say you need for emissions. (don't know what they demand.)

I purposely bought a pre SMOG era truck ie 1975 or older so that our state laws don't impose emission controls on it.

Originally Posted by donut

Have you tried tuning what you have first?

I will clean it up a bit, but have no intent on rebuilding the emission component plagued Quadrajet.

Originally Posted by donut

If it makes you feel better you can add about 100 hp by just saying so. (net vs. gross hp) Won't change how it runs though.

Horse Power is not the only goal here, the primary ones being, 1. Simplicity of operation, 2. Cleaner less cluttered looking engine bay.

Originally Posted by donut

What do you have now for emissions that you want gone?

All six stock Emission Control Systems are still present on the vehicle.

Positive Crankcase Ventilation
Exhaust Gas Recirculation System
Controlled Combustion System
Transmission Controlled Spark System
Evaporation Emission Control
Air Injection Reactor System

Originally Posted by donut

How about some history?

Essentially bought a one owner vehicle from an old farmer. Grandfather passed and gave the 40 year old pickup to his grandson who after six months or so sold it to me.

Originally Posted by donut

Are we dealing with a 150k engine and original carb?

Pretty much not sure about the miles, the odometer reads 38K but it must have turned over a bizzilion times I take it. But yes all 100% stock engine.

Originally Posted by donut

Has anything been done to the engine?

No, 100% stock at this point.

[RDrancher]

I'm in the process of doing basically the same thing to my '85.

I went with Summit's 600 cfm w/ electric choke. I've read good things about the carb. I also found a Weiand 8120 Action+ for cheap on ebay. http://www.ebay.com/itm/360675105342 Holley is selling out manifolds with the discontinued name. Now its called the Street Warrior. Holley is casting the Weiand manifolds in china if it makes any difference to you. I didn't know that until I opened the box. Still looks like a nice piece.

I received my parts earlier this week, but my back is out of wack so I haven't been under the hood to do the install.

[donut]

The year and California kinda through me. My '73 (federal emissions) just had a pcv system. That's it. (my '86 doesn't have some of that stuff)

Personally I'd keep the vapor can and pcv is almost a must for a street engine.
TCSS, don't remember how that works, haven't seen it since the early '90's.
CCS system I'd have to research also.
Air injector system can go.
EGR, pretty sure it can go. '86 has it, but not hooked up.

Questions weren't in vain, more info for some of the smart folks kicking around.

[cadillac_al]

A '74 Chev came with air injection and transmission controlled spark system? Dang the good old days ended early in Cali.

[Gregski]

Originally Posted by RDrancher

I'm in the process of doing basically the same thing to my '85.

Sounds cool, lets keep checking in with each other, what do you plan on using for the exhaust?

Originally Posted by RDrancher

I also found a Weiand 8120 Action+ for cheap on ebay. http://www.ebay.com/itm/360675105342

Yup, that's where I was planning on getting mine, $99 plus FREE shipping can't beat it. Or can you?

Originally Posted by RDrancher

I received my parts earlier this week, but my back is out of wack so I haven't been under the hood to do the install.

Wow, my back went out a couple weeks ago putting on my pants, 40's suck, lol

[Gregski]

Originally Posted by donut

The year and California kinda through me. My '73 (federal emissions) just had a pcv system. That's it. (my '86 doesn't have some of that stuff)

Yes big difference with even more to come the following year, as 1975 was the birth of the catalytic converter. (I'm a manual reading junkie, just cause it's fun to relive history and see how things were, the manuals were much different back then, I encourage you to give one a cover to cover read.

Originally Posted by donut

Personally I'd keep the vapor can and pcv is almost a must for a street engine.

I am still on the fence about the vapor can, and yes the PCV stays but it won't draw air from the Air Cleaner housing via a foot long black hose nor vent it back to the carb via another hose. These days you can get PCV breather caps.

[Gregski]

Originally Posted by cadillac_al

A '74 Chev came with air injection and transmission controlled spark system? Dang the good old days ended early in Cali.

Air injection may have been there as early as early as the late 60's, the TCS came on manual transmissions only and mounted up such gems as the two ugly solenoid sisters, Idle Stop Solenoid on the driver side in front of the carb, and the Vacuum Advance Solenoid on the passenger side, as well as the little 20 second count down Time Relay on the fire wall, the Temperature Switch in the right head, and the Transmission Swith in the good ol' 3 or 4 speed.

[geezer#99]

Originally Posted by Gregski

Yes big difference with even more to come the following year, as 1975 was the birth of the catalytic converter. (I'm a manual reading junkie, just cause it's fun to relive history and see how things were, the manuals were much different back then, I encourage you to give one a cover to cover read.



I am still on the fence about the vapor can, and yes the PCV stays but it won't draw air from the Air Cleaner housing via a foot long black hose nor vent it back to the carb via another hose. These days you can get PCV breather caps.

Maybe you should find a manual on how pcv systems work.
Air in via a breather. Hooked to the air cleaner or just on the cover.
The pcv on the other cover. A fancy pcv breather cap or a stock one still needs a hose to the big manifold port on the carb.
Or just eliminate the pcv and pretend you're driving an old harley and leave a puddle or two of oil everywhere you stop.
And of your list the air injection is the only detrimental one. The others help your motor produce more power.
Just sayin'!!

[RDrancher]

Originally Posted by Gregski

Sounds cool, lets keep checking in with each other, what do you plan on using for the exhaust?

I'll be using the Hedman mid-length headers eventually. For now I'm using cummins oil pan drain plugs for the holes in the OG manifolds.

Originally Posted by Gregski

Yup, that's where I was planning on getting mine, $99 plus FREE shipping can't beat it. Or can you?

Strange...they were $74.99 with free shipping just last weekend. I'd check their store. Maybe a better deal there somewhere.

[Gregski]

Originally Posted by geezer#99

And of your list the air injection is the only detrimental one. The others help your motor produce more power.
Just sayin'!!

I don't want to get into an argument over Emission Control Systems with you, so I will just ask how exactly does the EGR "help your motor produce more power"? Just askin'!! LOL

[Gregski]

Originally Posted by RDrancher

I'll be using the Hedman mid-length headers eventually. For now I'm using cummins oil pan drain plugs for the holes in the OG manifolds.

Tell us more, single or dual exhaust, what pipe diameter?

[RDrancher]

Originally Posted by Gregski

Tell us more, single or dual exhaust, what pipe diameter?

I'll be going with 2.25" true duals exiting out the sides at the rear bumper with old school Brockman Mellowtone steelpacks. I'd already planned on using Brockmans for my '56 Stude. Standard inlet/outlet size from them is 2", but they'll build it any way you want.

Here's Tx Firefighter's video using Brockman 2". I'll be running a Comp cam 268 as well.

http://www.youtube.com/watch?v=aIjenvDSpAw

.

[geezer#99]

Originally Posted by Gregski

I don't want to get into an argument over Emission Control Systems with you, so I will just ask how exactly does the EGR "help your motor produce more power"? Just askin'!! LOL

Leans down the intake charge to the cylinder.
Result is more timing= more power.
Just sayin'!!

[Gregski]

Originally Posted by geezer#99

Leans down the intake charge to the cylinder.
Result is more timing= more power.
Just sayin'!!

Geezer you probably forgotten more about engines than I'll ever know, so please don't think I am arguing, I am trying to learn. So, how come drag racers don't run EGR valves or do they, how come NASCAR does not use them or do they?

Since when is running leaner = to more power? Also the EGR absorbes less than 1% of exhaust gas or so, so how can that translate to any power gains at all. My VR6 Corrado ran better once the EGR got clogged up, not the opposite.

Again no need to be rude, just go on and explain furher, cause I am not convinced, in my readings and talking EGR = emission CONTROLS not power gains

Also any attempts to advance timing do to leaner mixture are quickly quenched by all the other Emission Control systems, it's their job.

[Gregski]

Another recommendation from Summit Racing website is a Holley 4175 Part #0-80555C Emissions Replacement - Classic Holley

I highlight the obvious differences between this 4175 model and the previously mentioned 4160. (beyond the slightly more CFM and the Spread Bore flange on this one vs Square Bore on the prior one, I am not sure what the differences are in layman's terms, perhaps someone on here can help us all out)

Barrels 4
Billet Color None
Booster Straight
Brand Holley
CFM 650
Choke Electric
Circuit 2
Finish Gold Dichromate
Fuel Gasoline
Fuel Inlet Single
Material Zinc
Model 4175
Secondaries Vacuum
Throttle Bore 1.375 inch

Designed as a bolt-on replacement for GM's venerable Quadrajet, Holley's 4175 carburetors utilize a front-mounted fuel bowl fitting, allowing you to reuse the stock fuel line. Other features include vacuum secondaries, power valve blowout protection, a spread bore flange, and a choke. The 4175 carburetors are available in your choice of universal calibration or direct fit replacement versions.

Just sharing with others my carburetor research, I am not an expert on this (that may be obvious) I am just trying to help, as this is a bit confusing for newbs like me

[JJLT1]

this is the difference, spread bore vs square bore..
they don't inter change normally, but some do.. and there is adapters..
a quadrajet is a spread bore..