Carb replacement question

[mjw930]

If you had a bone stock 7.4L (peanut port heads) that needed a carb or at a minimum a carb rebuild what would you do?

Taking into account that you expect to build the motor down the road with better heads, cam, rotating assembly, etc with a target of building a "budget" 450hp 454 would you:

a) Just rebuild the merc Q-Jet and motor on for a year or so?
b) Buy the Holley 650 cfm Q-Jet replacement http://www.holley.com/0-80552.asp
c) Buy a Holley 750 DP marine carb and detune it http://www.holley.com/0-9015-1.asp
d) Buy a Barry Grant Marine Demon 650 or 750 and detune it
e) Buy an Edelbrock 750 marine (direct, bolt on replacement, including fuel line)

Then, if you were to go with a Holley or BG would you do vacuum or mechanical secondaries?

Just throwing all this our there for discussion. I'm looking for some "been there, done that" analogies. I'll be asking my engine guy too but he spends most of his time on high HP, high dollar motors and uses BLP carbs almost exclusively so he doesn't have a lot of experience in the lower end of the spectrum. He also hates Barry Grant carbs but that's a whole different discussion.

[gcarter]

Nothing wrong w/a Q-jet. They run pretty economically.
Save your money for later.
I found a brand new Holley 800 on eBay for $350.00. Gotta keep your eyes open.

[VetteLT193]

barry grant... I just bought one for my boat and the quality is just awesome. I haven't installed it yet, but will soon.

reality is if you can buy a cheap used one to get you by until the build that is the way to go. I'm sure you are well aware that carbs aren't an all-in-one part. If you buy a new good one it either isn't going to be optimized for the current power or not be great for the 450-ish HP number.

[zimm17]

I've always run Edelbrock's. They are an improved Carter AFB carb. No gaskets below fuel level (like Holley), no power valves to blow out (Holley), you can change needles instantly. For jets, you remove the top and it's still easy to tune. They sell a nice tuning pack full of jets and needles too along with a chart of what to use based on rich/lean.

I ran them on my '71 Olds, '77 Ford F150, and my dad's 7 meter donzi with twin 302's. Yup, the 302's ran great with the 750's- used less gas than the 600's because the secondaries stayed shut at cruise.

[mrfixxall]

Rebuild the Q-jet,or go with the edlbroch,,most applications with the edlbroch just bolt it on and set the enrichment screws and go boating:wink:

[Trueser]

HolleY 650
HOLLEY 650 CFM MODEL 4175 4 BARREL MARINE CARBURETOR
Spread bore, Electric Choke
Part #: 0-80552
Brand new never used,
Features
Model 4175 w/Side Hung Floats
Dichromate Finish
30cc Accelerator Pump
Electric Choke
Vacuum Secondaries
Power Valve Blowout Protection
5" Air Horn
J-Style Vent Tubes
Meets Coast Guard Specifications
Single 5/8-18 Inverted Flare Fuel Inlet
Universal Spread Bore Quadra-jet Replacement
100% Wet Flow Tested
$ 300.00

Christmas price $ 200.00 this was never installed.

[BigGrizzly]

OK here goes. the first problem is the 450 budget puts you smack in the middle. Sooo, I would do the BG and reduce the ventory size with inserts so you can go bigger later. On that engine I would use Mec secondaries. The 750 is plenty. I can go on but it is unlimited. Remember it is the combination.

[Conquistador_del_mar]

I've always run Edelbrock's. They are an improved Carter AFB carb. No gaskets below fuel level (like Holley), no power valves to blow out (Holley), you can change needles instantly. For jets, you remove the top and it's still easy to tune. They sell a nice tuning pack full of jets and needles too along with a chart of what to use based on rich/lean.

I ran them on my '71 Olds, '77 Ford F150, and my dad's 7 meter donzi with twin 302's. Yup, the 302's ran great with the 750's- used less gas than the 600's because the secondaries stayed shut at cruise.

I thought I would chime in. I really like the Edelbrocks for the same reasons. They come stock set too lean, but I have not had to change the jets - just the metering rods and springs which can be done in about 5 minutes! I run a 750cfm on my 489HP stroked 427CID Ford in a Cobra, a 750cfm on a 450HP stroked 383CID Chevy in my 1980 Vette, and a 600cfm on my 330HP Vortec 350CID Chevy engine that I just installed in my 1971 18' Donzi restoration. None of them have had problems. Be sure to buy the calibration kits that Edelbrock offers so you can get the right comination of metering rods and springs for your application if you decide to get one. Bill

[Lenny]

BG mechanical 750... :D

I love BG carbs. The X and the LE now have 'em. I do not get into the "tuning/jet size stuff" (too stupid :rolleyes: ) but, I can bolt these on, sea level, the motors are not too rich or lean and just run and spark up instantly.

[mjw930]

Thanks for all the input.

Just to clarify, I was wrong about the Q-Jet, I have the 9780 WEBER carb. it's a 7.4L circa 1996, not the 454 that came in the boat in '87. That's why the Edelbrock is plug and play.

Trueser, What would you consider to be the maximum motor you could put under that 650 Q-Jet replacement Holley?

[mrfixxall]

Thanks for all the input.
Just to clarify, I was wrong about the Q-Jet, I have the 9780 WEBER carb. it's a 7.4L circa 1996, not the 454 that came in the boat in '87. That's why the Edelbrock is plug and play.
Trueser, What would you consider to be the maximum motor you could put under that 650 Q-Jet replacement Holley?

What is wrong with the current carb? does it idle fine then when you go to jump on plane it boggs down?

[mjw930]

What is wrong with the current carb? does it idle fine then when you go to jump on plane it boggs down?

Honestly, nothing's wrong with it. It could use some cleaning, the boat sat for the last couple months and when I went to fire it up Sunday to check all the exhaust fittings (replaced the exhaust tips) it wouldn't catch. I checked spark and fuel flow from the pump but the problem turned out to be a stuck float. A simple tap on the float housing was all it took.

Mostly it's just me wanting to tinker. You know the old saying, an idle mind is the devils workshop......

[VetteLT193]

Honestly, nothing's wrong with it. It could use some cleaning, the boat sat for the last couple months and when I went to fire it up Sunday to check all the exhaust fittings (replaced the exhaust tips) it wouldn't catch. I checked spark and fuel flow from the pump but the problem turned out to be a stuck float. A simple tap on the float housing was all it took.

Mostly it's just me wanting to tinker. You know the old saying, an idle mind is the devils workshop......

In that case, wait until the engine build and get the right carb for the setup.

Or just build the engine now:yes:

[MOP]

Milk it for all it is worth save your beans for the carb Griz is suggesting, now if it were a Qjet you would be nuts not to keep it. It is a very under rated carb, let the right guy get his hands on it and he will perform magic.

[Donziweasel]

I have messed with Holly's and Edelbrock. I like the Edelbrock for simplicity. You can change the jets in under 5 minutes, a very simple straight foward carb. Hollys are nice but to change power valves or jets takes a while and can be messy. People swear by the BG though.

[mjw930]

I'll probably just wait and do a carb when I do the motor but that will be waiting until next year. Too much uncertainty in the job market for me to be dropping big $$$$ into a perfectly good motor.

[BigGrizzly]

It is what your use to and the combination thats in the engine. My Cleveland in the Corsican doesn't like the Edelbroc, in any way shape or form. In the Mach1 it is passible, not good but passable. As for power valves Blow out was an old situation. Most people didn't even know it. The biggest problem is people did not put the correct one in to begin with. How many people actually know the acceptable vacuum at wfo. How many people have even checked it. I can tell you there are at least 3 on the board that have 0 Vacuum at wfo on normally aspirated engines.

[Sam]

Rebuild the Q-jet,or go with the edlbroch,,most applications with the edlbroch just bolt it on and set the enrichment screws and go boating:wink:

Ditto !!!!, haven't had a second of trouble with my bone stock Edlebrock.

[joseph m. hahnl]

Stick with the Webber:yes:.

[mjw930]

It is what your use to and the combination thats in the engine. My Cleveland in the Corsican doesn't like the Edelbroc, in any way shape or form. In the Mach1 it is passible, not good but passable. As for power valves Blow out was an old situation. Most people didn't even know it. The biggest problem is people did not put the correct one in to begin with. How many people actually know the acceptable vacuum at wfo. How many people have even checked it. I can tell you there are at least 3 on the board that have 0 Vacuum at wfo on normally aspirated engines.

Griz,

I hear you, I had a lot of preconceived notions back 10 years ago when I met the guy that builds my motors. We built a killer 454 and I assumed it would need something like an 850 dp and after listening to Bruce we put on a 650 BLP modified Holley and proceeded to pull 640 hp on the dyno and it ran perfectly for years. It's all about dialing in the right carb for the cam/head package, not about cfm's or brand.

My question here was about what to do on a bone stock motor IF I need a carb for the short term.

[BigGrizzly]

Let me say this stock motors are the same as hi po ones. Most people put big carbs on motors because they hide not fix a multitude of problems. Example, a guy comes into Garry and says he wants his vette motor dynoed because he just wanted to see ho much power it had befor he put it in his car. It had a 900
= cfm on it, a 350Cid, he bough it from a friend it was real cammy he said. Well it made less then stock. Johnny takes off the carb and it was a mess. He fixes it and still short on power. Garry's Son comes in and says he knew the car and it was a dog and always ran fat and mad your eyes water. Well Johnny takes a stock carb for that model and bolts it on it picks up 40 ponies and idles. Well the short part is it turns out to be a completely stock engine. but now because of all the fuel the oil has dilution. It ended up leaving the shop with a 600 cfm BG on it, new rings and bearings and no other changes. So I go back to my first post on recommendation. I have a 750 Eldbroch I keep because it looks pretty and Some day I may need it, so I have it.

[f_inscreenname]

Edelbrock is a great carb. And like the first post says, check eBay. I just picked up a Edelbrock 800 so new you couldn’t tell the difference if I set a one out of a store next to it. Shipped to the house $202.50
Just remember for some reason the Edl’s don’t flow like Holley’s do. I cant find the article I wanted to post due to new anti virus software killing off my “History” file to quick but here is a couple quick links.
http://amccars.net/cgi/yabb2/YaBB.pl?num=1202596786 (http://amccars.net/cgi/yabb2/YaBB.pl?num=1202596786)
https://www.fordmuscle.com/forums/1363342-post23.html (https://www.fordmuscle.com/forums/1363342-post23.html)
So when you buy a Edelbrock it’s not like buying a Holley. That’s why you see so many people like the EDL750 on their set up’s but find other carbs of the same cfm to be to big. A EDL750 is really like having a 700cfm carb. That’s why I’ll be using the EDL800 on the 454, the beast that it is and putting the 750 back on the Chrysler 360.

[SilverBack]

MJW...I had an old carb on my 23 Ragazza with a 350 MAG and I put the Edelbrock and was very happy with it. It was only on there for a few months before the tree fell and broke my boat. I think I took it off before I sold the boat for salvage but I can't remember. I will check when I get back home. If I still have it you can have it.

The penut head 454 should be around 330 hp from what I know about it. The Edelbrock will be just fine!! they are great on a stock type engine. If you build a hotter engine get something else later if you think you need to.

I will check on my old carb if you want me to...I think it would be fine!!