Carburetor choice (daily driver, 351cid, ~400hp, manual transmission)

[SadbutTrue]

I was hoping to get a few recommendations for a solid carburetor for my 351w, once i get the trick flow heads, cam and weiand stealth on it (rest of mods in sig... should net 400 hp). The car needs to be daily driver-able, so economy and being fairly easy to use/tune is desirable. I have a manual transmission, and it seems most people prefer to go with a manual secondary carb (especially since a mild cam, like the XE274H I plan to go with, makes vacuum less dependable).

I had liked the Holley 670 street avenger but it has a vacuum secondary, which like I said I'm not sure will go well with this cam (not that the cam is thaat extreme). Any recommendations are appreciated.

 

[htwheelz67]

I would run a 650 cfm speed demon carb with mech secondaries, if you want a bit better mileage run vac secs. the 650 demons flow around 780 cfm, even better get a mech secondary one with annular boosters, it would be about perfect and give good economy.

I run a 750 mighty demon annular on my 525hp 408 with a typhoon int and cnc ported 205cc TW heads with a typhoon int (steath clone) and it runs unbelievably well.

my car http://htwheelz.smugmug.com

if you go on ebay you can get reman demons for a great price including fuel lines, I have bought three so far and they work excellent.

 

[rbohm]

first the vacuum signal used to actuate the secondaries comes from the primary venturi and not manifold vacuum. the cam you selected is not radical enough to hurt the vacuum signal in the venturi.

as for a carb recommendation, a 600 or 750cfm edelbrock carb would do real nice. the smaller carb is nice for better fuel economy and throttle response, but if you plan on winding this engine out above 6500 rpm on a regular basis, use the 750 instead.

 

[htwheelz67]

I missed something here, where are the cam specs on this post? thats what I was looking for?

 

[SadbutTrue]

Already use an Edelbrock 600 on my current engine. Its the only carb I've ever really had experience with and does okay, but there's a consistent hesitation/bog between wheen i hit the gas and the engine responds. I sorta want to try a Holley derivative, but maybe I'll see how it runs with the 600 first.

 

[D.Hearne]

The 670 SA is an excellant choice. The vacuum secondary/manual trans isn't a problem at all. I've got a 570 on my 4 speed Toploader/roller 5.0 in my 89 Ranger that's my daily driver. ZERO problems.

 

[SadbutTrue]

The 670 SA is an excellant choice. The vacuum secondary/manual trans isn't a problem at all. I've got a 570 on my 4 speed Toploader/roller 5.0 in my 89 Ranger that's my daily driver. ZERO problems.

I've always had my eye on the 670 SA.

Any other recommendations (or comments on the vacuum secondary vs mechanical seconday question)?

I remember the days when a carb thread would ignite a minimum 4 page war between edelbrock and holley fans... boy this place has slowed down

 

[SadbutTrue]

I've always had my eye on the 670 SA.

Any other recommendations (or comments on the vacuum secondary vs mechanical seconday question)?

I remember the days when a carb thread would ignite a minimum 4 page war between edelbrock and holley fans... boy this place has slowed down

Anyone have experience with professionally rebuilt carbs on ebay? One place is offering 670 SAs for 260 shipped (about $100 off new price), seems like the feedback is pretty good...

 

[biggyfan1]

well i have a 347 with a holley 600 cfm carb on it. i havent driven the car yet but when i was putting it together i called holley and gave them all my info and the guy told me a 600cfm would be fine unless i have a high reving motor (anything over 7000) i would call holley up and they will tell you.

 

[Fast63]

Already use an Edelbrock 600 on my current engine. Its the only carb I've ever really had experience with and does okay, but there's a consistent hesitation/bog between wheen i hit the gas and the engine responds. I sorta want to try a Holley derivative, but maybe I'll see how it runs with the 600 first.

Did you do any tuning at all to the carb? I have noticed many people complain about bogging with edelbrocks, and any time I experienced it after first installing an edelbrock carb, it was very easy to get rid of the bog with simple changes.

With the upgrades you plan, get a 750 edelbrock. You want good economy and easy tuneability, that is exactly what edelbrock carbs are designed for. Holley definitely does not beat out edelbrock in that arena. Most people get holleys for more power, but I tend to disagree with that too. I just don't like holleys

If you decide on an edelbrock, shoot me some PM's and I'll do what I can to try and help you tune it. I put my 750 edelbrock on my 347 with Trick flow heads, solid cam, 10.5:1 compression, headers, air-gap rpm intake, etc. rated for 450hp flywheel. Turned out that right out of the box, the carb makes the engine run GREAT and gives the plugs a nice tan burn. No tuning required in my case there.

 

[69gmachine]

I've always had my eye on the 670 SA.

Any other recommendations (or comments on the vacuum secondary vs mechanical seconday question)?

I remember the days when a carb thread would ignite a minimum 4 page war between edelbrock and holley fans... boy this place has slowed down

I had excellent results with an Autolite 600 I had rebuilt by Pony Carburetors sitting on top of a Performer intake, mild hyd cam, TW heads and 1 5/8" headers. I had it on my 351W before I went crazy and built the 408. I got 23 mpg driving on the interstate from Washington DC to Dallas, Texas and back going 65 mph. I did have a 5 speed manual trans, but other than that it was nearly a stock restoration. Once I was driving around town, mileage dropped like a rock, but it had enough power to smoke the tires in 2nd gear.

 

[SadbutTrue]

Did you do any tuning at all to the carb? I have noticed many people complain about bogging with edelbrocks, and any time I experienced it after first installing an edelbrock carb, it was very easy to get rid of the bog with simple changes.

With the upgrades you plan, get a 750 edelbrock. You want good economy and easy tuneability, that is exactly what edelbrock carbs are designed for. Holley definitely does not beat out edelbrock in that arena. Most people get holleys for more power, but I tend to disagree with that too. I just don't like holleys

If you decide on an edelbrock, shoot me some PM's and I'll do what I can to try and help you tune it. I put my 750 edelbrock on my 347 with Trick flow heads, solid cam, 10.5:1 compression, headers, air-gap rpm intake, etc. rated for 450hp flywheel. Turned out that right out of the box, the carb makes the engine run GREAT and gives the plugs a nice tan burn. No tuning required in my case there.

Well, we tuned it quite a bit long ago to get rid of some detonation problems we were having with the old engine. Don't know if I've ever sat down and tried to get that hesitation out of there... it was alway smore of an annoyance than an actual problem.

I've messed with all the basic stuff... idle speed, idle mix, jet sizes/metering rods, etc... the hesitations always been there. I do like the design (changing jets/metering rod/springs is a snap), it looks cool, and its always been reliable... but that hesitation bothers me and if I'm dropping $2k in engine parts I don't want my beefy new engine to do that.

If you have any easy ideas that might help with the hesitation, I would try re-using the carb first. No reason not to see if it works before switching, I guess.

Plus, since I am still sorta new to this game... I figured I'd try a Holley for experience's sake. Not sure I want to do the hardcore thing and go rebuild some old double pumper, but the SA sounds like a good choice.

 

[SadbutTrue]

For whatever its worth, I called holley and the dude recommended the 670 SA as well. I mentioned I had a 600 cfm carb at the moment (didn't mention it was an edelbrock, heh) and that I was looking at the 670, and he said 'yeah, the 670 would work.' Didn't really elaborate, so its not exactly an end-all opinion, but... yeah. Now I just decide whether I want to try the Edelbrock I have first or just do it all at once and get the 670 now.

 

[matt0matic]

I found this a worthwhile read reguarding carbs:

http://*******.com/index.php/topic,8087.0.html

 

[SadbutTrue]

I found this a worthwhile read reguarding carbs:

http://*******.com/index.php/topic,8087.0.html

can you give me a hint as to what got 'bleeped' out?

 

[D.Hearne]

Anyone have experience with professionally rebuilt carbs on ebay? One place is offering 670 SAs for 260 shipped (about $100 off new price), seems like the feedback is pretty good...

I bought the 570 second hand off ebay.They're hard to come by this way, so you have to be patient. Paid less than $150 for it including shipping. I removed the bowls and filters (yea, there's one per bowl inside the inlet fitting) to verify it's cleanliness and changed the accellerator pump diaphram. Then bolted it on, adjusted the idle screws and ain't touched it since. Been running for the better part of a year. Tuning? What tuning? Spark plugs are two years old, look like new. It starts everytime with no pump shot to prime it. Even at 25* F.

 

[jikelly]

first the vacuum signal used to actuate the secondaries comes from the primary venturi and not manifold vacuum. the cam you selected is not radical enough to hurt the vacuum signal in the venturi.

as for a carb recommendation, a 600 or 750cfm edelbrock carb would do real nice. the smaller carb is nice for better fuel economy and throttle response, but if you plan on winding this engine out above 6500 rpm on a regular basis, use the 750 instead.

I agree. I've got a carter 750cfm carb on my 351w. Same carb design as the edelbrocks I like these carbs better than the holley style because they are easy to tune.

I had a 625cfm on my old 351w engine. It was fine and got better mileage on the highway than my 750 carbed engine. I thought the up in cfm would be good for a few more ponies. I don't think that was the result I got though.

 

[Fast63]

Well, we tuned it quite a bit long ago to get rid of some detonation problems we were having with the old engine. Don't know if I've ever sat down and tried to get that hesitation out of there... it was alway smore of an annoyance than an actual problem.

I've messed with all the basic stuff... idle speed, idle mix, jet sizes/metering rods, etc... the hesitations always been there. I do like the design (changing jets/metering rod/springs is a snap), it looks cool, and its always been reliable... but that hesitation bothers me and if I'm dropping $2k in engine parts I don't want my beefy new engine to do that.

If you have any easy ideas that might help with the hesitation, I would try re-using the carb first. No reason not to see if it works before switching, I guess.

Plus, since I am still sorta new to this game... I figured I'd try a Holley for experience's sake. Not sure I want to do the hardcore thing and go rebuild some old double pumper, but the SA sounds like a good choice.

Can you describe exactly when you get the hesitation? Some people have it during part throttle, others right off the line, others during more heavy throttle... Can you give an example?

 

[SadbutTrue]

Can you describe exactly when you get the hesitation? Some people have it during part throttle, others right off the line, others during more heavy throttle... Can you give an example?

It happens when I floor or apply a lot of throttle, regardless of whether its off the line or when i'm already in motion. I'll hit the throttle, the engine boggs for a second - then a second later starts taking off.