which carb for performance?
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which carb for performance?
To all out there. Have recently purchaced '78 F150 w/351M, headers and alum. intake manifold. Developed carb problems recently and mech. said needs rebuild (doesn,t recommend, says carb is junk). Have OEM on now and rus like dirt. Have older Holley 600 that will require time and effort to clean up. Co-worker offered a Demon 650 dbl pump for $200.00. was thinking about Street Avenger 650 for a couple bucks more. Don't know if anything internal was modified but would like some thrompin' performance for not alot of bucks. Don't use the truck other than the occassional trip to work and around town for things that won't fit in trunk of car. MPG now around 12. 250K original on clock. Maybe complete rebuild? Just had valve cover gaskets and main bearing seal replaced so no leaks. Any suggestions greatly appeciated and as said would like to thromp around town, maybe some light to light for fun once in a while. Sha doesn't look like much with typical rust and all for the year but has been good service vehicle and would like to keep and fix proper as was neglected from previous owner, neighbor.
Thankyou for any help!
RED
Thankyou for any help!
RED
Senior User
Joined: Feb 2003
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From: Michigan
351m/400 Carb
Last summer i did a carb/intake upgrade and went with an Edelbrock 650CFM AVS THUNDER SERIES, one of their newer carbs and a Weiand Action plus intake...so far so good.........it was worth every dollar, and really added some nuts...as far as the mileage, it is better than the stock carb...i get anywhere from 10-14 depending on if i open up those secondaries or not 
Fleet Mechanic
Joined: Oct 2003
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From: Green Springs, OH
I just pulled a holley 600 cfm vac sec off my 400 and replaced it with a edelbrock 1406 and it runs smoother and much better performance right out of the box and bolted on than my old holley could ever dream of plus you can change jets and rods without spilling any fuel and no pulling the carb. I would go with a edelbrock and all Ive heard those demons are, are polished up holleys essentially.
Elder User
Joined: Apr 2003
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From: Normal, IL
One thing I can tell you from experience is that vacuum secondaries do not work properly on a Cleveland or M block. Under hard acceleration, the secondaries need to be opened bruptly, and about halfway through the rev-band, they reclose. A Demon is based off of a Holley, but the only things that interchange are squirters, jets, power valves, etc. Holley and Demon Double pumpers are easier to tune than any VS carburetor. The Edelbrock gets the nod for bolt on and go, but for me, a Holley DP will always be easier to tune.
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Thanks to all that have responded. I'm sure that I'll have additional questions in the future. I picked up the Demon (Mighty) the other evening. Basically brand new unit. I need to get fuel delivery lines from local Speed Shop or Summit, etc. Was wondering if I should reset to factory settings before bolting in place or try and see how it runs? Also, the thought of maybe putting on a spacer while everythings torn down, Would this application help performance wise? Kind'uv new to the whole perfomance scene, but a machinist by trade so mechanically apt. By the way, Carb came in original box, papers, intructions, etc. Can't find a new list $ for it but still think 200.00 was a bargain and if doesn't work out someone else may have use for it. Thank you again to all. Nice place to find good people willing to share information and help, wish that in my endeavors I come across something that may be of use to everyone else.
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Elder User
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From: Normal, IL
For a street performance application, a 1 inch 4 hole spacer works very well. In cooler weather, with no choke, be sure to use an enclosed air cleaner assembly. Starting may be difficult in EXTREMELY cool weather, but 2-3 pumps of the gas and it should fire right up. Just make sure to take the time and tune it right, and you'll be happy. BTW, Barry Grant claims that the carburetors flow approx. 15-20% more than advertised, and maintain excellent throttle response.
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I need HELP!! just installed a mighty demon 650 carb on my 78 F150 351m w/ alum intake manifold(400 Edelbrock) I also installed a 1" spacer on the carb the kick down arm doesn't clear the linkage. is there a way to bend the arm or would i need to put a spacer/adapter piece on the arm if that is possible to clear. when I start the engine it is WAY above fast idle. The old carb had an elect. choke the new one does not. Should I install the old one . or could it be I do not have the idle set right? The idle screws are out the whole way, both primary and secondary. Could it be possible that I need to adjust the accelerator linkage as well. I wish to thank you for any help you would be able to give me.
Sincerley,
The other RED head
Sincerley,
The other RED head
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I like the Edelbrock Thunder series as well. Nice and easy to make adjusments externally for any application... 650 should work nice 4 ya... I have not had one long enough to tell how well they hold up but always had good luck with my other edelbrock carbs right out of the box with maybe a minor adjusment when installed. They don't need retuned all the time which is nice too... 250K is getting up there. I would want to think about that build myself but be prepared for the cost as parts are not real cheap for the 335 series... You can get a full RV kit for about $375 delivered though. Pistons, Cam, Lifters timing set and all... It's not a race set up but it's a good RV set up! I would'nt order anything until I got it apart and check the ware though. I just seen a virgin block with .010 oversized bore from actual engine ware... It surely should see a machinist and be refitted... Good guys at fastengineparts.com They shipped my parts same day and UPS delivered them in the morning so they did well! They really don't know what you need if you run into an issue but if you do I think they may save you some money...
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Hey to all! Sorry , my significant other was trying to help last night while I was at work, "LOL!!!". The problem was the kickdown linkage not fully allowing the throttle to close, secondaries were already kicking in. When I got home this evening I bent the linkage to take up the access play (ran fine after I disconn. the kickdown) so assumed this would be OK. Test drove after warm-up and alright except secondary or should I say "kick-down" comes upon at normal driving to and fro, not for long, 1.0 to 1.5 seconds and then normal op. Hope it is just an adjustment needed. Also fuel delivery is only rated between 2 and 4 PSI while running, even at full throttle. Spacer has an adjustable set screw, have it turned to snug and then back out maybe 1 full turn, could this have effect on everything , thought it was only to adjust mixture. At the very least I can disconnect the kickdown and drive with-out the advantage until properly calibrated. Thanks.
Elder User
Joined: Apr 2003
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From: Normal, IL
If you decide to unhook the kickdown at the carb, wire the kickdown (at the tranny) down. This will increase line pressure all the time, instead of just when accelerating. The only thing you might notice is increased firmness in shifting.