Hey guys im rebuilding my 351w at school and i wasnt really sure wich carb or whats size i should get so i thought i'd ask the pro's haha. Here's my specs for the engine, its a 351w board .40 over, my cam size is ad. duration is int. 262 Exh. 272 my lift is Int .448 Exh .472, i have gt-40 cyl. heads, and a edelbrock performer intake. If you guy can help me out and give me some feedback i'd really appreciate it.
Thanks, Jack
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Advertised duration is pretty useless in my opinion for comparing camshafts and getting an idea of what kind of duration they have. Instead, look at duration @ 0.050'' lift and give us those numbers. I see that the camshaft you've chosen is a dual pattern camshaft, so I assume it's going to be a little more than a towing cam, yet not an all out racing cam 9which would be useless on the street)?

The way you've got the motor set up, I'd put on a 600 CFM Holley 4bbl and go.

Any headers? What are you running for an exhaust?

 

Thanks for the feedback! but no it doesnt have headers on it now but im planing on getting some for it and for the exhaust no cats just a flowmaster 10 out to duals. but this is my first rebuild and i just want to make a fun truck, do you think the engine is going to turn out alright with that cam?

 

Thanks for the feedback! but no it doesnt have headers on it now but im planing on getting some for it and for the exhaust no cats just a flowmaster 10 out to duals. but this is my first rebuild and i just want to make a fun truck, do you think the engine is going to turn out alright with that cam?
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It should get you down the road. My lift on my camshaft is .469 and .495 for int and exh respectively. My duration at .050" is 203 and 216 for int and exh. My truck gets around 13mpg and has no problem getting up to highway speeds in a decent amount of time. It'll never beat a flat track record or anything...

 

Haha alright, that makes me feel a little bit better about it. Thanks

 

Hey Jack,
Sounds like it should work. A 600 CFM should be fine for this application. If you went with aftermarket heads, I'd suggest upping to a 750. I noticed in your public profile, you're in Virginia. I know they require state inspections, and if it came with a catalytic converter, and it did, it won't pass inspection without one. I suggest a high flow, aftermarket cat. It won't cost much, if any power, and will keep you legal. Good luck on your build.

 

Thanks for the feedback man! but i know about the cat. thing and when i first got the it didnt even have one on it before i sawed off the muffler.haha =D

 

I would say no less than 600 and no more than 750, so split the difference and go for a 650/670.

 

With the cam, heads, and intake you selected, I would go with a 600 cfm carburetor. All of the modifications you have chosen are designed to maximize low-end torque, and a carburetor of this size will take full advantage of your modifications and give you better performance off the line and much better throttle response. You will also get better gas mileage.

If you went with a larger carburetor, it would still work but you would sacrifice some low-end torque for more top-end horsepower, something you don't really want or need in a full-size truck nor will you even see with your modifications. Your cam, heads, and intake are all designed to work best from idle to about 5,000 RPMs, and that is how your carburetor should be sized:

(351c.i.d. x 5,000 RPMs / 3456 = 508 cfm)

As for which carburetor to get, that is totally up to you, and opinions vary on this subject like a Ford vs. Chevrolet war. I personally think the stock Motorcraft [Holley] 4180 4V 600 cfm carburetor that came stock on the 351 H.O. F150s and Broncos and the mighty 1983 - 1985 Ford Mustang GTs is a pretty good carburetor that offers good performance for a truck. This carburetor is sized correctly and has annular discharge boosters in the primaries for better performance and fuel economy. For aftermarket carburetors, the general consensus seems to be that the Holley is the better performer but they are higher maintenance and harder to tune, and the Edelbrock is easier to tune and offers better fuel economy.

It sounds like you have built a great truck engine so far! Don't make the common mistake of over-carbing the engine.

 

Very sound advice, LARIAT 85!

I attempted to "rep" you, but was told to "spread the love"!

 

Alright thanks for commeting, i think i will get a 600 cfm. Thanks for all the info!!!

 

I agree on the 600 holley/motorcraft/autolite. I dropped an 86 351ho in my 89. Dont have specs on the build but mostly stock .030 over and mild cam. The single biggest improvement i made was equal shorties into 2 1/2 true duals with walker high flow cats and thrush turbos. Believe me it sounds awesome too.

 

Thanks for trying, Chief!

 

I can't suggest a carb until I know a couple of things. First, can you tune a carb? Second, is absolute power or economy more important to you? The reason I ask is that, from my limited experience, an out-of-the-box Holley will give you more power but an out-of-the-box Edelbrock will give you better drivability and mileage.

My experience is with a "built" 351M. It is currently in Rusty, but is soon to be in Dad's truck. You can read about my experience with the carbs here: Rusty. But, I will summarize by saying that I got 12.25 MPG on the highway with a box-stock 4160 Holley, and those numbers improved to 14.25 MPG but simply bolting on a stock Edelbrock 1406. Further, the E'brock gave better or more crisp throttle response, although the Holley seemed to have a bit more punch on the top end - but that was subjective and I haven't measured it.

Having said that, if you can tune a carb then you can take either of them and make things better. However, I'm not convinced you could get the Holley to return the same MPG the Edelbrock gives. And, I'm also not sure you can get the 1406 to give the same power as the Holley, and that is because the 1406 is set up to give good mileage. But, the E'brock 1405 is essentially the same carb but is set up to give more power, so might be a good balance between the Holley and the 1406. And, I believe it could be tuned to give essentially the same MPG as the 1406 while still giving the good WOT acceleration.

All three of those carbs are 600 CFM carbs, and that should be adequate for your engine - in a truck. If you were running something light like a Mustang then maybe more CFM, but for a truck you need torque at low RPM and a 600 will give you better low RPM metering than a 750, which leads to better torque.