I have a friend who has just purchased a 79 ford 4x4 with a 351M and he was wondering were he could get a 4bbl intake for his truck and how much it would cost
Any help would be great
Steve

 

I have seen one offered by Etlbrock its allumium of coarse but works nicely if your going to do away with your egr stuff the one I looked at was not set up for it but it will work on your 351M

 

Edelbrock and Weiand both have 4V aluminum intake manifolds. You can get egr or non egr versions.

Check with:
http://www.summitracing.com/
http://www.jegs.com/

 

Thanks guys I will tell him, and since we live in canada egr equipment may as well go out the window.
Steve

 

I would check on Ebay, they sometimes go for $25 with no problems. I have seen several recently just search '351M' You don't really need a 4bbl intake because the 351M can only suck in 590cfm at full throttle. I would only get one if yours is defective or damaged

 

If you eliminate the EGR your engine will ping without other modifications.

 

How did you come up with this CFM at WOT? I doubt any V8 is MAXED at 590cfm... depending on his compbo and location more carb may very well be warranted. easiest way to tell is with a vac sec carb, it only uses the secondaries when the engine needs it, and i'm sure if you stomp on any v8 it will use those secondaries


I'm not sure this is always true either. most times the EGR is just a scavanging system for unbruned gases that some out the exhaust stroke, the engine recycles these gases and burns them on the next firing sequence, thus less unburned gases floating aroung the atmosphere. unless it's FI the air flow sensor and the oxygen sensor won't make any difference to the performance of the engine. Again, depending on the combo and parts removed, the results are varied... removing restrictive intakes and exhaust scavanging systems won't automatically cause pinging.

 

danimal,

Have you ever heard of the saying - "better to remain silent and be thought the fool, than to open your mouth and remove all doubt" ?

The calculation for determining carb size has been around for a long time. Trust him when he says that 590cfm is what a 351 needs.

What chaps my butt about the second statement is how authoritative danimal sounds when he makes it.

The idea that you can 'reburn' exhaust is so damned stupid that it staggers the mind. EGR is not an attempt to reburn exhaust gasses. It is a method for reducing combustion temperatures to prevent the creation of NOx, Nitrides of Oxygen. I'm not going to try to convince you how it works, I'm just going to state the facts for others to read and know.

And, yes, if you remove your EGR, you will need to retune the distributor because the spark advance will be all screwed up.

 

not trying to start anything with you pcmenton, but my prev response was an honest question/discussion.

EGR stands for Exhaust Gas Recirculation. The gases that stick around the engine are routed back through the air intake/intake manifold and sucked back into the combustion chamber and burned again on subsequent firings of the spark-plugs in the cylinder. http://www.allpar.com/mopar/emissions.html

The use of these exhaust gases also has the effect of limiting the amount of fresh o2 that is allowed into the combustion chamber thus limiting the amount of NOx that is created in the fuel burning process

http://ace.webspace.fish.co.uk/ia003487.htm

Also. the idea of burning or reburning exhaust is a totally feasible one. when a street-rodder puts a sparkplug connected to a coil in his exhaust pipe and we see flames shooting out the back of the car, that is buring exhaust fumes... he may have upped the mixture some to have additional unburned gas available to fuel his exhaust pipe flamethrower, but burning his exhaust is what he is doing.

----------------

Regarding the correct carb size for a 351 everyone can believe what they want. If you're talking about the carb sizing calculation provided on the Holly website, as well as about a million others I disagree with them 100%. I just did a search for the phrase "how to calculate carb size?"

http://www.prestage.com/carmath/calc_CarbSize.asp

the answer all depends on the input into the equation.

I selected 351, 5000max RPM, and 85% volumetric efficiency....this equation says I should use a 432 cfm carb??? but if the correct size (according to your previously mentioned "correct" size for a 351) is 590cfm shouldn't this calculation give me that answer? What I was trying to say is that when answering the question "what size carb for me?" it would be better to "suggest" starting with a 600cfm carb and going from there rather than saying 590cfm is all a 351 will ever need... how do you know what the combo is??? a race ready 351 that's going to hit 7000rpm with a single plane racing manifold, headers, and huge ported heads will probably want a LOT more than 675cfm (351, 7k rpm, 95% efficiency) "correct" size returned by these calculators.

also, if these calculations are so accurate...take a look at a 318 hitting 5k rpm and 85% efficiency. the calculator says 391cfm.. however, ChryCo sucessfully outfitted 1970s 318s with 800cfm thermoquad carbs from the factory.......... but the calculator says it doesn't need that much....hmmmmmmmm.

i never intended to portray myself as authoritive or a know-it-all, and I don't appreciate the slam against my intelligence level when we've never met outside of this one post. it's a web board of opinions and discussion, so quit letting it chap your butt.

 

OK..OK...take it easy guys. Let's try to keep in mind a couple of things about these 2 subjects:

First, engines designed to run EGR are generally calibrated leaner than pre-EGR engines for 2 reasons. First, leaner is better (to a point) for emissions. Second, since EGR replaces O2 with exh gas the engine simply can't burn the same amount of fuel as if it were burning plain ol' air. When the EGR is disconnected the carburetor can't adjust to the additional air it's getting and the mixture gets messed up and runs too lean. Leaner = hotter so the A/F mixture has a tendency to pre-ignite due to the hot spots created in the comb. chamber. In order to take advantage of the additional power offered by disconnecting the EGR you should change the main jets on the carb as well to fatten the mixture. Timing should also be changed as well.

Second, the calculations for max. CFM for an engine of a given displacement are essentially correct. So why would you need a bigger carb on an engine? Well it's fairly simple if you stop and think about it. Even tho' the engine can only use X amount of air for Y displacement making power is all about geting the air into the comb. chamber to be burned with the fuel at the right time. Why do you think people spend so much money and time working with flow rates and cam timing/duration.

Even if an engine can only flow a fixed amount of air it still has to have time to get it into the engine, if you only put a minimal carb on then you don't give the engine time to get the air where it needs it when it needs it. So you put a higher flow carb on and now you can get more air in less time and allow the engine to breathe. The better an engine breathes the more power it makes. Period.

The NHRA ProStock class are a great example. They have 500 CID maximum naturally aspirated engines so even if they were running over 100% VE (which is possible) they still wouldn't flow anywhere near 1000 CFM. Yet in order to make the most power they run dual 1000+ CFM carbs on them. Free flowing heads with big valves and high lift, long duration cams require that much flow capacity to get the air into the engine.

 

Sorry but that equation has been around for a long time and it's as bogus as ever. It doesn't consider the pressure drop through the carb that is used to flow test them.While a 600cfm is fine for lightly modified 351 I had better luck with a 750. Even at idle. A small carb has trouble flowing enough air at idle without opening the butterflies enough to expose the transfer slot.
I'm running a 750 Speed Demon that probably flows more like 900 wide open and it's not too much for my setup.

 

You have a fairly well built 351 then because I had a 750 cfm speed demon as well with the 4 barrel intake and it didn't run any better but it did suck in far more gas. I don't believe that these engines need the 4 barrel or a huge carb. I put the stock intake and carb back on and it runs great and the tank goes a lot further. That may be my opinion, but I don't think that you need a 4 barrel intake.

 

The airflow to power situation works both ways. The factory 2V carb works fine with the stock cam and exhaust manifolds. You can't simply increase the flow to the intake side without giving the engine a chance to get the exhaust out quicker as well. Also the 4 deg timing retard built in to the factory camshaft is not conducive to making more power by simply bolting on a bigger carb & intake.

 

I always thought that the 4v was better because it allowed more precise control of the flow of air at lower RPMs, even with the same top CFM. Either way, I did find one advantage to a 4v on an engine that I just built. I replaced the cam as well, but it sounds way better- I can hear it scarf the air now.
That certainly has to be worth something.
I'd have to agree with EGR not adding happiness and unburned fuel; it's dead gas to lower combustion temp, from all I've heard. Spark plugs in tailpipes are only good with exceptionally over-rich mixtures, IMHO. They lost popularity when EFI and plastic bumpers came out.

 

I should have added to check my sig. It's a highly modified 400 but still has a red line of only about 5,200rpm. One nice thing a bout a four barrel is that the front two barrels are generally smaller than the barrels on a 2V. If you tune the secondary springs and keep your foot out of it you can beat a 2V on economy.

It really boils down to your preferences on HP/econ and the individual engine.

And as always, "Everybody's entitled to their own stupid opinon!"

Now that's a joke son so don't jump on me, OK?