Best Motor

[sommerbronco]

I am sure this have been discussed before but.....

Is it best to rebuild the 302 or the 351 and is there a ggod list of pros and cons of both?

 

[Bully Bob]

"....302 or the 351"

1st.., are we talking an EB here.., or a FSB..?

Assuming EB..,

That would be for you to decide depending on intended use. Normal use---302. MUD &/or ROCK'N ---351. (but, this req. a lot more parts, time, & $$ than just an eng.)

Both good mills.., but the 351 can be a bit hard to keep cool. (Geography comes into play here as well.)

I guess I'm saying the question is a bit vague > :-B (fill-in your sig. page...& you may get a bunch of answers)

 

[tttgowyo]

IMHO,

Keep your 302 and STROKE it!! 347. That way you can keep the original block, and add some HP without crazy mods..

 

[Orangecrush]

I am sure this have been discussed before but.....
Is it best to rebuild the 302 or the 351 and is there a ggod list of pros and cons of both?

I am running a 351W. Now, I do have a/c, which creates a whole mess of problems that nobody in their right mind would want. I still would vote for a built 302. It fits better. You can do more with it. There are more parts for it. It stays cooler (generally speaking). It gets better mileage.

There you go.

 

[BLADE262US]

LOL I have to ask this why does everyone think that a 351 runs hotter than a 302 ? were not talking chevies here where they over bore the block to make a bigger displacement motor a 302 and a 351 both have a 4 inch bore its the stroke that makes the difference and its only 1/2 an inch . Anytime you take a motor and modify it to make more horsepower you generate heat where do you think the power comes from ? It cost no more money to rebuild a 302 than it does a 351 none . I have done both many times . For a truck I would pick a 351 with no question if you get a chance to tear them both down side by side take a close look at the crank the 302 crank is very light they did this around 78 in my opinion its not a good truck motor it was made for a car . A light car . The pre 77 302,s would make a decent truck motor but I would still pick a 351W . If you have your heart set on strokeing a motor PAW makes a kit to make a 351W into a 427 now that is a motor . /emoticons/[email protected] 2x" width="20" height="20" />

 

[sitting bull]

My 76 has a 1969 351w that stays constant at 180 degrees when running hard. Have even been in a couple long parades of stop and go traffic and no problem. If anything it sometimes runs cooler then normal.

 

[Orangecrush]

LOL I have to ask this why does everyone think that a 351 runs hotter than a 302 ? were not talking chevies here where they over bore the block to make a bigger displacement motor a 302 and a 351 both have a 4 inch bore its the stroke that makes the difference and its only 1/2 an inch . Anytime you take a motor and modify it to make more horsepower you generate heat where do you think the power comes from ? It cost no more money to rebuild a 302 than it does a 351 none . I have done both many times . For a truck I would pick a 351 with no question if you get a chance to tear them both down side by side take a close look at the crank the 302 crank is very light they did this around 78 in my opinion its not a good truck motor it was made for a car . A light car . The pre 77 302,s would make a decent truck motor but I would still pick a 351W . If you have your heart set on strokeing a motor PAW makes a kit to make a 351W into a 427 now that is a motor . /emoticons/[email protected] 2x" width="20" height="20" />

Everyone I've ever known personally, who are running 351w in ANY car or truck (old style with carbs), have at least some problems keeping them cool. I've always been told it has to do with the old stock iron heads, which do not allow for an efficient expulsion of heat energy.

My 351 is out of a '72. Here's my setup:

1) Howe OVERSIZED aluminum radiator

2) 60% water-20% anti-freeze - 20% water wetter mix

3) 7-blade RV puller fan

4) DUAL electric auxilary pushers

5) top air-damn to force all air through the radiator

6) cam timing is set perfectly (rv cam)

7) spark timing is correct, and all combinations have been tried

8) air-fuel is a little on the rich side, but not much

Now, without the a/c on, and temps below 100, I have no problems at all. If the a/c IS on, and it's 95+ outside, even with this setup I can have a bit of a problem in traffic. The only thing left to try is a hood with an operational scoop to allow air to pass through the engine compartment. Many people say that this is a design flaw on Broncos as they never were designed to house big engines and run hot.

 

[Bully Bob]

That's what I thought...... B)

I think O-crush is out here on the "left-coast" somewhere as well. At times, I've even seen 302's struggle a bit.

The only thing I can add... is, I've heard there's a mod that can be done to the intake manifold (in the back)

As I recall, it req. drilling & some hose work. The result is better flow back there...& ultimately a cooler runn'n 351.

Hopefully someone, who has done this, will chime in & confirm/reject this option. >

 

[Seabronc]

There are some real good books out there on rebuilding Small Block Fords. They are written by experts that have years of experience in rebuilding Ford engines and are available at most any book store. I'd suggest you go take a look.

As far as hot running, I have a 351 and it never runs more than 5 degrees above the setting I have for the fan to kick in and then only when the truck is setting still for an long time.

I have been running with an over sized radiator, Lincoln Mark VIII with an Imperial adjustable fan control plus a wheel chair relay to handle the fan current. I also flush my system to keep it clean at least once a year. The engine runs cool enough with that arrangement that the fan only runs around 5% of the time the engine is running. It almost never comes on in the Winter and on the hottest days in the Summer it only comes on when I am below 35 MPH for a few minutes. A few picture of my system below.

Keeping the system clean is a key in keeping it cool since the heat transfer to the coolant is less efficient in a dirty system as is the transfer of heat out of the system by the radiator.

The other problem is that your water pump is least efficient when you need it the most, low RPMs. That is a problem for off roading when you engine is running in the low RPM range for long periods of time and there is reduced air flow through the radiator. I haven't needed to, but one solution to this problem is a full time electric water pump. In both cases, heavy duty fans and electric water pumps, can add electrical load that a stock alternator is not able to handle. The result of that may be shortened battery life due to excessive discharging and recharging. In my case, I solved the electrical load problem by upgrading my alternator to a 130 Amp 3G system. Just a note: the Lincoln Mark VIII fan draws around 100 Amps when starting up and quickly settles down to 35 Amps continuous running current, (the reason for having a wheel chair relay in the system, they have heavy duty contacts that generally rated for 100 Amps continuous. The Lincoln fan would eat up the Imperial control relays contacts). This was not my original idea, I took the information from a couple of Ford Muscle Magazine articles and blended them to come up with my installation.

Here is Orangecrush's post on adding extra cooling by modifying the intake manifold http://broncozone.com/forums/index.php?showtopic=10602

A few pictures of my system: Left to right top to bottom 1. Fan Mounting 2. Fan control covered to protect it (held on by tie wrap) 3. Temperature probe 4. Scematic 5. Over ride switch and fan powered indicatopr light 6. The fan control and wheel chair relay

 

[broncoholic1]

Well I am kinda new here But I just got back from Arkansas and brought a 76 Sport towing a CJ5 on a 18' car hauler. Neve went above 195 even on the hills of the Ozarks.

My new little baby has the best of both worlds. 351w Street Boss Clevor. Now this is a trick setup a widsor oil system with high flow 351c 2v heads. Heads up stroke it to a 427 Clevor and you have a real Yates - Glidden nascar 2v motor real ford stuff. OLD SCHOOL from Bush Performance In Ft. Smith Ark. That is the best Real Ford Stuff!