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What motor do I have??

in2broncoz

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Feb 20, 2015
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OK...just picked up a 1970 Bronco... the seller only had it for a few months....and wasnt at all car savvy..so asking questions would have been pointless
the oem valve cover decal says 351.....but it doesnt have a flat plate, so...now it must be a 302 type....it is currently timed (plug wire ) in the 351 and 302 HO configuration.... maybe one of the reasons its running like crap...But before heading forward...is there a visual way to tell if its a 302 or 302 HO ??
 

Hotrodjohn

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easy way to tell is the distributor hold down, if near even to intake then 302, the 351w intake is about an inch higher than distributor hold down. The 351 intake is visibly wider too which is easy way to tell if you ve seen a few 302s.
 

triracer67

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Is it running? Firing order for 302HO/351w is different than 302/289. Check the order and google search your sequence.
 
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in2broncoz

in2broncoz

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easy way to tell is the distributor hold down, if near even to intake then 302, .

Well the Dist. hold down is about 1/4" from the bottom of the intake manifold

thought the front of a 351 block was flat, where the 302 has a water pump casing ???
 

sykanr0ng

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Well the Dist. hold down is about 1/4" from the bottom of the intake manifold

thought the front of a 351 block was flat, where the 302 has a water pump casing ???

The front of the 351 Windsor block is not flat, Ford did make more than one 351 engine which can cause confusion.
 

Hotrodjohn

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sounds like its a 302, another clue is the distance between front cover and deck, again about an inch as opposed to nearly even... 351 Cleveland is flat like your talking about on the front. Width of intake is around 9 inch on 302, 11 on 351.
 

Crush

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Alos where the water pump passages are in the front of the block on a 302 will right next to the head and on a 351 there will be about and inch of block between the water pump passage and the head
 

Broncobowsher

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As for a 302 HO (same as a 5.0 HO) it can vary depending on the year of the engine. An '82 HO motor is a standard 302 with the marine cam in it.

As for the different firing orders, that depends on the camshaft. You can switch firing orders on the engine with nothing more than a cam change. Without knowing what cam is in it, you won't know the firing order. The firing order cast into the intake was correct for the engine as it was built, but that doesn't mean anything if parts have changed.
 

SHX669

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I would think measuring across the intake manifold and/ or the oil pan would be a good way to tell the difference.
If you beed to find the firing order remove the valve covers, turn the motor over and watch what order the valves open and close.
 

DirtDonk

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Or the spark plugs. A finger over the #1 plug hole until the pressure builds up shows you when that one is coming up on TDC. As you rotate the crank past that point, the next cylinder to build pressure is either going to be #5 or #3 depending on which cam is installed.

Good luck. Sounds from that 1/4" description that you indeed have a 302 (or even a 289 for that matter!) and someone just grabbed some valve covers off of a 351W to fit.

As mentioned, the 351C and the 351M both have flat fronts and are part of the 335-series engine family. The "Windsor" family (really only the 351 got the name, but since the 302 is the same basic architecture we sometimes use that name for the 302 as well) share the same front timing covers, accessories, and many other things. You can even swap cylinder heads and exhaust manifolds between them, though there are minor differences there too (bolt hole size for one).
Same bell housing bolt pattern as well.

Intake manifold width, deck height (hence the raised rail/ridge above the distributor base), main bearing diameter, oil pan width, and stuff like that are where they differ.
But you can literally throw a 351w cam into a 302 or vice versa and they work just fine.

Paul
 

bmc69

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the oem valve cover decal says 351.....but it doesnt have a flat plate, so...now it must be a 302 type...

I think you are confusing the 351W with the 351C; the latter has a flat steel timing cover. The front of the 351w looks same as front of 289/302 as far as using the aluminum timing cover and same water pump configuration.
 

Broncobowsher

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A couple of pictures would clear this up real fast. Post the up. Don't make assumptions.
 
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in2broncoz

in2broncoz

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Ok...got her running well...
But now opens up more questions??

The firing order used on the intake Manifold 1-3-7....to get it running well
Which indicates 302HO or 351 ?? As stated before the valve cover decal (looking origional) states 351 but could be donor covers. It is not a straight plate front block...has block casting for water pump
 

DirtDonk

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All the 351's used the 137 firing order. But only the camshaft can dictate that, and an old 302 style cam can be installed into a 351 and necessitate using the old 154 firing order for the 302.
The only way you will know what firing order is to either watch the valves in action, feel the compression pressure as it builds up and pushes out the spark plug holes, or just taking it apart to look.

But since you say it's running well on the 137 firing order, I'd say that's a good indication right there. If it was using the wrong order, you'd have half the engine firing out of sequence. And you'd know that right away I would think!

Running well allows you to assume for the moment that it's using the 351 firing order.

It is not a straight plate front block...has block casting for water pump

And the thermostat housing/cover is in the intake manifold facing forward, correct?

Paul
 

Master Chief

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From https://www.fordification.com/tech/engineID-V8.htm

* The 351W has a taller deck height than the 302. (a 302 will have the intake almost flush with the base of the distributor... where it goes into the block..... a 351w will have about 1/2 inch lip there where the intake meets the block.)

* Since the deck height is taller the intake manifold is wider on the 351w than on the 302.

* The 351W uses a larger main journal than the 302. there are 2 physical ways of telling a 302 vs. a 351w. Also, in between the frost plugs on a 351W there will be what appears to be a triangle or diamond (the way I was told) indented cast into the block...a 302 doesn't have those.

* A 351W is wider between the heads compared to a 302 (the intake manifold is wider by about 1-1/2") and 351 pistons have a different pin height. You can use 302 pistons in a 351 if you stroke it to a 393

* Quick ID tip: The lower thermostat housing bolt on the 302 will be below the top of the water pump and you won't be able to put a socket on it. On the 351W you can remove the bolt with a socket.
 
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in2broncoz

in2broncoz

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Well................... the conclusion is 351

tried 302 firing order.....ran but but misfiring thru carb.....re-oriented plug wires and......351
 

Broncobowsher

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Well................... the conclusion is 351

tried 302 firing order.....ran but but misfiring thru carb.....re-oriented plug wires and......351
You have a 351 firing order cam, or a HO cam. On these engine the firing is not a guarantee of anything. Even off the assembly line they were running both firing orders in the same year of 302.

You stated the distributor hold down was only ¼" down from the intake, that says 302.
I still think you have a 302. Did you check any of the other tell tale signs between the 302 and the 351?
 

Attac

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Well................... the conclusion is 351

tried 302 firing order.....ran but but misfiring thru carb.....re-oriented plug wires and......351

Unless you have measured the intake and also the distrib hold down height you can't say it's a 351 because the 302HO has the same firing order.
 
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in2broncoz

in2broncoz

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Even off the assembly line they were running both firing orders in the same year of 302.

"only in america"

this is some of the dumbest stuff Ive ever heard.. they are cool rigs.....but sound like bastard step children....;D

Really dont give a rats ass..its running and running well.. Ill call it a 333 1/3
 
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DirtDonk

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He's not talking about Broncos. Our rigs had the same firing order through their entire run.
He's speaking of the transition from early firing order to late firing order in the early '80's ('81-ish actually) when Mustangs and MAF controlled systems making more power got the 351 firing order first, then the rest transitioned in within a year or two.

Paul
 
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