Well it's that time. The engine in my 67 f100 2wd is tired. The question I have to ask myself is do I rebuilt the original 240 backed by NP435 or rebuild the 351W that had a C-6 out of a 79 van. I will be keeping the NP435. I honestly am leaning hard towards the 351W. I know many people have swapped from the six cylinder to the 289,302, and 351W. My question is what changes as far as parts will I need to make the swap successful. I know I'll need a set of small block engine towers. Can you guy help with what else I will need before I get started. I just want everything I need here before I get started on the swap. I'm thinking a different flywheel, clutch, and starter might be needed. I'm not sure. Does anyone know if the clutch linkage from my six cylinder will work with the V8, or do I need to find that also.. What do you guys know?
Thanks Joe.

 

What is your budget overall and do you really want/need a high revving V8? Are you doing the work yourself or with a shop/mech? I am a bit biased but I'd say keep your I6 or get a cheap 300 and soup it up with a manifold and a sniper!

 

The clutch/linkage and bell housing will work. You will need mount towers off a 69-72 for a small block, an 11" flywheel for a small block 28 oz imbalance. If you have the HD towing radiator for the six cylinder it will have three rows of flues. If it does you can use it. If it only has two rows. but still has the wide tanks a radiator shop can put a 3-row core in it. The carb linkage is the only other problem I remember because it will be on the wrong side of the carb.

 

Steve it's not really about the the high revving v8 as I am more familiar with v8s Windsors. My experience with straight 6 engines is they are reliable but kind of dogs when it comes to power. I'll have a local engine builder do the machine work and put it together, but I'll be installing it. ect. Looking for a good sounding duel exhaust v8.

 

I forgot about the radiator. thanks. Mine is real small. Do you know if anyone makes a re-pop stock looking 3 core radiator? As far as the linkage goes I'm thinking of just going with an aftermarket setup.

 

Steve. I was told that if I'm going to rebuilding the six find a 300 bottom, and use my 240 head. People say that's a better combo.

 

It'll sound louder for sure. I have heard that a stock 300 vs a 351 you can't really tell too much unless you're annoyed with getting up to speed while towing or have a heavy load. I've driven both 300s and 351ws with the same rear end and it's actually kinda hard to tell the difference empty because their torque numbers are pretty similar but the 300 hits it a bit lower in the revs.

The 240 will struggle to get up to highway speed depending on the rear end though, maybe that's your trouble or it just needs a rebuild. I'm concerned that your tired 240 might have soured your I6 experience. How far gone is the current 240? Has it been tuned up and checked over for stuck valves or timing? Does it run rough? Have you run a compression or leakdown test? There's very little to go wrong on the I6s that it's pretty easy to tell if there was a specific set of issues or are you looking for an excuse to go V8.

@Red69 seems to have the full list from what I've seen except I think there's something about needing a clutch bracket since the I6's clutch linkage screws into the side of the block vs the v8 bracket bolts on using bellhousing bolts. You'll also need the transmission plate from a V8 because the starter is in a different place. The perch swap and the clutch should be the hardest part but it's still going to be a good bit of work for not a whole lot of gain imo unless you're also going to mod a 351w up...again unless it's a work truck or a street mod. Just a crusier, a proper 240 or 300 is real nice as long as you aren't looking for the loud V8 sound.


Yes, the 240 head has a smaller chamber so you'll have more compression. If you end up rebuilding a 300 with your 240 head, make sure to get a decent head gasket.

 

For perches, you use perches from 69-72 302 trucks and 73-79 302/351M/400 equipped trucks. Or buy new ones from Autofab:
https://autofab.com/product/65-79-fo...-motor-mounts/

 

Well I'm going Thursday to see what the engine builder suggest. Sometimes I just think that if you're put money into a 6 why not just do a v8. If I can find a 300 around here in Wisconsin maybe I'll go that route. It would be nice to keep it stock appearing. I hear the the 300s are everywhere. Maybe I'll start looking around for one.

 

66f250 If you keep the 6 you need to check out a company called Clifford Performance. They have pretty much wrote the book on everything that you need for a 6.

 

 

@Steve Mellen so you got me thinking with that video you posted. For what I'm trying to achieve I think a mild built 300 would work out great. It's going to make swapping a lot easer. So is there a certain year 300 that's more desirable than the other, and what years did they come duel exhaust manifolds? BTW I want to keep it carbureted.

 

This time last year I swapped from an EFI 300 to an EFI 351W in my '91 F150 (daily driver), and the difference is night and day. I can't really say anything bad about the 300 other than it was slow, but I enjoy driving the truck so much more with the 351W.
Also, I typically got about 15 or 16mpg with the 300 and I am getting the same with the 351W... I actually got 16.5mpg the last two tanks!

To be fair though, It's not exactly an apples to apples comparison. The 300 was fairly stock except for some mild port work to the head, and smog equipment delete. The 351 has GT40 heads, shorty headers, 1.7 ratio roller rockers, and a ported intake.

 

The late 80s and 90s EFI 351ws made the spread larger between the 300 in terms of HP especially when modded. In my experience earlier stock carbed 351ws didn't make THAT much of a difference in driving feel unless you needed to overcome the power to weight deficit while at speed towing or hauling heavy loads near the GWVR rating. And to be fair, they never have a problem towing or hauling, they just to it slower. I am surprised that you only got 15 mpg with the 300. I used to have a pretty leaky one and it still got 18 and most get around 20. Here's from the 90s F150 but remember this was post EFI!!


I agree, and swapping is dead simple this way. The only difference really from 64 to 86 was carbed and 87 to 96 was EFI. The exhaust manifolds are the 2-piece on 87 or later but will work with mild modifications on to the stock log intake or any of the aftermarket intakes. You can get some at a yard easy enough they were on every >87 300 (check vans too). Even Dorman makes them but fitment might be off requiring more grinding.

My understanding as that there really isn't any "better year" because they're the same from 64 all the way to 96. I don't think anyone has mentioned this yet but the only difference between a 240 and a 300 is the stroke. So if you got a 300 crank and rods, then your "240" is an ideal "300". The cam is even the same (replace the timing gear with a non-nylon coated gear if it's worn).

Over the years, there were some slight changes to bearing clearances, valve guides, gasket changes, some extra bosses for accessories, or slight coolant ducting improvements but nothing performance if you're sticking with a carb. In 87 with the changeover to EFI they removed the mechanical fuel pump provision and also made changes to the head kinda like the 240 head upgrade--they are different for a slight boost but I've never worked on an EFI--I'm 90% sure they are literally all the same pre-EFI. You can definitely ask the question over at the Inline 6 forum instead for more details--there are a few really knowledgeable guys there. You'll see different specs through the years because they changed from gross to net HP and some smog stuff affected performance.

But that series really shows how much of a difference it makes with as simple bolting on an aftermarket intake with a matching carb. Fair warning S&D as had those manifold costs jump because of that series popularizing the upgrade and current supply chain issues too probably so plan accordingly for costs/timing.

Ideally I'd take an existing block (only use an EFI block if you don't need a mechanical fuel pump especially if you're going Holley Sniper since you'll have to get a high pressure pump anyways), add an aftermarket Offenhauser C series intake and EFI exhaust or Headman headers. Then either single factory muffler (Dorman makes one cheap you can get from O'Reillys) or custom dual glasspack exhaust if you want some sound like this . Then match your carb to the intake...or since you're in WI, get a Sniper for dead simple tuning/starts and if you never want to tune again, a pertronix 1 or 2 (not 3) to replace your points. All of this is bolt on and I haven't done this all yet myself since my manual choke Carter YF works great in temperate NC, but I plan to grab a manifold and Sniper when prices hopefully come back down. This whole package is very common especially after the engine power episode series. Again, I'm heavily biased towards this solution and it's nice to have something different but not too far from stock. I'd take it over a V8 any day.

Biases aside, probably best to go with whichever good donor you can best find.

 

Very true. My 300 served me well from 1996 (when I bought the truck used) until last year. It always towed/hauled just fine and was very dependable...just slow.
I'm not trying to put him off of the 300...just sharing my experience going from 300 to 351.