Skookum 300 4bbl conversion write up - Ford Truck Enthusiasts Forums

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Skookum 300 4bbl conversion write up

 
  #1  
Old 09-15-2018, 01:33 AM
SixerFixer
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Skookum 300 4bbl conversion write up

So after much longer than originally planned on my build up thread has begun lol. My previous thread was very helpful in getting some litle headaches out of the way before tackling this and for that im very greatful to those who chimed in. For those of you just tuning in, the truck in question is a '96 f150 XLT Standard cab long bed 300 L6 M5r2 with an 8.8 running 2:73 rear gears. The conversion entails the use of an Offy C-series intake, a Summit street strip 600CFM carb and an HEI dizzy and some minor head work(more on that later ) Those of you touting fuel injection as the end all be all is fine, but please don't do it here (I'll even ask nicely). No offense, the FI is a good system, but not what im looking for out of the truck. Plus word around the schoolyard is that the 4bbls get better mileage(when feet are kept in positions other than smiles per gallon lol) This write up is going to be as detailed as possible for those wanting to convert in the future. Maybe not quite the same setup, but you get the jist. Stay tuned folks, it's gunna get good.

This ins't my engine bay as my truck is white, but it's one i scrounged off the internet that fit mine to a tee. The photo i had taken of my engine bay for before and after mysteriously disappeared....???
 
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Old 09-15-2018, 04:01 AM
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looking forward to following this! ive considered it myself although the generally problem free nature of the efi in these trucks has kept me saying "well, i dont really neeed it...." but if i remember correctly i think i got better mielage on my 84? seem to remember getting in the high teens. thatd certanly be a reason to do it if it does improve fuel economy.
 
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Old 09-15-2018, 05:26 AM
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Definitely following this!
 
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Old 09-15-2018, 12:28 PM
SixerFixer
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The head is off as well as the fuel injection stuff. As mine is a '96 it's a MAF style intake so if anyone wants some of the FI stuff PM me and we'll talk it over. Difficulties include, removing the EGR valve and either bending or cutting the tube for the EGR valve as they routed it through the runners for the lower manifold for the FI. My EGR valve was rusted to the flare nut so my approach was just to cut it off as I wasn't intending on keeping it. Make sure to take lots of pictures to anyone doing this; as you may remember what you took off and what order it went in now, but in a day or two things start to have doubt. Minor head work is to include using a die grinder to clean up the bowls, smooth em out and get rid of bumps or roughness in casting. Let me just say those heads are freaking heavy! Almost three feet long, and almost 90lbs..... but I digress. The removal of the EFI stuff is relatively straight forward. Vacuum hoses should be the first things to go as the intake cannot come off with them on, the EGR will be the hardest thing to get off as its location is less than ideal to get anything at it to loosen it. It's located at the back of the engine just under the windshield wipers and just behind and atop of the valve cover attatched only to the upper manifold. You can either find a way to loosen that flare nut, somehow find a way to get the two bolts holding it to the intake off, or just cut the tube where it comes through the runners. I went with the latter. I think putting some heat to it and finding a way to fit a pipe wrench on it (you'll have a helluva time finding a wrench that'll be big enough...) that could work, but i just didn't have the patience for it as i wasn't keeping it anyways. There are 7 bolts/studs holding the lower to the upper intake and two ofthem hold the hose for the air pump also. Here's where it gets trickey. to get the lower off as well as the twin exhaust manifolds you gotta find an extension long enough to get your socket in there between the manifolds but also short enough to not have your ratchet in the fenderwell or A/C box. I wouldn't reccomend an impact on these as they have a tendency to break when subject to stress. A 14" long or so ratchet should do you fine to get em off, they're only torqued to 30ft-lbs( a great site with just about every torque spec you'd need for these engines, Ford 4.9L-300ci-S6 Torque Specifications - TorkSpec - Knowledge for the Motorhead) Keep firm pressure and just let em turn. Don't smack on em or you'll break em and let me just say that is not something you'll want to have to undo. The fuel rail is next on our list. THis should be held in with two bolts and relatively easy to just pull off. The fuel lines are metal high pressure jobs so they have a funny looking flared metal over metal connection. These im told need a special tool to seperate. We'll see.... So now that all that FI stuff is off this should be roughly what your engine bay should look like. Minus the missing valve cover i have mine off as the head is coming off. There's no need to take the head off to do the conversion, It is a great thing to clean up the bowls and ports but the work to remove the head and keep it on something to work on it is imense.
 
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Old 09-15-2018, 01:08 PM
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Here's my diamond in the rough without the head on. Looks a little funny with no head or push rods. Ended up having to clean almost all of the coolant passages in the head and block as the previous owner said he had a leak where the heater core hoses went into the water neck so he pulled off the temperature sensor and tube put a pipe nipple and cap on and shoved a piece of wood in the heater hose. He never paid attention to the coolant condition either and the coolant was very brown....... the heater hose looks like a cave inside with stalagmites and stalactites.... so all that rust and schmoo was clogging all the cooling ports not the passages thankfully, just the ports so they were easy to clean out. Anyways lol, cylinders were in impeccable shape with very obvious crosshatch on all of them. Yay!!! 203,000 miles and still crosshatch.... gotta love these old sixes, built like tanks they were.

 

Last edited by SixerFixer; 09-15-2018 at 03:35 PM. Reason: Forgot photo
  #6  
Old 09-15-2018, 01:45 PM
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Well, won't hammer on ya for the downgrade but I'll put this out for discussion; a 4 bbl bigger than the 390 cfm Holley list number 0-8007 is really too big for your application. Keep in mind the original carbs used by Ford were about 265 CFM 1 bbl and really, they were plenty big enough for stock applications. Unless you're planning on porting the poop out of the head, raising compression and adding a cam and headers, that 600 CFM 4 bbl is too big. A better choice would be a Holley List number 0-7448 350 cfm 2 bbl. I've used one on a short track iron head 351 windsor when the track surface situation was slippery. Never ran out of carb and that was using an iron intake.

Just some things to consider.
 
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Old 09-15-2018, 04:43 PM
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Originally Posted by raystankewitz View Post
Well, won't hammer on ya for the downgrade but I'll put this out for discussion; a 4 bbl bigger than the 390 cfm Holley list number 0-8007 is really too big for your application. Keep in mind the original carbs used by Ford were about 265 CFM 1 bbl and really, they were plenty big enough for stock applications. Unless you're planning on porting the poop out of the head, raising compression and adding a cam and headers, that 600 CFM 4 bbl is too big. A better choice would be a Holley List number 0-7448 350 cfm 2 bbl. I've used one on a short track iron head 351 windsor when the track surface situation was slippery. Never ran out of carb and that was using an iron intake.

Just some things to consider.
I thank you for not pushing the FI thing, With all the research i've done on these beauties the group consensus over at FordSix.com, and The H.A.M.B (aka Jalopy Journal) is that yes 600cfm is a bit too big for an otherwise stock 300, but with vacuum secondaries it'll only draw as much as it needs. With some left over for future upgrades. You say that the stock one barrel of around 200-250cfm was plenty good enough for a 300? Well when you do the maff it checks out that a 300 is best suited around 390cfm which is why everyone is so pro Holley 390 along with the dual port. The 390 is a good carb and all, not one of my personal favorites (sacrilege i know, lol) but many have noted better fuel economy and better power from an eddy 500, 600, or even the few that have done a Summit 600 like mine. They all report back that throttle response with the Summit 600 is a night and day difference to anything else even the stock fuel injection. Annular boosters. Gotta love 'em. These engines love fuel/air and they were quite malnourished from the factory even in FI form. With a little work these things eat V8's for breakfast. Put a 1bbl off a 300 on a 302 and see how it runs. Probably wont be very impressive. The 300 is 50 cubic inches per cylinder vs 37.75 cubic inches for the 302. Wouldn't that mean it would need more fuel/air???? hmmmmmmm..... no hard feelings, or ill intentions, just wanting to stop the stigma that these poor undercarbed engines deserve the little fuel/air they get cuz "it's all they need". Discussions are great, they help bring about all kinds of info for people to learn. If you have any evidence of me being wrong please, by all means let's see it and ill go sit in the corner with my little dunce cap on. I'm no expert on these engines by any means, but i have read and talked to many people that are, and this is what they say. lol Yeah you can run a small carb on an engine that wants a bigger one and get away with it. Will it work? Yeah, but it won't be working to it's full potential. Just food for thought.
 
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Old 09-16-2018, 01:52 PM
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Head is back on, i wish i would've remembered to take some pictures of the head before and after cleanup but i just got so excited to put it back on that I forgot. Whoops... Well the head work done wasn't anything to write home about just taking a die grinder and some conical stones and cleaning up the bowls, making them noce and smooth polishing em up a little bit and cleaning up around the valves. The ports were just gone through and cleaned up smooth no polishing or port matching or anything of the sort. Just a nice clean up. Didn't remove the thermactor bumps as the A.I.R injection rail is still attatched to the head. Those stupid little plugs wont back out and just start crushing. What really sucks is that the power steering&A/C bracket had shifted when the head was taken off so when it was being put back on the dowels wouldn't line up enough to seat. A little persuasion with a prybar got it over enough to seat but the persuasion was apparently too much as the bracket broke.... bummer. The dizzy is in as well. It's nothing fancy like the DSII or the Durasparks, its an Ebay special from a reputable company that made in my book a pretty good product. Feels solid, looks good, oil pump shaft fit right in and dizzy dropped right in place nice and snug. Its a Ch*** stlye dizzy HEI coil mounted unit. 65k spark so it should be plenty hot enough. Now with the coil upgrade you're supposed to gap the plugs to .0050" so as the spark isn't wasted being squashed in one little spot. Another road block I stumbled into was the fuel system..... Being as my truck is a FI job the in-tank pumps put out about 45-50psi which is way way too much over the 7psi max the carb needs. So in my last thread i had talked about this, asking about possible solutions. We came up with a good one, using a little jigger pump mounted to the frame rail to suck the fuel through a Standard FV1 single acting fuel selector valve and just letting it suck through the in-tank pumps. Unfortunatley that plan hit the fan rather quickly as the metal fuel lines wont work very well with the hose barbs on the selector valve and fanagling it in there won't look very good, nor would it hold up very long. So against my original plan of not using a fuel pressure regulator and using the in-tank pumps, I am now having to do just that. The connectors for the HP lines to hose barbs don't exist at least not for both of them. The plan is to run straight threaded end connectors from hoses straight into the return line side of the regulator, and a 90* for the supply as this will be mounted on the firewall just up and to the right or directly above the valve cover. That is still undecided. This will give the exit supply line a straight shot to the fuel rail on the carb. The carb and manifold are hooked up but not completely as i just wanted to hear it running, so a jigger pump and fuel hose to a 2 gallon gas tank later the engine does run albeit doesn't want to idle any lower than 2000rpm and it's like standing next to a jet spooling up in terms of loudness. Need a second pair of hands to hold the intake while i manuver the exhausts and run the bolts in. So for right now the exhaust is wide open at the ports. Video to come of it running, just want to get the manifolds hooked up all the way so it doesnt sound like nails in a blender performing at a rock concert. lol
 
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Old 09-17-2018, 05:26 AM
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A comment on that 600 cfm carb; what you will be running 99% of the time will be a 300 cfm 2bbl, since you probably can't build enough vacuum to open the secondaries against the supplied secondary spring. Until you raise the compression and add a better exhaust system, you're not going to use the full potential of that intake/carb system.

I've done my penance with both small and large inlines from Ford. The head is the major restrictor for all inlines and this is proven by the small six having an aftermarket aluminum head for it that has better ports and valves. It's unfortunate the aluminum head for the big six never saw the light of day because that's what's needed to make good horsepower. The small sixes also have [email protected] exhaust ports with that insane shared middle port for 3 & 4. I was going to order the aluminum head for my '66 Fairlane until I sold it on. Now that I'm retiring, I'm on the search again for a inline six early 60's Ford to have fun with.

The inline build before the Fairlane was a '67 F-100 Bumpside standard cab short bed with a 300/C4 combination. It was fully blueprinted, Clay Smith street performance cam, big(!) valves and portwork, Duraspark Ignition, Clifford headers and intake with a 390 cfm Holley. It was a fun truck to stripe the street with and I did try several other 4bbl carbs in search of more power. I tried a 600 vac sec list 0-1850 and a 660 center squirter off of my boat for grins. Both were not as crisp as the 390 cfm carb. Chassis dyno said 225 hp, 350 lbs-ft at the rear wheels. The 600 gave about seven more hp and ten tq but it wasn't worth the trouble to live with the reduced throttle response. Let us know how that 600 works out for you.

As a point in case, the early 289, just 11 cid shy of your 300, ran just fine with a 240 cfm Ford/Autolite 2100 2bbl. I will caution about most of what floats around the 'net concerning Ford inlines. Clifford 6=8 is a great source for what's what for our inlines and I would peruse fordsix.com for information in the big blok six area.

Anyway, just my $0.02 USD worth. YMMV.
 
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Old 09-17-2018, 03:03 PM
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Following this. Let me know if you have any spare FI parts laying around.
 
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Old 09-17-2018, 10:14 PM
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Following this too.

If you part the stainless fuel lines, I'd be interested.
 
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Old 09-17-2018, 11:32 PM
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evan_nugget, yeah all the fuel injection stuff is going. What did you want off of it? I've got the MAF unit, throttle body, upper and lower intakes, fuel rail, fuel injection computer...etc pm me and let me know.
timbersteel, the stainless fuel lines will be kept as running new hoses would be anti productive being that for my pressure reg i need a return line. Why not just use the ones that are already there instead of running new ones right?
Speaking of the pressure reg, it finally arrived. Just gotta get the adapters for the spring connectors to attatch it to the hard lines. Still waiting on putting the manifolds back on completely as i have a friend coming over tomorrow to lend in hand in doing so. While test running the engine today it doesn't want to run any less than 2000rpm and has an off sound to it as though it has a miss. Replaced the spark plugs today hoping it was just that the plugs were old and needed replacing anyways, but no that didn't seem to be it. More than likely my issues are stemmed from the intake not being 100% sealed against the head it's on there with a couple bolts snugged down just to keep it on there and is fairly flush and snugged up, but not torqued down with all the bolts so not a perfect seal yet. Will wait till tomorrow when all the manifolds are all on and torqued down to see if there's any improvement.
 
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Old 09-18-2018, 12:56 AM
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Evan has 1st shot on the EFI stuff.

If he's not interested in the air box, snorkel, and the hoses from the air box to the TB, I'm interested.

And no problem about the fuel lines. I didn't know if you were going to keep them or route new lines for the carb.
 
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Old 09-18-2018, 01:02 AM
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Originally Posted by SixerFixer View Post
evan_nugget, yeah all the fuel injection stuff is going. What did you want off of it? I've got the MAF unit, throttle body, upper and lower intakes, fuel rail, fuel injection computer...etc pm me and let me know.
timbersteel, the stainless fuel lines will be kept as running new hoses would be anti productive being that for my pressure reg i need a return line. Why not just use the ones that are already there instead of running new ones right?
Speaking of the pressure reg, it finally arrived. Just gotta get the adapters for the spring connectors to attatch it to the hard lines. Still waiting on putting the manifolds back on completely as i have a friend coming over tomorrow to lend in hand in doing so. While test running the engine today it doesn't want to run any less than 2000rpm and has an off sound to it as though it has a miss. Replaced the spark plugs today hoping it was just that the plugs were old and needed replacing anyways, but no that didn't seem to be it. More than likely my issues are stemmed from the intake not being 100% sealed against the head it's on there with a couple bolts snugged down just to keep it on there and is fairly flush and snugged up, but not torqued down with all the bolts so not a perfect seal yet. Will wait till tomorrow when all the manifolds are all on and torqued down to see if there's any improvement.
I think once you have the manifolds torqued, the idle issues will resolve themselves. Take it easy when you torgue up that big, long manifold; they are real easy to warp if you don't work center out on them.

 
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Old 09-18-2018, 07:41 AM
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Well just from running it so far it seems to be much healthier and the throttle response is incredibly crisp. Before this the engine wouldn't turn past 4300rpm, but just with quick blips of the pedal it goes to 4500 and would probably go past it but i don't want it shedding piston skirts. Honestly it seems like it wants more. It definitely would rev to 5000-5500 no problem. With the stock cam and stock pistons im not going over 4000 with it, and probably won't see much over 3000 unless i want to put some punk in his place at the red light. lol A cam upgrade is in the forseeable future, but with my very tight budget the best i can do is an exhaust upgrade. Dual 2.5" exhaust with a Flowmaster 40 muffler and twin chrome tips exiting under the rear bumper. Should look very nice, and sound even better. Will post a video of exhaust once it's welded up in place. You're absolutely right on the manifold torquing. Gotta go inside to out, just like with the head bolts. Hence why i need an extra pair of hands, Holding up the intake, while positioning the exhausts, and running the bolts in all at the same time is very hard to do with three things to do and only two arms. More progress on the way.
 

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