I may be able to pick up a runnable 1985 351 HO, and by "runnable" I mean it doesn't but is supposed to run. (Yes, Ray & Paul/RW, it is one of the today's "finds".) Given that I'd like to know more about them.

I've searched the forum and read up on 351 HO's but still have some questions. First, my understanding is that they came w/a Holley 4bbl but otherwise the engines were standard 351W's: cam, pistons, rods, heads, valves, etc. And, they have DS-II ignition systems and cat's since this is an F150.

So, does that mean they don't have computers? If they do have, what does the computer run?

 

No computer at all. Holley 4 bbl and DS2. I dunno if there's any real differences between the HO and a regular 351W, aside from the carb and DS2, but they were decent running back in the day. Most were backed with a C6 and 3.50 gears, which helped to give the impression they made a lot more power than a 2bbl with the DS3 or TFI ignition.

 

Tnx. Sounds like a good candidate then. The guy said it just quit running and he thinks it is the pickup in the dizzy, and I have a newish dizzy in my engine. Think I'll check the MPC and try to figure out if the cam is standard, but would probably put the Comp Cams one in there while the engine is out. And, the life-time warranteed water pump and alternator.

So, did the HO's have the thermactor system? Without a computer what switches the diverter valve? Gotta go see this thing!

 

The HO got a 4bbl carb and intake and an old marine grind RV cam so it did actually make more HP than the plane jane motor from the same era. But just like every Ford truck ever built the stock exhaust is a complete cork and replacing it with just about anything else will release another 20-40hp.

 

So, going w/dual exhaust would help as it would eliminate the bottleneck in the cat. I'm sure headers would be better than the manifolds, but they don't look too bad.

What about a crossover pipe in the exhaust - all the duals I've seen have been separate but it would seem a crossover or h-pipe would help the flow. Or, are things so confined that you can't really get one in there?

What about the heads - how restrictive are they with the thermactor bumps in them? I could grind those out if, as it looks, they are very restrictive as I have 3 of the D8OE's sitting around.

 

I don't know about the thermactor system. As for the diverter valve, not sure how it is setup, but even my 80 300 has this valve. It's vacuum controlled, that's all I really know. My pump never had a belt on it, and the AIR check valve broke off at the ex manifold so I put a pipe plug in it's place. Also have no cat and a full 2.25" pipe with FM 40.

Conanski's post reminded me, they did have a slightly warmer cam than the 2bbl version. IIRC, they had slightly different heads too. Not sure what the difference is though.

The stock HO cam is not going to be quite as warm as the comp 260, as it still had to pass EPA testing.

As for "it just quit". Could be ignition related, could be timing chain, or could be fuel system. I believe they still used the fiber tooth cam gear. If the gear went "hillbilly" and lost it's teeth, the dist wouldn't turn, nor the fuel pump drive or cam.

 

The old motors had a wonderful butterfly valve just downstream of the passenger side exhaust manifold that often seized in the worst possible position.. closed or nearly closed. I believe it was part of the heat riser system or EGR, but whatever the case if you're doing the exhaust delete it. The crossover tube on a dual exhaust system does help low rpm scavenging which improves TQ so it's a good idea to include one. There is an old trick I have heard about where you paint the head piped a couple feet back from the headers/manifolds and then start the motor and get it warmed up. The place where the paint burns off first is where you place the crossover tube.

351HO cam specs are 206/221 duration at 0.050" and somewhere around 260/270 seat-seat, and 0.444/0.452" lift. The 2bbl cam only produced 0.416" lift and 260 seat-seat duration for comparison.

Heads were the same on both motors, and while they aren't anything too great they'll flow well enough for about 275hp with a decent exhaust system. It's not worth the trouble of swapping on anything similar.. ported or not since all the smog era heads('78-85) have massive combustion chambers, if anything look for a set of GT40s from an '96-97 Explorer(not GT40p), they flow about 20% better and will also bump compression up to about 8.8:1 from 8.3:1 with the stock heads.

 

When I did the H2O pump on my 86, I checked the timing gear and chain. Steel cam gear, double roller chain.

 

It's possible the HO was factory double roller chain, as I recall hearing someone else mention finding one in their HO.

Gary, that Lariat have dual tanks? Maybe it suffered from the same thing as Ray's truck, selector valve issues....... Just a thought.

 

Comp Cams says the spec's on my cam are 206/212 @ .050" and 250/260 seat/seat with .0461/.474" lift. Timing is -3/29 intake and 40/-8 exhaust at .050". Looks like the HO cam has longer duration but less lift. Wonder if it would be worth it to swap cams?

At the least I'd want to put the degree wheel on awa the dial indicator and check to ensure it has the HO cam. And, I'd put the Comp Cams timing chain set on since it's got less than 1,000 miles on it - just like the cam.

Yes, the pic's show it has two tanks. Seriously thinking I'll bring it up and wake it up in the shop - inc known good fuel, maybe from a bottle. Make it simple.

 

Ah, you have the comp 250. I was thinking it was a 260 for some reason. Hard to say which will give the better HP/TQ numbers or better MPG. Both should yield near the same emmissions though.

As for the "KISS" (keep it simple, stupid) method, if the HO still has the holley, they make it really simple with the bowl vent in the top....... Pull side plug, and dribble fuel into vent, stopping when it starts to dribble out the bowl plug.

BTW, did I see a pic of an edelbrock 1406 (600 CFM electric choke) among the "Finds" album? Might be a good option to top that HO off with.....

 

The XE cam likey has tighter LSA so it'll make more TQ.. and that's want you in a truck presumably.

 

Yes, it is the 250. Gives response from 600 R's, and they were truthing. Throttle response was quick. Liked it a bunch. So, if the HO's cam doesn't have the spec's shown above I'll swap, and may do anyway while its on the stand - assuming it runs in the '85.

And yes, the Edelbrock would be a good one for that engine - especially given the probability that the bowl gaskets are shrunk on the Holley and your awa my history w/Holley's. (Ray - Note spelling: Holley. Am assuming the proper spelling is w/o the "e" - right?)

Here's my thinking:

1. Drain & refill engine oil
2. Change oil filter
3. Top up cooling system
4. Check tranny lube - just to make sure it isn't dry
5. Rig up fuel source
6. Check carb for expected bowl leaks! Swap Edelbrock/Carter on?
7. Pull dizzy and spin oil pump
8. Replace dizzy - with the original or my known-good one?
9. Replace spark plugs
10. Crank it
11. Repeat diag's until it starts and runs
12. Warm it up thoroughly
13. Run a leak-down test
14. Assuming it is reasonably good, pull it out
15. Put it on the stand and clean it up
16. Pull valve covers and run the cam timing test
17. Make decision on replacing cam
18. Replace valve cover gaskets
19. Roll it over on stand and pull oil pan
20. Check main and rod clearances
21. Replace rear seal and pan gasket
22. Put it in the Explorer

Input welcomed.

 

Sounds like a fairly reasonable plan of attack to me.

I am guessing you know to make 100% sure that each lifter gets returned to it's original cam lobe, and the "tricks" used to keep them in order, so I won't even go into any details unless needed.

As for the spelling question, the one in my closet has "HOLLEY" cast into both float bowls, so I assume the "E" is 'sposed to be there......, unless I got a chineese made imitation.......

 

The spelling is an inside joke: My daughter's name is Holly as is Ray's wife's name.

Speaking of lifters, I'm thinking I "lost" the cam in the engine that was originally in the Explorer when I started it w/o priming the oil pump. But, the HO's been sitting quite some time as well. Is priming the pump going to put lube on the cam or do I need to pull the intake and pull/lube/replace each lifter?