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Discussion Starter #1 (Edited)
New guy here. I have a 1971 F100 that a previous owner dropped a 400/C6 combo from a '72 Galaxie/Custom/LTD into. The truck is in great shape, but the motor seems a little tired.

I've been reading the treads here (and elsewhere) about the 400. First thing on the list is to pry off the old manifold and put in a set of headers along with a new exhaust and a set of Cherry Bombs.

Obligatory pics:



 

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Nice looking truck. That Competition Blue is one of the best colors ever made.

I am a big proponent of the 400. And true one of the best ways to hop them (or any engine) up is to allow better breathing via better intake and exhaust. (Though I would recommend Dynomax Turbos and not Cherry Bombs.)

But if you engine seems tired, those bolt-ons might not be the "first thing" on your list. What I'm about to list is true of any engine, not just the 400.

First off you should do a compression test, or even better, a leak-down test. That will tell you how well the valves and rings are sealing. Secondly, pop off the distributor cap. Put a 15/16 socket on a breaker bar and rotate the engine clockwise via the crank pulley nut. Now rotate CCW while watching the rotor on the distributor. If the rotor lags instead of moving immediately as you change direction, then your timing chain is shot. Finally, how's your oil pressure? If it drops really low at idle, it's probably bearing time.

Getting the timing, sealing surfaces, and bearing surfaces up to snuff always takes precedence over bolt-on power adders. It might be time for a rebuild.

If your compression is down due to ring/cylinder/valve wear, it doesn't matter what you bolt onto the engine. It will always seem tired. Same goes for a sloppy old timing set. A new double roller timing set alone with a 4* advance keyway will snap some life into your engine. Ideally replace the cam along with the timing set since you're in there if you've got the cash. That would really make the intake/exhaust bolt-ons effective. But if you don't have the $200 for a cam/lifter set, still spend the $45 on a Comp Magnum timing set or equivalent. It allows you to correct the retard in the factory cam and gain a lot of torque.

As far as headers, they are made for late 70's trucks that came with the 400 as factory. Would they fit the 67-72 chassis? Never tried it. I do know that that chassis is a couple inches narrower than the 73-79. That might cause some fitment issues. But I'd say that the headers meant for the 73-79 frame would be your best bet as a start.

Hope this helps.
 

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Discussion Starter #3 (Edited)
Thanks for the advice, and letting me know about the timing set.

I'll have to pop the valve covers off to take a closer look, but I wouldn't be surprised to find the valve seals shot. the motor also has a nasty tap and occasionally pops (with a corresponding hiccup in power), especially when it's cold. It sounds to me like a misfire in the intake or carb.

As far as oil pressure, I'm not positive the gauge is working.

I was thinking headers and pipes because the pipes in it now are rusted and full of holes to the point that it heats the floor of my cab enough that it almost burnt my wife's hand when she tried to get something out from under the seat.
 

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The pop/misfire you are describing is classic worn timing chain.
 

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Discussion Starter #5
Just did a check of the dizzy response and put a compression tester on it. The dizzy looked fine and the compression numbers are (from #1-#8) 95-115-100-105-110-90-95-90; within the tolerance that my Ford BB engine rebuild book gives (no cylinder below 75% of the highest reading).

I put a light on it and it seems the advance slipped from 8* to 2*. When I adjusted it back the motor ran a lot smoother (go figure) with less tapping.

My oil pressure gauge reads consistently low, which makes me doubt how well it's working. The aftermarket vacuum gauge stays steady.

I don't have the $$ for the cam right away, but the timing set is something I'll definitely get.
 

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Discussion Starter #7 (Edited)
Nice looking truck. Not a fan of 400 so I should keep it to myself. I have Cherry Bombs on mine with 390 and I like the sound. I had a 1979 460 customers truck here the other day with glass backs and I could not stand it, it was way too loud.
Nice! I mentioned to my neighbor about the Cherry Bombs and he offered to give me his used Flowmaster 40's he pulled off his Camaro. Can't pass up that price, y'know?
 

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Yeah, having the ignition timing at only 2* can really kill the power and induce misfires.

The nice thing about replacing the timing set on a 335 Series engines is that the timing cover is just a flat plate of steel. Much less of a hassle than small block and 429/460's that have a million things bolted to or through a soft aluminum cover. You should be able to do a timing swap with the engine in the vehicle.

I'd get an inexpensive mechanical oil gauge to give you a better idea there. That's a critical bit of information to have accurate.

90-95 lbs is starting to get a little low for compression, even in an 8.0:1 engine. But if your oil pressure turns out ok, you should still be able to get quite a few miles out of it before a rebuild becomes a necessity.

But if your oil pressure is dropping to 5 or 10 pounds at idle once you get an accurate gauge hooked up, I'd say rebuild time is now.
 

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Discussion Starter #9 (Edited)
Drove it into work today and noticed a marked difference. There's still a tap, but not near as bad (perhaps because of the exhaust leaks?) but no pops or hiccups. And I have more power.

I'll probably do another compression test tonight with the better timing to see if the numbers improved.

The timing set is still on the menu.

Speaking of 460s, my neighbor also has a block + internals he's looking to get rid of. I may take it off his hands for a future swap.
 

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Ignition timing does not effect your compression. Only the condition of your valves' face/seat and the rings/cylinder wall effect how well your engine seals. (And maybe the spark plug threads but that's not a wear surface and rarely a culprit.) So no need to do another compression test.

Glad the advance in ignition timing helped. I prefer to run engines with as much ignition advance as possible without pinging. It helps with torque and makes them run a little cooler. Advancing the valve timing with that Comp Magnum set will have an even greater effect.

If that 460 is in rebuildable condition and cheap snap it up. I love 460's too. But keep in mind that a 400 is already more engine than needed for a 1/2 ton truck's payload and trailer capacity. When properly built and tuned, a 400 will use less gas than a 460 and is much lighter. But if you just want insane unbridled power, no engine holds a candle to the potential of a 460.
 

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I replied to your PM. Here are some close up pics of the engine with just the water pump on. Not much to removing the cover on a 335 Series. Sorry, don't have any pics with the cover off.








And here's a couple pics of the obvious advantages of an Edelbrock Perf 400 and some Hooker 6914's over stock pieces. This is the engine currently in my 79 F150 Ranger. The measurement at the rear flanges of the Hookers was 22.5" O-O and 14.0 I-I. Maybe you can measure between your frame rails to see if they'll fit. Even if it's close you could likely tweak them a bit to work.






You can see how much larger the plenum is in the Edelbrock unit. I usually paint aluminum manifold Ford blue for the stealth look. Same goes for the "400-2V" decal on the air cleaner. Leaves a lot of folks scratching their heads how an old "boat anchor" 400 just ate them for lunch. You have to look close to see the Autolite 4100 isn't a 2100.
 

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Discussion Starter #14
Yanked off the timing chain today. A few pics and notes:

- the water pump is rusty and filthy. What you see is what it was like when I yanked it off. the motor has been running pretty damn hot, so I plan to replace the water pump and thermostat, and while I'm at it the fuel pump.

- the timing chain was pretty loose, as you can see. The chain fell off the gears before I even got them off.

- there's some burnt-smelling sludge on the side of the motor. I'm thinking it may be a good idea to drop the oil pan and clean it out along with the oil pump screen (may be a cause of my low oil pressure?)

Pics:





 

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It looks like your cam is walking out to the front and rubbing pretty good on the cover. I would also do the water pump and t-stat but you may also want to get the radiator rodded out too. That may be a big problem with it running hot. On that old of a truck you may not know what was ever done and if anything was ever replaced. Maybe just a tune up may help alot.
 

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Discussion Starter #16
It looks like your cam is walking out to the front and rubbing pretty good on the cover. I would also do the water pump and t-stat but you may also want to get the radiator rodded out too. That may be a big problem with it running hot. On that old of a truck you may not know what was ever done and if anything was ever replaced. Maybe just a tune up may help alot.
What can be done about the cam walking out short of a rebuild?
 

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Discussion Starter #17
Something else:

Got the oil pan off an what I found on the bottom was a bunch of broken, plastic gear teeth. Can anyone hazard a guess as to what they are from? I'm hoping they are pieces of an old timing set that a previous owner didn't pull out of the pan.





 

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Should be a keeper plate that is behind the timing set that hold the cam in. Maybe the depth of the gear set has your fuel pump ring pushed out to far. Just looks like a lot of wear to me. Maybe more of these 400 guys may know more.
 

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Discussion Starter #20
Should be a keeper plate that is behind the timing set that hold the cam in. Maybe the depth of the gear set has your fuel pump ring pushed out to far. Just looks like a lot of wear to me. Maybe more of these 400 guys may know more.
What's interesting is there's another circle of wear on the other side...I guess it might be from the water pump impeller-thingy?
 
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