I've got a problem.. Finally go my project truck with the new 400 in it on the road and now I have an issue. Seemed to start mildly at first... here's the deal. Set 10 BTC, and the carb set up wrong, on it's first drive out I heard what I thought was a rattle of some kind. The performance sucked, adjusted for good vacuum( 18+ lbs), adjusted for 14 BTC and took it out again. Performance was better, but the rattle gets worse. Should be 8 or 8.5-1, new 670 truck avenger, Weinend single plane intake, headders, duals, msd coil, stock dist& box. I set it back to 10 BTC..other then the performance getting worse..no change in the rattle.

Doesn't happen at startup, and if you drive it a block or two when cold it doen't do it, even under load. Doesn't ever do it at idle, but once you get it even a little warm, it does it loaded or unloaded when you rev it up. Can't seem to figure it out.

Only happens after 1700 RPM. Seems to happen a tad less under full load, but consitent under partial load. Gets real bad off the gas 2000-3000 RPM Range. In the cab, sounds like bottom end ( god I hope not). Outside, couple friends/fellow engine builders say it's not deep/metallic/thud or low RPM enough to be bottom end..one suggested dump gas and run 94 octane ( just tried that tonight, no dice). Other suggested possible valve train ( although I thought that would be more of a tick). Sounds like a rattle, like marbles in a tin can going round.

2nd to the first- she still runs real hot. Going to buy another set of mechanical guages this weekend, and try to get a better handle on things..the set I had just popped the oil line( so I know there was pressure..lol) and the water never worked right for some reason.

Either way with a good antifreeze/water mix, well bled, and no stat ( same with one in , did it both ways) it pings,bubbles and rattles like an old steam radiator they used in houses... This can't be a good thing either.

Anyone have any ideas for me? Going to change the oil out tomorrow with soemthing thicker but I am sure that will not help things much either.

 

Common problem.

Either put the EGR system back on or adjust the vacuum advance in your distributor properly. There are many threads here on this problem. Check out threads with "EGR" and "ping".

 

The motor was built 10 years ago, run a bit then pulled. Got it off an engine building guy- had about 10 motors stored in his shop. He is more of a chevy guy so this one is not as valueable to him. I am beginning to see maybe why it was pulled in the first place. It sat on an engine stand for years before I bought it this winter, pulled it apart. All looked mint/new/clean- no wear and little carbon on anything suggested it hasn't been run much. Had BN 2WD headers on it, 2wd engine mounts and a 800 Double pumper ( god knows why) so I let him keep that.

Put it back together with new gaskets. Everything seemed in order at the time.

One thing i've been asked that I think I am sure of is if the head gaskets got on the correct side..( if not they may be blocking coolant flow. ) I mean I think I did..kind of a hard thing to check now..lol.

Timing seems to have little/no effect on this POS as far as this "knock" goes. You would think so..but doesn't seem to. It sure has an effect as far as perfomance goes though. The vacuum advace works/hold..but have not checked how fast the mechanical advance comes on at how many degrees that it does.

As for the compression..the things been done 30 over, but dished pistons so nothing fancy.. I thought stock 8 -8.4 to 1. In case I was wrong..I gave the 94 octane a shot.. still no difference.

My first bad was only pulling one bearing cap... they looked new/spec out ok..so I just re installed it....maybe should have checked em all.

Going to try and run with the vacuum pulled off plugged and off the distributor see if that has any effect. As stated I could pull it to recurve, but again I am not suspecting that is the knock issue.

It's looking more like pulling either the heads and checking the gaskets ( if she is getting that hot that could cause the detonation issues) or the engine and start over. If I do that, guess I will do the 9:5 to one badger pistons I wanted to try in the first place. May as well go all out if I am going to do that. OR...dump the 400 in favor or a 460...but that would mean another intake, cam etc as well as headers and engine mounts. Bummer

 

Head gaskets on wrong will definitely cause that problem. Running the compression up causes other problems. The compression must be matched to the heads, pistons, and cam. There are also many threads on that subject also. Go a little conservative on your design and you will be happier in the long run. Pushing the limits can be a maintenance and longevity nightmare. Reducing timing and adding expensive fuel can cost you more performance and $$$ than a conservative design in the first place.

 

Did you notice whether the heads are closed or open chamber heads? The stock heads are open chamber heads. Maybe someone put 'Aussie' closed chamber heads on it. These will push the compression ratio over 10:1. Even 94 will detonate with 10:1 and no quench and a high dynamic compression ratio like you would get with a stock cam.

 

I'd run a compression check first off. Make sure it's reasonable.

 

Compression pressure, approximate @ cranking speed :
8.0---140PSI
9.0---160
10.0--180
11.0--200

So you are looking for something ~165PSI or less to run pump gas.

Of course no matter if the compression is high or low you will still need to tear it down. Of course the compression test may give some nice clues.

Put on a nice Edelbrock #1406 carb on it.

 

"Doesn't happen at startup, and if you drive it a block or two when cold it doen't do it, even under load. Doesn't ever do it at idle, but once you get it even a little warm, it does it loaded or unloaded when you rev it up. Can't seem to figure it out."

doesn't ping while the choke is on. makes me think your carb may be running too lean. running lean can cause excess heat and pinging. try enriching it (jets?) before tearing into the motor.

but as the others say, if your static compression is too high you will need to...

 

Also check your vacuum advance plate inside the distributor, after sitting for a period of time these can stick or even lock up. If it is not working freely the vacuum will pull it advanced and the plate will not return to the proper position. I had this happen and it caused similar symptoms.

 

Today's update

Bought another set of gauges to check to see if the others were wrong. Possibly, but at least they are consistent. Temp readings when it makes the bubble/rattle and "ring" *( like an old house radiator) that made me think it is overheating.. seem to happen long before you would think. They read 100-160. I am beginning to think the mechanical gauges are not the way to go.... but as I don't have an infrared heat gauge...I can't verify the accuracy. Either way, oddly enough after an hour drive today, and it heating up to 200-210... when I stopped at home...there was no bubbling/rattle/ringing.... WTF? I had topped it up today( rad) and it since has puked a good amount of antifreeze ( time to install an overflow bottle) So...still not sure what to do with respect to this problem. Still undecided if I am going to pull the heads to check the headgaskets...but I think the intake started leaking oil today during my ride....so I may just go in all the way if that needs doing.

Now on to the knocking engine noise...Thought it may have something to do with oil or timing advance. Oil pressure drops off @ idle to almost nil after 160-170 degrees, so I dumped it and changed to 20W50. Better, till it hits 170-190...then same issue... reads 20-40 lbs under load- but drops right off at idle. Added a bottle of Lucas oil stabilizer just for fun... made a differece at the beginning...but then same once warmed up hot again. So nothing good/bad to report there.

Pulled the vacuum line off the dist and plugged it. With no advance, runs a bit rough at idle, but once the weights start to kick in after 2000 rpm, it's ok. Moreover.. the good news was the bad 1700 rpm knock has moved and is mostly gone.

It seemed to moved up to 2500-2700 RPM plus range, but not as bad as it was. Before @ 1700...Used to make the noise bad enough under load, but worse when you backed off the gas. Now with the vacuum line off...it doesn't do it till farther up the range...and then stops when you get off the gas.

I am thinking it's time for a new distributor..something that doesn't pull as much advance with vacuum hooked up...and doesn't advance as much with the weights at full RPM. I have yet to check the curve ( as I need a dark enough place to do it and some help). Will shoot for tomorrow at a buddys garage..and see how much advance comes on ( and when). I am really hoping that after I can nail down those variables, and possibly get a new distributor, this problem will go away.

Still welcoming more suggestions ?
Marc

 

Are you sure that you had your vacuum line connected to ported vacuum, not manifold vacuum. There should be no difference at idle between dist vacuum connected or disconnected and plugged.

It should not run rough at idle with the dist vacuum disconnected and plugged. Do you have a vacuum leak?

Have you measured the manifold vacuum at idle?

 

Well thank god it's not my daily driver.. I think on todays trip I got a whopping 4-5 MPG.

As i've been told it's very bad..Dumb question #345: What should my oil pressure at idle be when it's warm? When you are driving..it's steady between 20-40. On fire up cold it's over 60, then seems to hold 20 idling till you head out on the road for a drive. when you come to a stop sign/light it drops to 5 or so..hard to read that low. I know it's low...but I may have or will frag bearings if this is no good.

Tomorrow is re check specs days. I've been advised to do so many things...one is a compression check. Also, as it's running a little lope-y at idle right now with the advance disconnected...I am going to re adjust everything and bump idle to 650-700 ( it's hot idle is only 500 with the advance disconnected) .... re check/adjust base timing and adjust again for good manifold vacuum (was pulling 18 when I last checked). Will check for advance curve as well..as I haven't done that yet.

Stupid question #346- i've been getting conflicted answers as to timed/ported carb vacuum or full on manifold vacuum for the distributor...any suggestions for when I try to hook it back up ?

As for the oil issue...It would be a shame to get it running top notch and have to pull it for an oilpump at this stage...grrr.

 

For some background information read some of the old threads here on timing and EGR ping. They have a lot of good info regarding distributor operation, curves, ported and manifold vacuum, etc.

A good book on the theory of engine operation would be good also. Some to look at:
"Performance with Economy" by David Vizard, for more detailed information. It is the best one in my library. After that the "Desktop Dynos" book from the publishers of the DYNO-2000 program is good.
There are a variety of others available also:
How To Rebuild Your Ford V-8 351C, 351M, 400, 429 460
Ford Performance by Pat Ganahl
Power Secrets by Smokey Yunick
Performance Modifying Ford Trucks by Rich Johnson
Off Highway Operation Parts, and
Off Highway Newsletter, both available thru the Onl<! >ine Store.
Then there are various SAE design handbooks available at your local technical libraries.

It sounds as if your bearing clearances are too large. Did you plastigauge the engine during assy? The engine builder may have built it "loose" like the Chevy guys do which is the wrong thing to do with a 335 series engine. Use plastigauge and then shim the bearings. The cam bearings will require some specialized equipment to measure.

It sounds like you need to verify that the distributor is operating properly and you might be better off taking the engine back apart.

 

Stupid question #346- i've been getting conflicted answers as to timed/ported carb vacuum or full on manifold vacuum for the distributor...any suggestions for when I try to hook it back up ?

Answer to not-so-stupid question #346. I always use ported vacuum, but there are some that use Manifold vacuum.
If you use ported vacuum, set your timing with the vacuum disconnected to about 10 degrees BTDC. When you connect the vacuum, you will get no change in timing, because there will be no vacuum present. If you open the throttle you will get some vacuum advance. As the engine revs, mechanical advance will take over and you will get full advance.
If you use manifold, you must set you initial timing with the vacuum connected. I believe that people who do this set the timing higher than 10 degrees BTDC. When you open the throttle, the manifold vacuum will drop and then the mechanical advance will take over and you will get full advance.

I don't use manifold vacuum for a couple of reasons. It can make the motor hard to start, and it can cause pinging at part throttle. The factory setup is ported vacuum.

If you set the intial timng to 10 degrees BTDC with the vacuum disconnected and then connect manifold vacuum, you will get way too much advance at part throttle.

 

Actually the factory setup uses a temperature sensitive vacuum switch in the coolant to connect different vacuum sources to the distributor. The vacuum advance mechanism is connected to manifold vacuum when cold and switches to ported vacuum when the engine reaches operating temperature. Some valves also connect to manifold vacuum when the engine overheats. The stock system also uses a ~20° timing retard function in the ignition module while cranking.