Engine cam break-in - What should I do with my 340?

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Nidhögg

Nidhögg

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Hey, as some of you may know, Im restoring a 1968 Dodge Dart GT.
The car will get a 1971 340 in it, and I took the engine apart to inspect it (it hasnt been started since 1981...). The inside looks good (I think the piston ridge was less than 0.001"), but I want to treat it to some new bearings, piston rings, gaskets etc.
I also thought I should install a new cam while I have the engine apart.

This will be my first flat tappet engine break in, and as I understand it the engine need to be revved to 2-2.500 RPM straight away to get the oil pressure up so the flat tappets and cam can match properly, and run like that for ~30 mins.

Now, the problem is, the engine came without both a distributor and carb, so I will need to get new ones. And when installing those, I dont know how the fuel mixture will be, and I will probably be off on the timing since I dont have an existing distributor to pull off, and make sure the rotor is set the same.

So, setting both the carburetor and the timing will probably take some time, time that will be spent on both idle and higher revs.
Will this matter much for breaking in the cam?
Should I instead leave the current camshaft in the engine (the camshaft and crankshaft have not been removed) and focus on setting up everything else on the engine, and install and break in a new camshaft later on?
Since I havent touched those two I will probably have the cam degreed right, so that will save some time. Then I can focus on getting the timing and fuelmixture right, and after that change the cam.

It will be more work, but perhaps its the best thing to do?
Advice?
 
It's been a whole since I did mine but I believe I just had #1 on a compression stroke and the distributor pointed at it then fired it and broke in the cam then timed it. I had a carb that I knew was set up correctly though. Also make sure to prime the engine!
 
doogievlg said:
Do you have the carb you took off of it?
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Nope, the carb and distributor have been lost somewhere in the 34 years its been since it got taken out of the Barracuda it was originally in :D
It´s been gathering dust in a garage since then, I got the engine as a rent settlement (well, my dad got it) so we just got it as it stood.
 
Rotate the engine and stop at 10* BTDC. Drop the distributor in and align the magnetic pickup for #1 to fire. I assume you will be using electronic dizzy. Use a small funnel or syringe to put some fuel in the carb through the bowl vents. If you are going electroonic fuel pump you can use the pump to prime the carb. Use the good cam break in lube (crane sells it) it's a thick moly paste that does not drip off like the liquid type. Stick a box fan on high in front of the radiator for additional cooling during initial run. Also add the ZDDP 8 oz to your oil.

http://www.summitracing.com/parts/crn-99002-1/overview/

http://www.summitracing.com/search/...SortOrder=Ascending&keyword=cam break in lube
 
Also try to make the exhaust as quite as possible so you can listen to the motor.
 
I did the same thing as mderoy. Lots of lube for the cam install. I primed the motor with oil with a hand held drill with an allen wrench that I made to fit the oil pump
 
Nidhögg;1970733698 said:
Yeah, I guess the timing can be setup good enough to break in, but it would be bad if the engine would run lean for 30 mins with a new cam...
Click to expand...

Do you have another smallblock available to you, friend, family member?

If so, put that carb on their engine and tune it somewhat. That way when you have it on your breakin, you know it will fire and run for the 15 to 20 minute breakin period.

The timing should be fairly straightforward.
 
mderoy340 said:
Rotate the engine and stop at 10* BTDC. Drop the distributor in and align the magnetic pickup for #1 to fire. I assume you will be using electronic dizzy. Use a small funnel or syringe to put some fuel in the carb through the bowl vents. If you are going electroonic fuel pump you can use the pump to prime the carb. Use the good cam break in lube (crane sells it) it's a thick moly paste that does not drip off like the liquid type. Stick a box fan on high in front of the radiator for additional cooling during initial run. Also add the ZDDP 8 oz to your oil.

http://www.summitracing.com/parts/crn-99002-1/overview/

http://www.summitracing.com/search/...SortOrder=Ascending&keyword=cam break in lube
Click to expand...

Yeah, I will probably use a Davis Unified Ignition distributor to make re-wiring the car easier. I will use a mechanical pump, but I will make sure the carb has fuel (thinking of going with the Street Demon 625 CFM, and I think that one has pretty big fuel bowls).
Thanks for the links, I was checking around for lube´s but wasnt sure about which brands are good and not :)

doogievlg said:
Also try to make the exhaust as quite as possible so you can listen to the motor.
Click to expand...

I will probably attach an exhaust hose to the exhaust so I can vent the fumes as well as getting it quieter :)

Bad Sport said:
Do you have another smallblock available to you, friend, family member?

If so, put that carb on their engine and tune it somewhat. That way when you have it on your breakin, you know it will fire and run for the 15 to 20 minute breakin period.

The timing should be fairly straightforward.
Click to expand...

Well, that would be one of my dads cars, either a Desoto with a Fire Dome engine, or his Chevrolet Caprice, but Im not sure what engine it has, it could be a smallblock..

I will look it up :)
 
[ame]http://www.hughesengines.com/Upload/productInstructions/EasytoStartJuly2013X.pdf[/ame]
 
Great info 70aarcuda, thanks!

I talked to my dad, his caprice have a 400 smallblock, so I will probably mount the carb to that engine first and tune it somewhat, so I at least know its working.
But I haven´t really decided yet, the car havent moved since 1991 so I dont know if the fuel lines are ok and not full of slush, or that the new fuel pump will be working as it should, so I still havent decided if I should start the car as it is the first time and drive it around a bit, just to see that everything works as it should.

But I really want to thank you all for the help and info provided :)
 
-No.But almost.
-While that is the only way it will run, if on the top of the compression stroke, that part is correct. and so is the part about rotating the dist.
-However,establishing the time of firing is controlled by the reluctor passing by the mag. pick-up, or if points, the moment they break circuit with the coil.
-So using your example; Starting with the no 1 piston just before TDC on compression, you could line up the mark on the balancer to the 12* BTDC on the index tab, just as you describe. Then with the Ignition system powered up, you would remove the coil wire and lay it on a grounded surface with about 1/4 " air-gap, then retard the dizzy in the neighbor hood of 1/12 turn( exact amount not important), And finally advance the dizzy until a spark occurs. Then index the the tower that has the no 1 wire to the dizzy body, remove the cap and prove that the rotor is at or near to that mark. If its not; make it so.
-This means one of two things is wrong; either the hi tension wires need to be reclocked, or on rare occasions, the reluctor needs to be reclocked, or on even rarer occasions the the trigger polarity may be reversed. Iknow, I know, thats 3 things.But #three is rare
-The rotor only needs to be close to the tower, The coil will push the spark quite a ways over to it. If it gets to be too far away, sometimes it will fire to an adjacent tower. This is not good. So grab the rotor and rotate it to the end of its operating range to make sure its still closer to the indexed tower( the one you marked), than to any other tower.
-Earlier I instructed you to remove and air-gap ground the coil wire and watch for spark. This is a newbe method. You can just as easily leave everything together and just listen for the snapping noise that the spark makes as it arcs over to the tower. You could also pull the no1 wire off the sparkplug,air-gap ground it, and watch/listen for spark there. Either/any method will work.
-Instead of rotating the dizzy with the crank at 12BTDC, you can set the dizzy to 12* and back up the crank, then bring it forward to prove the spark jumps at 12*. Its just way harder, and overkill for first start.
-For first start and cam break in, I would do as you are doing. As soon as it runs crank up the rpm to 2000ish plus. First thing is to check for oil pressure, then leaks;first,fuel, then oil, then coolant. As soon as thats done I grab the dizzy and advance it as much as the engine likes. As long as the rpm is increasing shes liking it.Then return the idle to 2000. Then fiddle with the mixture screws listening to the engines response. As long as the rpms are increasing, shes liking it. This should only take a minute or three. Next grab your IR gun, and check the engine temp. After that take a deep breath and just sit back with your garden hose and IR gun at the ready, checking temp.every minute or so, and watching for leaks of any kind. The first 5 minutes can be hectic, so I suggest a rehearsal or 2, or 3.....
-If the carb has a fast idle cam, I might be inclined to use it, as emergency shut-downs are less dramatic if you blip the throttle to kick it off, just before you kill it. But it may not be the best idea for a first-timer.With all the busyness going on in those first few minutes,worrying about a break-in speed compromise, should the fast idle cam slip, need not be one of them. If you are diligent before twisting the key, it is usually a cakewalk.

Best of luck to you.
 
BTW, those "buttons" dont actually touch. Theres quite a bit of room between them at especially at the time of firing. The button on the end of the rotor is often referred to as the rotor tip, and the button on the cap is usually shortened to tower. If I have misunderstood your terminology, than my post may be in error. But if you dont understand my terminology, you can refer to here.
Hope thats clearer than mud.
And if you are referencing post #11, and calling those heavy black points in the pic, buttons, then the previous post still applys, because the picture fails to include the trigger/ vane relationship that needs to be synchronized to it.
And I guess I should add this; Going back to your post,#15, if, and only,if your set-up is currently correctly set with engine at top of compression on #1, and any one reluctor vane is more or less exactly across from the magnetic trigger metal core-piece, then she is real close to correctly set up. I say" more or less exactly across" because its just close. The exact moment of firing occurs when the magnetic field set up by the trigger is first sensed/interupted by the approaching reluctor vane. (In that sense it operates just as points do.Its just a sophisticated switch.The ECU just translates that switching action into a,command to fire,with matching power,that the coil can use.) When you rotate the dizzy to fire the coil you are fine tuning that moment.

-If dads carb bolts on to your manifold, and it is working correctly, you can borrow it for the break-in period, and even after. At 2000rpm, and light throttle applications, your engine is operating on the low speed circuits(easily tuned with screws). This means no jetting is required, and no tear-down. Just be sure to return things back, so dad wont get pissed.And be absolutely sure no fuel leaks, anywhere. You cant blame a fire on anything or anybody else,ESPECIALLY NOT DAD OR HIS CARB.
-Speaking of returning things: Timing. Earlier during break-in, you may have experimented with twisting the dizzy around. Well you more or less established the timing that the engine wants at break-in speed. This is a good target for you to incorporate during establishment of the other timing parameters. Bear in mind the total power timing needs to be limited to what the fuel used will support in your combo. Detonation is to be avoided at all costs. Instead of tuning to a number, let the engine tell you what it wants.
-Generally, iron headed, open chambered, sbms will ask for power timing of 34 to 37 degrees, at "normal" engine temps.Aluminum, or quench heads, are often happy with a couple to several, less. On the street, my a$$ dyno cant tell the difference between optimum and 3 or 4 less. However, 3 or 4 less in the midrange is easily noticed. And 3 or 4 less at idle can make or break your tune.So if youre building a streeter, concentrate your time on the idle/off idle, and sub 3000rpm timings. Track cars are somewhat easier; WOT timing,idle timing close, all in before launch, good to go. Fine-tune later.Streeters will come alive with a snappy spark tune. And do not neglect the vacuum advance timing. There is a world in there, that a lot of guys dont explore and as a result, are really missing out. Ok,track cars dont care.
-When you get it right, she will be a pleasure.
 
You make a good point that depending upon ignition component conditions and types, It is best to test from #1 wire to see exactly when the spark jumps onto the #1 tower. Your respond is greatly appreciated.
AJ/FormS said:
Oops, double post
Click to expand...
 
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