Breakin on newly rebuilt 302 FT cam engine starts and dies after 2-3 minutes

[Rockstar Bronco]

Been pulling my hair out for weeks on this... worried I'm gonna flatten my cam messing with getting this thing running for break-in! Here's what I'm working with in my EB: newly rebuilt 308, .040 over, decked, 10.5:1, aluminum heads, mild RV FT cam, Edelbrock 600cfm 4 bbl, longtube headers, new wiring, new Duraspark Module and Distributor, new tank, new fuel lines. The ONLY things that were not new (but worked prior to rebuild) are coil, rocker arms, pushrods (happened to be the right length), carb, intake and starter. Optima red top battery is older, but seemed to be holding charge.

After reading about all the nightmares online, I was super nervous about breaking in the cam, so I primed the oil pump, added lots of timing (with vacuum advance connected), changed the rods and springs on the carb to run richer, took the shims out of the valve springs to lighten them to 124/272 psi., and put 3 fans on the engine to keep it cool. I've started it 8-10 times now and it won't run for more than 2-3 minutes before stalling. I've poured gas into the float bowls each time to get it to run quickly without spinning the motor unnecessarily. The first several times, it started immediately and ran straight up to 2500 rpms, while I tried to dial in timing. It was running 25-30 btdc at 2500 rpms. By the time I tried to monkey with it, it would die. So I capped my vacuum lines and went to straight mechanical, trying to get it all in (about 32 degrees) by 2500-2800 rpms. It seems to be running worse now. Was sure this was a fuel issue, but just replaced the mechanical fuel pump (then tested the old one to find it was working fine). Also, removed fuel cap to make sure it wasn't creating vacuum (2nd vent tube is blocked so relying only on small filler tube and vented cap for equalization). Carb squirts fuel when throttled, choke is working fine. I put the stock rods and springs back in the carb to remove that variable and now it barely runs for like 30 seconds and dies (coincidence?). To add to matters, it barely turns over now. I'm thinking (hoping) the tired starter and battery are not up to cranking that tight 10.5:1 motor. Everything seems like a moving target at this point and I'm seriously worried about wiping out this cam. Will be replacing starter tomorrow, as the connector bolt is loose when I crank it tight, and then a new battery as needed, but that still only puts me back to square one. Plugs are clean, as is oil.

Given all that, where would you guys look first? I'm thinking coil, but still not sure it's not a fuel issue. It dies like it's fuel starved but I've heard that bad coils/modules can die when they start to get hot. Gotta get this right without too much messing around, so I'd rather replace parts than spend time and risk to the motor with testing old ones. If I had known the risk I would have spent the extra $1200 to go with a roller cam. Never again... ANY help/advice would be much appreciated.

 

[73azbronco]

I am not a throw money at a problem guy, but, Buy a new battery. You need it anyway, right? What is voltage running?

Buy a new coil.

Verify spark plug wires are going to right place for camshaft you have.

What is fuel pressure to carb?

You said carb worked before? Was fuel left in it, sounds like gummed up even if accel pump works.

What is cold compression on each cylinder?

What is vacuum while it runs?

Smell oil on dipstick, smell like gas?

Consider a different duraspark unit.

Was all wiring working before rebuild?

hypertetic pistons? Those dont like more than 32 ish btdc, or you blow a hole in them.

 

[Rockstar Bronco]

AZbronco, yes plug wires are correct (351/HO firing order). Battery voltage is 12.75-13ish. I have braided steel lines running to carb, so haven't checked fuel pressure, but I know new fuel pump is working and strong. Bought carb used. I mispoke on that. I had a 1405 before, and sold it to buy the e-choke model. Looks clean, but no, I haven't gone through it. Had no time to check vacuum while running. Had my hands full trying to get timing right, but as I said, vacuum is all plugged off. Suppose I could check compression, but why? Trying to avoid unnecessary cranking until cam is broke in. No gas smell in oil. Duraspark unit is brand new. New wiring was done during rebuild (was a total body off build). Yes, hypereutectic pistons ...no holes in them, but thanks for the heads up on that. Was more concerned about torching my headers, but will keep it under 30 btdc from here on. Installing new starter, battery tomorrow. Ordered new FlameThrower coil. Will have it Saturday. Will try that before pulling carb off.

 

[DirtDonk]

If a fuel problem, and the fuel squirts every time you rock the throttle, you should be able to keep it running by pumping the pedal.
If it still dies while you’re pumping fuel into it, then it’s likely not a fuel delivery issue after all.
I would not think anyway.
Are these adjustable rockers? If so, do you know how to adjust rockers properly?
Did you set them, or someone else?
Zero lash is an often misunderstood starting point. So just checking to make sure that that’s good in this case.

That would sort of fall under the previous mention by az of a compression test.
But you don’t wanna be cranking it unnecessarily as you know. So perhaps setting the lash manually would be better than testing for compression.

Is someone monitoring the consistency of the spark during the times it is running? Hopefully you’re not doing this by yourself, and can have someone monitor sparks at each plug by clamping a timing light to it. Sounds like you have a light, since your testing timing. This would be a very good time to verify that.

Speaking of ignition, you don’t happen to have an old points distributor laying around by any chance, do you?

 

[DirtDonk]

And in the interest of your cam, and pertaining to all the reading it sounds like you’ve done, did you add plenty of break-in additive to a good break in oil?

 

[Rockstar Bronco]

I tend to agree with you on the fuel issue logic. No additive, just Comp cams 10w30 breakin oil. I installed the oem rockers (non-adjustable) @ zero lash + 1/2 turn. To me zero lash is when there's no wiggle but you can still barely spin the pushrod. Some say zero lash is when you can no longer turn pushrod with your fingers. My thinking was I would rather err on the side of a bit loose than too tight. I can always tighten, and intend to check again after breakin. Would be interested to hear your recommendation on that. Yes, unfortunately, I am doing this by myself. I had some help, but he would drink all day and became a liability. I don't have the old point ignition. I converted my old dizzy to pertronix and tossed the guts years ago.

 

[Rockstar Bronco]

I'm working alone, but have tach, oil pressure and water temp gauges setup. It's all actually quite elaborate... with the gauges, 3 fans, battery charger, timing light, timer etc., there's barely room to move around quickly while it's running. I cranked up my idle screw to run at 2000-2200 and I vary it every 30-45 seconds. I had to stop the initial startup (when I had help) 5 minutes in when my brand new radiator sprung a pinhole leak. That seems to have started a domino effect...

 

[Madgyver]

runs out of fuel is my first thought.

 

[DirtDonk]

I installed the oem rockers (non-adjustable) @ zero lash + 1/2 turn.

Something is wrong with that statement.
Non adjustable rockers are, by definition, not adjustable. You tighten the bolts all the way.
You do not go to zero lash and then only go half turn. That is for adjustable rockers.
With non-adjustable ones, you can certainly set zero lash, and then check how many turns it takes to achieve full torque. But you don’t stop at a half a turn unless it is fully torqued.
It’s not a lot. Something like 25 to 28 pounds per bolt maybe? I don’t remember, but you must torque them.
If you did not, perhaps this is why it’s running worse and worse. Perhaps the rockers are getting loose.
If nothing else, you absolutely should pull the valve cover and check.

To me zero lash is when there's no wiggle but you can still barely spin the pushrod. Some say zero lash is when you can no longer turn pushrod with your fingers.

Both are essentially incorrect.
Zero lash is achieved when you can no longer gently push the rod up and down and feel no movement. No movement of the rod, and no movement of the rocker arm.
Even at way beyond zero lash, you can often still spin the pushrod by hand. So spinning is never, ever used as a setting method.
And you can’t use a lot of force with your hand either, at least not with hydraulic lifters, because you can compress the lifter spring.
You simply monitor the push rod while tightening the nut, until the rod and the rocker no longer go up and down.
Side to side and spinning are still going to happen even at zero lash.
So they are not pertinent to adjustment.

My thinking was I would rather err on the side of a bit loose than too tight. I can always tighten, and intend to check again after breakin.

Your theory is correct, as far as it goes.
But here again, non-adjustable rockers don’t give you that option. The only thing you do for nonadjustables is shim them. Which it sounds like you might’ve done from your previous mention of removing shims.
Unless you meant valve spring shims? Other than that, there is no loose or tight. There is only fully torqued.

Would be interested to hear your recommendation on that. Yes, unfortunately, I am doing this by myself. I had some help, but he would drink all day and became a liability.

To bed. Extra hands and extra eyes are almost essential during an initial break in.

I don't have the old point ignition. I converted my old dizzy to pertronix and tossed the guts years ago.

Also too bad. One of the benefits of the pertronix is that if the module ever burns out, which can happen with any electronic device, a set of points sitting in the glove compartment or toolbox can get you home.

But didn’t you say you have a Dura spark module? What are you doing with that, when you have a Pertronix Ignitor?

 

[Rockstar Bronco]

Thanks for being the "extra eyes" Dirt. You're right. I've built 2 roller motors in the last year and got that adjustment crossed up. That could very likely the problem. As for defining zero lash, we're on the same page and that's the way I did it during install, just said it differently. No shims in rocker arms. I was referring to spring shims. Will pull valve covers today and check to see where I'm at, and change pushrods if necessary (don't like using shims). As I recall, the oem rockers should torque at +/- 20 ft lbs at about 1 1/2 turns in from zero lash. I'll use my pushrod length checker and dial indicator to measure it up. I suspect this is the source of at least one problem.

BTW: I still have the old dizzy with the pertronix, but the wiring is in bad shape, so I replaced it. Could still carry as a backup...

 

[73azbronco]

Lash isn't going to make it stall in a minute. Dizzy shouldn't either nor a bad duraspark module which go when hot. Fuel will. Fuel pressure, clogged up carb my two bets.

But, set the valves right.

 

[Rockstar Bronco]

Copy that AZ. Just checked rockers and they haven't moved. That said, I do need shorter pushrods before moving forward. If it is in fact a fuel issue, it has to be the carb. I know I have pressure to the carb, acc pump is squirting, and when it ran, exhaust smelled rich? So it doesn't make sense that it starts, runs and then dies, or am I missing something? This is what's driving me nuts ...running in circles here. I have some painting to do over the next few days, while the weather's nice, then dial in the valve train, install new coil, and if that doesn't do the trick, suppose I'll pull carb and open it up next. What am I looking for specifically?

 

[73azbronco]

You know you have pressure to carb, what is it?

 

[Rockstar Bronco]

Haven't measured it. Braided lines. 99% sure I have sufficient pressure to the carb. When I tested the new fuel pump it shot fuel 10' across the room pumping it by hand. Braided lines are new, so not clogged.

 

[73azbronco]

I'm saying it might be too much pressure, flooding engine...

 

[Broncobowsher]

You stated aluminum heads, which ones?
I'm thinking not a fuel issue, you can keep it going on the accel pump. Or bottle feed it.
Spark is generally a good thing to check. Not only if it is there, but if it is strong.

Back to the heads. Rocker arms and pushrods. Maybe your zero lash is the lifter bottomed out and you didn't catch that? As the engine warms up the valve start to not close enough.

A trick I have been doing for several years now, and starting to see more of on the interwebs, use 2-stroke premix. When you are dumping too much fuel and washing down the cylinder walls, you will be coating them with lube.

 

[EPB72]

Gotcha. I've gone backwards a ways since our fuel supply discussion, based on Dirts comments that I set my lash incorrectly. I think this may have come about by my stating that the oem rockers are (non-adjustable). After asking around to some reliable sources, I did set the lash correctly ...BUT, what that conversation with Dirt inspired me to do was pull the valve covers to check them again anyway. They were fine, hadn't moved at all, but what I did find is a bunch of very fine shavings right under my pushrods and some slightly bigger shavings in the bottom of the top of the head, where the oil drains. My first thought was "that's where the oil is pumped in and those shavings must be from my ruined cam/lifters"! So I drained the coolant, disconnected everything, pulled the intake off and pulled 3 lifters - all looked absolutely perfect. So I go back up top and look closer at the valve train, and discovered that the pushrods had been rubbing on the guide plates and had worn off a significant amount of material, which created the metal powder. The silver lining is that the pushrods were worn evenly all the way around, which indicates they are spinning. This is consistent with the VERY light and even wear pattern on the lifters. Whhhheeeeewwww.... huge sigh of relief. So thanks Dirt for pointing me in that direction. Toasting the cam was my only real fear. This other stuff is barely annoying in contrast. Now, I can clean up the mess, change the oil, re-assemble, install the new starter, coil and battery, and go from there. If I still have issues, I'll look into the carb and fuel pressure. The thing is, as I mentioned before, the plugs are clean, like brand new clean. But yeah ...one thing at a time.

So some clarification.... You have aluminium heads as stated in first post, They have stud mounted rockers with guide plates correct? Not pedestal mounted? The rockers are they cast style and do they have rail guides at the valve stem end? If so they should'nt be ran with guide plates, The pushrods you say they are original? Yes? Are you sure there hardened push rods to run with guide plates??

 

[DirtDonk]

Did you say you reused the stock pushrods?
If so, that’s probably wrong.
I’m sure someone will correct me if I’m wrong, but with aluminum heads and guide plates, you don’t use stock (non-adjustable) rocker arms and you don’t use stock push rods.
Stock adjustable, rocker arms? That’s certainly possible.
But stock non-adjustables? Certainly no.
So now I’m guessing you have regular studs and adjustable rockers.
So all that claptrap about setting the torque would not apply here. But stock push rods are probably not hardened and so are going to wear out where they rub on the guide plates.
This is a key difference in various types of valve trains.

 

[Rockstar Bronco]

Exactly right. Stock rockers are on studs and adjustable, but yes, I need hardened pushrods. Sorry for the confusion...

 

[Broncobowsher]

The only stock adjustable rockers (and hardened pushrods) were used on very early small blocks. Typically the hi-po engines, but I think a few very very early regular engines also got them. Pretty much unicorn parts these days. Any original Bronco engine, or even late 60's and newer, has non-adjustable rockers and non-hardened pushrods.

Unless you have something that says you have otherwise, you don't have the right parts.

At this point I am going to say that the pushrod preload and general valvetrain setup is your issue.

The lifter preload is critical to not be at the limits. Not too tight where the plunger in the lifter bottoms out, but not so loose that the plunger bottoms out against the circlip in the lifter.

One more thing to check. You removed the shims under the valve springs. Just shims or the spring seat? The spring seat is there to keep the spring from digging into the aluminum. Removing preload shims for break in is fine. Removing the spring seat isn't.

It sounds like you will have a good running engine when done. Just need to get those last little things out of the way.