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Discussion Starter · #1 ·
Last fall I completed the build on my 496 with a Lunati flat tappet hydralic. I had the engine broken in and dyno'ed at the machine shop that did the engine work. It ran fine with 10-15 passes.

I installed the engine in the car and finished the rest of the rebuild in my Chevelle. I re-installed AC, electric fans, etc.

3 weeks ago I had everything finished, loaded it on a trailer and moved it to a exhaust shop to have the headers connected to the mufflers. I picked it up & drove it home. It needs a little timing adjustments and some quieter mufflers. I let the engine cool for half a day, checked fluids, & topped off the radiator.

I took it out again and after about 12 miles, I started to hear a ticking sound from the engine compartment. 30 seconds later, the engine died and will not restart.

I have checked a few things, power to the coil, distributor movement, inside the cap, wires, plugs, fuel, etc. I have not removed anything yet. It will crank but won't start. After a few cranks when I let off the key, it will "puff" out the carb like a backfire without the spark/flame.

My first thought is I flattened the cam. If I did, this one only lasted about 25 miles. If I pull the valve covers, what am I looking for, loose valvetrain?
I read some archive posts about measuring lift height at the rocker. I'm not set up to do that. Is there another way to determine if the cam is toast (other than removing it.)

A shame to have to start tearing into this.

Comments & suggestions welcome.

E.
 

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Sorry, simple question. You have power to the coil, is it 12V (checked with voltmeter or test light)? Spark at the plugs -- blue and "sharp"?

Assuming carb is full of fuel and strong pump shot.
 

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Eric,since it ran fine on the drive home from muffler shop the other day & then ticked
& died sortly there after 12 miles later the next day that would not normally be a bad cam IMHO.

Even if a few lobes went flat it would still run but not well on all cyl's,but it would not run ok,then all the sudden make a ticking sound like you stated and die a few seconds later,something else happened thats very likely ign or maybe fuel related.

You should go after all the easy stuff first.

* CHECK FOR 12V AT IGNITION

* CHECK COIL

* CHECK FOR SPARK AT PLUGS

* CHECK FOR FUEL GETTING TO & IN THE CARB

* CHECK TO SEE IF DIST CAP IS LOOSE

* CHECK TO SEE IF ROTOR IS LOOSE OR BROKEN.

* IF RUNNING GM HEI TYPE IGN/DIST CHECK TO SEE IF THE LITTLE CARBON STUD WITH THE SPRING THAT GOES INBETWEEN THE COIL AND DIST CAP IS BURNT/MELTED BECAUSE THEY CAN AT TIMES OVERHEAT AND GO BAD,THEY MAKE A SPECIAL ONE OF THOSE DOHICKIES THAT'S MORE RESISTANT TO BURNING OUT FOR GM HEI HI PERF APPS WITH HI OUTPUT COIL THAT CAN HEAT THINGS UP.

* CHECK TO SEE THAT DIST SHAFT IS TURNING WHEN MOTOR SPINS OVER TO VERIFY TIMING CHAIN DIDNT BREAK WHICH ISNT LIKELY WITH YOUR NEW MOTOR.

* IF ALL ABOVE CHECKS OUT THEN TAKE COMPRESSION TEST ON A FEW CYLS TO SEE IF THATS NORMAL .

Let us know how you make out with all these checks.

Scott
 

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Discussion Starter · #4 ·
Gents,

Many thanks for the input. I plan to start fresh on Sunday and start with the distributor, wires, plugs, etc. I will follow the suggestions and report back. Hopefully it will be something simple. During the whole drive, I don't think I had it much past 1/4 throttle. There is so much torque there, the car moves effortlessly.

One thing I am concerned about. The mufflers are the ones that came with the car and are stupid loud. That's not just a 40+ year old talking. There is way too much interior noise and resonance. Anyway, it is so loud I can't hear of the motor is pining with the 16-18 degrees of initial and 92 octane gas. If I get it running this weekend, I will dial the timing back 2-4 degrees until I can get the mufflers replaced. The exhaust shop recommended Magnaflows to quiet down the inside while keeping the outside deep toned.

Thanks and more info later!
E.
 

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The short-case MagnaFlows are quieter than the short case FMs.
But even a SBC with the short 14" case MFs is loud....2.5"
Do yourself a favor, get the longest case muffler you can squeeze under there.....

2x on the distributor needs to be checked thoroughly.
I've played with this stuff 35 years and I've had a distributor cap come off, cracked cap, weak or bad ign module. But the rotor turning in dist cap that is not on right...sounds like the culprit here.
 

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Discussion Starter · #6 ·
George,

I appreciate the feedback on the mufflers and the distributor. I am crossing my fingers that this is something simple. I hope to be able to post back Sunday at the latest.

E.
 

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Eric,

My 70 Elky has the 2.5 F-M pipe kit and 14" M-F case mufflers, mild 350.
Throaty is probably a better word than loud.....
I get asked all the time if I have a 396 in there.....
I have a 68 Vette with medium build 427, stock ext manifolds, repro 2.5" pipe, and repro Vette mufflers. Throaty.
Pretty comparable in tone....both geared about the same 3.36/3.42. AT the 2 hr point, HUH!? Whatcha say?
See pics in fotki
 

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Probably not the case but did you check to see if the distributor moved while you were driving the car? The distributor bolt hold down that locks the distributor in place could be loose.

I broke down in my old 1967 Impala Station wagon once. I had the car towed to a repair station and everything. It turned out that the bolt holding the distributor down got loose and the distributor advanced on its own causing the engine to die.

I know you mentioned that while trouble shooting, the engine will crank and spit out of the carb. This is an indication that the timing is too retarded or advanced.

Just a suggestion. Good luck!
 

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Discussion Starter · #9 ·
Probably not the case but did you check to see if the distributor moved while you were driving the car? The distributor bolt hold down that locks the distributor in place could be loose.

Snip ...

I know you mentioned that while trouble shooting, the engine will crank and spit out of the carb. This is an indication that the timing is too retarded or advanced.
I did check that the other day. The distributor will not move by hand. That isn't to say it has not moved. I plan to get into it tomorrow morning to start troubleshooting. The distributor will be the first thing I look at.

Thanks for the tip!!! :)

E.
 

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Discussion Starter · #10 ·
Okay, I think I am done.
Everything checked out okay. So, I loosened the distributor and tried to retard and then advance the timing. Retarding did not allow the engine to start, but advancing it did. Once it fired up and started running, there was backfiring through the carb about every second or two.

I guess that makes it official. The cam must have flattened, probably only one cylinder. I think the distributor did move as well, which is why it would not restart. Wonder if this sets a record. Flat cam in less than 25 miles? :sad:

I appreciate the feedback tips to check. I copied them to my notebook for future reference. Any other thoughts or comments?

Thanks,
E.
 

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Eric,dont give up yet,a rocker could have come loose due to bad nut or rocker stud could have come loose or broken.

Pull the v/covers and ensure all rockers ar still attached properly.

If yes have some spin motor over with ign diabled to see if all the like rocker/valves are going up/dn approx the same distance,thats a quick way to see it s lobe/s went flat.

If you found a rocker or 2 broken or off the valves then maybe you have vealvtrain interfearance issues or bad rocker nuts that loosened up or bad rocker studs,etc.

I still have a funn feeeling somehting else is wrong like dist gear or timing chain issue.

I say this becasue when a cam goes bad it doesnt go from running ok then 5 mins later tick & pop and top like you said.

When a cam goes bad even if3-4 lobes go bad/flat the motor will still run like crap on the other 4-5 cyls but the motor doesnt just all the sudden tick ,then pop, then quit.

Mayby it started when you adv the timing becasue the dist gear is going bad,the timing chain slipped,dist shaft broke,or the rotor is broken making cam/ign timing way off.

Are you sure its not a broken rotor or bad cam gear?

Bring the motor to #1 cyl on comp/firing stroke, then see where the rotor is pointing,that should tell you if dist shaft/gear/rotor are ok. If the rotor is noit on or close to the #1 firing position on the dist cap with motor on #1 firinf stroke the dist issue i just mentioned is where you need to look.

Pull the v/covers to do the quick dirty test to see if any lobes when flat like i stated above,then go from there.

But i am still not convinced its your cam by a long shot unless its been running poorly all along during dyno pulls and the 25 miles you drove it before it suddenly stopped and you never noticed it which i dont think is the case at all. That's because from speaking with you in the past here in t/chevelle you seem to know enough about motors to know if it was running poorly prior to it suddenly ticking/poping/anfd then stopping and you would have stated it had been running poorly if that was the case but you didnt say that.

Scott
 

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Discussion Starter · #12 ·
Scott,

Thanks a bunch for the feedback. I was able to confirm the cap, rotor, wires, plugs, etc are good. I had good spark too. I think maybe the ticking noise was from the distributor getting advanced. Since the distributor was retarding, I was loosing vacuum. Prior to the shut down, the tranny would not shift into 3rd. I figured that the trans fluid was low as I discovered a leak after I got it home.

I will pull the distributor and check the gear. The cam gear/chain set I bought is a Cloyes and is a double roller. I did remove the driver's side valve cover and everything looked okay. I have a digital caliper so I measured all the nut heights to the top of stud. All were pretty close. I did notice the #1 exhaust rocker was a little off center, but it was not loose. Several would wiggle side to side slightly and some were tight. I guess some were loaded by the cam lobes. I can remove the passenger side and check them as well. I borrowed a bore scope from work and looked down inside the lifter valley. I couldn't see much. I was looking to see if there were metal flakes. I tried to angle it to look at the cam lobes, but I couldn't get it to turn.

I will try the alignment to #1 TDC and check the distributor. I'll see how that works out, then pull the distributor, and the valve cover. I'll report back when I know more.

Again, I appreciate the help and support.
E
 

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Eric,here are a few ore things to chk if the other items i stated to chk all chk out ok.

BIG VACUUM LEAK could cause it to do what yoyu descibed too,did any lrg vacuum lines like for power brake booster or maybe the smaller vac live to your vac modulateor come off?

Scott
 

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Discussion Starter · #15 ·
Scott & Dwayne,

I will check. I think I looked at the mod when I was under it yesterday, but I don't remember if the vacuum line was on or off. Will confirm....

E.
 

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Discussion Starter · #17 ·
Gents,

Vacuum modulator is hooked up and hose is intact. I checked all hoses and they are intact as well and connected.

I pulled the passenger side valve cover and vola! One rocker arm sitting off it's rod and valve. The pushrod was bent and broken. I took the pick below. I managed to noob myself on this. The pushrod was in upside down. The weak end of the pushrod was at the top where the bending moment acts on the top of the rod. Its the exhaust valve #2. I pulled the intake valve as well and it is bent, but installed correctly.

I removed the rods from #4 and they look fine. I measured both of them to order some more.

A couple of things.

You guys ROCK!!! :hurray:
You kept me motivated to do the systematic troubleshooting and more importantly, kept my spirits up when I thought it was something major.
Thank you! :beers:

Next thing. Why did the rods bend? I measured the nut on the exhaust and it was about .020 deeper down than the exhaust on #4. I did not measure intake #2. It appears I may have noobed myself again by getting those valves too tight. My guess is I did not have the lifters on the base circle when I adjusted them. I inspected the rest and they look okay. I want to replace and readjust all of them. When I remove them I can inspect all of them.

When I built the engine, I checked movement on the valve tip and the rockers were right in the middle. I will also check with my engine machinist as well. The block was decked, the heads cleaned, and he confirmed my clearances. I actually went with a thicker .049 gasket to make sure.

E.

Broken - sorry for the blur
Bent
 

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Zoiks!!!!!
 

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Discussion Starter · #19 ·

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Eric,the tip came out of the pushrod which can and does happen from time to time with those pressed in ends.

But the thing that still bothers me is the motor quit and you could not get it restarted unill you cranked in motor timing.

The motor should have kept running on 7 cyls with the 1 rocker off with no problems,heck if 4 cam lobes went bad a v8 would still run like crap on 4 clys but run non the less,i have seen it before.

It strange but i would repalce all thoses pushrods with 1 pc hipo parts to ensure the tips dont come out if they are in fact 2-3 pc p/rods with pressed in ends.

Its when things like rockers pop off that tey can hit the top retainer and pop the locks and then you drop a valve so replace all thoses weak p/rods with pressed in ends to avoid that catsatrohpy .

But i still cant get past the fact the motor stopped running and would not start with one vlave not working untill you advanced the timing,thats no right at all so keep an eye out for when you try to set timing back to where it belongs.

I am assuming all is ok with valvetrain geometry because you stated it was checked uppon assembly and was ok but the bent pushrods say otherwise to me that there was some kind of mechanical interfearance,had youj ust got into it when this happended?.

Worst yet ,i was thinking the motor went through all the dyno pulls at full rpm just fine so why mehcnaical interfearnce now?

Well what if the someone at the muffler shop decided to road test the car and overeved it to valve float and thats where the interfearance came from when some valves hit the pistons durring float?

Its very strange that this didnt happen when the motor was on the dyno as i remeber you stating was done a while back in other posts and then just cruisng home there seems to be interferance bending pushrods and breaking one?

Too bad you didnt think to copy mileage down to see if anyone drove the while it was at the shop. I know someone that left their vette at shop for windshield change. The worker took the car out for lunch and total it ,fliped it over. Owner found out when cops called him asking if the person that wrecked car had permission to drive it and shocked the hell out of the owner hearing his vette was totaled/flipped over so these things can and do happed from time to time.

After you install new p/rod-s and reset valves,take a comp test (throttle wide opne for best results/diable ign) to see if things are ok. If all clys are close your likley ok but if you have a coulple cyl's that are way low on compression that could show bent valves (check for bad camlobes if that happens) which could verify someone over reved the motor and if it wan't you that over reved it then who was it?

You already know it rpm'd fine for mult dyno pulls and then ran fine before it went to the shop,now crsuing home at a reasonble speed it decides to bend p/rods from possible interfearance of some sort,sound's very very fishy to me. If you find low compression on a few clys you need to cont the shop that woked on it to tell them why you think they hurt your motor and also you need to pull the head/s to check for bent valves at that point.

You should also get the shop that dyno'd the motor to write up a notorized statement stating they dyno tested the motor and it was fine when it left the shop and that the only way the motor could have had bent pushrods & valves was from someone abusing/over reving the motor since the valvetran geometry was already check uppon assembly and it ran fine for high rpm dyno runs too and it ran fine at your home just prior to trailering it to the shop for ex work,very fishy indeed. Is there any rubber from back tires slung up under the qtr's anywhere to show they took it out and beat the crap out of it on the road of did that in thier parking lot?

Since this is a new motor i am assusing all is ok with timing chain/gear and there was no slippage or improper install which could also have bearing on this but not likely since dyno pull went just fine.

Scott
 
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