Another misfire in the Cobra!

[94cobra69ss396]

I was out shopping today and was almost back to my house when the Cobra developed a misfire and a tapping noise in the valvetrain. When I got home I pulled the valve covers which requires removing the upper intake manifold and discovered that one of the rocker arms broke. To be precise it was the exhaust rocker on cylinder 3. To my surprise the pushrod was fine. However, I pulled the intake rocker off the same cylinder and found that the pushrod was bent. So obviously something happened to cylinder 3 but I have no idea what as of yet. I went by Phil's house tonight and picked up his cylinder leak down tester to help determine what else is wrong. If I'm lucky the whole cylinder will be F&#%ed so I will have an excuse to build a 331 so that Eric's car won't be faster than mine.

http://media.motortopia.com/files/9911/album_cobrapics1/4d576a07b817e/tn_full_100_0829.jpg

http://media.motortopia.com/files/9911/album_cobrapics1/4d576a22c42fb/tn_full_100_0830.jpg

[kdracer73]

Holly crap !

[09sscalicobalt]

damn that sucks lol is it a 4.6 or 5.0

[94cobra69ss396]

It's a 5.0.

[Redondo Jon]

Holy crap is right. The rod is trying to turn itself into the letter S.

[09sscalicobalt]

oh ok and haha yea it coulda been alot worse tho

[94cobra69ss396]

oh ok and haha yea it coulda been alot worse tho

It might still be. I still don't know what caused the valves to bind up enough to break a rocker and bend a pushrod. I'm going to do a leak down test tomorrow and go from there.

Holy crap is right. The rod is trying to turn itself into the letter S.

That's kind of what I'm use to seeing. The shocker was the broken rocker. The only time I've broken a rocker before this was when my dad and I first built the 396 in the Chevelle when I was 17. The guy who built the heads didn't set them up for the lift on the cam we had and the springs went into coil bind and pushed the pushrods right through the back of the stock stamped steel rocker. We then had the heads redone and my dad bought the Crower roller rockers that are still on the car today.

[94cobra69ss396]

This morning I pulled the plug from cylinder 3 so that I could run the leakage test. The plug looked fine so it doesn't look like anything was inside the cylinder. I did the leakage test and it only has 10% leakage. Not bad for having 80,000 hard miles on the engine. So going to order a new rocker and pushrod and put it back together.

http://media.motortopia.com/files/9911/album_cobrapics1/4d58392c492d0/tn_full_100_0831.jpg

[Damian]

Lucky. Did you see anything wrong with the piston at all? Not sure if you have a borescope or not. Or even just looking in there with a flashlight.

[94cobra69ss396]

I can't get down there to look into the spark plug hole and I don't have borescope. However, I did compress the valve springs down to make sure they moved freely. The 10% leakage tells me that there isn't a broken piston ring, blown head gasket, or even a hole in the piston. I'm not sure where the piston is at relative to the stroke but I probably should make sure it is at bottom dead center and do the leak down test again. That way I can make sure that there isn't a crack in the cylinder wall.

[Throttle Crazy]

That's actually 16% leakage, but still good.

[Vettezuki]

I can't get down there to look into the spark plug hole and I don't have borescope. However, I did compress the valve springs down to make sure they moved freely. The 10% leakage tells me that there isn't a broken piston ring, blown head gasket, or even a hole in the piston. I'm not sure where the piston is at relative to the stroke but I probably should make sure it is at bottom dead center and do the leak down test again. That way I can make sure that there isn't a crack in the cylinder wall.

I think he's on the road, but big2bird has a bore scope if you want to take a look.

[94cobra69ss396]

I ordered the new rocker arm and pushrods. I'm just going to bolt it back together when they come in and see how it runs.

[enkeivette]

If there was a crack in the cyl wall or the piston it would puff air out of the rocker cover like a steam engine.

Can you see the lifters?

[enkeivette]

When I first assembled my motor I had pushrod guide plate clearance issues. Check yours to make sure they haven't shifted, causing binding.

[94cobra69ss396]

If there was a crack in the cyl wall or the piston it would puff air out of the rocker cover like a steam engine.

Can you see the lifters?

I thought about that later. I don't have guide plates because I have shaft mount rockers. Take another look at the first picture.

[Shaolin Crane]

did you inspect the lifters and that portion of the cam to see what could have caused the bind? One lifter might have extended out of the block and thats what bent the pushrod or snapped the rocker, i would investigate further while you have everything apart.

[94cobra69ss396]

The lifters are fine. I can't see the cam and I don't want to take the front end apart to pull it. I'll put it together and then hand cycle the engine over a couple times to make sure it all looks good. If it does then I'll put the intake back on and do a compression test as well as another leakage test. If they both come out good I'll start it up and see how it runs.

[enkeivette]

This is so strange. I can't visualize what might have happened.

[94cobra69ss396]

Phil and I are at the same point. It broke the exhaust rocker and bent the intake pushrod but everything seems fine. The valves move freely and are sealing so they're not bent. The leak down shows that the rings and piston should be fine. I'm just hoping what happened is that the rocker was fatigued and broke and some how caused the intake to bind momentarily which bent the pushrod.

[enkeivette]

http://www.speedtalk.com/forum/viewtopic.php?f=1&t=25496

[enkeivette]

Now I'm thinking you had some intense valve float, which allowed the pushrod to escape from the rocker, causing it to bind and break the rocker...

[Leedom]

I did not read Adam's link but what if when the rocker broke it somehow hit or got lodged by the intake rocker and did not allow the intake rocker to move through the entire movement for a cycle of 2 and caused the pushrod to bend.

Possible?

[94cobra69ss396]

Yes, that's possible. I'm really not that worried about it. I think everything is okay and that I'll be able to put it back together and run it.

[94cobra69ss396]

Pushrods and rocker arm came in yesterday. I have people telling me that the leakage percent seems high and that I should check some other cylinders so I'm going to try and do it today if I can.

[Throttle Crazy]

I read that other thread and agree that the rocker arm had to break first like we talked about. Also I never said that 30% was what I normally see on an 80,000 mile motor. I normally see 12% to 20% but anything under 30% the cylinder should be fine. On a burned or tuliped valve I see 60% or more. If the valve were bent or the piston broken it would be even higher. It is always good to check against the other cylinders to see where they are at. The bottom line is that 16% is an acceptable leakage. If the cylinder next to it only reads 10,12,13% what difference does it make. Put the rocker arm and push rod in it, fire it up, and drive the shit out of it for another 50,000 miles.

[enkeivette]

I didn't know Throttle Crazy was your brother, and you've had your car to 175mph? Holy crap.

[94cobra69ss396]

Yes and yes.

[enkeivette]

It's amazing what some of the aftermarket cars on the road can do. We should have more super street challenges with street driven tuner vehicles.

[94cobra69ss396]

Well I got the Cobra put back together and it's running great again.

[enkeivette]

Well I got the Cobra put back together and it's running great again.

:beer:

[Leedom]

Well I got the Cobra put back together and it's running great again.

Take at least 1 car off the Motorgen "Not Running" List! :sm_laughing:

[Shaolin Crane]

Add a few more months to my car :(

[94cobra69ss396]

Add a few more months to my car :(

Why?

[Shaolin Crane]

Pushrods were back ordered a few more weeks, and i need more dental work

[94cobra69ss396]

So I think this happened again. I ran to the store last night and on may way back something let go. The engine has a knocking sound but I can locate from where and I'm down a cylinder or two. I'm hoping that I just broke another rocker but we'll have to see.

[Shaolin Crane]

Time for a 347...

[fiveohwblow]

Time for a 408...

Fixt

[94cobra69ss396]

331 if the bottom end is an issue but I don't think it is. Otherwise it will just be some porting on the heads and intake and then to Pacific Engine for the valve job and new springs.

[Shaolin Crane]

Fixt

Too much weight, too much of a combo change

[fiveohwblow]

Too much weight, too much of a combo change

Negative nancy!

[Shaolin Crane]

He would need new blower brackets, heads, pushrods, intake, accessories, hood, tuning blah blah. Or just put a 347 shortblock and call it a day

[Leedom]

So I think this happened again. I ran to the store last night and on may way back something let go. The engine has a knocking sound but I can locate from where and I'm down a cylinder or two. I'm hoping that I just broke another rocker but we'll have to see.

So when I come out next week we work on the Hyundai on Saturday and the cobra on Sunday? :jester:

[94cobra69ss396]

No. I'm going to wait until we have the Santa Fe done so I can put it in driveway next to the Ford. Just in case I have to pull the engine.

[Leedom]

No. I'm going to wait until we have the Santa Fe done so I can put it in driveway next to the Ford. Just in case I have to pull the engine.

Well when you get to the point of doing the Cobra you can count on me for an extra pair of hands.

[94cobra69ss396]

So I cleaned out the garage today to make room on my work bench to take the Cobra apart and then this afternoon I started on it. Turns out that I broke another exhaust rocker and bent the intake pushrod but this time it was on cylinder 1. So I pulled the head (still need to pull the drivers side) and am going to port them. Then have Pacific engine do a machine then if needed, do a valve job and install new valve seals and springs.

http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020025.jpg

http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020027.jpg

[Leedom]

So I cleaned out the garage today to make room on my work bench to take the Cobra apart and then this afternoon I started on it. Turns out that I broke another exhaust rocker and bent the intake pushrod but this time it was on cylinder 1. So I pulled the head (still need to pull the drivers side) and am going to port them. Then have Pacific engine do a machine then if needed, do a valve job and install new valve seals and springs.

What are the odds that happens on 2 of your rocker? That is crazy. Any idea what might be causing it? You will probably have that thing up and running again before we start on the Santa Fe.

[94cobra69ss396]

The concensous last time was that it was caused by valve float. So instead of doing the same thing I did last time which was to order a new rocker and pushrod I'm installing new springs. I'm also going to port them while I have them off and have Pacific engine rebuild them so I definately won't have it done before next weekend. While I have it apart I'm also going to throw a new water pump on.

[Leedom]

The concensous last time was that it was caused by valve float. So instead of doing the same thing I did last time which was to order a new rocker and pushrod I'm installing new springs. I'm also going to port them while I have them off and have Pacific engine rebuild them so I definately won't have it done before next weekend. While I have it apart I'm also going to throw a new water pump on.

Sounds good. We are still on for next weekend right? John you still coming?

[Shaolin Crane]

Coil bind could definitely be an issue. Probably the best idea to have everything gone through after breaking 2 rockers. I have a new set if lifters if you want them and those ARP head bolts as well.

[94cobra69ss396]

Sounds good. We are still on for next weekend right? John you still coming?

We are still on. Are you driving your truck out because we need to pick up my engine hoist from John's house. I also don't have a spare engine stand since the 454 is on one, Guy has one and John has another.

Coil bind could definitely be an issue. Probably the best idea to have everything gone through after breaking 2 rockers. I have a new set if lifters if you want them and those ARP head bolts as well.

Thanks, I do need lifters because the exhaust one on cylinder 1 took a beating but I already ARP head bolts.

[Shaolin Crane]

Well they're yours anyways for the spare engine i know you'll build. Lifters are a bit dusty but i'll clean them up before i give them to you.

[Leedom]

We are still on. Are you driving your truck out because we need to pick up my engine hoist from John's house. I also don't have a spare engine stand since the 454 is on one, Guy has one and John has another.

I will bring the truck. We can grab both the hoist and stand from John (if John does not mind us borrowing it). I need to figure out what Upper BJs I need for the truck so maybe we can figure that out as well. The Guy at Outlaw off-road suggested a moog K6292 which is for a Chevy after seeing my upper arms, but he said he could not be sure without seeing my stock ones to check some measurements.

[94cobra69ss396]

I've spent about 30 hours now porting the heads and I'm finally done. I hope what I think will flow well actually does or I just ruined a set of $1,600 heads. That would suck! I'm going to take them over to Pacific Engine sometime this week. I'm also port matching the lower intake but just barely started that tonight. Here are some pictures.

Before.

http://www.motorgen.com/pic/data/500/2012-07-10_21_27_50.jpg
http://www.motorgen.com/pic/data/500/2012-07-10_21_28_27.jpg
http://www.motorgen.com/pic/data/500/2012-07-10_21_29_14.jpg
http://www.motorgen.com/pic/data/500/2012-07-10_21_29_47.jpg

After.

http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020105.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020106.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020117.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020118.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020119.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020120.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020122.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020124.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020125.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020116.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020114.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020104.jpg

Intake manifold.

http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020112.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020113.jpg
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020111.jpg

[Shaolin Crane]

Is there any reason why you didnt blend the valve pocket into the runner? Unless you did and I cant tell from the pics.

[Vettezuki]

:popcorn:

[94cobra69ss396]

I did, it's just hard to tell in the pictures.

[Shaolin Crane]

I was just going by this picture
http://i395.photobucket.com/albums/pp40/94cobra69ss396/P1020124.jpg
Looks like the sharp edge of the pocket is still there and it could still be opened up a ways towards the seat.
It's my understanding that the largest gains come from opening up and smoothing the pocket. Then again its difficult to tell. Work looks great either way, did you find somewhere to flow test them?

[94cobra69ss396]

If you're talking about the short side radius I circled in the picture, then no I didn't touch it. It looks sharp in the picture but it's not. It has a nice round shape to it already so I didn't have to reshape it. The same goes for the exhaust.

http://www.motorgen.com/pic/data/500/circle.jpg

[Shaolin Crane]

gotcha, thats why i was asking. My AFR's looked horrible so i assumed yours would look similar if untouched

[Leedom]

Looking good Ron!

[94cobra69ss396]

gotcha, thats why i was asking. My AFR's looked horrible so i assumed yours would look similar if untouched

Yeah but before you bought yours they were ported by a blind person with ALS.

[enkeivette]

Looks good! What sorta tool/ bit did you use to do it? What kinda heads are those?

[enkeivette]

Ya my AFRs looked clean and perfect fresh out of the box. If yours didnt look good Guy someone hacked them up before they got to you.

[94cobra69ss396]

Mine are AFR 165's. I used a Dremel with a pencil attachment and various bits and a die grinder with 1/2" x 7/8" cutting bit.

http://www.motorgen.com/pic/data/500/20120802_140612.jpg
http://www.motorgen.com/pic/data/500/20120802_140619.jpg
http://www.motorgen.com/pic/data/500/20120802_140636.jpg

[Shaolin Crane]

Yeah but before you bought yours they were ported by a blind person with ALS.

That was just the "awesome" gasket matching that yielded the PO 12rwhp :rolleyes:

The pockets and exhaust ports were untouched. The machining grooves were so deep i could grab them with my finger nails.

I looked at your heads before I took them over and the face of the pocket and inner edge of the seat were untouched, this is what I was looking at in the pics, the most gains come from smoothing and blending that all into one piece.

[enkeivette]

Mine are AFR 165's. I used a Dremel with a pencil attachment and various bits and a die grinder with 1/2" x 7/8" cutting bit.

http://www.motorgen.com/pic/data/500/20120802_140612.jpg
http://www.motorgen.com/pic/data/500/20120802_140619.jpg
http://www.motorgen.com/pic/data/500/20120802_140636.jpg

Oh ok, thats how I ported my victor jr. Wasnt sure that would work with heads... very cool. I dont think I would have had the stones to cut into my heads like that.

Im very much a do it yourselfer, but on a pair of expensive heads... eek. :beer:

[94cobra69ss396]

Oh ok, thats how I ported my victor jr. Wasnt sure that would work with heads... very cool. I dont think I would have had the stones to cut into my heads like that.

Im very much a do it yourselfer, but on a pair of expensive heads... eek. :beer:

That's why I didn't go wild on them. I'm just hoping for an improvement over stock. I did less to the Chevelle and picked up 2 tenths so hopefully what I did to these will give me the same return or maybe a little better. I'd be happy with that. If they flow worse and I lose power that will suck and I'll just have to pick up some AFR 185's.

[Shaolin Crane]

If they flow worse and I lose power that will suck and I'll just have to pick up some TW 225's.

fixed

[94cobra69ss396]

They're not smog legal that's why I would go with the AFR 185.

[enkeivette]

My 195s are CARB legal, but who the hell can tell?

[Shaolin Crane]

They're not smog legal that's why I would go with the AFR 185.

I got carried away, forgot about smog. Then TW 205's would be my next choice.

[94cobra69ss396]

My 195s are CARB legal, but who the hell can tell?

The bigger Ford AFR heads don't have the hole drilled for the smog pump which the emission legal 165 and 185 have.

The issue with upgrading to heads like that is I would not only have to buy the heads but then I'll also need new rockers.