Ignition Module Failure....???"

[LannyL81]

Gerry,
Yes, I have good oil pressure, above 40.
I had set the initial timing just as you wrote.
Engine would not start. Rotated distributor as far clockwise as it would go....would not start. Rotated distributor as far counter-clockwise as it would go and engine started.
Removed cap, noted position of rotor. Pulled distributor out to move over a tooth, put back in. Engine fired right-up. Had to again turn distributor a bit CCW to get to idle better. That is when I could hear the knocking or hammering sound. I pulled #3 wire off distributor and nothing changed....pulled #1 and got nailed by the voltage. Seems to me that spark was alot bigger with #1 than it was for #3. Going to look into this further. I have another coil I can try. Wish I had another ignition module to try...do not want to buy another one as they are not returnable.

Oh well.....the fun continues.

 

[GerryLP]

Lanny,

Yeah, I hear you. I only have a 4-pin module laying around -not a 7-pin one (from my Acadian's dizzy).

The coil does sounds suspect to me, if only because you were saying that the cylinder's exhaust port were cool to the touch on those cylinders in between the hot ones and in the firing order.

The spark is created by the rapid collapse of the magnetic field in the coil, and if there something wrong with the coil, it could alter the length of time required and thus the timing (in my opinion, but these are rare events or far a few in between).


Keep at it, pal. You are inspiring many of us to chase those problems down.

 

[LannyL81]

Okay....checked timing with computer connected....about 30 BTDC at idle....very rough idle.

Disconnected computer.....timing was about 12 or BTDC. Need to recheck this.

Engine idled better with computer disconnected.

Pulled one spark plug wire at a time...no real difference, but with #3 off idle seemed to get smoother for a few seconds, then almost died. Spark good on all.

At this point I do not where to go....:confused

 

[LannyL81]

Think I found the problem

Took valve covers off again to check rocker arms & pushrods. Found #4 exhaust rocker was quite loose....went ahead and loosened all the rockers arms and pulled each pushrod out and looked at it.

What I noticed was the #4 exhaust spring height was lower than the #4 intake....then noticed that #4 exhaust seemed to be lower than the other exhaust valves. Finally did a quick measurement and yes it is indeed lower....about 1/8".

Put air into the cylinder with both rocker arms off and air just flowed out the exhaust port.

Looks like head is coming off as I have no idea if the piston/rod is damaged or not.

Oh the fun....I sure hope its just the head.

 

[Peer81]

This is the kind of problem that gives me the creeps!
I'll watch this topic closely but sorry I don't have any idea where to even begin. Good luck!

Greetings Peter

 

[strokin383-c4]

Check your injectors, or your Harmonic balancer is slipping? or distributor rod may have cracked in the block? I had similar issues in my truck

 

[LannyL81]

Going to be awhile before I get the heads off...but it is either a dropped valve seat...doubtful...these are hardened seats afterall....or broken ring that has wedged in the exhaust port, or the bronze valve guide is somehow keeping the valve from closing. I am sure I saw all cylinders rocking...but...whatever.

 

[GerryLP]

....or broken ring that has wedged in the exhaust port, or the bronze valve guide is something keeping the valve from closing. I am sure I saw all cylinders rocking...but...whatever.

Or broken spring perhaps? But loose valve rockers sound only like loose rockers...I would venture out your way (on a weekend) if you lived any where between ABQ and Flagstaff, but you are in Phonix, right?

 

[LannyL81]

Gerry,
I am in North Tucson...not Phoenix....ugh.....will hardly even go to Phoenix...much less live there....:L

If the valve spring broke...I sure cannot see where. The retainer is all tight and nothing in the valve cover. I may put the #4 exhaust rocker arm back on and rotote the engine...just to see if the valve moves for sure or not.

But I know I would have noticed if it was not moving when I checked that all rockers were moving a week ago.

So I am thinking there is something keeping the valve from closing. Hope to get the head pulled this weekend.

I hate draining the coolant....always makes such a mess.

 

[LannyL81]

Here are the results:

#4 Valve:

#4 Piston:

So what you guys think.....am I looking at pulling the engine out, and doing almost a complete rebuild.....or.....would just cleaning off the tops of the pistons, put a new set of heads on....check to ensure that timing did not jump...do not think it did.....and be good for 100k miles....??????

Suggestions....................

 

[GerryLP]

Lanny,

Is that an optical illusion? Clean the #4 cylinder walls with a rag and brake fluid, and make sure that there are no grooves on the cylinder walls. If no grooves, then the cylinder should be ok. Coat the walls with a little oil to prevent rust.

If the motor never has been refreshed with machine work since the factory, then I would suggest that you do rebuild it; However, if funds are a concern, or you need the Vette to be running right now (if you pull the motor, chances are, you'll lose it for the entire summer), then fix that bent valve, get new gaskets, and get her running again.

Next winter, pull the motor out and work on getting the engine nicely rebuilt or something in preparation for Spring/Summer 2012.

You know, it would cost you about $150 bucks to refresh those heads somewhere locally. They can clean them, repair valve seats, leak check them, and get them ready for installation. All you have to do is re-install them.

 

[bill81vette]

I lightened up your pics and there looks like a hit on the cylinder wall,I think your going to bore or/sleeve that cylinder :ugh :ugh :ugh

 

[bill81vette]

 

[LannyL81]

The bright spot in the #4 cylinder picture is a flash reflection. I should have rotated the engine and brought the piston to the top, but didn't at the time.

The engine has gone through 2 rebuilds...first one was a 0.030 bore and the second was just a quick hone. The 2nd rebuild was after about 2500 miles from the first. There were two errors made in the 1st rebuild, one mine and one the machine shop.

Anyways the #4 wall looks very good...can still see the hone marks.

And no way am I putting those re-worked 882 heads back on. I want to go with a set of Edelbrock E-Street aluminum heads...70cc ones, as I think the 64cc ones with a zero decked block would be like 11.3 static compression....too much.
Am concerned about piston to valve clearance though....working on this.

 

[bill81vette]

Im glad its a reflection and not damaged....I was kind of concerned about it!!!!

Sent from my DROIDX using Tapatalk

 

[GerryLP]

....And no way am I putting those re-worked 882 heads back on. I want to go with a set of Edelbrock E-Street aluminum heads...70cc ones, as I think the 64cc ones with a zero decked block would be like 11.3 static compression....too much.
Am concerned about piston to valve clearance though....working on this.

My L81's current set-up

My Vette's Iron heads are at a true 9.5:1 ratio set up, and the car is running fine. You can opt for either one, the 70 or 64 CC's. The decision hinges on fuel consumption. Aluminum heads can easily absorb the increase in ratio in your case up to 2 full points (so for example 9.5:1 to 11.5:1 increase) because the aluminum helps dissipate heat and you won't face detonation. Additionally, you can play a little with the combinations between the two aluminum head chamber sizes (70 and 64 CC's ) and the gasket used.

Measure the BDC piston's distance to the deck (which I surmise to be a 9.000 deck) and the distance to the deck at TDC, and I can use these numbers in my performance trends CR ratio calculator.

Actually, are the basics as the numbers you had sent me in 2007???

GerryLP :cool

P.s. More importantlyly, we want to hit the best quench, which is the closest we can get to 0.040"

 

[GerryLP]

Hey folks,

In helping Lanny with several head xhmaber sizes and gasket thicknesses, what are the commonly available gasket sizes?

I know about the ones that are 0.015" (what my L81 is using now), but what other sizes are there? I think 0.021" and 0.031" as well as 0.039" and 0.041". Any others?

 

[Peer81]

Sorry don't know much about headgaskets but on the CR. Like Gerry says first try to get as close to 0.035 - 0.040 as you can. Then look at what cam you like to use (or what you're using). Then look what head cc is best and after that look again at the cam to get the DR to a perfect fit. I would say go with the 70cc so you can also go to a 383 if you want to. If you want a big cam then it's another game.

Greetings Peter

 

[LannyL81]

My L81's current set-up

My Vette's Iron heads are at a true 9.5:1 ratio set up, and the car is running fine. You can opt for either one, the 70 or 64 CC's. The decision hinges on fuel consumption. Aluminum heads can easily absorb the increase in ratio in your case up to 2 full points (so for example 9.5:1 to 11.5:1 increase) because the aluminum helps dissipate heat and you won't face detonation. Additionally, you can play a little with the combinations between the two aluminum head chamber sizes (70 and 64 CC's ) and the gasket used.

Measure the BDC piston's distance to the deck (which I surmise to be a 9.000 deck) and the distance to the deck at TDC, and I can use these numbers in my performance trends CR ratio calculator.

Actually, are the basics as the numbers you had sent me in 2007???

GerryLP :cool

P.s. More importantlyly, we want to hit the best quench, which is the closest we can get to 0.040"

Gerry,
I do not know what the distance is between top of piston when at BDC and the block deck is....is that supposed to be 9.000cm?

At TDC the distance is zero to slighty negative by a few 0.001's....will have to measure again.

The head gaskets I have found have a compressed thickness of 0.040"....but I do not have the bore dimension in front of me...4.066 to 4.125....or so.

With the 882 heads I had a static CR of 9.1 something and that was with 75cc heads. If I went with a 64cc head the CR would be well over 11:1 and would require higher octane than pump gas. Now with aluminum I could go with 70cc or 64cc....more likely 70cc and still get by with 91 octane pump gas.....64cc may be pushing that a little due to the hot air temps of summer in Tucson.

The cam is only the Comp Cam 280H and I am using 1.6 roller tip rockers. The E-Street heads from Edelbrock will go for over 0.500 lift where I am about 0.480. Not changing cams as I have the CCC and this is supposed to be the largest cam I can use and still use the CCC....at least that is what Comp Cams told me.

Also I really do not want to pull the cam out. I do need to check the lobes and need a good method for doing that.....know one?

 

[Peer81]

To ge honest, the CR gives you a good indication. But with the program Gerry has you have to look at the DR! Your 280 cam with 1.6 rockers will bleed off so much air (or compression) that I think you can get away with the 64cc's.

When I look at Gerry's compression a CR of 9.5 is nice but the DR is 7.0 and 8.25 is about the max you can have with iron heads. So still a full piont of compression to squeeuze out/improve.

Greetings Peter