SmokinBBC
Well-known member
So you have the same problem with 2 different dist. and carbs?
Engine shuts down at 4,000 RPM
- Thread starter Blain
- Start date
Blain
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- Aug 26, 2008
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Thats correct.
Went the easy route and took the module from the spare distributor and put it in the car. No change.
Swapped the whole distributor assembly. No luck.
Swapped out with a fresh Holley off of a friends truck that broke a rocker assembly. No luck.
Replaced condensor, rotor, cap and coil. One at a time. No luck.
Installed an electric fuel pump in line with the mechanical. No luck.
Pulled the pickup unit from the fuel tank and removed the sock. Ditto.
Completely bypassed the mechanical and tank-hardlines by drawing out of a 5 gallon can with an electric direct to the carb.
Clamped secondaries closed, although Lars said that the butterflys still actuate so this test was flawed. Still did the same thing.
mrvette
Phantom of the Opera
Gotta be springs, they hitting a harmonic in there where the coils are in a bind, lucky they maybe not broken....here or somewhere I seen high speed movies of that shit, them springs going every which a way but loose,
talk of a devious SOB, damn.....:search::shocking:
Blain
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This is sucking the fun out of my project.......
Old cam, new Z28 springs. Have not lifted valve covers yet. I could be wrong but it doesn't sound like floating valves. No other overhead noise.
Timing does not drift while looking at the marks in the 2,000 range. I can't bring myself to put my face close enough to see the marks while bouncing against 4300 rpm.
I'm going back to the HEI with a new module today. It just feels spark related but don't understand why it would fire the sprobe if it was loosing spark. Something else I saw while I had a scope connected; the voltage of the spark rises to its peak then drops off into the saturation mode-all looks fine-until I wind it up to the magic RPM, about 43000, and the spark voltage pattern reverses on the scope and drops below the baseline. Now it would help if I knew how to use the damn thing but all I was looking for was if it was firing and at what voltage. I'm not sure if the scope is telling me something I should know or I just don't know how to set it up. Probably should explore this some more.
jsssgrl1209
Banned
hhmmmm
I just checked this post out tonight and must say, from your video it looks like you have valve problems. Most likely from the springs.
That is why when you keep the car running wide open and it starts to die you see the gas vapors shooting up through the top of the carb every time it dies.
Your valves arent acting properly and you are getting compression back through the intake. Thus pushing the gas vapors back out of the carb.
But that is my .02 cents.....its all trial and error from this point. I would rule out distributor and carb problems though.
I just checked this post out tonight and must say, from your video it looks like you have valve problems. Most likely from the springs.
That is why when you keep the car running wide open and it starts to die you see the gas vapors shooting up through the top of the carb every time it dies.
Your valves arent acting properly and you are getting compression back through the intake. Thus pushing the gas vapors back out of the carb.
But that is my .02 cents.....its all trial and error from this point. I would rule out distributor and carb problems though.
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mrvette
Phantom of the Opera
I agree, as my head shop guy, Ralph, next door basically....when doing my L98 aluminum heads made a comment about those Z28 springs, my heads needed the spring seats ground down a bit because they did not spec out correctly on coil spacing, them springs need the heads altered when they are used.....
Ralph always been right on about heads, it's all I know.....:gurney:
pcf_mark
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- Aug 22, 2008
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- 218
You either getting cross fire across the plug wires or some type of valve train failure. The valve springs may be installed incorrectly and shimmed too tight and they are bouncing after the bind. Or your lifters are not pumping up (hydraulic). It is not all cylinders all the time. Check your plug wires for cross fire next.
If that checks out take you can take off the valve covers and start looking at the rockers when it hits this same piont. You need the clips that go on the rockers to stem the fllod and a cut down valve cover to keep the oil in the engine.
If that checks out take you can take off the valve covers and start looking at the rockers when it hits this same piont. You need the clips that go on the rockers to stem the fllod and a cut down valve cover to keep the oil in the engine.
jsssgrl1209
Banned
z28 springs
These springs are a decent spring, which are generally good for .500 lift. I am pretty sure they do require your heads to be machined to accept them and work properly. But hey, I'm a big block guy, so check on it to make sure.
These springs are a decent spring, which are generally good for .500 lift. I am pretty sure they do require your heads to be machined to accept them and work properly. But hey, I'm a big block guy, so check on it to make sure.
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78anniversary
New member
Did Blain ever get this figured out? Curious to know what it was
Blain
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- Aug 26, 2008
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Well, things went way wrong.
First I found the cam 4 teeth off. Not sure how it got that way. At this point I could have just put it back in time at the cost of a couple of gaskets. But no, I decided while I was there I would replace the old Erson grind with a Comp 287. I think that is the number. Anyway the popular small block Chev cam by Comp.
After 30 minutes of 2500 RPM break in I hear a tick. I might have missed an adjuster. So I take the lash out and about 10 minutes of running it develops another. After this takes place about 6 times I come to the conclusion something is wrong. Found one that I knew I had tightened but is loose again. Pulled the rocker and reached down with a magnet to pull the lifter out. Hummm, it gets stuck in the bore. Thats a bad sign.
5 lobes on the Comp cam are GONE. Went by the book on install and break in. Sent the cam back to Comp for a possible warranty.
Flushed the oil system out with clean oil, diesel, solvent and air pressure.
Decided against another Comp. Went with the 410 HP Edelbrock. 25 minutes of break in. This time I only lost 1 lobe, and a 500 mile engine. Hyper-u pistons were embedded with cam debris, the crank was cooked, cyl walls scored, etc.
The iron from the first cam is impossible to flush out of a block while in the car. Lesson learned.
The engine is now at a machine shop. Going 383, Vortecs, Roller cam.
All this could have been avoided by leaving the Erson cam in the engine. For the cost of a couple gaskets.
Blain
First I found the cam 4 teeth off. Not sure how it got that way. At this point I could have just put it back in time at the cost of a couple of gaskets. But no, I decided while I was there I would replace the old Erson grind with a Comp 287. I think that is the number. Anyway the popular small block Chev cam by Comp.
After 30 minutes of 2500 RPM break in I hear a tick. I might have missed an adjuster. So I take the lash out and about 10 minutes of running it develops another. After this takes place about 6 times I come to the conclusion something is wrong. Found one that I knew I had tightened but is loose again. Pulled the rocker and reached down with a magnet to pull the lifter out. Hummm, it gets stuck in the bore. Thats a bad sign.
5 lobes on the Comp cam are GONE. Went by the book on install and break in. Sent the cam back to Comp for a possible warranty.
Flushed the oil system out with clean oil, diesel, solvent and air pressure.
Decided against another Comp. Went with the 410 HP Edelbrock. 25 minutes of break in. This time I only lost 1 lobe, and a 500 mile engine. Hyper-u pistons were embedded with cam debris, the crank was cooked, cyl walls scored, etc.
The iron from the first cam is impossible to flush out of a block while in the car. Lesson learned.
The engine is now at a machine shop. Going 383, Vortecs, Roller cam.
All this could have been avoided by leaving the Erson cam in the engine. For the cost of a couple gaskets.
Blain
jsssgrl1209
Banned
Well the cam being that many teeth off expalains the vapors shooting through the carb.....valves opening and closing at the wrong time.
mrvette
Phantom of the Opera
U a HELL of a lot more calm than I would be, I"d be slinging sledgehammers into traffic a mile away by then.....
I faced a similar but not exact operational thing on a Dodge van engine some months ago, I had done a timing chain, I actually wasted a day tearing it apart again to check them marks, they were fine....turned out some redneck bubba had the rong size injectors in there....put in a old set from the vette, and it ran like a raped ape.....can't win, some daze....:flash::crutches:
78anniversary
New member
That Sucks! :cussing:
Blain
Active member
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- Aug 26, 2008
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- 26
Hey, lesson recap while I'm just hangin' around;
Never rule out the obvious
Things might go wrong-deal with it
Flat tappets and todays oil won't work
Estimate the time/and or money to complete the project then cube it. ($x$x$)
A video will demonstrate what you can never explain (Youtube link)
The value of car forums are a resource the younger guys will never fully appreciate
My car will take a little longer to complete but it will be bitchin' when done!
Thanks everyone for the input during this thread
Blain
Never rule out the obvious
Things might go wrong-deal with it
Flat tappets and todays oil won't work
Estimate the time/and or money to complete the project then cube it. ($x$x$)
A video will demonstrate what you can never explain (Youtube link)
The value of car forums are a resource the younger guys will never fully appreciate
My car will take a little longer to complete but it will be bitchin' when done!
Thanks everyone for the input during this thread
Blain
