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Thread: Looks like the heads may be coming back off :-(

  1. #1
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    Looks like the heads may be coming back off :-(

    Haven't been on here in awhile. Between working so much the past few months and getting disgusted with tuning progress I haven't made much time to play with the truck but I finally tore into it this past weekend. Short story, Dave W has been my tuner. The start up bin went better than expected, truck started and ran pretty well but rich. Did some data logs and sent them to him. Bin #2 showed seemed to show some mild improvements, but still rich. More data logs and on to Bin #3. Down hill, very rich, particularly at idle and low throttle, can smell the fuel in the exhaust. Cold start would barely idle and stall if you tried to give it gas. Only way I could get it to restart was to hold the throttle wide open. Quickly developed a bad miss. This past weekend I pulled the plugs and this is what I found.

    Attachment 9997

    These were brand new plugs with probably less than 100 miles on them, just some casual driving and data logging. Cyl #4 was wet and as you can see not carbon fouled. Ran a compression check and found to only have 55lbs on that cyl. Pulled the valve cover and found a broken intake rocker stud.

    Attachment 9998

    Pulled the #4 exhaust rocker arm and put some air to the cylinder, its leaking down, I think past the exhaust valve so it looks like I'll be pulling at least this head. As to why and when the stud broke is beyond me. I'm pretty sure those comp rockers are considered long slots and I couldn't see any evidence of the slot hitting the stud. I use Mr Gasket screw in studs. Are they worthwhile or should I replace them all?

    Obviously I've got some mechanical issues to fix but let's get back to the tuning. I was hoping to get anywhere between 325-375 fwhp out of this build. I converted the fpr to adjustable by installing a screw in the base, still used the stock spring. I used the EP377 fuel pump. I installed a schraeder valve between the fuel filter and TB inlet. I was running 17-18 psi at start-up (as I'm sitting here typing this I'm thinking, hmm, maybe I should check to see if this is still where I'm at now) and I'm using cop car injectors cleaned and flow tested by Mr Injector in a 46mm bored throttle body from SRP performance. Am I pushing to much fuel for this build? Should I lower the fuel pressure or try to tune to it?

    Problem during initial start-up, erratic high idle. IAC valve was apparently bad on rebuilt throttle body, replaced with the one off my original throttle body and problem went away. Any other throttle body issues I should be looking for?

    Here are the start-up files that Dave gave me and the data logs that followed.

    skip down a few posts

    Looking for tuning help and using tuner pro RT.

    Thx
    Last edited by old truck guy; 12-18-2015 at 02:57 AM.
    95 GMC K2500, 4l80e, 4.10 gears, 355 L05 4-bolt block, ARP rod bolts, Speed-Pro H423DCP-30 pistons, moly rings, 217 heads, vortec cam, TBI mods, cop car injectors, headers, 2 1/2" Y-pipe and 3" single exhaust with high flow muffler and cat.

  2. #2
    Fuel Injected!
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    Ok it didn't upload my pictures. How do I do that on here?

    Disregard. Figured it out.
    Last edited by old truck guy; 12-16-2015 at 07:58 AM.
    95 GMC K2500, 4l80e, 4.10 gears, 355 L05 4-bolt block, ARP rod bolts, Speed-Pro H423DCP-30 pistons, moly rings, 217 heads, vortec cam, TBI mods, cop car injectors, headers, 2 1/2" Y-pipe and 3" single exhaust with high flow muffler and cat.

  3. #3
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    Ok my links for the bin files and data logs don't seem to be working. What is the best way to upload these?
    95 GMC K2500, 4l80e, 4.10 gears, 355 L05 4-bolt block, ARP rod bolts, Speed-Pro H423DCP-30 pistons, moly rings, 217 heads, vortec cam, TBI mods, cop car injectors, headers, 2 1/2" Y-pipe and 3" single exhaust with high flow muffler and cat.

  4. #4
    Fuel Injected! Dr_Grip's Avatar
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    Quote Originally Posted by old truck guy View Post
    Ok my links for the bin files and data logs don't seem to be working. What is the best way to upload these?
    Click "go advanced" in the reply window, scroll down, use the "attach" function. :)

  5. #5
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    Attached Files Attached Files
    95 GMC K2500, 4l80e, 4.10 gears, 355 L05 4-bolt block, ARP rod bolts, Speed-Pro H423DCP-30 pistons, moly rings, 217 heads, vortec cam, TBI mods, cop car injectors, headers, 2 1/2" Y-pipe and 3" single exhaust with high flow muffler and cat.

  6. #6
    Super Moderator dave w's Avatar
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    I'm trying to understand what happened? Did you have a mechanical failure?

    Remote tuning can require several data log / .bin files, because the changes to the .bin are smaller in nature when I'm not actually with the vehicle.

    To date, the best performance I've achieved, that was actually dyno'ed, with an engine similar to yours was 330 RWHP. I might have achieved better performance, but most tunes I've done don't go to the dyno. Most tunes I've done are usually budget builds that can limit performance options.

    dave w

  7. #7
    Fuel Injected! Roadknee's Avatar
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    I'm almost certain 17-18 psi with the stock spring has the spring coil bound. If it is the fuel pressure will not be constant as the fuel demand through the injectors changes and the engine will run erratically. IIRC, BLG355 from this forum installed a 1995 K1500 brake cylinder spring inside the stock spring and was able to get over 20 psi. I think you'll need at least 18 with the cop car injectors (68 pph?) to supply your engine. I recommend you fix your mechanical issue, get fuel pressure squared away and give it another whirl. Unless that air leak is really bad, you might try swapping that rocker stud, reassemble and check compression before tearing it completely down.
    1995 K1500, Stock LO5, 4L60e, 3.73 gears, 265/75-16 tires, L&L Products Ultra-flow headers into 2-1/2" Y-pipe and 3" single exhaust

  8. #8
    Fuel Injected! brian617's Avatar
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    Quote Originally Posted by Roadknee View Post
    I'm almost certain 17-18 psi with the stock spring has the spring coil bound. If it is the fuel pressure will not be constant as the fuel demand through the injectors changes and the engine will run erratically.
    I second that, I even had and TBI Chips "18psi" spring that coil bound at 17.5psi caused all kinds of problems because the fuel pressure wasn't consistent.
    89 K1500 Scottsdale 5.7L 5spd 3:42 RamJet cam Dart iron TBI heads 427 PCM swap
    95 C2500 Cheyenne 6.5L turbo diesel 4L80e 4:10 DB2-4911 Manual pump conversion 0411 PCM trans control 2Bar COS
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  9. #9
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    I have a comment for the mechanical part only because I've been there done that. I had the exact same thing happen to me once. I can tell by how far down the set screws are in your poly-locks that your rocker studs are too short. I'm willing to bet the little bit of broken rocker stud that was left is only 3-4 threads long. I had one pop just like that 50 miles from home once. It happened at a stop light in my case nothing but the stud and a pushrod were damaged. I ordered a set of +.200" studs. Fixed it right up

  10. #10
    Fuel Injected! Roadknee's Avatar
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    Quote Originally Posted by V8Astro View Post
    I have a comment for the mechanical part only because I've been there done that. I had the exact same thing happen to me once. I can tell by how far down the set screws are in your poly-locks that your rocker studs are too short. I'm willing to bet the little bit of broken rocker stud that was left is only 3-4 threads long. I had one pop just like that 50 miles from home once. It happened at a stop light in my case nothing but the stud and a pushrod were damaged. I ordered a set of +.200" studs. Fixed it right up
    Good catch! I suppose if the rocker ball is riding on the threads instead of the shank of the stud the stresses during operation can form a crack in the threads and ultimately shear the stud.
    1995 K1500, Stock LO5, 4L60e, 3.73 gears, 265/75-16 tires, L&L Products Ultra-flow headers into 2-1/2" Y-pipe and 3" single exhaust

  11. #11
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    From the photo it looks like you're running standard non self alining roller rockers.
    I could be wrong on this but I thought if you had standard tip roller rockers and round pushrod holes in the head then you needed to use guide plates.

  12. #12
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    Quote Originally Posted by dave w View Post
    I'm trying to understand what happened? Did you have a mechanical failure?

    dave w
    Yes obviously a mechanical failure, and fouled plugs I'm assuming from too much fuel at low rpm's. Will get back with you once back up and running and fuel pressure straightened out.

    Thx, Mike
    95 GMC K2500, 4l80e, 4.10 gears, 355 L05 4-bolt block, ARP rod bolts, Speed-Pro H423DCP-30 pistons, moly rings, 217 heads, vortec cam, TBI mods, cop car injectors, headers, 2 1/2" Y-pipe and 3" single exhaust with high flow muffler and cat.

  13. #13
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    Quote Originally Posted by Roadknee View Post
    I'm almost certain 17-18 psi with the stock spring has the spring coil bound. If it is the fuel pressure will not be constant as the fuel demand through the injectors changes and the engine will run erratically. IIRC, BLG355 from this forum installed a 1995 K1500 brake cylinder spring inside the stock spring and was able to get over 20 psi. I think you'll need at least 18 with the cop car injectors (68 pph?) to supply your engine. I recommend you fix your mechanical issue, get fuel pressure squared away and give it another whirl. Unless that air leak is really bad, you might try swapping that rocker stud, reassemble and check compression before tearing it completely down.
    Eaglemark has a thread stating EP377 pump with gold spring good for 16-26 psi. Where do I get it?
    95 GMC K2500, 4l80e, 4.10 gears, 355 L05 4-bolt block, ARP rod bolts, Speed-Pro H423DCP-30 pistons, moly rings, 217 heads, vortec cam, TBI mods, cop car injectors, headers, 2 1/2" Y-pipe and 3" single exhaust with high flow muffler and cat.

  14. #14
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    Quote Originally Posted by V8Astro View Post
    I have a comment for the mechanical part only because I've been there done that. I had the exact same thing happen to me once. I can tell by how far down the set screws are in your poly-locks that your rocker studs are too short. I'm willing to bet the little bit of broken rocker stud that was left is only 3-4 threads long. I had one pop just like that 50 miles from home once. It happened at a stop light in my case nothing but the stud and a pushrod were damaged. I ordered a set of +.200" studs. Fixed it right up
    Agreed! Went with the Mr Gasket 1076 because they didn't require machining of the bosses and I already had the heads back from the machine shop when I decided to go to screw in studs. Got cheap for a moment. Just ordered the ARP 1.75 installed height studs. Gonna pull the heads anyway and do it right.

    Good catch and thanks!
    95 GMC K2500, 4l80e, 4.10 gears, 355 L05 4-bolt block, ARP rod bolts, Speed-Pro H423DCP-30 pistons, moly rings, 217 heads, vortec cam, TBI mods, cop car injectors, headers, 2 1/2" Y-pipe and 3" single exhaust with high flow muffler and cat.

  15. #15
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    Quote Originally Posted by Roadknee View Post
    Good catch! I suppose if the rocker ball is riding on the threads instead of the shank of the stud the stresses during operation can form a crack in the threads and ultimately shear the stud.
    Those Mr Gasket studs are only 1.48" installed height. Definitely looks like I'm at least partially on the threads.
    95 GMC K2500, 4l80e, 4.10 gears, 355 L05 4-bolt block, ARP rod bolts, Speed-Pro H423DCP-30 pistons, moly rings, 217 heads, vortec cam, TBI mods, cop car injectors, headers, 2 1/2" Y-pipe and 3" single exhaust with high flow muffler and cat.

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