I'm going to have to look at the tune in my 02 8.1 suburban. It's crazy touchy taking off
Vortec MPI injectors "click"?
- Thread starter Skip Fix
- Start date
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L31MaxExpress
I'm Awesome
To think that the Avalanche/Suburban have a much slower throttle opening rate than the Express vans in the tune and you still find yours touchy.
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I'm not sure what has been done to it but it shifts at 6k wfo and I've never hit the speed limiter on it. With 373 gears it turns sideways taking off and turns sideways shifting into second and third. Third is 105 never run it to 4th gear wide open. I drive it real easy and get 14 with it. If the wife drives it it's about 8 lol.
Skip Fix
OBS Enthusiast
So here are the pictures of the rockers on the Blueprint motor. You can see the wear pattern is not centered and actually a faint wear spot up the
alignment ramp. I think having no guideplate (yes i know the iron Vortecs do not but the have slots-nothing on Fast burns) the ball rocker allows some rotation and the side to side movement. the Harland Sharps with a much tighter clearance on the valve tip as well as having the trunnion that prevents side to side rotation is better. Driving it the past week and good smooth power quiet when started cold but the click comes as it warms up still.
alignment ramp. I think having no guideplate (yes i know the iron Vortecs do not but the have slots-nothing on Fast burns) the ball rocker allows some rotation and the side to side movement. the Harland Sharps with a much tighter clearance on the valve tip as well as having the trunnion that prevents side to side rotation is better. Driving it the past week and good smooth power quiet when started cold but the click comes as it warms up still.
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My new engine with comp cams adjustable valvetrain and comp magnum roller tip rockers also has a few ticks. I even took the left side cover off and ran it to find the source. I backed off nuts one at a time in the area I thought it was coming from. But when they got actually loose, the sound was much louder, like a hammer on steel. So I put them all back to 1/2 turn preload and put the cover back on. The ticks come and go now, but I'm not going to worry about it til something gets worse. It has new bosch injectors, so I don't think they have anything to do with it.
I just happen to have first hand experience with this. And I spent some money I
really couldn't afford at the time to find the following out. :0)
Traded in my first new vehicle ('82 S-10 2.8L V6/4-speed) for a Quadrashock-equipped
'84.5 Mustang GT 5.0/5-speed. (175hp/245tq, exhausting through a set of
cast iron exhaust manifolds. Although I missed having a truck, I certainly appreciated
the night/day improvement in the acceleration department. :0)
About 6 car payments in, the '85 5.0 GT is released, in it's 210hp/265tq roller-lifter,
factory tubular exhaust configuration. (Same Holley 4180-4V induction) This
s*cked for yours truly, for the "2nd place is 1st loser" lifestyle was visited upon
moi. :0)
After licking my wounds & evaluating my options, as part of my recovery plan I
removed the cast iron exhaust manifolds and installed a set of brand spanking
new '85 tubular headers sourced from the old Acton F**d parts dept. This
plus a sharp tuning effort (including pulling the intake for port matching +
the old Holley multi-colored secondary spring kit trickery) allowed me to keep
up with the competition.
****
The punchline? The stock cast iron exhaust manifolds were inert/dead quiet
with the stock exhaust. The only change to the exhaust I made was the
new factory tubular headers. And I'm here to report that like you stated they
didn't tick or ping.
But they did have a distinct tinking sound. And not due to any leaks, for
I am pretty fussy about that, and on purpose used the associated '85 fasteners
& gaskets. (Figuring I would take advantage of the engineering that went
into the car having a 75K mile emissions warranty?)
No kidding, I can still hear that unique tinking sound in my Mind's Ear. I
actually liked it, and even noticed that the sound varied from heavy throttle
to disappearing during closed throttle overrun.
Of course I could go on to describe what cheap/tinny aftermarket headers
sounded like when my buddies & I would install those...but that's a different
story where everybody already knows the punchline -- so I won't.
And for what it's worth, it's the only tinking sound I can remember from all
the different engine bays that i spent any quality time in.
That's all I've got to say about that. - F. 'Road Trip' Gump
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Sean Buick 76
I'm Awesome
I got a custom tune on my 2012 L-96 6.0 and it removed all the throttle lag!
L31MaxExpress
I'm Awesome
Yep I know the hollow tapping under load all too well. My 83 G20 had the OE GM tubular stainless manifolds on it for several years and it had been around years before that. Headers are probably most pronounced when the engine sits under your right foot through a fiberglass like engine cover.
Rotary engines are still burning the fuel when it enters the exhaust. Headers on rotaries ping loudly, if you can hear it over the braap.
You just reminded me of one of the most glorious days in my short career as a hired wrench... (introduction)
Back in the summer of '80, a new customer came in with a 'new to him' 5-6 year old Chevy van.
He complained that if he drove around town, everything was fine, but if he tried to pass someone
on a 2-lane highway, the van would suddenly cut out, right at the wrong time. Could we figure
this out and fix it?
The customer left his van behind for us to troubleshoot & repair. Since this sounded like it had the
potential of being a lot more fun than most jobs (ie: replacing a windshield-steaming heater core, etc)
I wrapped up whatever I was currently wrenching on post haste and got right on this opportunity.
A quick look-see at the engine got the manic mechanic juices flowing a bit. Instead of a straight 6 with
a Monojet, the customer had a stock 350 with a Quadrajet. During the test drive it seemed like
the secondaries weren't opening? But since that wasn't the complaint, I probed a bit further. Sure
enough, the customer's concern revealed itself in short order.
You could run 'full throttle' for maybe 8-10 seconds, and then the engine would suddenly starve,
and then nothing. (No doubt the customer experienced some serious pucker factor when that
happened to him during the aforementioned passing maneuver. :0) If you waited a few
seconds, everything would return to normal. The good news was that you could repeat the
problem at will, so at least there wasn't the peek-a-boo intermittent troubleshooting to deal with.
After returning to the shop, my boss & I discussed it for a bit, and we agreed that either the
fuel line got deformed/smashed somewhere, or the fuel pump must be losing it's mojo? The
carb should be rebuilt, and a full tuneup performed. (The engine looked like it hadn't been
touched since it left the showroom floor?)
Since we had the correct carb kit on hand, I went to work on that, and while it sat disassembled
and soaking in the dunk tank, (filled with the old school ominous carb cleaner) I did a full tuneup
on the engine. (cap, rotor, points, condenser, plugs, wires, etc.) Hmmm, the old plugs looked like the
engine was running a bit on the rich side? (insert head-scratching sound.)
Putting the carb back together, all looked well. The original fuel filter in the carb had plugged up,
so of course the fuel pump had pushed the filter off it's seat and against the bypass spring,
which explained why we found quite a bit of sediment on the floor of the fuel bowl?
The fuel line from tank to fuel pump passed a careful visual inspection, but the fuel pump
was pretty janky looking. On a hunch, we checked the engine oil. It was somewhat overfull,
and more importantly, the oil smelled like gasoline?
So of course we suspected that diaphragm inside the fuel pump was failing, so we swapped in a
new mechanical fuel pump, and also performed an oil & filter change.
Putting the carb back on the engine, I ran it on the Sun 1115 engine analyzer in order to adjust
the idle screws, set the timing, and verify that all 8 cylinders were contributing equally to the
task at hand. I went to adjust the idle screws, and observed that the choke had never fully
opened up?
Pretty quick we figured out that the bimetallic choke spring was tired, and the
choke did open some, but never fully. (This explained both the dark plugs and the fact that
the Q-Jet secondaries weren't opening, for the choke linkage locks them out until the choke
is fully off. (ie: the engine is fully up to operating temp.)
Went to the parts store, got a fresh choke spring, mounted it on the intake, and now
with everything sorted out, I finished the tune up, and took the van out for a post-fix
test drive.
With the doghouse off.
And just to be absolutely sure that all was working properly, I also left the air cleaner lid off.
The first on-ramp to the nearby highway told the tale. Not only could I hold WOT as long
as I wanted with no interruption, although the sound of the primaries was mostly hissy,
when the twin 2 1/4" secondary throttle blades opened and the air valve subsequently went
vertical, the sound was simply g l o r i o u s as the engine sang it way through the gears.
Goose bumps then. And goose bumps typing this in. Better than most concerts I've attended,
and I like concerts a lot.
And I also finally got to satisfy my curiousity of what it looked like when a Quadrajet
is busy combining a couple hundred horsepower worth of fuel with the air rushing by.
I can still see it. Hope I never unsee it. :0)
And in the interest of ensuring a quality repair, I gave this van a nice, long functional check flight.
Unfortunately, Radio Shack hadn't yet started selling their decibel meters, or I would have
driven home and used that to quantify exactly how loud and proud that 4 barrel barber
shop quartet was all uncorked in the interior of that van.
I returned back to the shop with a big goofy grin on my mug & a thumbs up out the window.
The boss came up, looked in, saw my test setup, and just shook his head. But he was smiling too.
Air cleaner lid reinstalled. Doghouse back on. And on to a more normal boring job awaiting in the queue.
Epilogue:
The customer paid his bill, hopped in his van, and drove off.
A few days later he swung by and said that the van had been transformed by us.
He had heard about us by word of mouth, and was going to give us all his
business from that point on.
And he did.
****
Thanks for rekindling that memory for yours truly. Years later, while sitting in the
computer lab and waiting for memory diagnostics or a system exerciser to complete, I
would remember that test drive and sincerely wish that the machines in my new gig were
nearly as much fun to test drive after working on them.
True story. @L31MaxExpress, I have no doubt you have subjected yourself to the same
thing...in the interest of science/pursuit of knowledge. :0)
Cheers --
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