drop back to basics

Grumpy

The Grumpy Grease Monkey mechanical engineer.
Staff member
Ok ok, here I am again. Angry. My engine will not agree with me no matter what I try to do. So here's what's going on. 350 with a .040 over bore. 64cc aluminum heads, about 9.5:1 compression (Static) port matched intake and heads, single plane high rise intake, 750 CFM carb. I can not get the timing to agree with me it would seem. If I set it to where it performs the best, I can't cruise in the car because it just misfires and spits and generally runs like crap. If I give it even the slightest bit of throttle, it smooths out and runs fine, until I let out of the throttle again. Initially I thought it was running lean, so I upped the jets even though the spark plugs read that it was about right. Didn't fix the problem. New pressure regulator. Holds constantly at 6.5 PSI. No change. Added more jet, checked power valve. No change except for black smoke from the pipes when I jam the throttle because now it runs pig rich. I retard the timing. It begins to run smooth. Runs like crap on the top end. Overheats. Advance the timing. Runs like a bat out of hell. Cruises like crap. Stays cool. Recurve distributor with heavy springs. Reset timing. No difference. Replace vacuum advance with lower vacuum rating. Check total timing and advance. Same story. Tried new plugs and wires. No difference. New cap and rotor.
The cam is the same one from my last motor and it never had these issues. All parts, intake, carb, cam, rockers, all came from the other motor. Main differences are the bore (.040 vs the old .030) and the aluminum heads that actually seal now vs my old leaky iron 882's. Same headers. Same exhaust. Same ignition box. Same fuel pump. 3K stall converter.
No difference. Checked plug gap. In spec, no problems. Compression and leakdown test. All happy. Rechecked TDC. Balancer was slightly off. Reset timing. No difference. Running out of ideas, dying slowly on the inside. I will try ANYTHING at this point.
without testing you simply guessing
never guess, deal in verified FACTS!
guessing is a waste of time
think logically, isolate and test


yes IM aware some guys would rather dig out their eye with a red hot fork than to read links, but if you take the time to actually research the problem and isolate and test you,ll soon find the answers
infrared thermometers are a very useful tool to track down issues with tuning, or mal functioning sensors , without verified facts your guessing.
this is the most consistently accurate I.R temp gun I've used for testing
42545.jpg

http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products
having the correct tool to verify the engines operational temps would be helpful
http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products
INFRARED TEMP GUN


always drop back to the basics and don,t assume a darn thing!
its almost certain a logical isolate and test procedure will locate the cause!
first
VERIFY TDC DON,T ASSUME THE TIMING TAB OR DAMPER IS CORRECT, and yes VERIFY THE FIRING ORDER EVEN THOUGH YOUR 100% SURE ITS NOW CORRECT!
vgauge.gif

pressuregag.jpg


chevyengine.jpg

http://garage.grumpysperformance.com/index.php?threads/finding-top-dead-center.967/

did you degree the cam in or just assume that a DOT-TO-DOT install would work?
have you verified the cam lobes are not worn?
have you verified the cam was degreed in correctly?
(DOT-TO-DOT has been incorrectly indexed many times)

http://garage.grumpysperformance.co...ectly-and-get-it-to-last-cam-install-info.90/

http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/

http://garage.grumpysperformance.co...ng-cam-and-shifting-the-lca.10553/#post-44949

http://garage.grumpysperformance.com/index.php?threads/cam-degreeing.9010/#post-35474

THEN VERIFY YOUR TIMING CURVE LOOKS LIKE THIS TO START, you might not fid its ideal but it will get you a solid start point
chart3e1.jpg


NEXT VERIFY THERES NO VACUUM LEAKS
http://garage.grumpysperformance.com/index.php?threads/locating-vacume-leaks.882/#post-45944
http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/

YEAH I KNOW YOUR 100% sure the valves are correctly adjusted>>>DO IT OVER AND DO IT AT IDLE AND USE A 1/2 TURN PRELOAD

http://garage.grumpysperformance.com/index.php?threads/adjusting-valves.196/

http://garage.grumpysperformance.co...em-will-eventually-cost-you.11810/#post-56645

YOU NEED TO GET A FUEL GAUGE AND VERIFY YOUR GETTING 5-6 PSI and at least a GALLON a MINUTE of fuel flow reaching the carb
http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/

http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/

ID TRY A DIFFERENT CARB, THEN READ THIS THREAD AND LINKS
http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/#post-6685
my dad always stated..

"A couple hours , well spent in doing carefully documented &,detailed research,
before.... jumping head first off the dock,
into any project,....can prevent you from wasting month's of non-productive work and a wheel barrow full of cash!!"

without testing you simply guessing

http://garage.grumpysperformance.com/index.php?threads/drop-back-to-basics.12943/#post-67323

http://garage.grumpysperformance.co...oven-facts-if-your-in-doubt.13051/#post-69824

http://garage.grumpysperformance.co...hink-logically-don-t-assume.12484/#post-62772

http://garage.grumpysperformance.co...-test-seems-to-be-a-forgotten-art-form.11838/

http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/

http://garage.grumpysperformance.co...oven-facts-if-your-in-doubt.13051/#post-69824
How do you diagnose the problem? Since obviously there are no computers on old trucks, and I'm looking at a early 1950-60s truck, How do you figure out what went wrong?

now I read this and I had to stop and wonder,
about the newer generations approach to vehicle maintenance,
and the mind set of the younger members, who never dealt ,
with a basic pre-computer controlled, non-efi engine.
yes its totally understandable if your less than 25 years old, because you were raised well after the majority of cars no longer were built using the older basic automotive systems most of us older geezers were brought up working with.
you start with the basics
SPARK
FUEL,
COMPRESSION
,

youll want to start verifying compression, verify you have fuel pressure,at the carb inlet port, verify the carb float levels are correct, verifying your ignition spark is arriving at the spark plugs and verifying the engines timing with a timing light.
the first step is to pull a plug wire off a spark plug and hold it by inserting a #2 Phillips screw driver blade with a plastic handle into the spark plug wire and holding the insulated handle while holding the exposed metal of the screw-driver shaft about 1/4" from the engines metal surface, and having someone try too start the car, the plug wire should arc to ground intermittently.
if you remove the fuel line from the carbs inlet port and add a 6 foot section of 3/8" rubber fuel line carefully and securely clamped to the existing fuel feed line , so you can allow the fuel pump to feed fuel into a empty 2 liter bottle it should fill that at least 1/2 and preferably totally in less than 45 seconds of cranking the engine on the starter.
you can pull each spark plug and use a compression tester to verify your getting compression, the results should not vary more than 5%-8% between cylinders.
a fuel pressure gauge,
feulpres.jpg

a multi meter,
image_12926.jpg

vacuum gauge,
vgauge.gif

a compression test kit,

62638.jpg

a leak-down test kit is optional but useful
62595.jpg

a timing light
timinglite4.jpg

and a dwell meter
dwellSL500_AA300_.jpg

and the instructions to correctly use those tools will prove very useful


related info

http://garage.grumpysperformance.co...se-valve-train-or-rod-knock.13846/#post-70866

http://garage.grumpysperformance.co...han-assume-you-know-answers.13217/#post-68926

http://garage.grumpysperformance.co...the-source-of-exhaust-smoke.13030/#post-67772

http://garage.grumpysperformance.com/index.php?threads/drop-back-to-basics.12943/#post-67323

http://garage.grumpysperformance.co...-t-get-it-running-correctly.12495/#post-62966

http://garage.grumpysperformance.co...hink-logically-don-t-assume.12484/#post-62772

http://garage.grumpysperformance.com/index.php?threads/blue-oil-smoke.12198/#post-59193

http://garage.grumpysperformance.com/index.php?threads/vacuum-gauge-help.9453/

http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/

http://garage.grumpysperformance.co...and-a-bit-of-experience-make.6778/#post-21751

http://garage.grumpysperformance.co...em-will-eventually-cost-you.11810/#post-56635

http://garage.grumpysperformance.com/index.php?threads/the-trucks-just-not-running-well.13435/

http://garage.grumpysperformance.co...r-basic-performance-concepts.9731/#post-48391
having a few basic meters,gauges etc.
IT sure helps too have basic tools, when isolating issues



MULTI METER

INFRARED TEMP GUN

TIMING LIGHT

COMPRESSION GAUGE

PRESSURE/VACUUM GAUGE
chartvac.jpg
 
Last edited:
Need cam specs to give my opinion if the cam is to large he might be trying to compromise timing to give the motor what it wants at different rpm. I was just reading about it the other day.
 
20161107_200119-800x600.jpg
It also goes into how big cams may require mixtures as rich as at idle to eliminate surging starting at 12.5-13.0 (.85-.89 lambda) and leaning out with spedd and loading
 
another good point, in the engine function to check out!
most guys have little real experience at isolate and test procedures and many can,t use test equipment or even fully understand what to look for.
DON,T PAY FOR IT ...DO IT YOURSELF!!!
IT WILL COST LESS EVEN AFTER PAYING FOR THE TOOLS, than paying for it AT MOST GARAGES.
A compression test,ALONE, IS NOT A LEAK DOWN TEST, a LEAK DOWN TEST WILL GIVE YOU THE COMPRESSION TEST INFO, ALONG WITH OTHER INFO

you'll find that you'll gain basic skills, own new tools and PAY LESS MONEY

http://en.wikipedia.org/wiki/Leak-down_tester

http://www.carcraft.com/techarticles/11 ... index.html


https://www.harborfreight.com/11-piece-noid-light-and-iac-tester-set-97959.html
8789.jpg



https://www.jegs.com/i/JEGS/555/W89...MIoLGlpLnz3gIVDFYNCh36aAK4EAQYAiABEgKTIvD_BwE

noidtest.png


BEFORE YOU GET INVOLVED WITH TESTING , YOUR ENGINE,READ THRU THESE THREADS, AND LINKS AS THEY WILL HELP ISOLATE THE PROBLEM, and THEY HAVE A GOOD DEAL OF USEFUL INFO
you really need
42545.jpg

http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products
INFRARED TEMP GUN
timinglite4.jpg

a timing light,
image_3330.jpg

http://www.harborfreight.com/3-1-2-half ... 95670.html
multi meter,
vacuumgauge.jpg

vacuum gauge,
feulpres.jpg


fuel pressure gauge

http://www.harborfreight.com/cylinder-l ... 94190.html
image_2899.jpg


HARBOR FREIGHT, UNDER $40

http://buy1.snapon.com/products/diagnos ... pv309a.asp

SNAP ON $330

http://www.summitracing.com/parts/SUM-900010/

http://www.summitracing.com/parts/OTC-5609/
otc-5609_w.jpg


SUMMIT $80-$100
compression test /leak down tester

image_1450.jpg
18512.jpg

dial indicator with stand

degreew1.jpg

and a degree wheel
918999.jpg

damper tool

and a shop manual
and more related reference material
certainly won,t hurt

http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/

http://garage.grumpysperformance.com/index.php?threads/bare-minimum-tools.11026/#post-48779


http://garage.grumpysperformance.com/index.php?threads/no-computer-now-what.13973/#post-71209
 
Last edited:
Back
Top