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Gary, Technician
Category: Car
Satisfied Customers: 16888
Experience:  GM master tech for 15 years/ASE master tech for 20 years
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gm 400: gm400, have spark and fuel. timing at 12 deg without

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gm400, have spark and fuel. timing at 12 deg without vac advance. fireing order 18436572.
starts but wont run. sound like its running on four cylinders and pops thru the exhaust
will it pop up through the intake also ?
your 100% sure when you droped in the distibuter it was on TDC ?
Customer: replied 4 years ago.

i have an 8" balancer the tdc mark is at approx 2:00 oclock. i checked for the compression stroke and stopped the mark at approx 15 degs on indicator. drpooed the distributor in with rotor between 1 and 2 degs. set the #1 plug approx in line with rotor. with attempting to keep it running, terrible with some dark smoke, i set it at 12 degs w/out vac adv.

is it also popping up through the intake?
what kind of rockers are you running? how did you adjust the valves ?
Customer: replied 4 years ago.

its a reconditioned engine i purchased from secon hand with 1500 miles. and it is not popping thru the carb. it has standard stamped rockers

before we go crazy here can you perform a compression test?if that is done its realy going to cut the problem in 1/2
now one quick thing when you dropped the distibuter in was the rotor pointing at the # XXXXX spark plug tower
also when you drop that distibuter in the crank balancer line should be at 0 degrees
Customer: replied 4 years ago.

i will do the test. the dist. was more towards the #3 plug and the timeing was at approx 15 degs

if the compression on all 8 is above 100 put it up on TDC 0 drop in the distibuter with the rotor pointing at the # XXXXX spark plug wire tower on the cap and try it
let me know ill be here when you need me
Customer: replied 4 years ago.

let you know for tomorrow

no more than likey will come down to the timing being off or low compression due to the valves not adjusted correctly
you can always get me back through this post at anytime with any follow up or questions with this issue even after you rate us here at Justanswer !
Gary and 3 other Car Specialists are ready to help you
Customer: replied 4 years ago.

reset the tdc and distributor last night. i moved it up oone tooth. before it was pointed at #3 now it is at approx 5:00 or juist past #1. going to check the compresion tonight. let you know tomorrow. you have done a good job, i will take care of the rating tomorrow.

no problem keep me up to date !
Customer: replied 4 years ago.

what is a good compression number?

120 or more
what do all 8 have ?
Customer: replied 4 years ago.

#1 was 160 still working on it

after you did the distibuter retime did you start it up yet ?
if they are all over 120 should be good
160 at all is outstanding
Customer: replied 4 years ago.

without the gage i have pressure on all but the #3!!!

all others have @ 160 ?
and # XXXXX has 0 psi ?
Customer: replied 4 years ago.

havnt gaged the rest yet, ill let yu know

ok find out how many are not at 160 tell me all cylinders and what you have for psi numbers
then we will fix the low or no compression cylinders
Customer: replied 4 years ago.

im not going to be happy if i have to pull the head off. the guy i baught it from better do it for me. ill keep you posted.

well it may be just a valve adjustment.dont worry yet
Customer: replied 4 years ago.

im hoping or is it hopping?

if any are 0 we pull the valve cover and check the valve adjustment and go from there
Customer: replied 4 years ago.

got it

Customer: replied 4 years ago.

ok, if youre there, 180psi in all but #3

if i remember correctly you set both valves closed, loosen the rocker until they are loose, tighten the rocker to slight push rod snug andb then 1.5 more turns on the rocker, yes?

turn the engine over so the push rods are not pushing # XXXXX valves
loosen rocker untill the pushrod is loos
tighten slowely until 0 lash is there
then go 1/2 turn down
pay attention when doing this and make sure the lifters are NOT pushing down when you do this adjustment
do that and see what the psi is after you adjust # XXXXX valves
Gary and 3 other Car Specialists are ready to help you
Customer: replied 4 years ago.

i hooked up a jumper fro the starter to help me and in the doing fried me ignition switch and screwed up the tumbler. how do i replace them.


all cyls are now 180psi

great im glad the compression is good now
what year and make and model is this vehicle ?
Customer: replied 4 years ago.

78 GMC truck C2500

i do not have any information on something that old
its a matter of buying a new ignition switch and ignition lock and installing them both
Customer: replied 4 years ago.

you have been great, thank you. how do i contact you?

look me up by name anytime
Customer: replied 4 years ago.

whats your name?

Customer: replied 4 years ago.

i thought i gave you a rating, but just recieved a request. are we ok?

yes we are thank you for the good rating
Customer: replied 4 years ago.

well its finaly running but have some abnormal vibration. this was an engine swap, whan i hooked up the alternater it charged for 5 minutes and then burnt up and quit, what do you think was the cause?

is this an internal regulator alternator?

one big power wire to the back and how many small wires go to it ?


Customer: replied 4 years ago.


Customer: replied 4 years ago.

yes one power and one connecter w/2 wiers one red and one white

more than likey this alternator failed internally
these are self chaging alternators
big wire should have 12 votls from the batter
the white i think is for the charge light and what is the red wire reading next to the white wire ?
Customer: replied 4 years ago.

red wire reads 12 v

ok that alternator more than likey internally failed at full charge due to the internal voltage regulator stuck on
these just need to big power wire with 12 volts and the red small wire 12 volts for it to change
Customer: replied 4 years ago.

did you get my last comment/

yes i did
that alternaotr more than likey failed internally
you have the 2 powers for it to work and it is internal self charging and regulated internally
Gary and 3 other Car Specialists are ready to help you
Customer: replied 4 years ago.

i got another and the same results

the new alternaotr worked fine for a little while then blew up ?
Customer: replied 4 years ago.

yes, have any ideas?

what year and make and model is that alternator out of ?
Customer: replied 4 years ago.

its a street rod truck 78gmc w/gm400 and 700r4 2 alternators purchased from seperate sources one new and one rebuilt

this is an odd one
lets see if another expert knows more about this
hang on another expert will replay back to you
Customer: replied 4 years ago.