Vortec Test

[tommays]

Re: Vortec Test

I gonna go out on a limb here Tony but i think Rod wants you to learn buy doing it <br /><br />I am no expert but after you find and mark TDC on all 8 cylinders you will have learned a LOT and you can do the leakdown test at the same time <br /><br />The KV tester is just like a clamp on amp probe but for ignition tests <br /><br />You will find out very fast if one cylinder has a fireing problem<br /><br /><br />

Verify DIS spark plug polarity.<br /> Ignition test under load.<br /> No-start spark test.<br /> Intermittent Misfire Monitor.<br /> High and low kV quick check.<br /> Touch-and-go quick testing.<br /> Firing kV test for integral-coil distributor systems (such as Delco HEI and Toyota).<br /> Quick tests for dual-plug ignition systems (such as Nissan NAPS-Z, Mazda RX-7, and Ford 2.3L 4-cylinder DIS).<br /> Snap acceleration test for worn spark plugs.<br /> Coil output test (breaker-point or distributor type).<br /> Coil polarity test for distributor-type systems.<br /> Motorcycles! The MT2700 can do a quick and easy spark plug output check without removing the tank or unhooking spark plug wires.<br /> Boats, Same quick and easy testing, even in the water under load.

tommays

 

[FreeBeeTony]

Re: Vortec Test

I don't understand you point.....I do intend on doing it.<br /><br />Only problem I have at the moment is the leak down test.

 

[Bt Doctur]

Re: Vortec Test

noticed 1 thing in the posts,first #3,then #2. havent see it mentioned yet. how about a weak/cracked valve spring(s).

 

[Buttanic]

Re: Vortec Test

"So if the V8 fires every 90* then 2 plugs will fire at each mark."<br /><br />Only one plug fires every 90 degrees but it takes 2 revolution or 720 degrees (720 divided by 8= 90) to fire all 8. Firing order is 18436572. 184&3 fire during the 1st revolution and 657&2 fire during the second revolution.

 

[rodbolt]

Re: Vortec Test

I already mentioned how to check weak valve springs, and usually a vacum guage will find it.<br /> the DVA will measure primary ing coil voltage, usually its in the 130-175 Volt range.<br /> while a specific number is not posted I am looking for it to remain steady at all RPM's.<br /> the Kv tester is an inductive tester that will display the amount of Voltage required to arc. usually on that 5.7 you will see 5-8 Kv (Kilo means thousand). way high and look for excessive gaps or poor plug wires. way low and look for fouled plugs,loss of compression or a lean condition. over rich can cause it to go either way depending on how much its over rich.<br />with an idle vacum if 19-20"Hg I would not spend a lot of time chasing valvetrain issues.<br /> not seeing or hearing your rig coupled with the fact its no longer as designed all I can do is tell how the test equipment works.<br />post us a list of everything you can think of that will cause an explosion in the intake manifold rather than being contained in the cylinder.<br /> I made a kid really mad at me a few weeks ago, he is a tech but not very experienced.<br /> he came to me with a question and I would not answer it.<br /> I made him list what the engine was supposed to be doing, then what it was not doing, then make me a list of possible causes for his symptoms.<br />time that job was done he was huffy, however he learned some lessons <br />sometimes it helps to write down the lists

 

[FreeBeeTony]

Re: Vortec Test

an explosion in the intake manifold......<br /><br />it's not backfiring through the carb, more of a sputter<br /><br />so are you still asking me what would cause an explosion in the intake?

 

[lilmandavis]

Re: Vortec Test

if its just sputtering in the manifold, id really think its a valve not lapped in good. if its hit or miss its probably when the valve rotates to the right spot. i just dont see bad electrical causing ONE cylinder to pre detonate. unless one of the pickup teeth is off. or a distrubutor post is bent. combine that with the weak stock springs and at fast rpm pop pop pop bang. im no expert. but i have done alot of engines. and redone alot of "new" engines. im really curious to see what the prob is. ill keep digging through information as well. whats the vacum gauge look like at wot?

 

[FreeBeeTony]

Re: Vortec Test

another question on the voltage measurements....<br /><br />where am I measuring the 130-175 volts? on the output of the coil?

 

[rodbolt]

Re: Vortec Test

I do belive you posted it backfired and lost power.<br /> and the last description of pop pop bang is aboput as close to a backfire as you can get.<br /> what your hearing is the fuel rapidly vaporizeing in a spot on the engine its not supposed to be.<br /> the coil primary peak voltage can only be measured with a peak reading type multimeter or DVM with a DVA adapter.<br />for this type of problem I prefer my analog meter due to the faster meter response time.<br />the valve rotators are there to aid in keeping the valve seats clean.<br />the stock vortec springs are good for 5K rpm with no issues.but like I said there is a tester to test them without removing them.<br /> so far I have seen no test results that isolate any cylinders.<br />if your ign timing is advancing so far that it lites up the airfuel mix while the piston is that far down the bore that the intake valve is still open you will have other issues as well, constant pinging being one of them.<br /> the leakdown test will verify cyl sealing ability, the vacum gauge can find weak springs. the engine mechanical can be eliminated as a culprit rather quickly.<br />4 hours or so depending on access.<br />you will find the leakdown test is a pain to run but its the most accurate method of testing the ability for the cyl to seal.<br /> did a competent machine shop do your head work?

 

[FreeBeeTony]

Re: Vortec Test

the heads were new from GM.<br /><br />I did post that the engine backfired a few times during the first run, then appeared to clear out.<br />I changed the fuel filter and that problem went away........now I am back to the sputtering.<br /><br />no pinging either

 

[Buttanic]

Re: Vortec Test

I don't know if it is coincidental or not but you said you think the problem moved from #3 to #2 cylinder. 2 and 3 are 180 degrees apart in the firing order. I don't have an idea what that might mean other than the distributor body is installed 180 degrees from where it was before and it moved the problem 180 degrees. If this is the case it would indicate the problem is somewhere in the distributor/cap assembly. Caution, this is one wild *** guess.

 

[paulie0735]

Re: Vortec Test

Tony, i still wanna know if this engine has ever run healthy for you or did you buy it like this?

 

[FreeBeeTony]

Re: Vortec Test

I bought it this way paulie........

 

[lilmandavis]

Re: Vortec Test

too bad it wasnt FORD !!!! HAHAHAHA im gonna make enemies now i guess... ill be quiet

 

[lilmandavis]

Re: Vortec Test

"Thought the coolant was coming from a cracked head or bad head gasket. Did not see any coolant in the cylinder, assumed it was getting there by the condition of the top of the piston" <br /> was the pick up ever changed? was there any carbon buildup? might be a weak pickup post to as well...

 

[lilmandavis]

Re: Vortec Test

"Thought the coolant was coming from a cracked head or bad head gasket. Did not see any coolant in the cylinder, assumed it was getting there by the condition of the top of the piston" <br /> was the pick up ever changed? was there any carbon buildup? might be a weak pickup post to as well... what exactly was the condition of the top of the piston??

 

[olbuddyjack]

Re: Vortec Test

Going back to searay3's post, Have you tried this yet?<br />

Something else to try...have a partner at the helm and with the carb uncovered, close the choke a little and see if it picks up. If it does, your running lean...

I was helping a guy with a similar problem at the end of last year. New carb, would bog and pop when it got to speed, held a rag partialy over the primaries and it straightened right out...

 

[FreeBeeTony]

Re: Vortec Test

Unfortunatly yes, I tried that and it didn't help.

 

[paulie0735]

Re: Vortec Test

Tony, was this engine in the boat when you bought it? Or did you purchase the engine separately?

 

[FreeBeeTony]

Re: Vortec Test

It was in the boat, was hoping it was just a tune-up!