intake pressure test

[maddogxx]

ok so I have read the tech article below about the pressure test and need some help. I have my timing at TDC (the marks on the cam gears are aligned and the timing mark is at 1 TDC) my question is how far do I turn the crank clockwise to acheive 40 deg BTDC. Also BTDC confuses me what does that mean in regards to TOP DEAD CENTER?? Thanks in advance for the help.

http://www.dsmtuners.com/forums/art...-boost-leak-test-how-boostpro-net-tester.html

 

[Spoolin98]

BTDC stands for Before Top Dead Center. The T on your timing cover is top dead center. There is a 5, a dash, and a 15 to the left of the T on the timing cover. Thats stands for 5* BTDC, 10*BTDC, and 15* BTDC. Turn the crank colockwise till you hit 40* BTDC. There is not a mark on the timing cover for 40* BTDC, I just guess as to where it is in reference to 15* BTDC.

 

[delta448]

Did you happen to see this image at the bottom of the page? Each labeled valve timing event happens only every other crankshaft revolution. Remember the 4 cycles; intake, compression, power and exhaust. Also, remember that cylinders 1&4 are on opposite cycles, as are 2&3 and that there is 180 degrees between 1&4 and 2&3 on the crank. Also, the firing order is 1-3-4-2.

I have my timing at TDC (the marks on the cam gears are aligned and the timing mark is at 1 TDC) my question is how far do I turn the crank clockwise to acheive 40 deg BTDC.

To answer your question, for 40degrees BTDC on #1, you'd turn 320 degrees clockwise until the mark is pointed slightly past due northwest on a compass, or slightly beyond halfway between left and up.

However, as seen on the diagram, anywhere that the intake valves are closed will work, so there's a range there.

 

[maddogxx]

thank you so much guys, and yes I saw the diagram but it only confused me more, . I am pretty sure I know what to do now. Again thanks for the info!

 

[slayer450]

Is this something you have to do when boost leak testing? Some thinks you read say to, others say doesn't matter.

 

[Spoolin98]

Sorry just realized you have a 2g, thats how a 1g motor is. Maybe someone with a 2g 7 bolt can chime in on the timing cover.

 

[maddogxx]

Is this something you have to do when boost leak testing? Some thinks you read say to, others say doesn't matter.

Actually that is what I am trying to do "Boost leak test". The reason I posted is because when I pressurized the system I can hear the air going through the exhaust, either that or I have a huge leak in the hard piping

 

[Calan]

Is this something you have to do when boost leak testing?

Yes.

Otherwise, air will blow right past the open intake valves and out the exhaust....or into the crankcase if you have worn rings.

 

[slayer450]

Yes.

Otherwise, air will blow right past the open intake valves and out the exhaust....or into the crankcase if you have worn rings.

Never had that happen but it does come out the valve cover

 

[slayer450]

Actually that is what I am trying to do "Boost leak test". The reason I posted is because when I pressurized the system I can hear the air going through the exhaust, either that or I have a huge leak in the hard piping

Have someone pump the air in and go listen by the exhaust to make sure that's where it's coming from.

 

[1Gina2G]

Can someone help me with the marks? I see the diagram says it's for a 2G, and to change it if you have a 1G. Since I have a 2G head on a 6 bolt block this means I just follow the diagram as it is correct?

I also see that the timing marks on the crank pulley are opposite compared to the crank sprocket, so you just move the crank 320 degrees clockwise right? will this bring it 40* before TDC?

 

[delta448]

It all depends on the cam timing. If you have stock 2G cams straight up, then that diagram is accurate.

There's 360 degrees in a circle, you should only ever move the crank clockwise, so 320 degrees clockwise from TDC is 40 degrees BTDC. In reality all you need to do is just make sure the cylinder in question is on it's compression stroke and beyond the 51 degrees from BDC where the intake valves are closed.

 

[1Gina2G]

So as long as I move 320* clockwise from TDC, I will be good for a boost leak test? Is it any easier to use the crank sprocket rather than the crank pulley? My pulleys rather old and the sprocket is new. Had trouble looking at the pulley, all I saw was a 2 and H