need help! timing issues on my build

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kevin1969

kevin1969

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Hello everyone. So I finally got my 340 holley TBI turbo build started. All the steps I'm about to tell you is with the intake from the turbo disconnected and carb hat off. I was just trying to get it started with a base map then move on from there. So I hooked up the computer and set up the base perimeters with all looking good I cranked the engine just as always I turned the distributor till she fired up. Once running I let it warm up for a bit all was looking good and running good. I pulled out the timing light to set the timing before any further tuning. once hooked up I checked it at a idle it was around *40 BTC. this is where my problem lies... I tried to adjust it back to a reasonable number it ran bad and stalled. So I tried again with the idle up some and same result. So basically I'm lost right here. I got it to about 30* at idle and around 48 almost 50* but any less and it runs bad. at idle the vacuum gage reads 5 pounds of vacuum.

A little background on the set up its a 10.5 to 1 340 with a mopar purple cam 526 lift and 292 duration. J heads 2.02 1.60 cast light polish work. MSD 6al box. I've had this motor for about 10 years in my 72 dart with a tunnel ram and two 450 holleys its always ran good. I don't remember what the timing was because I had built it so long ago.

I know this is not the ideal turbo motor but plan to build a replacement bottom in the future and don't plan to run much boost there is a 4psi spring in the waste gate. thanks for any help. my build thread is in the forced induction section.
 
Are you sure the balancer hasn't moved and it's not really 30 degrees BTDC?

A TDC timing mark verification may be in order.
 
The balancer is a brand new sfi one from summit racing. I put the engine at TDC because that's the first thing I thought right away. It seem to match up as it should. Thx
 
check your timing light as it might be like mine and giving you a wrong reading. I was trying to set my timing at 38 degrees and my engine would hardly run used another timing light and found it was running at about 7 degrees.
 
Are you using a dial back timing light? If you are, you cannot use it with a MSD ignition box. You must use a regular old timing light or else your indicated timing will be all over the place.
 
Late model cover with an early balancer or the other way around? Find TDC and mark your balancer again and go from there....
Does your engine have the bolt on stamped steel timing tab or the one cast into the aluminum timing cover?
 
Simple things first, is the distributor 180* off?? They have been known to run like **** being 180* off.

Have you messed with the timing chain? If valve timing isn't right it will crave a lot of advanced ignition timing to burn all that fuel before the valve opens at the wrong time. And your vacuum would be in the gutter as well since it's not getting a full strokes worth of intake air.

Also, are you sure you have every sensor hooked up correctly? Mainly the MAP sensor. If it's reading atmospheric pressure and not manifold pressure then I'm sure the computer will give it 40 degrees btdc as it thinks the throttle is wide open. so, does your map sensor and vacuum gauge have the same readings?

Other than that you'll need some timing tape and a piston stop to verify tdc and go from there.
 
T56MaxTorq said:
Simple things first, is the distributor 180* off?? They have been known to run like **** being 180* off.

.
Click to expand...

An engine won't run at all "180 out". In fact almost always, a light show out of the carb results, perhaps burned eyebrows.
 
kevin1969 said:
I'll try to find another timing light and try that. Might have to buy a new one I suppose
Click to expand...

I asked you above to explain what you did to resolve TDC. Sometimes, when we ask you ****, we are serious about getting an answer


mguner said:
Late model cover with an early balancer or the other way around? Find TDC and mark your balancer again and go from there....
Does your engine have the bolt on stamped steel timing tab or the one cast into the aluminum timing cover?
Click to expand...

X2.............It's called a "piston stop"

attachment.php



So slipped timing marks........

slipped / wrong cam timing.........

something broke in distributor drive gear.......

or something wrong in the distributor..........

or just plain set up incorrectly
 
Yeah, really tight valve lash will put the vacuum in the basement too.
Reverse polarity if using a mag-trigger will mess you up.
My 292/549 had plenty of vacuum (enough to run the booster even), at 14* initial and 800ish rpm. I put that cam in several different ways, and it ran swell.I have never run MSD stuff, but have tuned cars with MSD boxes.Not every lite works on them.They should have a bypass switch.I ran that cam on an old Orange box. It ran great. Not much torque down low, but screamed after 5500.
Seems like it would be totally wrong for boosting.Best of luck to you.
 
Sorry misses have missed that.. I cranked the engine around till the number one cylender was on the compression stroke the manually spon the engine till the piston reached the top of the cylender. Then verified it was not the mark on the crank as well as 0 on the cover.. my timming cover it a aluminum one with the timming mark casted in it on the driver side just below the number one cylender. The distributor is a brand new pro comp mag pick up. I will verify that the wires arnt crossed tomorrow. I've never run a msd box so I'm not to sure if that's what's throwing it off. The crazy thing is it fires right up and idles good where it's located. My map sensor and vac/boost gauge are on the same vac sircuit. I did load a different default tune and the vacuum picked up at idle. I'm hoping it's just a mix up with the marks. Thanks for all the help guys.
 
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