HELP!!!..........Anybody???

[Aaron jackson 87]

Here is the scoop... i have a 1987 k1500 blazer originally a 305 tbi. I bought it from a guy with a blown engine, the 305 had been converted to carb already. I bought a 1995 tbi 350 block, tore it down and rebuilt in my drive way this winter. Stock rotating assembly. I put in the summit 1102 camshaft and lifters, bolted on garage ported 193 swirlport heads, edelbrock performer intake, and the edelbrock 1403 500cfm carb that was on the 305 when i bought it, also transfered the hei distributor from it as well. I broke the engine in, went well. I have 250 miles on engine since rebuild and it runs "well" enough. Here is my problem... i did the break in set a 4° advance, everything disconnect and pluged as usual. Upon reciving more advice i wanted to advance to 8°, or more for optimum performance. Idle is set to 800rpm, timing at 4°, hook up light, plug vaccume, turn dst to advance to 8°, idle increases to 1100rpm~. I adjust idle screw back down to 800rpm. Re check timing and its back to 4°. So i did it again... same result. Every time i adjust the idle down to where i want it, it throws the timing back off, its an endless cycle... advance timing....turn down idle speed, timing decreases. Re set timing, idle increases, i lower idle speed, and timing drops again. Is this normal operation? How do i know my timing is staying where i want it? I cant run 8° or 10, or 12, or whatever without idle around 1 200 rpm. I cant run 800 rpm without timing going bac to 4°...... any thoughts on malfunction? Any ideas or suggestions please! Ive picked poor pauls brain apart as much as i can, and if i keep goin he wont have nothing left for himself!

 

[6872xtc]

My first thought is that maybe the advance springs are so light, that it is bringing one the centrifugal advance that early.
I would wonder how far you can advance the timing to get a change in the initial setting at 800 rpm.
I would suggest to play around and see what happens. Take it for a drive a see what happens. I never used a timing light for a long time, just drive it and listen for knock, and see how it runs.
A test drive should give you some feedback and sense of what to do next.

 

[tRustyK5]

Once you advance the timing are you tightening the hold down bolt? I can't see how the dist could retard itself if you have the hold down tight...

 

[Aaron jackson 87]

My first thought is that maybe the advance springs are so light, that it is bringing one the centrifugal advance that early.
I would wonder how far you can advance the timing to get a change in the initial setting at 800 rpm.
I would suggest to play around and see what happens. Take it for a drive a see what happens. I never used a timing light for a long time, just drive it and listen for knock, and see how it runs.
A test drive should give you some feedback and sense of what to do next.

I have played with it a bit, i tried turning the dst as advanced as i could, several inches actually to try and get it to ping at idle, and it never reached that point. I run out of toom before i can turn it far enough to get it to ping. Is it worth spending the few bucks for some springs to see if it makes a change? Thanks for the reply!

 

[Bent77]

@6872xtc is volunteering to work on your truck.
I would, but its a bit of a drive...

 

[Aaron jackson 87]

Once you advance the timing are you tightening the hold down bolt? I can't see how the dist could retard itself if you have the hold down tight...

Yes sir i sure do, i was at the point where i checked the timing literally ever 1/4 turn of the wrench to make sure i wasnt moving it on accident.

 

[Team208Motorsports]

Forget base timing. What's the total advance?

 

[Aaron jackson 87]

@6872xtc is volunteering to work on your truck.
I would, but its a bit of a drive...

Thank you and no worries! Im gonna get a manual and quadruple check everything i have done first, last thing i wanna do i waste someones time over some obvious mistake i am overlooking. After that ill take any help i can get!

 

[Aaron jackson 87]

Forget base timing. What's the total advance?

As of a few days ago NOWHERE in the valley has a dial back timing light or friggin timing tape for the balancer in stock, so im gonna have to order something on payday, so i have had no way to check total timing yet... #1 or 2 on thing to do list...

 

[Bent77]

As of a few days ago NOWHERE in the valley has a dial back timing light or friggin timing tape for the balancer in stock, so im gonna have to order something on payday, so i have had no way to check total timing yet... #1 or 2 on thing to do list...

I've been known to use the old lady's fabric tape (them flexible tape measure things) and a silver sharpie. Based off 0-10*, make marks on 10* increments out to 50*, each a staggered length so you can tell the difference

 

[Team208Motorsports]

2╥R is your friend.

 

[blazer74]

X2 on the mechanical advance coming in too soon, when u lower the idle speed mechanical advance drops out and timing drops.

 

[Aaron jackson 87]

I've been known to use the old lady's fabric tape (them flexible tape measure things) and a silver sharpie. Based off 0-10*, make marks on 10* increments out to 50*, each a staggered length so you can tell the difference

Ok not a bad idea, basically measure out the marks on my timing cover and transfer them onto balancer going up to 50° or so? I want 34 to 36 degrees total, sound about right?

 

[Aaron jackson 87]

X2 on the mechanical advance coming in too soon, when u lower the idle speed mechanical advance drops out and timing drops.

That seems logical to me, ill see if i can find a set or two tomorrow, see if it makes a change and check total timing

 

[blazer74]

Could be one missing or broken.

 

[6872xtc]

You won't get it to ping at idle, just run NOT right.
Take it for a quick drive and it will tell you stuff.

 

[Blue85]

Let me ask how you're disconnecting and plugging the vacuum advance line. Because having vacuum advance still hooked up would obviously change your timing - as idle speed changes, so does vacuum. You would also be setting the timing way retarded of where it should be.

 

[Aaron jackson 87]

Let me ask how you're disconnecting and plugging the vacuum advance line. Because having vacuum advance still hooked up would obviously change your timing - as idle speed changes, so does vacuum. You would also be setting the timing way retarded of where it should be.

I remove vac line from dst and plug it with a bolt, vac line still connected to carb, but is blocked. Sick as a dog today or id be out playing with it, that and 3 inches of snow doesnt help either...

 

[CGT80]

If you didn't already buy a timing light, and want a new one, I would recommend
INNOVA 5568 Pro-Timing Light.

I bought it on amazon and got the 3 year warranty with it. The manufacturers warranty sounds like junk. It has a tach, voltmeter, and degree adjustment. It doesn't look like there are any really great lights out there with a tach and blue point and snap on were not worth the money for how little I use one. In the past, I used my uncle's blue point.

You can get by without a fancy light, but it was so much easier to make notes on my centrifugal, vacuum, and even carb ports. I had a vacuum gauge on the carb port while I watched the tach on the light and revved the engine, to figure out what rpm gave me vacuum. This is on an edelbrock afb style carb. Then, I ran a vacuum line from the port tied to the vac advance, in the cab and to a gauge siting on the dash. I checked my adjustable vac advance can with a vac pump and timing light so I would know when it operated and how much advance I got. It has really painted a picture as to why my truck has been pinging, but seemed like it still wanted more advance.

Mark out a scale or use a fancy light
use a vac gauge and pump
figure out how the centrifugal and vac advance respond
check the port going to the vac advance to see if the vac advance settings are compatible with the signal it gets.

Once I really made notes on what I had and wrapped my brain around how it all worked, I was able to see what was wrong and how I can improve it.