timing issue on a 340

[11.2]

iv'e posted this on another forum and there has been a ton of replies in the past couple of days but it's gone stale and i think iv'e made some progress today.
to make a long story short i was tuning at the track on the weekend and i found my weights to be totally seized at 24*. after we got them working i was getting 38* but to my suprise there was absolutely no gain or loss. this got me suspisious so iv'e been playing with the timing and this is what i come up with.
first i checked the tdc of the #1 piston and it is in perfect time with the 0 mark. i have used 2 different lights [dial back and a basic strobe] and i come up with the same #'s. i ear timed at 3,000 rpm and this is definately where the car runs the best. 25* initial and 45* total.
with what is done to the motor it should pull way better and having to ran that kind of timing leads me to believe i have a problem. what would be my next step?

 

[fishy68]

You can't always go by what your ear tells you in neutral as you proved by saying it runs the same with 38* total as it did stuck at 24*. 38 degrees is pretty far advanced unless it's a low compression 340. And of course 24 is pretty retarded. Did you try setting it at 33-34 total to see how it runs? It's possible that 38* is way too far. Enough to drop the perf. by as much as you lost when it was stuck on 24* therefore maybe somewhere in the middle would run better. If you can post all your engine specs. it would be helpful so I know if were dealing with a stock low compression 340 or a 11 to 1 engine with a big cam.

 

[340sFastback]

And open chamber heads with no quench usually like a little more advance. I run my all stock '69 340 at 13 initial and 38 total. Vacuum is adjusted to only add 10 degrees under max vacuum conditions under moderate cruise. If I had closed chamber heads with good quench I believe less total would work better.

 

[11.2]

yes we started at 34* with heavy springs and ended up at 38* with the lightest with no change whatsoever.
i bought this car with the engine done so i cannot confirm this is all true but here's what i know: 10.25:1, msd box with msd distibutor, ported x heads, cam is a crane 500/520 lift and 228*/238* dur.
something that i find strange is i can keep advancing and i get no ping but lose major power and it turns over fine. is it possible my cam is so far out of time that i'm not necissarily detonating but my valves are getting so far out of sinc.

 

[fishy68]

I have seen a couple that I could not hear spark knocking with the timing way advanced but they were low compression engines. I have a 360 with approx. 9.9-1 comp. and a high torque starter and it will kick back on the starter anything above 23 degrees. Strange yours doesn't do that. Are you sure yours is 10.25-1 comp? If you bought it assembled they might have told you that but it may not be true. Cam timing might be something to check if you don't mind pulling down the front of the engine. Awhile back I did a test with several timing chains to see how accurate they were and I found no 2 alike. There was anywhere between 2 and 6 degrees diff between them.

 

[11.2]

i can't confirm that it is a 10:1 but it does have the x heads, roller rockers, full msd ignition, large oilpan, yada,yada. so i would presume that the guy would'nt bs me on the compression.
i have all the specs on the cam, once again i can't confirm that these are the proper specs but assumeing they are can i pull off a valve cover and use a degree wheel on my balancer and a dial indicator on my valve spring to check cam timing?

 

[340sFastback]

The early 340s actually have about 9.5:1 compression. The factory compression rating is way higher then the actual compression. My stock '69 will ping on regulator fuel but with 93 premium I can run 40 total timing and it won't ping at all. Just runs better with less timing so I run 38 total.

 

[SGBARRACUDA]

Have you checked the compression? See what the cylinder preasure is and that will give you an idea of the CR.

 

[earthmover]

not saying this is your problem but I found out on my 340 as you said went from 32 to 38 and did not gain and did not loss with a locked out dist.(welded) took motor apart and the chain was so loss. got a new chain (the one for line bored blocks) and still had slack so you may have that..I plan to use the ten. this time when it goes back together.....maybe this will help this was a 11.5.1 to 12.5.1 comp. motor with 185to 190 cly pree. and dome tops....

 

[11.2]

sorry i havent replied for a while but i had some time to work on it.
my compression is 160 - 165 psi on all eight, my timing chain has just enough slack that you can feel it when you rotate the engine backwards i'm guessing about 1*, my valve lash is all dead on.
on my cam specs it says my exhaust valve should close at 0* tdc, so since i don't have the proper tools i tried something a little crude but maybe it will help. i rotated the engine slowly with a screwdriver on the piston and watched my rocker as i turned, when the piston came to tdc the valve was still closing, the piston had to go down a little bit before the valve fully closed. i don't have a proper dial indicator or degree wheel so i can't give specifics but am i way off by thinking that there's something wrong?

 

[fishy68]

It's quite possible the cam timing is retarded a few degrees. Last year I was doing an engine and rounded up 3 different timing chain sets to see how accurate they were because I have heard they can be up to 4 degrees off. I have the proper degree kit and found the best to the worst was 6 degrees difference. Wow was all I could say. They tested anywhere from 1 to 5 degrees retarded. I think if I were you I'd find a way to properly degree the cam in and go from there. The ones I used for the test was a Comp cams magnum set which was the closest at 1 degree retarded. Next was a Cloyes true roller set, it was 2 degrees retarded. Last was a Summit billet set and it was way off at 5 degrees retarded.

BTW: Do you have the heads off? If so all you need is a degree wheel and a magnetic base dial indicator. If the heads are still on it you'll also need a piston tdc stop.

 

[11.2]

everything is still on, the only thing i have off is the valve covers. am i on the right track, if the specs say exhaust closes at 0* then when the piston is at tdc the valve should be closed right??
when i done my crude screwdriver test, the piston goes down at least 1/4'' before the valve closes.

 

[fishy68]

I believe it should if that's what the cam card says.

I have to say though that the cranking compression is really good. Good enough that I wouldn't suspect it's way off.

 

[11.2]

oooops, i'm an idiot.
that spec is at .050. so i put a dial indicator on the valve and it's to close to tell with my backyard tools.
i have a dumb question in regards to a tranny. i should have a manual valve body but if i stick it in second gear at a standstill it goes to first until about 10mph and i do get some rpm flaring between 2nd and 3rd. should this tranny be going to first or directly to 2nd?

 

[fishy68]

Yeah it's hard to check unless you have all the right tools. Degrees of rotation are such a minute amount it's impossible to tell a few degrees.

If your trans has a manual valvebody it should be in 2nd when you put it there no matter what speed it is and should never shift automatically, only when you move the shifter. Shouldn't flare up any between gear changes either. That doesn't sound like a manual valve body by the description. Was it supposed to be?

 

[11.2]

the guy i bought the car from claimed it to be manual, all i can tell you is it has a tci sticker on the bellhousing and stall is aroung 3,000 rpm.
is there any other way to tell if i have a manual without taking it apart?

 

[fishy68]

the guy i bought the car from claimed it to be manual, all i can tell you is it has a tci sticker on the bellhousing and stall is aroung 3,000 rpm.
is there any other way to tell if i have a manual without taking it apart?

I hate to say it but I think you got taken because no manual valvebody will automatically shift at all. When you put it in a gear whether it's 1st, 2nd or 3rd that's the gear it'll be in. But one other sign is to look and see if the throttle pressure (kickdown) linkage hooked up? The kickdown linkage is allways eliminated with a manual VB.