Tuning headache

[anotheridiot]

With the Jet carb, the vacuum gauge is consistent, but it is still around 8 or 9.

well, 8 or 9 is still better than 6-8

I am guessing your duration numbers are at .050, so closer to .280 from your first post, but the cam card says its .296 and 300 at 108 degree lobe separation. The split overlap on the middle stroke is what kills vacuum, the time exhaust is still open while the intake is open which is what creates the lope. We still got a lopey cam when we went roller, but having the 115 lobe separation instead is what got us vacuum again since the both open time was reduced. But we are up at .600 lift.

I still dont think everything is right, but a clear definition of that crank gear is still needed. i saw another post like this on Facebook, which even had a different angle picture of that crank gear and I still see no difference in where the crankshaft would be if you use a different A2 keyway and timing mark or the zero and dot.I dont see the crank moving.

[brotherGood]

well, 14.7 is supposed to be the number you want, but ultimately, its just a number. What are your corresponding vacuum numbers? Did they improve when the AFR got back in range?

With the Jet carb, the vacuum gauge is consistent, but it is still around 8 or 9.

[anotheridiot]

well, 14.7 is supposed to be the number you want, but ultimately, its just a number. What are your corresponding vacuum numbers? Did they improve when the AFR got back in range?

[brotherGood]

Forgot to upload it, but here is the comparison between tbs restored carb and the Jet carb at idle/rev in park in the driveway.

https://youtube.com/shorts/ePKn9SkSVx0?si=pqvEY0di3ZoTSzKN

I've not had a chance to drive it around, but already the numbers are much closer than they were with the restored carb.

Engine guy can receive after the 1st of the year, so I probably won't mess with it much more.

[SuperBuickGuy]

I'm befuddled! Eating my popcorn and waiting......

what's a fuddle?

[DanStokes]

Man, I hate these gear sets. When you sit back and look at them, the 0 on the crank is the same position as the dot. The A2 on the crank, is the same position from the A2 on the tooth. You move to A2, but you still use the actual dot, isnt that the way these are supposed to work? To me it looks exactly the same if you us 0 and dot, or put the A2 on the crank and use the A2 tooth as your new mark. The crank is not turning to advance or retard,

All this time I just thought you were not at cam mark at 180 and keyway on balancer lining up to your timing mark on the cover.

I'm befuddled! Eating my popcorn and waiting......

[anotheridiot]

Keyway was the A2. The outer "A2" is what got lined up with the dot in that case.

Man, I hate these gear sets. When you sit back and look at them, the 0 on the crank is the same position as the dot. The A2 on the crank, is the same position from the A2 on the tooth. You move to A2, but you still use the actual dot, isnt that the way these are supposed to work? To me it looks exactly the same if you us 0 and dot, or put the A2 on the crank and use the A2 tooth as your new mark. The crank is not turning to advance or retard,

All this time I just thought you were not at cam mark at 180 and keyway on balancer lining up to your timing mark on the cover.

[SuperBuickGuy]

The cam was off from the assembly shop. He installed dot to dot without degreeing it, and claimed there's no need to degree a cam. The timing set used was also a cheap NAPA set, that we were able to verify was off as well.

once we were able to find zero, and verify zero against the new timing set, we measured the same way and that's how we landed on the A2. It was between 2 & 4 as to where we needed to be, and we were advised to just go ahead and put it on the A2 as it's much closer than the 20 degrees retarded that it was to start with.

as I said, I'll be interested to hear what it really was....

[brotherGood]

The cam was off from the assembly shop. He installed dot to dot without degreeing it, and claimed there's no need to degree a cam. The timing set used was also a cheap NAPA set, that we were able to verify was off as well.

once we were able to find zero, and verify zero against the new timing set, we measured the same way and that's how we landed on the A2. It was between 2 & 4 as to where we needed to be, and we were advised to just go ahead and put it on the A2 as it's much closer than the 20 degrees retarded that it was to start with.

[SuperBuickGuy]

I'll see if I can dig up the sequence of events from when we degreed it. With the first timing set on it, measuring everything out it was something like 20° retarded. With the new timing set it corrected a large portion of that. (Note, the first timing set was new when the engine was assembled in '22). I can't remember what the number landed on off the top of my head, but IIRC we technically are still a degree or so off (retarded) from where the cam card calls for, but had we installed at the A4 it would've been too advanced.

This was tripled checked with the engine guy (Olds pro who has run this cam in multiple builds) on the phone.

when I find the cam is way off - it's usually... no... it's always me who messed up. the cam card says it's ground 2 degrees advanced. I believe, given your setting, that with where your a2 set is that you added another 4 degrees to that for a gross of 6 degrees advanced. Let us know what you find when the motor comes out - maybe it was Isky and I'll say "well, that was unexpected" ;)

[brotherGood]

It is 2:30 am and I'm headed out the door to drive to SEMA (actually Ely). but in my time warped head, I think you're at least 6 degrees advanced (between cam grind of 108+2 and setting it at A2). It would explain the inability to start it at 18 degrees - reality you're at 24 degrees....

why would you want so much advance?

but as I'm driving today, I'll try to math this in my head....

I'll see if I can dig up the sequence of events from when we degreed it. With the first timing set on it, measuring everything out it was something like 20° retarded. With the new timing set it corrected a large portion of that. (Note, the first timing set was new when the engine was assembled in '22). I can't remember what the number landed on off the top of my head, but IIRC we technically are still a degree or so off (retarded) from where the cam card calls for, but had we installed at the A4 it would've been too advanced.

This was tripled checked with the engine guy (Olds pro who has run this cam in multiple builds) on the phone.

[brotherGood]

Numbers are good!

Having them, yes. The readings..not so much. In conversation with my engine guy (note, not the the one who has touched this one, but the Olds professional who I've leaned on for parts and help) this combo should idle and cruise around 13.5:1

[SuperBuickGuy]

Keyway was the A2. The outer "A2" is what got lined up with the dot in that case.

It is 2:30 am and I'm headed out the door to drive to SEMA (actually Ely). but in my time warped head, I think you're at least 6 degrees advanced (between cam grind of 108+2 and setting it at A2). It would explain the inability to start it at 18 degrees - reality you're at 24 degrees....

why would you want so much advance?

but as I'm driving today, I'll try to math this in my head....

[DanStokes]

Numbers are good!

[brotherGood]

Got the wideband hooked up, and we took it up the block to get some numbers recorded for the carb builder. Hopefully we can get it squared away by the time the engine needs to come out.

https://youtu.be/_Q9Y6ldOkNo?si=pR55cUEEkeDDpkhX