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First test drive...
https://slantsix.org/forum/viewtopic.php?t=52656		 Page 2 of 4
Author:  Reed [ Wed Jul 10, 2013 5:24 pm ]
Post subject: 
How long had the motor been running when you took that video? Was this the first cold startup of the day or had it been idling for a while? If the motor was still cold then it may just need to warm up a bit since you don't have a functioning choke.

What modifications have you done to the motor? Do you have a wild cam in there? I ask because a vacuum gauge needle that fluctuates around 10 inches at idle indicates either a fairly aggressive cam, a huge vacuum leak somewhere, badly misadjusted valves, and/or incorrect base timing.

I would start by verifying that you sealed the intake to the head correctly, that all vacuum hoses are properly connected, that all unused vacuum nipples on the carb are capped, that all vacuum operated accessories (choke pulloff, dash mounted vacuum gauge, etc...) still hold a vacuum, that the carb is correctly mounted, and that the throttle shaft isn't severely worn.

If all the vacuum issues check out, then I would verify that your base timing is in the 5 degree BTDC neighborhood AND that the vibration dampener still indicates TDC correctly.

If the timing is OK, then I would double check your valve lash. On a stock cam I say set the lash to .012 intake and .020 exhaust with the motor idling and as hot as you can get it. Spec is .010 and .020 but set it a little loose if you are trying to verify that you aren't losing vacuum due to too tight of a lash setting.

If the vacuum, timing, and valve lash all checks out, then you need to start looking at more exotic problems like cracked plug wires or cap, mis-timed cam to crank relationship, bad gas, a plugged fuel pickup in the gas tank, etc...
Author:  DusterIdiot [ Wed Jul 10, 2013 5:53 pm ]
Post subject:  Nice...
Quote:
If the timing is OK, then I would double check your valve lash. On a stock cam I say set the lash to .012 intake and .020 exhaust with the motor idling and as hot as you can get it. Spec is .010 and .020 but set it a little loose if you are trying to verify that you aren't losing vacuum due to too tight of a lash setting.
If you used the OCG 791 that sounds normal (and meaty...and the V-8 guys will now think you swapped in a small block...LOL) and lash is .015/.020, but I might be tempted to go .017/.022... I would play with it and watch the vacc gauge and stick with the settings when you get peak vacc.

You may find the BBD is a start but is not calibrated to handle that kind of build, the Holley 7448 will be your next mod, probably. Since the engine is hipo and running at 10" at idle, what is the reading at 1200 rpm? If it increases the engine won't be totally happy at 800 rpm...Some of this is the cam and degree, some of it will be the need to recurve the distributor to get the mech advance to come on a little quicker but to limit the slot so you can run some initial (it'll like that), but limit at 30 mech+ initial...(once you are done fiddling with the other stuff you might set the dizzy to 10BTDC static and see if it runs better, then run it up to 2500 rpm without vacc advance and see what the total timing is there...

:wink:

-D.Idiot
Author:  jhdeval [ Wed Jul 10, 2013 7:08 pm ]
Post subject: 
Okay so here's what I got.

Oregon Cam Grind (791) 231 intake and exhaust
Cylinder Bored .040
Crankshaft -0.010
38 CC Chambers
Deck .161 down

Duster Idiot recommended I set the lash to 17 and 22 and I have left it there. The car had been running about five minutes but I was manually setting the step and using a wire to hold pressure on the throttle butterfly. It was the first start up. I shaved the head and deck as indicated above. I am pretty confident the intake/exhaust are seated well. I took the thinnest gauge I had and tried to slip it between the head and gasket and intake/exhaust and gasket and I was unable to fit it. The port on the intake is sealed with the vacuum gauge. On the carb I found one vacuum port near the fuel/air mixture screws that I sealed off.

My machine shop did not set my timing marks properly but I found top dead center and am using a mark on the block to determine TDC. The timing is set at about 12-14 degrees or so.
Author:  Reed [ Wed Jul 10, 2013 7:44 pm ]
Post subject: 
At this point I would increase your idle speed and verify your timing.
Author:  jhdeval [ Wed Jul 10, 2013 7:50 pm ]
Post subject: 
Any suggestions on idle? 800-1000?
Author:  DusterIdiot [ Wed Jul 10, 2013 8:21 pm ]
Post subject:  I would...
Quote:
I am pretty confident the intake/exhaust are seated well.
set the idle where it's solid as possible and take a can of carb cleaner or brake cleaner and spray at the runners near the head, near the base of the carb, if the idle fluctuates at any spot you have a leak...I have had carbs with bad shafts and been able to toss a rag over the airhorn and the engine didn't die (but did low idle...).

I'd set neutral idle at 1000-1200 rpm and go from there...

-D.Idiot
Author:  Aggressive Ted [ Wed Jul 10, 2013 8:26 pm ]
Post subject: 
DI,

Is that where that cam has to idle at? or can it idle at 750 rpm like a stock cam? What should the vacuum show at 750? or at 1000 rpm?
Author:  DusterIdiot [ Wed Jul 10, 2013 8:44 pm ]
Post subject:  No...
Quote:
Is that where that cam has to idle at? or can it idle at 750 rpm like a stock cam? What should the vacuum show at 750? or at 1000 rpm?
No, he should have more idle vaccuum than that, like Reed I would be dubious of the centerline of his intake as the cam is really low I expect something closer to min 15-16 on rough in if the cam was set to 101-102 for low end torque...being more than a 3/4 cam I also expect that idle will be a little higher. I have yet to loose mileage with a higher idle since the circuit is a squirt gun compared to the mains, but the idle in gear should be closer to 800-900 if everything was assembled correctly and degreed advanced for lowend torque/street use....

If no leaks, I'm thinking carb is worn out (and outside it's calibration zone) and also would question the intake centerline of the cam. 10"hg is not normal for that duration of a cam, I'd expect it with something like 240/250 @.050...

-D.Idiot
Author:  jhdeval [ Wed Jul 10, 2013 9:00 pm ]
Post subject: 
Well Duster Idiot I am pretty sure I got the carb from you. I did notice a little bit of gas rolling off the throttle shaft.

What do you mean by the intake centerline?
Author:  DusterIdiot [ Wed Jul 10, 2013 10:20 pm ]
Post subject:  Lol...
Quote:
Well Duster Idiot I am pretty sure I got the carb from you. I did notice a little bit of gas rolling off the throttle shaft.

What do you mean by the intake centerline?
Yep like all BBD's eventually it needs the throttle shaft rebushed sooner or later...you'd be able to tell by spraying some carb cleaner at the shaft and seeing if the idle perks up or slows down....That's part of the problem.

Part 2:
When you degree a cam you are setting the centerline of the intake lobe to the specs of the grinder...if you want more low end torque then you advance the cam, if you need to pass smog or need top end power you retard the cam.... If the cam grinder put 104 as the intake centerline...and you followed the cam card events for IVO @ .050 and IVC @ .050 the cam is 'straight up' with no advance or retard....when you rolled the crank around you would see that about the middle of the "max lift" on the dial indicator should have been about 104....you would then either change a keyway or drill and put the appropriate bushing in the cam gear to advance or retard it...if going for 4 degrees of advance you would install the bushing then roll the crank/cam over and notice that the center of the max lift would be 100...you would also notice that your .050 opening and closing events have shifted 4 degrees earlier (say the cam card said IVO of 17, with the new setting it would be 13).

If you set the centerline retarded like 8 degrees ("112"- the IVO would be 25)...retarded cam would lack grunt but work great at very high rpms...

What was your IVO when you set the cam?

-D.Idiot
Author:  DusterIdiot [ Wed Jul 10, 2013 10:27 pm ]
Post subject:  Round 3
One of your previous posts says you has 28-30" Hg while messing with the timing?

What happened?

You don't have one plug wire not firing and throwing the whole smash off?

:?:

-D.idiot
Author:  jhdeval [ Thu Jul 11, 2013 5:09 am ]
Post subject: 
Okay so rebushing the carb shaft same as doing a door pin? Find a brass bushing and drive it in?

Second the camshaft IVO. I did not put the bottom end together my machinist did but based on what you are saying I believe we are about where you indicate. TDC is pointing almost straight up the motor. It is probably 5-7 degrees ATDC from pointing dead straight up. Which my best guesstimate would be about 100 degrees from the timing marks 0 degrees. I do not think my machinist redrilled the cam keyway. If he did he did not charge me like everything else.

For the 28-30" I was reading the outside gauge when I should have read the inside gauge. oops.

As for a vacuum leak I was thinking this morning and remembered I had blocked of the EGR valve with a plate. I did not put an gasket sealer but I used a make your own gasket roll and cut it to the plate size. Is it possible there is a leak there?
Author:  DusterIdiot [ Thu Jul 11, 2013 7:17 am ]
Post subject:  umm..
Quote:
As for a vacuum leak I was thinking this morning and remembered I had blocked of the EGR valve with a plate. I did not put an gasket sealer but I used a make your own gasket roll and cut it to the plate size. Is it possible there is a leak there?
Yes, you can confirm while the engine is running, spray some carb cleaner at it, you may need to goop it or get a standard EGR gasket.
Quote:
Second the camshaft IVO. I did not put the bottom end together my machinist did but based on what you are saying I believe we are about where you indicate. TDC is pointing almost straight up the motor. It is probably 5-7 degrees ATDC from pointing dead straight up. Which my best guesstimate would be about 100 degrees from the timing marks 0 degrees. I do not think my machinist redrilled the cam keyway. If he did he did not charge me like everything else.
The IVO for your cam should be some where BTDC...you may need to reconfirm what its really set at and compare to your cam sheet. If he didn't drill the gear and you don't have an adjustable crank gear (i.e. roll master set), he might have lined up the dots and that would only be dumb luck that it phased the cam correctly to the crank.
Quote:
Okay so rebushing the carb shaft same as doing a door pin? Find a brass bushing and drive it in?
You'll ream the holes and press a bushing/sleeve in and reassemble.
Author:  jhdeval [ Thu Jul 11, 2013 9:28 am ]
Post subject:  Well I am in idiot...
Okay so in hopes of correcting the issue. I checked the intake and exhaust bolts. The center and left top bolt was a little loose. I tightened them. I also decided well maybe I didn't tighten the carb down enough so I found they were fairly loose. So I tightened them. Then I checked the carb again for any open vacuum ports and I found one. Oooppppssss. Sometimes you are just blind. Anyways I was able to get the vacuum up to about 16-18 at 1000-1500 but any time I came off the stepper I would die almost immediately and the RPMS would drop. I tightened the curb idle screw ALL the way down and still the same thing. Is the carb just worn out?
Author:  mattelderca [ Thu Jul 11, 2013 10:15 am ]
Post subject:  Re: Well I am in idiot...
Quote:
Is the carb just worn out?
DI said previously,
"he might have lined up the dots and that would only be dumb luck that it phased the cam correctly to the crank."

I hate to have to say this, but,
Quit chasing the carb for now and verify you cam timing. You could be chasing things in circles for ever without that information.
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