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long rod
https://slantsix.org/forum/viewtopic.php?t=50796		 Page 2 of 3
Author:  akbmotorsports [ Mon Jan 21, 2013 4:43 pm ]
Post subject: 
hello. DI and mpgmike, the solenoid will do the trick as far as run-on. thanks. as soon as i find my other compression gauge i will see what that one reads. i may just leave the head gasket as is, since there is no audible pinging, still debating with myself on that.

have a great day, andy.
Author:  akbmotorsports [ Tue Feb 12, 2013 12:49 pm ]
Post subject: 
hello. update - (hope this makes sense) installed vac gauge today and here is what i got. with engine warm, idle set at 1000 rpm no load i get 10 inches vac, as i lower the rpm, vac drops and is at zero by 600 or so and engine dies. when rpm is raised, at around 1200 vac jumps quickly to 15, rpm raises and thats when it seems to "come into it" and run as it should. then when i back off throttle at about 1200 vac drops to 10 and gets lower as rpm gets lower and seems to struggle to stay running. it just seems something is wrong to me.

i am 99% sure there are no vac leaks and have tried different carb.

i am considering changing cam to one with a wider lsa but am looking for ideas.

would retarding the cam increase vacuum signal?

thanks again, andy.
Author:  billdedman [ Tue Feb 12, 2013 2:56 pm ]
Post subject: 
Quote:
hello. update - (hope this makes sense) installed vac gauge today and here is what i got. with engine warm, idle set at 1000 rpm no load i get 10 inches vac, as i lower the rpm, vac drops and is at zero by 600 or so and engine dies. when rpm is raised, at around 1200 vac jumps quickly to 15, rpm raises and thats when it seems to "come into it" and run as it should. then when i back off throttle at about 1200 vac drops to 10 and gets lower as rpm gets lower and seems to struggle to stay running. it just seems something is wrong to me.

i am 99% sure there are no vac leaks and have tried different carb.

i am considering changing cam to one with a wider lsa but am looking for ideas.

would retarding the cam increase vacuum signal?

thanks again, andy.
Have you ever tried killing the engine without taking it out of "drive"?

Sometimes that will alleviate the run-on problem with no other changes.

Bill
Author:  Dart270 [ Tue Feb 12, 2013 2:58 pm ]
Post subject: 
What is the valve lash? If less than about 0.024/0.028", try opening them up more.

Lou
Author:  Doc [ Tue Feb 12, 2013 3:29 pm ]
Post subject: 
Quote:
... would retarding the cam increase vacuum signal?
Do you know the intake closing point on the current cam... at lash?

Yes, retarding the cam will help vacuum but it will also shift the power, higher into the RPM range.
DD
Author:  akbmotorsports [ Tue Feb 12, 2013 4:48 pm ]
Post subject: 
doc, intake closes at 56, mocked up number one valve train during assembly and degreeing the cam, and measured with dial indicator at valve retainer at recommended lash of .012, and have since set lash at .024ex/.020in. that has been the only change i have made that has had any positive effect.

lou, i haven't tried setting them that loose yet, but will do that tomorrow and report back. am i right in assuming this is reducing overlap?

bill, i have done that and works some of the time, but i think the throttle solenoid will cure the run-on.

thanks for the replies.

andy.
Author:  Dart270 [ Tue Feb 12, 2013 6:39 pm ]
Post subject: 
Andy,

Yes, you will reduce low lift overlap by opening lash. Most cams that size run more lash than you are at. Not sure this will work, but worth trying.

Lou
Author:  Doctor Dodge [ Tue Feb 12, 2013 7:10 pm ]
Post subject: 
Quote:
..Doc, intake closes at 56,...
56 degrees IC should not cause much low speed reversion...
How much overlap is there at lash?
DD
Author:  akbmotorsports [ Tue Feb 12, 2013 7:29 pm ]
Post subject: 
doc, the cam card says 19* @.050. i did not take that measurement when dialing it in, but both valves numbers matched the card at the lifter if that helps.

andy.
Author:  ceej [ Wed Feb 13, 2013 4:39 am ]
Post subject: 
I had problems with the ZFR5N plug at this compression level. (11:1/10.7:1) Found the Autolite cross to the NGK ZFR6-FIX worked best. Right now I have the NGK in there, and it's off a bit. The ZFR6 is a non-projected electrode. I'm going back to the Autolite.

2¢

CJ
Author:  akbmotorsports [ Thu Feb 14, 2013 1:48 pm ]
Post subject:  update
hello. update;

loosening valves did help some, vacuum still dropping out but at a slightly slower rate. better but still wants to lose vacuum signal.

measured overlap, these numbers may be off a little as i did this in the truck. i use a bolt in the front of the crank and drilled and tapped it for a 3/8 bolt to mount the degree wheel for just this type situation.

at .028/.024 lash,
48* overlap
ex closes 15 atdc
in opens 33 btdc
middle point of overlap event is about 15 btdc

ceej, i am currently using ngk bpr5ey (67 drool tube head), tried the br series (non projected) and got a noticeable drop in performance and did not cure anything. i have thought of trying another brand but haven't gotten to that yet. will give it a try though.

thinking maybe i need to take out the 4 degrees advance and put cam at "straight up" 104 icl, and put a aussie head gasket back on to get the compression back up. (dropped from 200 to 160 cranking pressure when i put the double felpros on, and had no positive effect) i feel like i am right on the edge of correct.

i may be getting cam-theory-itis, and may need an ectomy soon. :D

thanks for all the replies, andy.
Author:  Doc [ Thu Feb 14, 2013 4:10 pm ]
Post subject: 
Intake open at 33 degrees BTDC will allow a lot of exhaust gas into the intake track, seeing that exhaust gas volosity is still pretty strong, at that point in the cycle.
This effect is called "inturnal EGR" (Exhaust Gas Recirculation) by many and it leans-out the intake mixture, at low engine speeds.

Inrceasing the intake valve lash, retarding the cam and increasing exhaust scavaging will all help reduce the amount of inturnal EGR.
DD
Author:  akbmotorsports [ Thu Feb 14, 2013 4:54 pm ]
Post subject: 
thanks doc, thats a great description of how its acting. do you think 4 degrees change is a good starting point?

andy.
Author:  Doc [ Fri Feb 15, 2013 11:44 am ]
Post subject: 
Retarding this cam will help but retarding the cam is also going to change the DCR number, by delaying the IC point.

So with 4 degrees retard you should get a 29* IO & 19* EC overlap event with a 60 degree ABDC IC.

I would be temped to try 6* retard if the DCR stays around 8.0
-6* should get you a 27* IO & 21* EC overlap event and a 62* IC point.

Here is the "rub"... With the SL6, I start to see see intake track reversion, from the later IC point, at around 60* ABDC IC (Intake Close)
The good news, intake track reversion does not impact the idle quality as much as inturnal EGR does.
DD
Author:  akbmotorsports [ Thu Feb 21, 2013 1:13 pm ]
Post subject:  progress
hello. i got the cam retarded 6*, changed head gasket, and have a better vacuum signal and a healthier idle. haven't test driven yet.

i would like your opinions on these two things to maybe gain a little more.

1. drilling the throttle plates. would this negate the use of the solenoid to shut plates at shutdown?

2. "splitting" the intake manifold. would this reduce internal EGR and/or reversion?

also just wondering if the longer piston dwell time with the long rods would be a contributing factor?

thanks for everyone's input.

andy.
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