need Help with idle in gear
 

Hello, i would need advice which direction should i go with carburator or ignittion? My problem is rough idle but only in D or R. Park is now perfect. Sorry but I must write a little story.
In the spring Camschaft installed and degree and all values ​​were like in camschaft Card. First I have little vacum leak on Carb. Gasket, then I have lifters very noisy but I can also solve that with more preload (from 8 o`clock to 9 o`clock), then I have rough idle in park but I also solved that, I found that float level was too high, little Play with mixture and everything is perfect in the park.
Now I have the following values, car drive and pull great, it works best:
-withouth vacum (disconnected) 14 ° innitial / purple busching on MSD total 32 ° with Hard Silver and one light Silver comming by 3250 rpm.
- with manifold vacum connected 28 ° idle and when I slowly turn up all in 48 °
- MSD Vacum can also give me 14hg vacum in idle
- idle mixture 3/4 both rear, front are 1/8 more than rear ( best vacum )
- idle vacum is 16hg and stedy, not move, not a little, Perfect idle.
- RPM drop in gear ( I think it is OK ), 150rpm, idles on 950rpm and in gear 800rpm.
- My Lambda is at idle about 13 and in cruising 12.5 it looks like is little rich but that is my best vacum
Now my problem comes when I go in R auto jerks very strong and vacum drop to 11.5. Vacum is not steady, moving very slowly between 11.5 and 12.5 hg.
(Maybe overlap) and RPM drops to 800 RPM. I feel little vibrations, that's just D or R.
How can I stabilize my vacum in gear and improve idle?
Ignition? Carburator?

My set up: Lunati roller camschaft 231/239 at 0,50 lift, LS110, Centerline 106, 4 ° advance build in, cam was degree all correct like in cam card, Morell lifters, 1.5 Scorpion Rockers, MSD Probillet ready to run, MSD 6AL, Holley Street HP 950 84/84 jets - 6,5PV. Edelbrock Heads / Ed. RPM intake, all Parts from Butler

Sorry for my long story Ivo

I prefer running the initial at 20 with no vacuum advance and having the mechanical bring in 14 to 18...

I never liked how the vacuum advance seemed to destabilize the idle, its like your always waiting for things to smooth out. Without it they always stay smooth.. Then there's that weird skip-miss-stumble sound the exhaust makes from too much timing at idle...

Have you greased the universal joints lately? Turbo 400s do go into gear hard.. Try lowering the idle, you can run it down pretty far without the vacuum advance connected..

If you have a stock size Balancer ( stock diameter) first confirm that your Balancers timing mark is correct with number 1 at TDC.

36 degrees will be 2 1/8" around on the Balancer, or in metric numbers 54.864 MM.

A 950 cfm Carb is pretty big for stock Edelbrock heads if you do not have atleast 10.7 compression if you ask me!

If you need to bring in any level of vacuum advance to get a motor to idle good in gear then you have too much Cam , too little cylinder pressure or a combination of both , or a plain and simple vacuum leak, or valves that are adjusted too tight!

What CID is the engine and what is the compression ratio?....

Hi Clif, Engine it is 455 YC block, 469 CID, 10.2: 1 cranking comp. 190-192 PSI all cyl.
I have read almost all your posts, and here we have already discussed Idle.
https://forums.maxperformanceinc.com...92#post6028892
I have my idle perfect now, I know you want to say "USE PORTED PORT" but I loved driving manifold vacum, it runs much cooler,
and yes Balancer is also new
I am looking for a manifold solution

My Ed Heads are 87cc (from Butler) My studs are 7/16 and Morel said adjust with aluminum heads .30 preload. It is little more than 1/2 turn pasz zero lash. So were the noisy. I've adjustedet at 3/4 turn and no noisy anymore

Sorry can not correct, ALL IN with Vacum connected si 46°!!! not 48
sorry:mad:

What List # is your HP 950?
How much vacuum are you getting in gear?

Ported vacuum does EXACTLY the same thing when you drive your car as manifold vacuum, timing from the VA is "all-in" unless you are coasting or at idle, so running cooler wouldn't even be part of the equation unless you spend a LOT of time idling.

Anyhow, the engine combination should not want, like, or need as much timing as you are using at idle. Having it at 28 degrees initial timing tells me that the engine is not happy with the camshaft at it's current compression ratio. Maybe the carb needs a little help as well, or the distributors vacuum advance needs a light spring in it?

A 10 to 1 compression ratio 455 with a 231/239/110 cam should idle just fine with 10-12 degrees initial timing and no additional timing from the VA. It should also idle fine well below 900rpms, that is a pretty high idle RPM, it should settle in nicely around 750rpm's and drop may 50 rpms or so when placed in gear.

In most cases when we see a big RPM drop when the trans is placed in gear the distributor is retarding the timing slightly.

I've also tuned a few engines where they were trying to run a LOT of timing at idle and the throttle plates were so far closed the idle was "stable" when the trans was placed in gear and engine loaded slightly......Cliff

PS: the Morel HR lifters run much better with less oil under the plungers that more. I started adjusting them up from bottomed out vs down from zero lash and they run a LOT quieter......

It is 82951 SA, Yes that is my Problem, Vacum is not steady, needle moving very slowly between 11.5 and 12.5 hg and running is not good, 800rpm in gear

Does your carb have the rear idle adjustment screw for the throttle blades?

Rear buterflys I have Open Like recomended, 0,20