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| New build will not idle in gear https://slantsix.org/forum/viewtopic.php?t=67175 |
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| Author: | Green72 [ Sun Apr 02, 2023 1:24 pm ] |
| Post subject: | New build will not idle in gear |
Hello everyone, first post here but have been lurking for awhile. Ok so I built a 225 slant for my 1972 Scamp. Mostly stock with block and head milled for 10:1. Cam is an Oregon Cam regrind (specs) in attachment. 904 auto. Start up of the motor and breaking went perfect. Engine idles and revs like it should. When I put the car in gear it either idles extremely rough or more often dies. It does this hot or cold. The car will drive down the road extremely well. But as soon as I slow for a stop it runs very rough or dies. Timing is at 10 degrees. I have tried going both directions with timing, no change. I have about 15 vacuum at idle, seems low could it be due to the cam? Let me know any other info that might help send me in the right direction |
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| Author: | Charrlie_S [ Sun Apr 02, 2023 1:35 pm ] |
| Post subject: | Re: New build will not idle in gear |
Need more info. Cam specs? carb? ign system, and timing curve (not just initial). What torque converter? |
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| Author: | Green72 [ Sun Apr 02, 2023 2:03 pm ] |
| Post subject: | Re: New build will not idle in gear |
Thanks for the reply Carb is a 1920 Holley Hei conversion Torque converter is stock 10 deg initial 34 all in Cam s a Oregon Cam 2106R Lobe sep. 108 Intake centerline 104, exhaust 112 Cam lobe lift intake 296 exhaust 289 It feels to me like the torque converter is stalling? Idling at 900rpm |
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| Author: | Green72 [ Sun Apr 02, 2023 4:47 pm ] |
| Post subject: | Re: New build will not idle in gear |
Any suggestions? |
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| Author: | Charrlie_S [ Sun Apr 02, 2023 5:46 pm ] |
| Post subject: | Re: New build will not idle in gear |
I don't see that grind number in Oregon cams listings. What is the duration? Also, did you actually measure the compression ratio at 10-1 or are you guessing? By the lift numbers you listed, that seems to be a comparatively mild cam. And that's a lot of compression for a mild cam. Did you degree the cam or just install it dot to dot? What is the idle speed in neutral? |
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| Author: | Green72 [ Sun Apr 02, 2023 6:07 pm ] |
| Post subject: | Re: New build will not idle in gear |
Duration at .050 is intake 214 exhaust 210. Is that what you wanted? I did measure for compression, took a look at my notes and it was actually 9.5/1 I degreed the cam with degree wheel Idle speed does not change from park to neutral 800rpm |
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| Author: | SlantSixDan [ Sun Apr 02, 2023 6:16 pm ] |
| Post subject: | Re: New build will not idle in gear |
2106R is the Dutra RV10-RDP, a good choice. The Holley 1920, especially the '70-'73 units, are not good carburetors to begin with and they age poorly; eventually they reach a hard end of their service life and cannot be dragged back out of the abyss. "Remanufactured" carburetors of whatever description are hopeless. But perhaps your carb isn't a zombie yet; carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download. If this gets worse as the engine heats up, double-check your valve adjustment. |
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| Author: | Charrlie_S [ Sun Apr 02, 2023 10:41 pm ] |
| Post subject: | Re: New build will not idle in gear |
I agree with Dan, that it is probably a carb problem. But you will/should modify your ign curve. I have a 170 engine with 9.5-1 CR, a mild cam with similar specs. and a holley 1920. I had a heck of a time modifying the ign curve so the engine would idle, but not "ping" when getting on the throttle, at cruise rpm/load. PS: My car is a 3 speed standard, not automatic. |
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| Author: | Green72 [ Mon Apr 03, 2023 4:29 pm ] |
| Post subject: | Re: New build will not idle in gear |
The carb that I have on the Scamp is not original. It is a 1920. As a matter of fact it was a NOS unit that I purchased from you (Slantsixdan) about six years ago. It has very few miles on it. I will read the material that you provided and see what I come up with. The valves are adjusted correctly. Let me ask this, I really feel that when it is put in gear it is being pull down by a load. Is there any scenario where the transmission could be the problem? Transmission has 5000 miles on it and functioned fine before I removed it |
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| Author: | SlantSixDan [ Mon Apr 03, 2023 10:28 pm ] |
| Post subject: | Re: New build will not idle in gear |
Quote: The carb that I have on the Scamp is not original. It is a 1920. As a matter of fact it was a NOS unit that I purchased from you (Slantsixdan) about six years ago.
Probably not dead, then, but might still be ailing. Clean out the idle circuits—spray the air bleeds with carburetor cleaner with the engine running above idle, then use the fast-idle cam and screw to hold the engine at a fast enough idle that it won't stall when you remove the idle mixture needle and spray in the resultant hole, then reinstall the idle mixture needle and see if anything's improved.Transmission fault doesn't sound likely, especially with a non-lockup trans. |
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| Author: | Dart270 [ Tue Apr 04, 2023 1:16 am ] |
| Post subject: | Re: New build will not idle in gear |
I highly suggest you redo the valve lash adjustment. I assume you are using 0.010" intake and 0.020" exhaust, like on a stock cam, since that cam is basically stock. You can also try opening up the lash to 0.014"/0.024" and see if idle improves. Forget what Oregon lists on the cam card for valve lash. I have never found that lash settings from an aftermarket cam company work well, EXCEPT for Mopar Performance cams and maybe one old Crane cam I ran. I have run perhaps 10 different aftermarket cams, including 4 different ones from Oregon that I custom spec'ed. Lou |
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| Author: | Green72 [ Mon Apr 17, 2023 4:15 am ] |
| Post subject: | Re: New build will not idle in gear |
I wanted to update and thank everyone for the information. I used the information that Slantsixdan provided to service my carb. After several attempts I was only able to “change” my issue but not resolve it. I purchased a remanufactured carb (I know Slantsixdan I know I know). The car immediately ran much better, but I started to notice that my stalling issue was now more prominent after the car was warmed up. I used information provided in this thread and opened lash up to .014/.024. I now have a newly built slant that runs perfect. I have put several hundred trouble free miles on it. The accurate and concise information provided on this forum is a welcome change! Thank you very much |
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| Author: | Dart270 [ Mon Apr 17, 2023 5:39 am ] |
| Post subject: | Re: New build will not idle in gear |
We are so glad to hear you have a nice running Slant now! You might try tightening the lash to 0.012" and 0.022" (or maybe 0.012" and 0.020") and see if the idle is still stable when hot. No hurry, but when you get a chance. If it starts to get rough when hot, you can back it off again. Slant on! Lou |
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