Author Topic: Custom Tuning on Weekends  (Read 538 times)

Offline Cliff Ruggles

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Custom Tuning on Weekends
« on: April 19, 2021, 03:36:44 AM »
For several years now I've been opening up a couple of Saturdays a month for custom tuning.  Been having a great time with it and have met some really nice folks and had quite a few "troubled" carbs and entire vehicles brought here to custom tune.

I thought I'd start sharing a few of the stories as we get to see some pretty cool vehicles and a lot of different combinations.  I'll not mention any names, just going to talk about the what I did to fix the issues.

Last Saturday had a later 70's Corvette driven here with a pretty "fresh" 383 stroker engine in it.  It was topped with Pro Comp heads, about 10 to 1 compression and Comp XE256 cam.  I know it's a pretty small cam for that engine combo but we were able to get it sorted out pretty good.

When it showed up I checked the timing and it was at 26 degrees initial, 52 total and another 11 from the vacuum advance for 63 degrees at cruise.  The curve was pretty quick but not adding any timing at idle speed.  With that much timing in it at idle backing the speed screw clear off it was still running WAY too fast at idle for my liking, probably around 850-900 rpms.

I moved the timing to 10 initial, which provided 36 total plus 11 VA for 47 at cruise.  This dropped manifold vacuum at idle to about 18" and I could lower the idle speed to about 700rpm's, so good to go there.

I dove into the carb next, the owner had no idea who, what or when it was worked on last.  It had a good NAPA blue pump in it but recent "soft" blue seal which was already swelled up and failing (sticking in the bore).  The N/S assembly was the typical small windowed variety showing up in all the kits from the parts store and on-line sources. 

The power piston hanger arms were purposely bend down about 3/8" and the tips of the 54K metering rods had been removed.  Not quite sure what was up with all that but the jets were stamped #71 but drilled to just past .080".  I scratched my head on that one for a few moments then moved on.

The carb had been converted to electric choke but the vacuum was still open to the choke housing so it was sucking dirty air thru the engine.  Blocked that off, left the bypass air alone and ultra-sonic cleaned all the parts and started putting it back together.  I installed 75 main jets and my full tapered 44 custom rods with .026 tips.  Removed the plug from the airhorn for APT access and installed a 3/8 set screw in it.  Installed a solid high-flow N/S assembly, new accl pump, orange PP spring, and new secondary spring.  Replaced the CH rods with DA rods.

Since it was making PLENTY of vacuum at idle with only 10 degrees timing I left the idle tubes and DCR's stock, and all airbleeds idle and main at the stock sizes.

The choke pull-off had no restriction in it so I replaced it with one that I modified with a tiny hole" hole in the inlet for a clean/quick/smooth release to prevent hesitation/stumble/bog going quickly to full throttle.

....continued

Offline Cliff Ruggles

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Re: Custom Tuning on Weekends
« Reply #1 on: April 19, 2021, 03:37:03 AM »
Put the carb back in place and it fired right up.  Very quickly set the pull-off open angle, fast idle speed, then curb idle speed and mixture screws.  Once fully warmed up I did a "tip-in" test and raised the APT as it was pretty lean (I started with it bottomed out).  Ended up just past 4 turns up from seated which produced about 150rpm increase with the tip-in test.

I had the owner take it for a test drive, then tweaked everything once again since it was fully heat soaked, and good to go.  The engine sounded great and he said it made good power (he roasted the tires on the main road in front of the house), smooth off idle and pulled hard thru the gears w/o any issues........Cliff

Offline Mudsport96

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Re: Custom Tuning on Weekends
« Reply #2 on: April 23, 2021, 08:25:48 AM »
That's awesome Cliff. I wish i lived closer, id pay to have mine "super tuned". Ive got your HP kit and APT parts in mine and it actually starts and runs fine(even this winter at 15 degrees it fired as soon as the bowl was full)... but i know that it's missing something, hell it may not even be the carb. It may be im just expecting too much out of an 8.5 to 1 350 haha.

Offline silverminer

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Re: Custom Tuning on Weekends
« Reply #3 on: April 23, 2021, 09:54:03 AM »
Cliff - I hope you enjoy writing these summaries as much as we enjoy reading them. I do hope you'll continue to give us this unique insight into your work.

Offline Too Fast

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Re: Custom Tuning on Weekends
« Reply #4 on: July 27, 2021, 08:43:39 AM »
I really enjoy these reads as well.  Thanks Cliff!

Offline Cliff Ruggles

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Re: Custom Tuning on Weekends
« Reply #5 on: July 28, 2021, 07:40:57 AM »
Thanks, it's been a crazy summer so little time for weekend tuning.  I have been doing a few carb builds on weekends and a few local folks swing by during the week.

Yesterday had a customer come in with a 1967 Olds 442 carb that had a stripped fuel inlet.

Was hoping to just install a fuel filter housing with more threads but the carb had other issues so I ended up going into it.  The day before it was brought here the owner installed a rebuild kit from NAPA.  I told him the accl pump was junk and the N/S assembly was too small, and guess what?

The acc pump had already swelled up to nearly twice it's normal size and rolled right off the end of the cheap plastic pump when removed from the carb.  The N/S assembly was way too small for the Olds 442 engine so we replaced those items while we were in there 

The bottom plugs were leaking profusely even though someone had smeared a ton of JB Weld over them at some point.  So we got to make a repair there as well.

I attached some pics of the pump and seal removed with on of my seals beside it so you can see how much it swelled up in less than 48hrs contact with this new fuel.  It woln't even stay on the pump at this point.  The seal I sell will not swell up at all, even after many years of service and it comes with a lifetime warranty.......Cliff


Offline Too Fast

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Re: Custom Tuning on Weekends
« Reply #6 on: July 28, 2021, 09:00:41 AM »
More proof about cheap quality stuff.  I bought a rebuild kit from Cliff about 9 years ago, I've had the top off to do some changes this summer.  The accelerator pump still looks/functions as new.

Offline Cliff Ruggles

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Re: Custom Tuning on Weekends
« Reply #7 on: July 28, 2021, 10:30:31 AM »
Coincidentally I had the top off of the carb on my Ventura over the weekend.  I swapped the 8AN line back on from the regulator to the carb and forgot to blow it out.  Almost immediately after starting the engine is started running rough.  I shut it down and found a BIG pile of trash in the filter inside the fuel filter housing.  Looks like a mud dabber has set up home inside the line as it saw on the work bench for quite a while.

So I pulled the carb, blew it out, and the accl pump looked just like the day I installed it.  It's been in there since 2004 and went right back in for another 20 years or so!..........