1978 Lincoln Continental Coupe

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Maverick
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Re: 1978 Lincoln Continental Coupe

Post by Maverick »

Since the fuel pressure varied from 5-7 PSI, with the temperature of the bypass regulator, it was moved to a cooler position on the front side of the under-engine cross member just inside of the frame. It should be safe and cooler there. I didn't like moving it further from the carb since it added about 3' between the regulator and carb. Would be better to have circulated, cool fuel closer to the carb.

I can't be sure the varying fuel pressure was caused by temp change in the regulator since the temp of everything under the hood was probably changing with the temp of the regulator. If the pressure still varies, I can always move the regulator back closer to the carb. Anyone have experience with varying fuel pressure?

Power valve restrictions were changed from .061" to .065". We'll see the effects of the two changes when we get another test run, currently planned for Tuesday. Hope to see a fatter mixture when the power valve is open, with and without the secondaries.

We were looking at the newer version of WXO's AFR gauge when he noticed the gauge is set to read AFR for non-alcohol gas. We may need to get as much as .5 richer for gasohol. Still need to sort that out. I'll probably make a call to their tech support and see what they say.

We're tentatively planning a trip to Rockingham Dragway on 12/3 to see what it does in the 1/8th (hope for less than the 9.0 we got at Dunn Benson) and 1/4 mile. I need to get WXO's AFR guage back to him so he can see if the TB SS needs some tweaking. Might want to run both vehicles on 12/3.
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Re: 1978 Lincoln Continental Coupe

Post by Maverick »

We got another test run today. The new location for the fuel pressure regulator seems to help. The fuel pressure was quite stable at about 6 PSI, dropping to 3-4 with high flow.

.065" power valve restrictions were replaced with .069". We got a good reading on the primaries only with open power valve. In high gear, the throttle was opened slowly till the power valve opened but still no secondaries. AFR leaned out to 16 just before the power valve opened then fattened up to 14.5 with the power valve. Better than before but still too lean. I think maybe .073, the biggest QuickFuel offers, might do it. But, I'll try to drill out a pair of smaller ones since QF wants $12 shipping for these tiny jets.

Here's a run we did for fun. https://youtu.be/TAsgV2k10Pc Thanks to WXO for putting the video online.
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Re: 1978 Lincoln Continental Coupe

Post by GMJohnny »

I like how the dashboard looks like some type of secret corporate test vehicle,
and how the tires break loose from a roll!

GM
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Maverick
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Re: 1978 Lincoln Continental Coupe

Post by Maverick »

Lighting the tires from a roll with a guy in the back seat seemed more intense than before. Think we're making more power. :mrgreen:

Drilled out some smaller restrictions to .073" with a #49 drill. We're planning another T&T on Friday.

WXO had a good idea to make a jig for holding these tiny restrictions for drilling. Suggested we drill & tap (6-32) a piece of sheet aluminum to hold the restrictions. With these larger bits, there's not a lot of material left to put in a drill press vice.

Handy chart of numbered, letter, and fractional drill bits ordered by size: http://www.gearhob.com/eng/design/drill_eng.htm
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Re: 1978 Lincoln Continental Coupe

Post by wxo »

Cycling through the frame by frame burnout video, with the #69 power valve restrictors, I did not see the full lean (16.00) AFR we had been seeing when the secondaries opened up. I'm assuming the secondaries were open during the burnout. This tells me that richening the power valve circuit has had an overall richening effect and that we may not have to change the jets on the secondaries (or maybe not as much as we thought).
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Re: 1978 Lincoln Continental Coupe

Post by Maverick »

I'm thinking, since opening of the secondaries is controlled by air flow thru the primaries, that should be happening at a fixed RPM with WOT. We should verify that and, if true, note at what RPM the secondaries open with WOT. Then I can watch the tach and announce for the video when we hit that RPM. Might still need the webcam for less than WOT. We'll also want it when we get to adjusting the vacuum opening of the secondaries.
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Basement Paul
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Re: 1978 Lincoln Continental Coupe

Post by Basement Paul »

Like mad scientists at work!

-BP
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Re: 1978 Lincoln Continental Coupe

Post by Maverick »

Right!! :mrgreen: :mrgreen: Although, we're probably more at play. :wink:

.073" restrictions didn't do it. Drilled some smaller restrictions out with a #47/.0785" drill bit. Can't go any bigger or it'll be too close to the 6-32 threads. I see why .073 is the largest restrictions QF sells. Don't know if the picture will show it but there's very little material left between the orifice and the thread.

Image

Idle was showing AFR in the 15s. Fattened it some and picked up idle RPM and an inch or so in vacuum. Installed the .0785" restrictions and took it out for a run but wasn't getting consistent AFR readings. It sometimes moves 2 numbers with no change in load or RPM. Sometimes seems to be reading 2 numbers too fat. Got consistent readings on the first part of the run but on the way home it showed too fat while still running really well. Maybe an exhaust leak messing up the AFR meter? Anyway, I think we're done with the primaries. We'll go to bigger secondary jets to get AFR in the 12s at WOT. Have another run with WXO and friend, Jim, tomorrow AM.
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Re: 1978 Lincoln Continental Coupe

Post by Maverick »

WXO, Jim and I got out for another test today.

We learned that the AFR meter readings drop about 2 points after a few heavy throttle runs. Re-booting the meter has no effect. 30 minutes of cooling off makes it regain those 2 points. No idea what's causing it but I believe the higher readings are correct. We just have to take breaks to recover accurate readings.

I'm satisfied that we have the primaries tuned and we've moved on to tuning the secondaries. The web cam shows the secondaries snapping open IMMEDIATELY when the pedal is mashed. No need to mess with the opening of the secondaries.

WOT is still somewhat lean in the 13s. Replaced the #96 jets in the secondaries with #99s, the biggest in the kit, with no improvement in WOT AFR. Something other than the jets is restricting fuel flow. :(

WOT at high RPMs drops the fuel pressure from 6 to 4 PSI. I've been thinking that 4 PSI is adequate but am changing my mind. Steady 4 PSI would be good but dropping the pressure by 1/3 means the submerged portion of the floats is also 1/3 less because 1/3 less pressure on the needle valve is necessary to stop fuel flow. Less of the floats submerged means lower fuel levels in the bowls, leaning out the AFR.

So, how to reduce the 1/3 drop in fuel pressure?? Maybe replacing the 3/8" fuel supply line with 1/2"? Man, I really don't like that idea. If the pressure regulator is adjusted up to 10 PSI, a 2 PSI drop to 8 would yield only a 1/5th drop in fuel pressure and a similar change in the submerged portion of the floats and smaller reduction in fuel levels. That's easy and might give an improvement.

Tomorrow we'll move the webcam from the secondaries vacuum motor to the site glasses for the primaries and secondaries. We'll probably then adjust the regulator up to 10 PSI and re-shoot the site glasses to see if there's less fuel level drop and also see if the AFR at WOT is improved.

I'm really happy with the improved smoothness and seat of the pants power. I wouldn't be unhappy with leaving everything where it is. But, we'll look into it a little more.
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Basement Paul
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Re: 1978 Lincoln Continental Coupe

Post by Basement Paul »

Keep in mind here that pressure does not equal flow. You can have a lot of fluid volume flowing without pressure. Pressure drop in this scenario might just mean the fuel finally has somewhere to go without the obstruction that was slowing it down. It's a common misconception, and might be what you're seeing here.

-BP
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Re: 1978 Lincoln Continental Coupe

Post by Maverick »

Edited to delete redundant post.
Last edited by Maverick on Sat Nov 19, 2016 9:58 pm, edited 1 time in total.
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Re: 1978 Lincoln Continental Coupe

Post by Maverick »

I moved the webcam from the secondary vacuum motor to the primary site glass. Jim & I took it out to see what we had. What we saw was shocking. Under WOT & high RPMs, the fuel level dropped past the bottom of the site glass giving a view of the float which sat motionless at the full down position. That while maintaining about 4 PSI of fuel pressure. The primary inlet is before the fuel pressure sensor so we know it was still getting decent fuel pressure.

Moved the webcam to the secondary site glass and did another WOT run. Fuel level again fell below the site glass and the angle of the top of the fuel was so steep (still getting good acceleration) it might have been exposing the jets to air.

Adjusted the pressure regulator up to 10 PSI and adjusted the floats to put the fuel level 3/4 of the way up the site glasses. Did another WOT run with nearly the same results. This time the fuel was still visible near the bottom of the site glasses.

Seems like something in the carb inlets is restricting fuel flow. That would explain no increase in AFR when switching secondary jets from #96 to #99. I think WXO found the solution: larger replaceable needle valve kits. The Holley carb tuning book didn't have anything to say about larger needle valves/seats but Holley and QF both sell them.

Don't know what size needle valves are in the carb now but it looks like they're inadequate. I ordered a kit with .130" valves from Amazon. Not sure if they'll fit or if they're bigger than the current ones but Amazon has a good return policy.
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Re: 1978 Lincoln Continental Coupe

Post by Maverick »

The .130" needle valves are here and they look like they'll fit the QF Slayer carb. They'll replace the .110" originals.

Also ordered, from ebay, secondary jet extensions and float kit that should help the secondary jets remain submerged during hard acceleration. http://www.ebay.com/itm/HOL-116-10-Holl ... 8w&vxp=mtr UPS estimated delivery is still a week off. :roll: Hope it doesn't take that long.

It'll be interesting to see what AFRs show up if/when the fuel levels don't fall so much on WOT and high RPM. We're wondering if smaller jets will then be needed.
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Re: 1978 Lincoln Continental Coupe

Post by Maverick »

The ".130" needle valve/seats Amazon sent were really .097". :x Must say they recovered nicely. Immediately sent out the right ones, gave me a return shipping label to print and 30 days to return the wrong ones. They'll only charge me again if the return isn't received in 30 days. All that accomplished easily online.

Everything arrived today: .130" valves/seats from Amazon, .150" valves/seats from (don't remember), and secondary jet extensions and compatible float from ebay. The .130" valves/seats were installed along with the secondary jet extensions. Turns out the carb came with the notched secondary float to accommodate the jet extensions. Carl thought the QF Slayer carb came with jet extensions but mine only had the compatible float. Wonder if some 12-year old Chinese girl neglected to install the extensions.

Adjusted the float levels again, 1/4 turn in one the idle mixture screws, and it idled nicely with AFR in the mid-12s.

I'm not sure why they make so many sizes of valves/seats. Don't know why one that's bigger than necessary would be a problem. Seems like they'd do like like they do with accelerator pumps where there are two sizes, normal and big, nothing in between. But, not understanding why bigger might not be better, I used the .130" valves/seats. If they're not adequate, the .150s, which I think are primarily for alcohol, will go in.

Would have taken it out to see AFRs with the new parts but by the time they were installed it was Happy Hour. First things first. Test run after Happy Hour seemed like a bad idea.
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Mad Scientist #1

Post by wxo »

Just thought I'd post a picture of our head mad scientist at work.
Mad scientist 1 small.jpg
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