Carbureted 302, regulated elec pump, heat soak causing lean AFR change

[superj]

its been a while for me too but i am putting one on the old bmw in the garage now. its bolted in place but i need linkages and other stuff so its slow going

 

[corerftech]

I believe I nailed the jetting yesterday. Was out of town most of the week on work. Last drive I felt it was driving lean and it was, both tangibly and measured. I had to adjust again my ideals of best AFR. With E10, Stoic is a lower number than pure gas. As well I had to adjust my thinking in Lambda by comparing pure gas numbers to Lambda and then begin tuning based on widely known numbers. I had thought 1.10 lambda (10% lean) was viable at cruise and it is not. Nor is it ok at Idle, at least on my 302. Nor is it OK anywhere except maybe a throttle plate change blip.

So Idle has been set to 3% target lean, 1.03, getting to .05 sometimes and .10 after a heat soak before everyone cools off and normalizes. 1.10 is fine for idle but it gets slightly rougher and is not like an EFI idle. 1.03 is supreme.

Low Speed has been set to a range of about 0.93 to 1.01

Tip in around town, when the metering rod pops up, it will go to 0.85-0.87 and has supreme response and power. Basically a slight accel from steady state around town.

Cruise is 0.99-1.02, and it is that narrow, at 65-75 mph. At slower speeds it pulls a bit more fuel and will dip into 0.93-0.96, flat ground.

There is a slight flat spot that I wont be able to remove w/o compromising economy. It is just a slight lack of response, I need to tip in slightly deeper and then the metering rod pops and I get fuel. Ideally due to my very high vacuum of 22 1/2 inches at idle, the 9 inch spring is still about 1 inch from being ideal. If I coluld get a 10 inch spring, I would change metering a tiny bit leaner.

WOT is 0.85-0.87 period. That is in the right gear, 2500rpm to redline.
My TCU is still not curved perfect and isnt downshifting to 3rd when the throttle is slowly laid into on the highway. Pressing the throttle really slow to WOT in 4th simply never forces a downshift. At that point my ratio goes to 0.77 flat which is way rich. This is I believe due to too much tension on the seondary air door spring. I had been tuning to get rid of the SLAM factor on secondary opening and when the throttle is stuffed, it is like EFI smooth. But too much tension on the air door ignores a slow increase of vacuum and the secondary which runs perfectly at 0.85-0.87 never gets enough airflow to get above the 0.77. I will attempt today to back off a tick of spring tension and the jet/rod combo is just where I want it. As well the TCU may not downshift based on CURVES and the issue of vacuum staying HIGH due to the slow decrease in 4th gear accel. The vacuum ramp is to slow. Stuffing it is abrupt, easing into it is not. If air door never opens then vac stays high (er) than TCU shift point needs to gear down.

Oh and finally, no ping. I pulled about 1.25 degrees more out of it. I have a timing tape error of about 2.5 degrees, with 10 degree mechanical limiter. So my TDC is at -2.5.
I am now set at a tape of 12, plus 2.5 equals 14.5 base time. Add 10 which is really about 11 and I am at about 25-26 degrees. The heads are GT40P on Walmart/Kroger 87 octane. The heads are said to not take more than 30 ever and 28ish on premium when swapped into mustangs and such. Taking 2 degrees out for fuel quality is just fine. It may seem awful short on timing and the idea of 30-34 for a Ford 302 is stuck in my head. But the fast burn head simply will not take it. Still running one step colder plugs which may not bee needed anymore but they will stay until they read as a problem.

I can clearly say aside from air door adjust, the carb and timing is now complete. I need not bother with the engine (except to fix the failed AC compressor). I can now focus on transmission tuning while on road trips with the wife.
I expect a slight dip in fuel economy but still expecting 20 MPG on the highway. I adjusted form a 73/42 rod to a 71/42 since last economy calc drive. Ill be happy with 18 but will rejoice if it is 20. I have grown tired of having to punch it constantly to go WOT for bursts as it is a waste of fuel and $$$ just testing. I am please the punching it can end! Just drive like a grandma and enjoy the car again.

Almost forgot---- the biggest improvement was moving from manifold VAC to ported VAC for advance can. I had some controversy over what would run better, give better MPG, crisper throttle at low speed, etc. Bobby Walters had schooled me on ported and my research indicated that is what SBF likes. But then some data more than suggests manifold has its place. I have been running manifold and about 42 degrees at idle and low speed and indeed it was lean/mean (ish) behaving. But the AFR would bounce and surge a tick at idle, the PUH/PUH/PUH of the exhaust was annoying and the idle needed more fuel to be smooth than was my target level. Like it needed to be at 0.85 to run smooth, horribly rich. Once I nailed down the balance of the tuning last weekend I pulled over and swapped the hose. Instantly the car idled like EFI, I mean smooth. It was still set to an excessively lean mixture of 1.10-1.13 at that time but it was night and day. Thereafter a short drive was also night and day for driveability. Following this last metering rod change and idle mixture at 1.03, this car idles at 875 in park, 750 in gear, I believe will take AC compressor ON w/o needing an idle stop solenoid added. It may make enough torque at idle to still run, but I have slight doubt that when the brakes are pressed changing vac conditon and.... with AC and in gear, may be intolerable w/o the solenoid.
26 degrees max timing, ported vac advance of 42 degrees, 71/42 rods, silver 9 inch springs and 98/100 jets on an Edelbrock 1905 with a Performer 289 manifold, Pertronix billet Ignitor II. Engine runs great.

 

[bobbywalter]

I believe I nailed the jetting yesterday. Was out of town most of the week on work. Last drive I felt it was driving lean and it was, both tangibly and measured. I had to adjust again my ideals of best AFR. With E10, Stoic is a lower number than pure gas. As well I had to adjust my thinking in Lambda by comparing pure gas numbers to Lambda and then begin tuning based on widely known numbers. I had thought 1.10 lambda (10% lean) was viable at cruise and it is not. Nor is it ok at Idle, at least on my 302. Nor is it OK anywhere except maybe a throttle plate change blip.

So Idle has been set to 3% target lean, 1.03, getting to .05 sometimes and .10 after a heat soak before everyone cools off and normalizes. 1.10 is fine for idle but it gets slightly rougher and is not like an EFI idle. 1.03 is supreme.

Low Speed has been set to a range of about 0.93 to 1.01

Tip in around town, when the metering rod pops up, it will go to 0.85-0.87 and has supreme response and power. Basically a slight accel from steady state around town.

Cruise is 0.99-1.02, and it is that narrow, at 65-75 mph. At slower speeds it pulls a bit more fuel and will dip into 0.93-0.96, flat ground.

There is a slight flat spot that I wont be able to remove w/o compromising economy. It is just a slight lack of response, I need to tip in slightly deeper and then the metering rod pops and I get fuel. Ideally due to my very high vacuum of 22 1/2 inches at idle, the 9 inch spring is still about 1 inch from being ideal. If I coluld get a 10 inch spring, I would change metering a tiny bit leaner.

WOT is 0.85-0.87 period. That is in the right gear, 2500rpm to redline.
My TCU is still not curved perfect and isnt downshifting to 3rd when the throttle is slowly laid into on the highway. Pressing the throttle really slow to WOT in 4th simply never forces a downshift. At that point my ratio goes to 0.77 flat which is way rich. This is I believe due to too much tension on the seondary air door spring. I had been tuning to get rid of the SLAM factor on secondary opening and when the throttle is stuffed, it is like EFI smooth. But too much tension on the air door ignores a slow increase of vacuum and the secondary which runs perfectly at 0.85-0.87 never gets enough airflow to get above the 0.77. I will attempt today to back off a tick of spring tension and the jet/rod combo is just where I want it. As well the TCU may not downshift based on CURVES and the issue of vacuum staying HIGH due to the slow decrease in 4th gear accel. The vacuum ramp is to slow. Stuffing it is abrupt, easing into it is not. If air door never opens then vac stays high (er) than TCU shift point needs to gear down.

Oh and finally, no ping. I pulled about 1.25 degrees more out of it. I have a timing tape error of about 2.5 degrees, with 10 degree mechanical limiter. So my TDC is at -2.5.
I am now set at a tape of 12, plus 2.5 equals 14.5 base time. Add 10 which is really about 11 and I am at about 25-26 degrees. The heads are GT40P on Walmart/Kroger 87 octane. The heads are said to not take more than 30 ever and 28ish on premium when swapped into mustangs and such. Taking 2 degrees out for fuel quality is just fine. It may seem awful short on timing and the idea of 30-34 for a Ford 302 is stuck in my head. But the fast burn head simply will not take it. Still running one step colder plugs which may not bee needed anymore but they will stay until they read as a problem.

I can clearly say aside from air door adjust, the carb and timing is now complete. I need not bother with the engine (except to fix the failed AC compressor). I can now focus on transmission tuning while on road trips with the wife.
I expect a slight dip in fuel economy but still expecting 20 MPG on the highway. I adjusted form a 73/42 rod to a 71/42 since last economy calc drive. Ill be happy with 18 but will rejoice if it is 20. I have grown tired of having to punch it constantly to go WOT for bursts as it is a waste of fuel and $$$ just testing. I am please the punching it can end! Just drive like a grandma and enjoy the car again.

Almost forgot---- the biggest improvement was moving from manifold VAC to ported VAC for advance can. I had some controversy over what would run better, give better MPG, crisper throttle at low speed, etc. Bobby Walters had schooled me on ported and my research indicated that is what SBF likes. But then some data more than suggests manifold has its place. I have been running manifold and about 42 degrees at idle and low speed and indeed it was lean/mean (ish) behaving. But the AFR would bounce and surge a tick at idle, the PUH/PUH/PUH of the exhaust was annoying and the idle needed more fuel to be smooth than was my target level. Like it needed to be at 0.85 to run smooth, horribly rich. Once I nailed down the balance of the tuning last weekend I pulled over and swapped the hose. Instantly the car idled like EFI, I mean smooth. It was still set to an excessively lean mixture of 1.10-1.13 at that time but it was night and day. Thereafter a short drive was also night and day for driveability. Following this last metering rod change and idle mixture at 1.03, this car idles at 875 in park, 750 in gear, I believe will take AC compressor ON w/o needing an idle stop solenoid added. It may make enough torque at idle to still run, but I have slight doubt that when the brakes are pressed changing vac conditon and.... with AC and in gear, may be intolerable w/o the solenoid.
26 degrees max timing, ported vac advance of 42 degrees, 71/42 rods, silver 9 inch springs and 98/100 jets on an Edelbrock 1905 with a Performer 289 manifold, Pertronix billet Ignitor II. Engine runs great.

this is fun to watch.


yes. there are dictates that change the scenario and that is based on goals and actual efficiency of build..

and using an afr gauge with a carb past a certain point will be an exercise in futility.. there are even setups that alter ported/man vac in certain temp ranges...and worked for the time. until...everything works great until in a given set of conditions.


a carb will never produce a clean emissions perspective burn across the spectrum. or altitude. use in range of elevation dictates tune.

it just can not do it reliably. they are useless for that. luckily it is not a confine for you.

but one great thing about a carb, they can harmoniously give the engine what it needs close enough and be tuned for a few specific conditions and even result in better top end power and mpg's...in some cases much better hiway mpg.

they can not do that in regards to measured emissions though.

and full drivability coast to coast in winter going from nyc to san fran via us 70. that isnt happening.

 

[Brain75]

I found even a change of 1800' in altitude made my setup run crappy... went from 5000 (just east of Denver) to 6800 (Bandimere speedway in Morrison west of Denver) and it was enough to make me dislike my tune, drove home and it was happy again. I never used a AFR gauge to find perfect spot I just used a vacuum gauge to find highest vacuum in the shop, set it and left it - and that was a difference of 0.2 is all, the engine had 17.8 across the whole range and a solid 18.0 at the sweet spot.

 

[bobbywalter]

yup. for what most people do a small primary 4 bbl will be just peachy, and run as good as most would wish for. even across the ranges it will get by ok.

for many many years, over a decade i always had a 2bbl manifold and dizzy ready for my rig.

though, its been a dizzle since 2008....but it is modified to run on an array of fuel.


for me though, i run my truck at angles that you have to be waaaaay under carbed to even get by. which is miserable and defeated the purpose of the small block.

 

[corerftech]

It’s a backup car for the wife to drive at our current altitude. Road trips and altitude changes are ok by me. And I fully expect a winter and summer fuel tune. It has already shown itself as we have driven it tuning at 20 degrees and in the same weekend, 60. Yep, changes everything.

The cool part of the Edelbrock is the rod change speed. I pull over in a neighborhood with my wife and in about 4 minutes swap rods, done in pouring rain, 13 degrees and wind chill and sweating 90 degree/95% in total darkness. If the car runs lean, to a point of issue, I’ll add some fuel. If I go to CA and sit in Torrance, and it’s wet, I can pull fuel. I used to jet my Weber 32-36 on my 76 beetle (and efi convert due to a machinist error on a flywheel surfacing, removing the trigger magnet unbeknown to me), every time I head from LA to Lake Isabella. I would stop just below the Grapevine and Jet, and then reverse on way home. Check oil while under the lid. Ran like a top no matter where I was. And I enjoyed doing it. Made me feel like I was doing something of merit.

No different here. The Gauge is teaching me things, and you guys are right, with a carb and gauge you just chase a tail in a circle, for a bit. Then compromise and give up. But at least I know what number equals what driving condition and can correlate less or more fuel to what my ass feels, very precisely. That will help on a road trip and being at 4000 feet rather than Memphis LOW and know to go 2 steps up on a rod and make it happy. W/o a gauge installed. I need that gauge for the next project, the 1990 Frankentruck 2.3 conversion.

Bobby- as usual- you were spot on. Ported vac makes everything better. I believed you up front, but it was good for me to experience the issues with manifold. Again, great learning experience w/o destruction of parts.
I have family flying in from Seattle for a wedding in April. This car, as crappy as it may be, will provide good reliable economic transpo for the four. Lots of people flying in for my youngest son’s wedding and one less group w/o a car.

Appreciate you folks!