Holley 1850 low speed tuning

[Nick_nl]

Hi guys,

For some time now i have been working on my Holley 1850 and the car is running pretty good. With the current speed limits over here most highway driving is done on the transfer slots @ 2000rpm. I would like to try en get some mileage improvement. Therefore i have been increasing the PIAB up to 1.9mm (0.075") This provides a 15.2 AFR on the highway, yet on the on ramp the vacuum drops and the AFR hits 16.5 and that's to lean.
Highway 100kph (63mph) @ 2000rpm is transfer slots and gives 17" Hg
Highway 120kph (75mph) @ 2400rpm is main jets and gives 15" Hg
Highway 130kph (81mph) @ 2600rpm is main jets and gives 15" Hg
Onramp is about 10"Hg, AFR 16.5-17
As soon as the power valve opens the mixture gets rich again.

I did pull a plug and its really white, so more fuel is needed.
Would it be a good idea to reduce the PIAB and install TFSR in the primary side ? My reasoning is this would keep the mixture richer and only limit the actual amount that's available.
It might also help to flatten the fuel curve a bit.

Thanks

Nick

[RFSPHPbb]

what value PV is in there? tried a quick opener 105? what size is the engine?

[Nick_nl]

The current pv is the stock 6.5.That would be a easy fix.
The engine is a SBC 355.
With a Lunati 60102 @0.050 219 int./227 exh.
The heads are Trickflow super 23 175cc head, resulting is 10.8:1 compression.
2.5inch ramshorn Manifolds and 2.5 inch stainless exhaust with mufflers
The distributor is a MSD 8360 with vac advance. 14* initial and 33* total @3500 vac advance is 10* this is a very slow curve to prevent part throttle ping.
I do use e5 (98 Ron) fuel.

[GTO Geoff]

The best way to improve mileage is to replace the Holley [ use it for a door stop ] with a Carter/Edelbrock 600 - 625 cfm AFB. Or the new Edel 650 AVS2.
All of these carbs have an 'Economzer' jet inside the primary booster, to improve low speed cruising economy. Carter took out a patent on it.

A little known FACT. Before Edel started re-making the Carter AFBs, they were selling modified Holley carbs. Yes, Holleys! At that time, the Holley period, they tested a 6619 600cfm Holley against a 625 Carter AFB on a Chev engine. The AFB made 17 hp more, 17 ft/lbs more & used less fuel doing it.
once

[rgalajda]

Can you give us a little background on this. What year was Edelbrock selling Holley carburetors? Did you mean quadrajet carburetors?
6619 Holley was an emissions carb in the 70's.

[Nick_nl]

GTO Geoff ,

Thanks for the information. Could you provide some more? I do have a Edelbrock 1406, but that one never ran as "sharp" as the Holley. It did run OK at best, but never really impressive even after a lot of jet and needle changes.
Making more power with less fuel is always a good thing, it means the engine efficiency did increase by quite a bit. Though I'm not surprised that the Edelbrock tested by Edelbrock did out perform their direct competitor.


I did change the power valve for a 10.5 one. I did notice a odd thing, the old one came with the Holley rebuild kit and was stamped 65, yet using my vacuum gauge it would open around 4 in Hg. The new one isn't a Holley product and does open at the specified point.

Thanks,

Nick

[ojh]

Seems to me with the AFR at 15.2 you are too lean as it is and, therefor, you aren't going to get better mileage. If you want a hotrod SBC then it'll take 'X' amount of fuel to make horse power, leaning it out will just break things you don't want broken. Its all about physics.

[ojh]

[Nick_nl]

Oké, I didn't know that the way you apply the vacuum changes the opening point.
spark plug

Yes this shows the car is running lean.

[TheTestPilot]

Hi Nick
was this plug sooty before you leaned the carb?

Tp