HOLLEY CARB

[boxer]

Have recentley fitted a 4160 holley carb with vacuum secondary chokes as this was not a new unit is there any way of checking that the secondaries are actually opening engine runs fine and accelerates well but i dont know if its well enough have read somewhere about putting a paper clip on the secondary diaphram shaft but that seems a bit hit and miss any other ideas would be welcome

Bob

[comeinhandy]

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I have just also fitted a holley 4160. I have been playing around with the jets to overcome a hesitation, caused by the secondaries opening too early. I worked out it was the secondaries by disabling them and feeling the difference. To stop them opening I removed the link from the primary/throttle side to the secondary butterfly, and then put a stiff spring on the secondary tied to a nearby point in order to stop it opening by the normal vacuum pressure.

You could try this to see if it drives any difference to driveability/power. I must say on mine it feels a lot quicker with the holley and branch manifolds etc.

I have also just ordered a miniture camera(£10 from amazon) that I will wire into my car radio/dvd player with the camera monitoring the secondary valve, so I then see when it opens on the screen while driving.

[comeinhandy]

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I've got the camera in now and wired up, so now I know when the secondary throttles open, not too surprisingly its when at full throttle and the revs are building up, like over 3000 rpm.

They opened to a maximum of about 60 degrees at 4-5000 rpm onmy quick test run, as shown in the following pics (quality not too good as it's a video recording of my car dvd player screen with a digital camera, soit's a picturefrom a video of a video!)

The first is at closed throttle, the next at 4-5000 rpm.

Probably wont make much sense unless you know what to look for. A white line has been painted on the secondary throttle control plate, you can see the angle has changed.

And for real overkill on this subject I also puta videoon youtube! (The stag V8 noise is one of the best engine noises!):

http://www.youtube.com/watch?v=-woacnvP0ZQ

Or am I a bit sad!?

[boxer]

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Definately not sad more ingenious i think have you played around with the springs in the diaphram housing or are they the springs that were in there when you bought it

[comeinhandy]

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The Holley was bought secondhand and the secondary diaphram springs are the same as when bought, but I am not sure what rating they are. I was tempted to get a set of springs and a quick change housing and have a play around, but haven't done so yet (http://www.realsteel.co.uk/do them if you are interested).

Mine runs a bit weak at partial throttle and I wasn't sure if it was the secondaries doing it, hence the camera. It doesn't look like it is, so at some time I will probably increase the promary jet sizesagain...53 size currently on both secondary and primaries.

Do you know what jet sizes you have? I find that a lamda/oxygen sensor in the exhaust (wired to a multimeter in the cab) is invaluable for check the fuel mixture strength.

regards - Jon

[boxer]

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Mine was secondhand as well but i have to say it runs really well .It was already fitted to a stag and the only thing i have changed are the primary jets on the advice of monarch who suggested changing from what looks like 51 to 48,s i think this is mentioned in previous threads.I do have a copy of Holley 4150/4160 by Mike Urich which i,m find quite useful

Bob

[BlueMK2]

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Are you using an adapter plate or a modified inlet manifold for the Holley, I had the one that had the centre machined out and a plate welded to it and I had a flat spot on acceleration that would not tune out, I was told that with all the manifold cut away it messed up the gas speed and the fuel entering the inlet manifold could not atomize properly and just got dumped into the manifold , changed the inlet manifold and used an adapter plate from Tony Hart and now no more flat spot and more power. The only adjustment I had to do was the two idle mixture screws and idle speed.

[comeinhandy]

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Interesting. I use an adapter.

It did have quite bad hesitation and very lean running on 49 & 51 jets, but now drives ok when warm, but the lamda sensor shows it running lean on part throttle. Drives ok so I'm not in a rush to fix it. Goes a lot better than with original Stromburgs and original manifolds (branch extractor ones now).

When I've run in my piston rings I will give it an acceleration test on my old Gtech SS gadget - should then be able to see the power & torque curves before and after results over rpm.

As for the adapter.... I had a "cunning plan" for DIY route, I also felt like a challenge so I bought a Qjet to holley adapter (ebay new approx £20), which fits the holley end but of course not the stag side. I then got some Aluminium wire & argon for my MIG welder and cut and weld filled the adapter until I got the right shape for the stag end.

After a lot of grinding and welding I ended up with the picture attached, which seems tofit ok (no vacuum leaks).

You could be right about the fuel not atomising enough although the shape & depth of this plateshould be similar to Tonys.

I have a little suspicion it might be my crankcase ventilation setup.. but that's another long story, or it could be that you can never get perfect air/fuel ratios with a carb. I'll report back if I ever get around to finding out or fixing it.

[Stagdad]

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comeinhandy wrote:

Interesting. I use an adapter.

It did have quite bad hesitation and very lean running on 49 & 51 jets, but now drives ok when warm, but the lamda sensor shows it running lean on part throttle. Drives ok so I'm not in a rush to fix it.

Hi Jon


Same as me ,thought i was the only one that 49's and 51's gave a flat spot ,Be interested what you do to sort it ,mind you mine was running a 3.45 diff .be interesting to see what my now lower gearing will do.I reckon the pumper nozzles need to go up a size or 2 and i'll be playing around with it this year.

I'd love to fit a wide band lambda ,is that what yours is ?or is it narrow band?

Cheers Steve

[mjheathcote]

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Its nearly 15 years ago since I jetted my Holley.

I fitted a secondary jet plate with screw in jets, and at the time it was running rich so I jetted down, by what I recall putting the primary screw in jets into the secondary, and fitting new smaller 49's into the primary (I have the empty card so deffo 49's). The secondary most likely 51's...

My wideband sensor on cruise maybe a touch on the lean side but not by much. The previous jetting (as supplied by HRS) was deffo rich though with real black exhaust soot so I can't imagine getting any better than what I have.

[comeinhandy]

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Stagdad wrote:

is it narrow band?

It's a general purpose,4 wire, narrow band one welded into the left hand down pipe, which is quite easy to get to. A wide band one would be nice, but more expensive. For fuel injected cars, the narrow band ones are fine, but with carbs I think they are never going to indicate a perfect mixture ratio for any length of time. Even so they are a good enough guide. It certainly shows a consistent very lean mix at very light throttle.

I might try some yet bigger jets, or I wonder if it is the transition phase mixture that is out. It needs a bit more fiddling, drives well enough for now though. Keep us informed if you improve yours.

Current project is to build a beter air/fuel ratio display - the multimeter is not ideal for monitoring it.

[V Mad]

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Narrow band sensors only tell you whether your mixture is lean or rich. Wideband sensors tell you how lean or how rich it is.

Using narrow narrow band sensors for tuningis a bit like trying to steer your car with a left/right/off switch (if there was such a thing). :shock:

[comeinhandy]

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It is true wide band ones (£70) are better than narrow band sensors (£10), butany sensoris better than nothing.The narrow onescan indicate theair fuel ratio from 13:1 to 16:1 if you have a precise means of voltage measurement (see attached response curve).

On a perfectly tuned setup the indicated output from the narrow band sensor will constantly fluctuate evenly from high to low. An averaging of the reading (mechanically or electronically) gives an improved interpreation of whether it is in tune or not.

Each cylinder can vary in its richness due to differing fuel flow, which also makes thesensor the reading change,this tends to help blur out the overall response curve of the sensor so giving some useful range when the readng is averaged. My A/F meter in my other carwill often sit on indicating a perfect ratio due to the averaging out of the readings, so it is still useful. Most modern car ECU systems use narrow band ones for cheapness and rely on avergaing the reading in order to control mixture.

[boxer]

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My holley is fitted with the hart adaptor which i have flowed into the standard inlet manifold it runs pretty well perfect.The only thing i am trying to get my head round is the fact the secondary choke diaphram is fitted with a plain spring does not open the secondary,s until the engine is reving to 2240 and according to Mike Urichs book does not fulley open until 8160rpm can that be correct whereas the yellow spring opens at1620rpm and is fulley open at 5680rpm anyone played around with the springs

Bob