Holley 4BBl Performance

[porkbun]

Bob Sharp manifold arrived today. Theres a little rib inside intake before the 3 & 4 runners that is not on the Arizona Z Car manifold that I think was put in there to prevent cylinder distribution issues? Just a guess but it looks pretty restrictive. Any ideas? Heres the inside view and the bottom view. You can see where it juts out on the inside view and its looks nowhere near as narrow from the bottom.

[porkbun]

Ive had everything installed for a week or two and I think ive got the whole tuning thing down. Went from having to turn 2-3 screws on the SU's to 7+! Notice the sweet return spring setup!

Much easier to install with no balance tube in the way (I had to do it twice since I had to tighten the coolant fittings on the bottom and my header was in the way). Most difficult part was the throttle cable install. The BSR manifold has the throttle linkage posts which just got in the way of the recommended spectre install hardware so I had to cut that up.

The stupid black plastic piece that goes on the end of the sheath cracked as soon as I installed it and then I had to pull everything apart and bore out the plastic piece because it was preventing the cable from moving freely

I love the setup pulled the plugs and they were uneven and so dark!!

This explained my fuel economy and gave me some info about my mixture but it also happened to be the complete opposite of what people told me I would see, 3 and 4 were the leanest! Yesterday I cleaned the plugs, lowered the floats and also brought my timing down to 15 degrees from 20(so much for that supposed increase in fuel economy). Pulled the plugs again today and saw all the plugs were a light brown but 3 and 4 were a little richer than 1 and 6. Im hoping that by going to the FSM recommended 17 degrees (Not the random sources on the internet :stupid:) Ill have a nice even mixture across the board. 0-60 run will have to wait until there isnt as much snow on the ground and piled on the side of the road.

[Zed Head]

The only time the engine sees at the initial timing point is when the throttle is closed, assuming ported vacuum is used for the vacuum advance, and the centrifugal is stock and working properly. Otherwise, throttle open applies vacuum advance and increased RPM applies even more. Those two will determine how the engine runs when driving.

In short, make sure your advance mechanisms are working properly and they're what you want for mileage and power.

[olzed]

Nissan sold the 240Z with a downdraft DAF carb outside the USA.

No DAFs down here in NZ.

[porkbun]

Zed Head, your post caused me to look up how my distributor actually works . I read a couple places that advancing the timing a bit more could get me better fuel economy around town but I think it made it worse. This car has NEVER gotten very good gas mileage(compared to some of the numbers I see posted), I think the best ive ever gotten out of all the carb setups Ive tried was 22/15(shifting at 2k) with the ZTherapy carbs but I have no idea how much the cam/close ratio 5sp/3.90 affects it. Maybe I should take closer look at the distributor? Interested to see if the timing can really change the color of my plugs

With that super wealthy and advanced setup I had before I was getting ~10mpg but its also hard not to floor it with the pedal/throttle response (probably my favorite part of the swap). I think I might get this carb tuned up as well as I can and put in a super stiff secondary spring if my fuel economy isnt where Id like. My car is my daily driver and only car so I have to worry about these things

Edited February 16, 2014 by porkbun

[porkbun]

Took some shots of the plugs today at 17° initial timing. I just cleaned up both electrodes before I reinstalled them last time. The white/grey looking stuff is anti-seize

(especially on #6!) that managed to get on a few plugs but wouldnt wipe away entirely

Plugs 1 and 3

ClassicZCars you saw it here first. Ive managed to run a Holley lean!

Edited February 17, 2014 by porkbun

[ozconnection]

Porkbun, great work with the Holley et al. I'm a devotee to this way of thinking and I endorse completely what you've done to your engine!

I personally would love to see your theoretical manifold design for the four barrel carb. I've done my own research and looked carefully at several manifolds for the L and other engines and if I had the time and money, would've created that manifold.

As it turns out, I use an AZC on one of my cars and a Clifford 6=8 on the other. The Clifford intake supports 212 rwhp on my L28 normally aspirated!!

Keep up the great work, Cheers.

Edited April 3, 2014 by ozconnection

[porkbun]

Its been a while since I updated! Regarding the manifold design, I emailed Dave @ AZC. The BSR has a lower divider, narrower runners, and those ribs before the #3 and #4 runners. Dave said "...The divider in plenum makes a dramatic improvement in low end response, I also opened up the runners for improved top end. Overall performance is excellent." So the AZC appears to be better than the BSR.

A couple months ago I realized that I was only getting ~11-12 mpg which didnt make any sense. I finally decided to get a vacuum gauge and hooked it up to the base of the carb: at idle I was pulling ~5mmhg (is that the right unit? I dont have the gauge in front of me and I just took a Chemistry final ). I had a 6.5 power valve in the car which means that the power valve was open as soon as I started the car (thanks a lot cam! My old carb had an 8.5 in it!). Went to a 2.0 power valve and #55 jets from #51 jets (each jet size is a 4% increase in fuel) and my fuel economy went up as well to ~14-15mpg city and but only 19mpg @80mph on the highway . I was getting decent fuel economy but the crazy speed was gone. I threw some #60 jets in got some oomph back but a big drop in fuel economy and the plugs were only the tiniest bit browner. Seems like I can jet wayy richer for performance but im learning that performance and fuel economy dont really go hand in hand. I would go out and get some 0-60 videos but I got wider tires and ruined my u joints after a couple of hard launches . Im interested to see the 0-60 times as is, with the pig rich setup (#51 jets, 6.5 power valve), and the ultra wealthy setup (#55, 6.5 power valve depending on how the plugs look after the first run).

Thinking about switching back to SU's or maybe triples if a cheap set pops up. Nothing wrong with this setup but Id like to mess with SU's and see if I can get similar performance(and maybe pick up a wideband!). I just past the year anniversary of the day I got this car and ive done 5-6 carb swaps already :stupid: For some reason I just cant leave the car alone!

[black gold man]

I just picked up a Clifford 6=8 not that i will be using it anytime soon.

[porkbun]

Dont tempt me! Im going to go back to SU's and try and get it setup using a throttle cable (also going to ask a guy I know who restores E-types if he has any 2" SUs). Ill probably go back to a 4bbl eventually but its time for a change and some experimentation now that the weather is nice!

[porkbun]

Went off the deep end and have a 600cfm on the way. Already have an idea of how it will perform but I still want to test it out. Will post results when its all setup

[240260280z]

Fuel droplets make high speed 90 degree turns just like cars.... they don't.