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Discussion Starter #1 (Edited)
I have a freshly rebuilt hot road motor with the following Specs:

1974 2L Spica Block
Motronic 10:1 pistons
RJR Full prep head shaved .030 for a measured 10.4/1 compression
RJR 472+3 intake cam 12.1mm lift
RJR 785 Exhaust cam 11.7 lift
Cams set to int 104 exh 104 lobe centers
Weber 40 DCOE 27 carbs rebuilt and jetted by GR
33mm chokes
135 main jets
190 air correction
F-16 emulsion tube
55F8 idle jet

123Tune bluetooth distributor
DP racing 10lb Alum flywheel

The motor has a distinct lack of torque below 2,800 rpm. Though it is not broken in yet (limited to 5.5K RPM) it seems to run well above that rpm.
Any thoughts on getting better torque at the bottom end?

Aloha,
Mark
 

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Discussion Starter #4
I think your right, it seems like the cam timing needs correcting. They were set up off #1cyc TDC at 104deg int and 104deg exh as recommended by RJ.
I am thinking of retarding the intake to 107 to reduce overlap, but would like to get some advice here before I start changing things arbitrarily.
Thanks,
Mark
 

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I think your right, it seems like the cam timing needs correcting. They were set up off #1cyc TDC at 104deg int and 104deg exh as recommended by RJ.
I am thinking of retarding the intake to 107 to reduce overlap, but would like to get some advice here before I start changing things arbitrarily.
Thanks,
Mark
While retarding to 107 would reduce overlap it would have the opposite effect of what you are trying to achieve. Going to 102 degrees and increasing overlap would likely pick the lower end up a little. That said it won't make much difference. You likely won't even notice it.

My guess is that you need to run it in on a wheel dyno with a sniffer in the exhaust and get the mixture exactly right before you mess with the cam timing. Also accept that an engine with a lot of cam like that is going to give up on the lower end everything it gains on the top end.

Good luck. Sounds like a great engine.
 

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basic setup recommended by Rj is indeed 104/104. Searching this site and from personal experience many times the best result is with 102/106/7. And you will notice the difference. See the topic Alfaparticle has on the RJ cams and his route to the best setup.
and check RJ himself. He is open to help his customers with advice.
 

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Have your checked your 123's advance? A quick and dirty test would be to substitute a stock distributor and see if there's a difference.
 

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71 Berlina 74 GTV 17 Giulia Q4
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I have pretty much the same exact motor as you except I ported my head to JimK specs. About the only difference is I'm running 200 air correctors and a 410 rear end. I had a hard time with it bucking and barely able to pull up a gentle hill in fourth under 2500 with the Centerline distributor. I switched to a RML and it pulls sweet and strong now. My point being I'd play with the advance curve, you might be getting to much to soon. I also have a 472+3 on the intake and tried a 785 but I never could get it to work. Others have so maybe it's just me. I switched back to the Centerline 11mm lift cam they have for the intake and on the exhaust it works great, for me.

 

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Discussion Starter #12
Hi Gigem75,
Great video!
Do you know how the head prep in Jim K's book differs from what RJ does?
It sounds like you have aftermarket exhaust. What are you running?
Aloha,
Mark
 

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71 Berlina 74 GTV 17 Giulia Q4
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Thanks! I have no idea of the differences but it's the same theory so I'd venture to guess they are not that much different. My exhaust is stock except for the old, old, Shankle headers. I did cut open the stock middle muffler and took all the stuffing out and welded it back up and just a straight pipe for the rear section. Have a good un!
 

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Discussion Starter #14
Heres a couple of pics of my Alfa, a early 1966 Duetto (June 66). I have pulled the 1600 and replaced it with the 2L described above.
I will be having the suspension rebuilt next as all of the rubber bushings are rotten. The car had not been on the road since 1989.
When the suspension is done I will take it to a chassis dyno and try to get the motor set up properly. I plan on driving it to Monterey Historic's after that is finished. Then ship it to HI.
Aloha,
Mark
 

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Richard Jemison
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Tuning

From the video I suggest that both the timing is off and the engine is running lean.
The 472+3(6) is a short version of the 550, but with less off the seat duration to make higher torque. The 785 exhaust is a proven high torque exhaust only lobe design. There are several other BB members running this and similar RjR intake cams with this exh cams. Perhaps they might speak up. I`ve see the profile of Joe`s 11mm intake cam. It is a good mild INTAKE cam designed for Carb intakes but early duration is high and if I remember correctly was described as a high overlap cam design, and not an appropriate exh application. If tuned correctly the 472+3/785 pairing should easilly accelerate in 5th gear from 2000 RPM.

As to timing, the 123 distributor should be set at the "D" curve with max advance at 34 degrees. That will result in static timing of 13 degrees BTDC and this curve is a straight line with advance not starting till 1000 crank RPM, and maxing at 4000 RPM (21 degrees total). Again a proven setting.

From the picture I see you are running old type metal wire for the coil & spark plugs. I would be concerned that you might have interference and as well check the rotor as it is a resistance type which are prone to failure. However if the 123 is only triggering to a coil with a primary resistance not lower than 1.0 ohm using modern spiral wound resistor wire then you shouldn`t have 123 failure or rotor burn out.
 

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71 Berlina 74 GTV 17 Giulia Q4
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Mark, that is sweet looking, very impressive! congrats
I'm confused. The video is of my GTV with an RML and according to the plugs and AFR I can assure you it's not running lean. Maybe RJ is speaking of a different video?
 

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Discussion Starter #18 (Edited)
I put off the tuning, In the mean time I have had the suspension rebuilt and new red koni shocks installed.

My plan is to take the car to a rolling dyno on 8/14 and get the carbs and timing sorted.

Then have the break-in oil changed out and the head re torqued. The next day I will drive it to Monterey for the historics. If all goes well I will show the car at Concourso Italiano.

The following week I will drive it to Oakland and ship it home to HI.
Once here I will adjust the cam timing and finish the tuning.

Aloha,
Mark
 

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Discussion Starter #19
I would welcome any advice as far as what jets to take to the dyno session.
Here is what RJ recommended and what I am starting with:

Weber 40 DCOE 27 carbs
33mm chokes
135 main jets
190 air correction
F-16 emulsion tube
55F8 idle jet
35 pump jet
35 pump exhaust
200 needle and seat

Thanks,
Mark
 

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Richard Jemison
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Jetting

That was with the RjR785 exhaust cam, which if timed per the setup sheet will make far more HP and torque than the Centerline cam installed. Typically a higher overlap (intake design) as Centerlines will require more fuel due to mixture loss out the exhaust pipe on overlap.

Why did it get removed?
 
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