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Nissan4Eva
Re: Competition camshafts profile
#21
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When measure with dial indicator got around 12/12.2 mm valve lift.

Now I have it in an A15 engine...using ford vs39 competition springs,I am having some trouble revving it pass 8200rpm.twin 40dcoe with 36 chokes, 45pump jets, 45f9 idle, f16 tubes with 205 air and 150 mains.

Any suggestions??? Using electronic dizzy with .032 plug gap using cdi ignition box and msd blaster 2 coil.

Posted on: 2016/8/22 1:36

Edited by Nissan4Eva on 2016/8/22 1:52:21
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ddgonzal
Re: Competition camshafts profile
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Open the plug gap up to 0.39 and see if it runs smoother. Even a standard points ignition runs good at 0.35, Datsun Electronic Ignition is good for 0.39 or more and CDI even more (typically 0.44)

Posted on: 2016/8/22 5:04
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benny
Re: Competition camshafts profile
#23
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Quote:

Nissan4Eva wrote:
...using ford vs39 competition springs,I am having some trouble revving it pass 8200rpm.twin 40dcoe with 36 chokes, 45pump jets, 45f9 idle, f16 tubes with 205 air and 150 mains...


The mains seem a little large. 135 -140 may prove better. Also the choke tubes are too big IMO. If in doubt for choke tubes, go smaller. 33 -34mm I think will be closer to the money. Makes for better mid-range and good decent peak power. Also the Cam will dictate the RPM that the peak power will occur. Generally speaking, most hotted up A-series make peak in the low to mid 8000 RPM range. More revs and power is probably dropping off.

Have you re-graphed the advance curve in the distributor?

Posted on: 2016/8/22 6:01
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ddgonzal
Re: Competition camshafts profile
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12mm lift is big. The biggest cam Nissan competition sold was 12.2mm (Nissan 99996-H1030 by Electromotive). It was one step up from their 82 cam


Quote:
having some trouble revving it pass 8200rpm ... Any suggestions???
That's right around where the cam's peak power is made, but should rev higher with reduced power

Most common cause of not be able to rev is valve float
* Spring pressure too weak to rev higher
* Coil bind at high RPM. Dual and triple coil designs are to help prevent this

The Nissan/Electromotive springs should have an installed height of 1.61" and a seat pressure of 130 lbs/in

The VS39 springs are a lot lower pressure, and call for shorter height. Are you running some kind of spacer under the springs?

Ford VS39 specs
VS39 DOUBLE
* 34.0mm installed height (1.34")
* 90 lbs installed pressure
* 21.0mm minimum height (0.84")
* 250 lbs maximum pressure
* 20.0mm coil bind
* 16.0mm I.D.
* 28.8mm O.D.
* 13.0mm maximum lift

Nissan Competition also called for an "oversize cam follower" with the Electromotive cams. I'm guessing that had to do with longevity/durability. They recommended 13231-78201 which is a stock lifter taken from the Nissan R16 engine and are still sold by Nissan

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Posted on: 2016/8/22 6:21
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ddgonzal
Re: Competition camshafts profile
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Quote:
Quote:

Nissan4Eva wrote:
...using ford vs39 competition springs,I am having some trouble revving it pass 8200rpm.twin 40dcoe with 36 chokes, 45pump jets, 45f9 idle, f16 tubes with 205 air and 150 mains...


The mains seem a little large. 135 -140 may prove better. Also the choke tubes are too big IMO. If in doubt for choke tubes, go smaller. 33 -34mm I think will be closer to the money. Makes for better mid-range and good decent peak power. Also the Cam will dictate the RPM that the peak power will occur. Generally speaking, most hotted up A-series make peak in the low to mid 8000 RPM range. More revs and power is probably dropping off.

Have you re-graphed the advance curve in the distributor?
Recurving the distributor is a good idea for lower RPMs, but shouldn't affect power above 5000 RPM (see Spark Curve)


For the jetting, the Weber books says it depends on the venturi (choke) sizes. Baseline is venturi X 4, so 36 x 4 = 144. The Air Correction Jet should be 1.25 to 1.50 of the Main Jets. So 1.25-1.5 x 144 = 180-216

Posted on: 2016/8/22 7:45
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Nissan4Eva
Re: Competition camshafts profile
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Thanks Benny will try 34 chokes and rejett..

ddgonzal....yes I use a spacer to get installed valve height, figured these springs wud be able to do the job. All the other Nissan springs I had coil bind before full lift, that is with modified spring seats already....
Will have to order some or see if the machinist can give me more clearance..

Thanks a lot guys.

Posted on: 2016/8/22 14:02
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ddgonzal
Re: Competition camshafts profile
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Those springs you have might be alright. Nissan Competition sold special springs for the Electromotive cams, as no stock ones fit the bill

* Tomei sells high-RPM springs for the A-series
* Bprojects sells springs good for 13mm lift racing valve spring
* The popular Isky springs are good for 10,000 RPM but only with lift up to 11.4 mm

Posted on: 2016/8/23 5:30
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ddgonzal
Re: Competition camshafts profile
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Benny has a good point about the 36 mm chokes. While the Weber charts say to use 38 mm chokes for 1.5 liter @ 8000 RPM, SCCA racers use 32mm chokes for 150+ hp A15 engine (see dyno sheet)

So up to at least 150HP, it seems smaller is better

In any case the large chokes are not holding back your revs. Can you exceed 8200 RPM in 1st gear? Or in neutral? If the problem only happens in 4th gear maybe you are running out of power to push the car over say 200 kph ...

Posted on: 2016/8/23 6:06
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Curlys
Re: Competition camshafts profile
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Today I want to thanks to "clyons8" because the information that comes from your space has served me a lot, although the techniques of preparation and special materials and technology of today have varied a little and you can extract more power than before making these Beautiful engines more reliable than I thought, 9k rpm with 1,298cc.
Thanks to "ddgonzal" you all for contributing greatly and from which I have learned many of you friends.Quote:

clyons8 wrote:
Definitely a FWD Engine with the deep Alloy Sump and those headers.

What a great piece of history having such an engine. It seems some of the highest performing A-series engines of that era were featured in FWD Datsuns.

Are you the person who has just downloaded my catalogues? Hope you enjoy them and they come into good use.

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jpg  14556546_1103152579780330_3766570269894019563_o.jpg (123.85 KB)
16700_58b4fe1f4c357.jpg 1314X876 px

Posted on: 2017/2/28 4:36
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