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Discussion Starter · #1 ·
Gday Guys,

IM after some oversized valves for ga16de. Here in aus its pretty hard to get any at all.
Was wondering if there is a manufacturer in the US that supply these? Or if you guys have worked with an different combinations of valves.

Im also after adjustable camshaft sprockets. Absolutely noone in Aus makes them!
 

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Nothing off the shelf here in the US I'm afraid, they'd have to be custom made. That in itself is no big deal but as you know it can get costly. I presume you are heading in a direction that entails some healthy camshafts too, and significantly raised compression? I ask this because with some modest porting work on the GA16 head and stock valves, there is sufficient airflow to support 200 or so horsepower (flywheel). But unless you are extracting the maximum from the rest of the engine, large valves may be a bit redundant.

Here it is commonplace to do all the 'bolt ons' and stick in the JWT cams, but those are modest performance boosters at best, and I've only heard of one professionally built GA16 racing engine here (231 flywheel hp), and that was done nearly 10 years ago, and at extremely high cost (steel billet crank, billet rods, billet cams, 48 mm throttle bodies w/ standalone ECU, titanium oversized valves, etc).

Haven't seen any aftermarket camshaft sprockets either for the GA16.

Cheers,
Bob
 

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Discussion Starter · #3 ·
you say the valve sizes are capable of flowing to 210hp, by that do you mean forced induction?

ive already gone the n/a route, making 103kw wheels, but lacking torque, hence the second stage of my project is entailing a new/reworked head and a new intake.


Im running around 10.5 compression and have some serious cams in it so far. Cam specs are 278 duration, .3617 lift with lobe centres of 110.

These cams i got made to custom specs for 660 aus dollar. Valve springs ive lost the specs on but i can recall something about 130pound seat pressure at half lift - i may be totally confused here though.
 

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n14_unleashed said:
you say the valve sizes are capable of flowing to 210hp, by that do you mean forced induction?
Well, actually I said 200 hp...:)
What I meant is that based on a commonly known 'formula', for a given amount of airflow through the head, you can potentially achieve a certain amount of hp at the flywheel. This of course, is assuming everything is optimized to do so. So street cams and street compression will never get it done. This is assuming natural aspiration, not forced induction.

With standard valves, and modest (street) porting, I've seen 115.5 cfm of airflow through the intake ports at 10" of water on my flowbench on a GA16DE head. The formula I spoke of insinuates that for every cfm of airflow through the inlet tract, .43 hp potential exists. So, 115.5 cfm x .43 = 49.665 hp, x 4 cylinders = 198.66 hp. In 'real life', you'd be hard-pressed to hit more than 80-85% of that number on anything less than a pure racing engine, so look at 158-166 hp as being achievable and still somewhat streetable. Just because it has not been done yet does not make it impossible. Granted, with more airflow (larger valves and more intese porting), then more hp potential is available to you, with an othewise lower engine specification. I have yet to flow my own GA16 (turbo) cylinder head I ported with stock valves, albeit more aggressively. The exhaust is where the majority of the work needs to be done BTW.

Im running around 10.5 compression and have some serious cams in it so far. Cam specs are 278 duration, .3617 lift with lobe centres of 110.
Those are actually seemingly modest cam specs. The stock (US-spec) small-port GA16 cams are in fact .360" lift on the intake and .340" lift on the exhaust, with the intake duration @ .050" being only 202* inlet, and 198* exhaust. I had some reground to .380" and 212* (intake and exhaust), but tightened the lobe separation by 2*, it had heaps of torque but ran out of steam upstairs. Compression was also 10.5:1, which runs readily on 93 octane pump fuel with 15* BTDC timing. It could certainly handle 11 or 11.25:1 compression with larger cams and still run pump fuel. I'd like to see some cams in the realm of .450"-.460" with another 30 or so degrees of duration @ .050", I believe that would 'wake the beast'. Add another 6 degrees to the exhaust side to make up for the lazy exhaust port design and to help with scavenging at higher rpms, and I think you could have a nice engine that could give a 4AG street engine a run for it's money but with greater torque. If I had more disposeable income to buy the custom cams and valves I'd try it myself, as I have not only access to my own flowbench, but to an engine dyno and two chassis dynos for no investment on my end.

Cheers,
Bob
 

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Discussion Starter · #5 ·
Woa mate thats some good infromation! I Thank you very much!

i was hoping my cams were quite aggressive:(. SO you beleive maybe 290-300 duration with 450 lift? wouldnt that cause interfearance? Ive got the money to throw into it, so exactly what specs al up would you reccommend. Will they be streetable, i basically drive the car every second day.

The new head that im working is a series one head, ultimately after port work and what not is that still capable of some descent hp?

The ignition system of the ga16de worries me a little, would there be a need to convert it to multicoil setup and use an s14 ecu but chipped with my map?
 

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n14_unleashed said:
(. SO you beleive maybe 290-300 duration with 450 lift? wouldnt that cause interfearance? Ive got the money to throw into it, so exactly what specs al up would you reccommend. Will they be streetable, i basically drive the car every second day.
With standard pistons interference *may* be an issue on the inlet valves. When I had my own custom 10.5:1 pistons made, I spec'd a greater valve depth than standard, and even with the bigger cams I had ground I had almost .250" (6.35 mm) of valve clearance when I mock-assembled the engine. I could easily have used the larger cams I spoke of previously. The lift really isn't the clearance issue, it's the duration and lobe separation (e.g., the overlap).

As far as streetability goes, that depends on your tolerance for such things as well as the tune of the engine. A standard ECU would not be able to handle it, you'd have to upgrade, preferably to a programmable ECU. I'm doing the same for my turbo setup, too many variables from standard, and I don't trust someone trying to 'reflash' a standard Nissan ECU from 2500 miles away for a custom engine combination they know nothing about!
The new head that im working is a series one head, ultimately after port work and what not is that still capable of some descent hp?
If the head is properly reworked you should be able to feed a decent amount of air to the engine. As I stated previously the area where a lot of work needs to be done is the exhaust ports, in standard form they flow only 67 cfm @ 10" (102 cfm inlets). After some bowl blending and cleanup work (keeping velocities high for torque), I achieved 115.5 on the inlets and 83.5 cfm on the exhaust side. So the proportion was slightly better, improving from 66% to 72%, but I'd prefer to see 78%-80%. With the (factory) smaller exhaust cam the proportion is worse yet. I suspect that with more radical work and larger valves you could potentially see 130+ cfm on the intake side and 100 cfm on the exhaust side, but that's speculation on my part.
The ignition system of the ga16de worries me a little, would there be a need to convert it to multicoil setup and use an s14 ecu but chipped with my map?
The standard ignition is quite capable, I wouldn't worry about it yet until you get into the realm of very radical cams and high compression ratios. But if you use a stand-alone ECU, then you might as well convert to a crank triggered multiple coil setup rather than using the standard distributor as your trigger.

Bob
 

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I found my original 'Cam Doctor' results from a stock 1991 GA16DE engine. They're a little bit different from what I posted above, since I was merely going from memory when I posted those specs.

Intake: .342" valve lift - 208* duration @ .050"
Exhaust: .312" valve lift - 196* duration @ .050"

Lobe separation angle is 115.5* (static). It changes due to the variable cam timing during engine operation.

Hope this helps,
Bob
 

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Discussion Starter · #9 ·
Woa i never knew there was so much of a difference between the rods!

these jdm ones you show me, are they from jdm made vehicles that were exported or were they for japanese market only vehicles. The reason i ask is because we had two runs of the n14 in australia, the earlier was aus built and then from 93 til 95 it was jap built.
 

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I finally flow tested the GA16DE cylinder head I prepped for my street car. It has standard valves, and fairly aggressive porting. Thought these results might interest some of you.

Intake:
.100" - 45 cfm
.150" - 64 cfm
.200" - 82 cfm
.250" - 94 cfm
.300" - 104 cfm
.350" - 112 cfm
.400" - 115 cfm
.425" - 115.5 cfm

Exhaust:
.100" - 31.5 cfm
.150" - 46 cfm
.200" - 61.5 cfm
.250" - 70 cfm
.300" - 74.5 cfm
.350" - 78 cfm
.400" - 80 cfm
.425" - 81 cfm

Interestingly, you'll see that the peak intake airflow only just matched the mildy ported head I did for Tim Mather's rallycar years ago (115.5 cfm). And the exhaust flow was actually a couple of cfm less (peak).

The low-lift airflow was much better than before however, leading me to believe that what these heads really need is larger valves in order to perform. Still, the torque and the area under the curve should be excellent with the low-lift airflow numbers.

This was flowed on a Superflow 110 @ 10" of water, and the head casting is a 'small port' 1991 GA16DE. I have not flow tested a later GA16DE with the larger intake ports for comparison.

Bob Legere
 
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