revolve40

Mystery Cam and 123ignition Curve

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Hi everyone,

 

While I was adjusting my valves yesterday (.006 intake/.008 exhaust according to engine builder), I took some photos of the cam. He claims it is a regrind with 330 duration (it says "360 SRA" on the front of the cam).

 

The car idles pretty well, is pretty drivable, but is in desperate need of further tuning to really get back to where the motor was 10 years ago (~155 rwhp). I've been told that 330's are nearly underivable and primarily for race cars... what says the FAQ from what you can see?

 

IMG_4927.thumb.jpg.2d2f25bd878cebe14defb093d8c91f24.jpg

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IMG_4913.thumb.jpg.dd669a762e17c28fc34a745d2d92d2ef.jpg

 

I also installed a 123ignition bluetooth distributor and set the static timing at idle of 12 degrees BTDC. Any tips on curves for a 10.5:1 stroker? I know that with higher compression and EFI I won't need as much advance as most motors, so would love to have a safe curve to start from.

 

Thanks for any tips!

 

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Those anodized rocker locks are awesome.

 

Judging by how deep the back face of the cam lobe is ground into the cam, I'd say it may very well be a 330. My 292 is ground in about half that I think. I think that's how it works... they take off that extra material behind the lobe in order to get the steeper angle.

Edited by flagoworld

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Thanks for the quick reply. A recent dyno showed 143 rwtq at 2900, but only 109 rwhp at 4600. Evidently the motor was built to rev to 8000, but given I plateaued so early I let off the gas at 5500. Definitely need to iron out fuel delivery and now will be able to adjust spark as well.

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I think... doesn't not enough timing also cause it to plateau out like that?

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Remember, that cam will be reducing the dynamic compression on your engine so you may be able to enjoy more advance than you think assuming that you are rich enough on fuel. 

 

I would use the “tune” function that lets you advance the ignition as you drive. Combine this with some uphill runs above 3,000 rpm to find out at what point you get detonation. You can then dial the max advance back by a few degrees from there. You can then build that into your curve. Obviously the best way to do this is to combine into a dyno session. If you are organised you can try and standardise your uphill runs and time yourself, looking for your best time to complete the run that doesn’t detonate. Might be better to spring the cash and get a dyno tune done. 

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Thanks, Simeon! 

 

I thought so too, but part of the mystery is that when I did a compression check this weekend, I got the following results:

 

1 - 215

2 - 210

3 - 210

4 - 210

 

Motor was warm, throttles were open. Very high, which made me question the claimed 330 cam.

Edited by revolve40

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That seems very high compression. I am often skeptical about absolute compression figures as it does assume that the gauge is accurate and in calibration. I think they are more useful in gauging the relative compression between each cylinder. 

 

Advice stays the same but, as you know, just be cautious of detonation (and use the highest octane gas you can find). 

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The "SRA" designation was used by Norris.  I think the 360 refers to the lift (.360") at the cam.  I have an old data sheet on their 380 cam (.380 lift) that shows 330 degrees duration.

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Thanks, Jeff! Really appreciate the insight. Any guesses as to the duration of mine? Not sure of the relationship between duration and lift, or if that varies by manufacturer/re-grind. My naive assumption would be less duration than the Norris 380 since mine is evidently a Norris 360.

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Went for a drive with the below curve. Ran fine, but I was pretty easy on it. To Simeon's point, will benefit from some time on the dyno.

 

Static advance: 12*

 

RPM    123    "All-In"

500        0         12

1000      0         12

1300      0         12

1800      7         19

2600     14        26

3500     18        30

8000     18        30

Edited by revolve40

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I feel like you can be allot more aggressive on the advance than that. What carbs are you running? Looks like DCOE's.

 

I'm on a 292 cam with DCOE40's and I was running as much as 38 degrees total advance, but have it backed down to 34 degrees @3000rpm, and 36 total @6500 redline. 

 

At 1000 RPM I think I have 22. 

 

I want to get it properly tuned, and let a guru crank the timing up to match.

 

Edit- The above is what worked for my setup... And I'm not knowledgeable enough to arm-chair what you should use curve-wise for what appears to be a high-compression motor with a rather aggressive cam, but I'm confident some of the peeps around here who are more familiar playing at this level will chime in!

 

Edited by 2002Scoob

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BTW. That motor has some serious bling in it... Those rockers and locks are sex, somebody spent some money on that power plant, that's race-level stuff. 

Edited by 2002Scoob

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On 10/7/2018 at 12:07 AM, revolve40 said:

Thanks for the quick reply. A recent dyno showed 143 rwtq at 2900, but only 109 rwhp at 4600. Evidently the motor was built to rev to 8000, but given I plateaued so early I let off the gas at 5500. Definitely need to iron out fuel delivery and now will be able to adjust spark as well.

 

Makes me think that you didn't have the throttle all the way open or there is some significant issue to be fixed. Referring to the specs you know and the pictures, the power should be going up, up, up at 5.5k.

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7 hours ago, 2002Scoob said:

I feel like you can be allot more aggressive on the advance than that. What carbs are you running? Looks like DCOE's.

 

I'm on a 292 cam with DCOE40's and I was running as much as 38 degrees total advance, but have it backed down to 34 degrees @3000rpm, and 36 total @6500 redline. 

 

At 1000 RPM I think I have 22. 

 

I want to get it properly tuned, and let a guru crank the timing up to match.

 

Edit- The above is what worked for my setup... And I'm not knowledgeable enough to arm-chair what you should use curve-wise for what appears to be a high-compression motor with a rather aggressive cam, but I'm confident some of the peeps around here who are more familiar playing at this level will chime in!

 

 

I'm currently running TWM 40mm ITB's. Yes, can definitely get more aggressive, but I'm taking it slow with the high compression.

 

4 hours ago, Tommy said:

Screw the locks but are those Lester Owen rockers!? That's a serious build you have there!

 

Not sure about brand - the build sheet shows "racing steel rocker arms - custom made". Titanium spring retainers, etc.

 

4 hours ago, Tommy said:

 

Makes me think that you didn't have the throttle all the way open or there is some significant issue to be fixed. Referring to the specs you know and the pictures, the power should be going up, up, up at 5.5k.

 

It's possible and I agree - shouldn't be running out of steam that early.

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