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Tuning my new engine

General engine tech -- Drag Racing to Circle Track

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travis
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Tuning my new engine

Post by travis » Sat May 16, 2020 4:38 am

I’m looking for suggestions on tuning my new engine. I’ve never run this much compression with this small of a cam so I’m not sure which direction to go here.

.030” over 351w, aluminum 180cc heads with 2.02/1.60 valves, 10:1 compression, .045” deck height, Jones hydraulic roller 264/268@.006, 218/222@.050, 112 lsa/109 ica, .544” lift. Weiand stealth intake with a 670 street avenger carb. The distributor has 24* mechanical advance all in by 3000 rpms.

I’ve got the initial timing at 12* with the vacuum advance disabled at the moment. Would 36*@3000 be a little much for this? The idle is rattier than I expected for the short cam timing, although I suspect the carb may be more butchered than I initially thought. It was an absolute mess when I pulled it off the other truck (I bought it this way). I’ve got the idle mix screws out 1.5 turns as a baseline vs the 1/4-1/2 turns out as it came off the other truck. Throttle response is pretty soggy under 2500 rpms. Afaik, the carb is completely stock. I’m hoping to have my a/f meter setup today but I wanted to get the timing close before trying to tweak the carb.

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Re: Tuning my new engine

Post by Caprimaniac » Sat May 16, 2020 7:07 am

Tuning is a smart move....

SBF close to what you have and 40 degrers at 3000.
Vic jr heads.

However with your cam... Did you check compression pressure at starter motor speed?

I was as loe as 160 psi, and that can conrtibute?

Depending also on what heads/ comb chambers you have.
But in my book 36 is not far off. If you do not have a dyno and knock sensor, you just have to tune by the ear... If you hear pinging... back off a couple degrers and try again.
How to turn GURU in an instant.....

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Re: Tuning my new engine

Post by RevTheory » Sat May 16, 2020 8:05 am

12 to 15* max is probably about right for base timing. Getting the vacuum advance on manifold vacuum will definitely help pull any remaining snot out of it. Should be all carb settings from there.

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Re: Tuning my new engine

Post by Baprace » Sat May 16, 2020 8:46 am

travis wrote:
Sat May 16, 2020 4:38 am
I’m looking for suggestions on tuning my new engine. I’ve never run this much compression with this small of a cam so I’m not sure which direction to go here.

.030” over 351w, aluminum 180cc heads with 2.02/1.60 valves, 10:1 compression, .045” deck height, Jones hydraulic roller 264/268@.006, 218/222@.050, 112 lsa/109 ica, .544” lift. Weiand stealth intake with a 670 street avenger carb. The distributor has 24* mechanical advance all in by 3000 rpms.

I’ve got the initial timing at 12* with the vacuum advance disabled at the moment. Would 36*@3000 be a little much for this? The idle is rattier than I expected for the short cam timing, although I suspect the carb may be more butchered than I initially thought. It was an absolute mess when I pulled it off the other truck (I bought it this way). I’ve got the idle mix screws out 1.5 turns as a baseline vs the 1/4-1/2 turns out as it came off the other truck. Throttle response is pretty soggy under 2500 rpms. Afaik, the carb is completely stock. I’m hoping to have my a/f meter setup today but I wanted to get the timing close before trying to tweak the carb.
I would shorten that intial timing to min 20* - 24* at idle with a cam like that, not sure on the total but 36* seem's like a lot with a modern cyl head, I'm not an expert on Fords but the Race Ford N351 design heads seem to want only 29* - 31* max timing. On the vacuume advance I would add about 6* more maximum. JMO.

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Re: Tuning my new engine

Post by travis » Sat May 16, 2020 10:48 am

The initial post should have said .045” quench, not deck height.

My thinking on the total was somewhere in the 32* range, based simply on what many of you guys post on here. The heads have a modern heart shaped 60cc chamber, and I’ve got FM H336P pistons that have 4 big nasty looking valve reliefs with 12cc of total volume.

I just fired this thing up yesterday, so I haven’t had a chance to check cranking compression yet, or idle vacuum. I will check both of those things here shortly if it will quit raining for a while.

I was also curious about using ported vs manifold vacuum. Based on some stuff I have worked on lately, it seems that nearly stock stuff with small cams, heads, and intakes idles better with ported vacuum. My other truck in particular definitely gets a low speed miss with manifold vacuum (too much low speed advance). I’ll try both of course.

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Re: Tuning my new engine

Post by travis » Sat May 16, 2020 12:05 pm

In between rain showers, I managed to get a little bit done.

180 psi cranking compression on #1 cylinder. Less than I expected, but not a bad place to be for a street engine in a 4900 pound truck.

I’ve still got a little idle surge, but about 1 1/4 turns out on the idle mix screws seems to be about the best spot. 16-17” idle vacuum at 850 rpm. It seems happier at 16* initial, at least for starting and idle quality, with manifold vacuum hooked up. Throttle response seems much better now.

Now to secure up the temporary exhaust system and go for a test drive.

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Re: Tuning my new engine

Post by RevTheory » Sat May 16, 2020 1:35 pm

16* initial timing and then hook up the manifold vacuum, as opposed to some crazy low initial timing plus vacuum that equals 16*, right?

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Re: Tuning my new engine

Post by travis » Sat May 16, 2020 2:18 pm

RevTheory wrote:
Sat May 16, 2020 1:35 pm
16* initial timing and then hook up the manifold vacuum, as opposed to some crazy low initial timing plus vacuum that equals 16*, right?
Correct. It certainly gets soggier when initial drops below 12* even after plugging it in to manifold vacuum. Looks like I’m going to have to limit the total mechanical advance because I think the 40* mechanical I’m at now is too much

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Re: Tuning my new engine

Post by GLHS60 » Sat May 16, 2020 5:09 pm

Not sure what carb you have but 351W 4 bbl got me thinking.

The OEM 351 H.O. Holley had reverse idle mixture screws.

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Re: Tuning my new engine

Post by jeff swisher » Sat May 16, 2020 7:27 pm

I am in the minority of people that does not run vacuum advance.
My part throttle passing usually keeps my vacuum above 11" and too much timing causes pinging.
This will be seen very easy on a heavier vehicle.
My carbed Ford Van at 6000 lb with a 302" I built liked NO vacuum advance but my timing curve was 20° at idle and 35 total all in by 2400rpm.
You need it all in by cruise RPM or MPG will take a hit.

If you are running a lazy curve that is not all in my 3000 rpm your power below 3000 will be weak when you ask for power because enough throttle opening and your vacuum advance disappears.
Now you are sitting at 20 something total and trying to make power to pass a vehicle or just accelerate.

All my stuff has iron heads and high compression and high cylinder pressures 200+

My current 350" in my 3600lb 57 chevy has 10.78 compression and has ran like that with iron heads for over a decade 22 initial and 35 total.
I can run 38 total and make 3 more HP at the wheels but with 35 I do not change anything when pulling a 4000 lb boat to the lake.

Do not be afraid to jack that initial to 18-20 and remove the vacuum advance.

My 6000 lb Van got 17.6 MPG 90% of the time and that is including pulling a boat or trailer..Vacuum advance only created pinging and loss of MPG.
If I dialed in more than 35 total MPG went down.

Try it.
Not like you can't put it back.

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Re: Tuning my new engine

Post by GARY C » Sat May 16, 2020 7:56 pm

What happens to your vac reading and carb adjustment if you increase the initial timing?
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Re: Tuning my new engine

Post by travis » Sat May 16, 2020 10:17 pm

GARY C wrote:
Sat May 16, 2020 7:56 pm
What happens to your vac reading and carb adjustment if you increase the initial timing?
I didn’t get to do whole lot today. I gave up trying to do things outside between rain showers and worked on some inside projects instead. Maybe tomorrow

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Re: Tuning my new engine

Post by travis » Sun May 17, 2020 1:38 pm

I managed to put a few miles on this thing today.

16* initial, 40* total at 3000, no vacuum advance. Idles at 650 rpm with 15-15.5” vacuum but will only do this when fully warmed up. I raised it to 700-ish otherwise it’s pretty cranky until it warms up.

I’ve got a wicked off idle stumble, and pretty poor light throttle response. I guess the first thing to try would be some bigger squirters?

Light and heavy throttle response above 2400 or so rpm is very responsive.

I’ve got a Hughes heavy duty 2500 stall converter. It feels just like the stock 1500 converter except when pulling away at very light throttle, and then it’s only barely noticeable. Hopefully that will improve

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Re: Tuning my new engine

Post by travis » Sun May 17, 2020 2:22 pm

12* initial, 36* mechanical, + manifold vacuum. Definitely better off idle but still a pretty bad stumble. 60’ stripes without trying very hard says I’m going in the right direction :lol:

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Re: Tuning my new engine

Post by novafornow » Sun May 17, 2020 4:54 pm

Throw some squirter at it. Maybe jet up

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