[Formulajones]

Originally Posted by mgarblik

The little test kits with the graduated syringe or the vile that you mix the fuel sample with water are pretty accurate. The new law just signed last week allows 0-15% ethanol for road use with a sticker on the pump. When the limit was 10%, we used to sample fuel all the time. A class project was for students to bring 9 fuel samples from 3 different gas stations. Then we would test them. This would give us a couple hundred different samples in a typical test. We would use the home test, (water method) and the electronic tester sold through Kent Moore/SPX to GM. Results were all over the place. From 0% alcohol to a high of 13.5% the last time we tested which was a year ago. With the limit now raised to 15%, I wouldn't be the least bit surprised to see 17%-18% out there. Your lawnmower won't like that stuff.

I would expect it even a pinch higher just based off what I saw years ago, if the fudging stays the same.

[421mike]

Interesting Tom. My Yukon is a 2016 and performs almost exactly the same as yours. We just went to Lancaster and I noticed the mileage dropped to19+ on the way back but was in the low 20s on the way there. Might have something to do with the wind direction but who knows. Like you I always run 87 octane, usually Chevron. Hint buy gas at Vons in Bishop for about 5 cents cheaper than anything in town. Mike

[Stan Weiss]

Originally Posted by Formulajones

Isn't elevation figured into the equation? It should be.

I'd use a formula that includes it if that's what you're looking for. Or better yet, just figure it at sea level then you'll know it's fine everywhere.

Yes it is. But if you don't leave the mountain then you are leaving a lot on the table by tuning for sea level.

Stan

[Formulajones]

Originally Posted by Stan Weiss

Yes it is. But if you don't leave the mountain then you are leaving a lot on the table by tuning for sea level.

Stan

I can't imagine not leaving the mountain.

Shucks around here I can't even drive 20 miles in any direction without the elevation changing one way or the other. I keep the sea level tunes in the cars and it's been fine up here. You lose power up here regardless, about 3% for every 1000 feet gained. I can lean them out a tad and pick up a pinch, and maybe add another couple degrees of timing if I wanted up here, but I don't want to fiddle with them every time I drive down to Phoenix. Not real practical on our daily drivers.

[25stevem]

And just how is raising the level to 15% going to help with the big main problem, that being getting every day products to stores and in the making of many of those products from petroleum?

[tom s]

Mike,its cheaper at the Indian station just north of Independence!Also last trip the Speedy gas in Bishop was cheaper unless you had Vons points for a discount.E85 down here is 3.99 and 87 is 6.05.Tom

[w72]

You guys are nerds and I love it. I'm just curious which fuel would get into detonation or pre-ignition first. I'm about to fire up a new 467, going to try it with the Sniper running timing control as I don't have a suitable carb handy.

I'm sure the efi unit can handle the fueling for break-in, but not keen on taking chances with the built in all-or-nothing timing setup that brings all the advance in at once. I'm comfortable setting up a 2d timing table in the Holley software. Any input on a good starting place?

It's a fresh Len Williams 467 (4.25" stroke), zero-decked, Melling SPC-8, 1.65:1 rockers, RA manifolds with the larger collectors, RPM intake. I've seen people recommend wildly different timing specs for similar mills. I'm more concerned with a safe first 1000 miles than maximum power for now.

[w72]

I'm getting stupidly excited, haven't driven this bird in 3 years, it had a stock 220hp 400 when things went south for it. Dropped compression on 2 cyl, then the next week the neighbor's house burned down and toasted the paint job. I'll post about the whole build once she's running. The only moving parts that remain stock are the steering column and wipers.

[zippy]

Originally Posted by w72

You guys are nerds and I love it. I'm just curious which fuel would get into detonation or pre-ignition first. I'm about to fire up a new 467, going to try it with the Sniper running timing control as I don't have a suitable carb handy.

I'm sure the efi unit can handle the fueling for break-in, but not keen on taking chances with the built in all-or-nothing timing setup that brings all the advance in at once. I'm comfortable setting up a 2d timing table in the Holley software. Any input on a good starting place?

It's a fresh Len Williams 467 (4.25" stroke), zero-decked, Melling SPC-8, 1.65:1 rockers, RA manifolds with the larger collectors, RPM intake. I've seen people recommend wildly different timing specs for similar mills. I'm more concerned with a safe first 1000 miles than maximum power for now.

Nice build. What heads and CR? I am 470cid, 4.25" stroke, .040" overbore. Running the SPC-8 cam, 1.65 lifters on the rare #64 HO heads 87cc. Puts my CR like 10.6:1. Been thinking of Sniper. But funds are stupid tight right now and I can't seem to finish this rebuild form the crappy Comp cam going flat a few years ago.

Oh and with the XE274 cam, I used to have to have 16* initial. I think I was 32 total,, all in by 2800. With approx 12* vac advance on manifold vacuum

[GoreMaker]

Originally Posted by Formulajones

Just for giggles, and I'm sure someone here may know the answer.

There are formulas available to plug numbers in and figure your dynamic compression, which is useful for figuring octane requirements.

I recently revived this one from the distant past:
http://www.projectpontiac.com/ppsite...tio-calculator

The rest of the site is a decades-old irrelevant mess, but the dynamic compression ratio calculator is still valid and useful. It's remarkable to see how a different cam results in completely different actual compression ratio, which is what really matters when it comes to octane. This is why some people can get away with running 91 octane with 10:1 static compression and iron heads, while others will be pinging with 9.25:1 under the same circumstances.

[Formulajones]

Originally Posted by GoreMaker

I recently revived this one from the distant past:
http://www.projectpontiac.com/ppsite...tio-calculator

The rest of the site is a decades-old irrelevant mess, but the dynamic compression ratio calculator is still valid and useful. It's remarkable to see how a different cam results in completely different actual compression ratio, which is what really matters when it comes to octane. This is why some people can get away with running 91 octane with 10:1 static compression and iron heads, while others will be pinging with 9.25:1 under the same circumstances.

Yep, that's how I'm able to run 11:1 with iron heads and 91 octane

[Jay S]

Originally Posted by w72

You guys are nerds and I love it. I'm just curious which fuel would get into detonation or pre-ignition first. I'm about to fire up a new 467, going to try it with the Sniper running timing control as I don't have a suitable carb handy.

I'm sure the efi unit can handle the fueling for break-in, but not keen on taking chances with the built in all-or-nothing timing setup that brings all the advance in at once. I'm comfortable setting up a 2d timing table in the Holley software. Any input on a good starting place?

It's a fresh Len Williams 467 (4.25" stroke), zero-decked, Melling SPC-8, 1.65:1 rockers, RA manifolds with the larger collectors, RPM intake. I've seen people recommend wildly different timing specs for similar mills. I'm more concerned with a safe first 1000 miles than maximum power for now.

It would be nice too know what elevation range you expect to drive the car in.

If you want to be safe it isn’t a bad idea to start out around 28-30 degrees total on the timing to get a good feel of the fuel it likes. I don’t tune stuff much different jumping back and forth to and from ethanol blends, for me that small blend falls with an acceptable range for how the engine is tuned.

I have a friend running a similar mid 9s SCR 455 (467) combo in a 4x4 pickup. It gets driven 8-10K miles a year, it is pushing 40k now..He has more intake port flow than 250, but the exh side of the heads is almost stock, running Rhoads Vmax’s (set to .010”) and a 60919 Crower, which builds more compression than a SPC-8. Not a lot more, seems to be about .25 of a point. It ran the first 20K mile with the timing backed off to 30 and run 87 octane with ethanol. I gave him a hard time about it and he uses 91 now and more timing. It has a much tougher life than most peoples muscle car, pulls 17K trailers out on county rock roads. It has a hard life, secondaries get kicked in pretty frequently…shifts at 5500, sometimes 6. If he hasn’t killed that yet, don’t be too worried, they are pretty tough

[zippy]

Originally Posted by GoreMaker

I recently revived this one from the distant past:
http://www.projectpontiac.com/ppsite...tio-calculator

The rest of the site is a decades-old irrelevant mess, but the dynamic compression ratio calculator is still valid and useful. It's remarkable to see how a different cam results in completely different actual compression ratio, which is what really matters when it comes to octane. This is why some people can get away with running 91 octane with 10:1 static compression and iron heads, while others will be pinging with 9.25:1 under the same circumstances.

So my static is 10.6, Dynamic via calculator is 6.3. What is that telling me?

[GoreMaker]

Originally Posted by zippy

So my static is 10.6, Dynamic via calculator is 6.3. What is that telling me?

Well, a stock W72 400 (6X-4 heads, 8.2:1 static compression ratio, very pump gas friendly, 38 to 40 degrees total advance stock) has a dynamic compression ratio of 6.42:1. That means that at low RPM, your engine actually compresses the mixture less than a stock W72 does. But depending on your LSA, your volumetric efficiency might increase a lot more as RPMs go up, so cylinder filing is probably higher in that range. Honestly though, if you're running aluminum heads, you're probably fine with 87 octane. If cast iron, you'd likely want 91 or 93 just to ensure you don't ping at WOT. That's a pretty low dynamic compression ratio.

[w72]

I live 350ft above sea level, hoping to have no issues anywhere east of the Rocky Mtns. If I do head out west with the car, it should be easy to reprogram the Sniper to compensate. I can usually get 93 non-ethanol at a local gas station, but sometimes they get a truck of 91. At least they re-label the pump when that happens, pretty much everyone in Memphis with a cool car fuels up there.

[zippy]

Originally Posted by GoreMaker

Well, a stock W72 400 (6X-4 heads, 8.2:1 static compression ratio, very pump gas friendly, 38 to 40 degrees total advance stock) has a dynamic compression ratio of 6.42:1. That means that at low RPM, your engine actually compresses the mixture less than a stock W72 does. But depending on your LSA, your volumetric efficiency might increase a lot more as RPMs go up, so cylinder filing is probably higher in that range. Honestly though, if you're running aluminum heads, you're probably fine with 87 octane. If cast iron, you'd likely want 91 or 93 just to ensure you don't ping at WOT. That's a pretty low dynamic compression ratio.

Thx, ya Ported #64 HO heads I've always ran 91 in the past. Just wanting to be sure. I kept my timing back to 30-31 because with the headers and flowmasters, I could never hear pinging clearly. But in spring and fall I ran mid grade a few times and she seemed OK. I never pushed her on it tho so.

It's a Melling SPC-8 cam. advanced 4 deg if it helps

[TRADERMIKE 2012]

Mikes reply:

This might help, good info!

I have never tried an octane booster, have you? I would read the label to see if they have a product without any type of Alcohol!

https://boostane.com/?fbclid=IwAR1_6...2SHXa5vnz7e2uI

[w72]

I should be able to tune for pump gas no problem. The combo I'm running has been scienced to the moon and back by people way smarter than me, and was assembled by a well-respected pro. I plan to run 93 non ethanol whenever possible. It won't need octane booster or race gas.

My question is if the good stuff is unavailable, will I be better off with 91 non-ethanol or 93 with ethanol?

I think I tripped a circuit breaker on the forum by mentioning "041 cam" and "Rhodes" in the same post. Next thing you know we'll be 18 pages in and folks will be playing winning lottery tickets using random timing advice numbers.

[TRADERMIKE 2012]

Originally Posted by w72

I should be able to tune for pump gas no problem. The combo I'm running has been scienced to the moon and back by people way smarter than me, and was assembled by a well-respected pro. I plan to run 93 non ethanol whenever possible. It won't need octane booster or race gas.

My question is if the good stuff is unavailable, will I be better off with 91 non-ethanol or 93 with ethanol?

I think I tripped a circuit breaker on the forum by mentioning "041 cam" and "Rhodes" in the same post. Next thing you know we'll be 18 pages in and folks will be playing winning lottery tickets using random timing advice numbers.

Mikes reply:

You won't know what your motor likes until you have tested and tuned it for some time and stay away from Alcohol in the gas at any cost, my 2 cents! Unleaded 91 is my choice! I wish I could get 91 unleaded here in south Florida.

[Formulajones]

Originally Posted by w72

I live 350ft above sea level, hoping to have no issues anywhere east of the Rocky Mtns. If I do head out west with the car, it should be easy to reprogram the Sniper to compensate. I can usually get 93 non-ethanol at a local gas station, but sometimes they get a truck of 91. At least they re-label the pump when that happens, pretty much everyone in Memphis with a cool car fuels up there.

You won't have to do much at all with the Sniper. We run 2 of them, mainly because of the mountains and elevation changes, and they handle the changes quite well.

As long as you still have compensation limits up around the 10% range it will adjust the fuel as needed. If you need more compensation than that to deal with the mountains then the base fuel table probably needs more work.

I just turn the learn percentage down because I don't want it to corrupt the learn table when I'm dealing with elevation swings.

You can even have a different tune at the ready with the compensation and learn where you want and quickly load that in before you tackle the mountain, and let the Sniper adjust to those elevations and then save that tune to use when needed. Only takes a few seconds to load one. I've done that before too and then compared notes of the differences.

This kind of stuff is one of the biggest reasons to have this EFI