Thoughts on tuning engines

[Sharps40]

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[66Submarine]

Oh, none of that was intended at you. Lol, sorry for that. My distaste is to the guys who call themselves "engine builders", then put something together that blows up and blame it on something irrelevant, when it was in reality their own fault. In working with or around these guys I just get kind of disgusted of it at times. (Most of them)

Kind of like another thread where a guy said he kept spinning rod bearings on an SBC going down the highway; the "builder" told him it was because he was "driving too fast". (Guess he doesn't know about all the SBC's screaming wide-open in boats, dumptrucks, circle track cars, etc. )

My point was just that the ethanol content of gasoline doesn't cause something to blow up. Sure, you cracked some pistons, but the same thing would have happened with "pure" 87, too.

Interesting that your new Wrangler pings, though. I thought everything today had a pretty sophisticated computer controlled anti-knock setup that keeps the timing right below the ping point?

[Sharps40]

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[Sharps40]

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[Sharps40]

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[PGSigns]

Well you have a couple of things wrong. Full advance will be at cruise with the ported vacuum. When you step on the gas the vacuum will drop off and it will retard the timing from 0 to the full 10 degrees depending on engine speed and the manifold vacuum level. One other assumption you are making that the timing pointer is correct. Very common for them to be off a couple of degrees. Go up 2 degrees at a time and see what you get. Also no were do you talk about reseting the idle air setting after each timing change. So you may have 4 degrees set but only 1 or 2 actual. The statement that a weber carb needs more timing does not make sense. Its job is o meter fuel and the brand of carb if both running about the same AFR should not matter.
Jimmy

[Sharps40]

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[Sharps40]

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[PGSigns]

So what was the goal of all this timing work with the vacuum gauge? It will be totally dependent on idle speed and throttle blade position. changing the timing and resetting the idle speed should get you back to the same vacuum setting. They are great for setting the carb up and for picking the springs in a vacuum secondary carb but I have never used one for setting timing.
Jimmy

[Sharps40]

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[Sharps40]

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[AcampoDave]

Hey Sharps, I'm one o' them small block guys, but I have been following your tuning with interest so I got out my ragged old Chilton's truck and van manual. It covers 1971-78. As you said timing was 4 degrees before tdc in '71 and '72 but in '73 mine says 6 before tdc and '74 says 8 btdc. I'm gonna assume the h.e.i made its debut on the 250 in 1975 because the point gap spec is replaced with the word "electric" in 1975-thru the end year of the book which is 1978. Here's the thing tho', those motors call for 10 degrees btdc. Soooo as you are running the h.e.i., your experimentation led you to roughly the same setting as my Chiltons for what I assume to be an h.e.i equipped 6 cyl in the years 75-78.

[Sharps40]

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[tincan1966]

Okay, I'll be the devil's advocate here- been following along thru MONTHS of tuning and tinkering, a lean-burnt blown engine and basically the same practices after installing another new engine.
My main question is:
What are you trying to achieve and tuning for?

I guess my ignorance can't let me wrap my head around what is so complex about tuning a carb'ed I6 to drive every day. All this fuss about how bad computer vehicles are and yet, I ,like a lot of others, installed a EFI system ,shut the hood and been driving ever since. Any issues I have had, have nothing to do with the computer. it's simple and it works. If I had to tune and adjust every day for 4 months, I'd give up! LOL!

You can change the amount and rate of advance by recurving the distributor to bring in the advance quicker or slower to fit your needs/conditions. That's an easy fix.

There's only so much you can gain, and knowing when to stop and enjoy it is relevant.

You've got a great truck, Sharps, one many would be proud to have, the work you've done and upgrades make a great daily driver, but PLEASE, stop adjusting and drive the damn thing and enjoy it! LOL
That is meant with all sincerity and honesty and tongue-in-cheek.- hate to see you seemingly beat your head against a wall on this.

Something to note and this was done by testing fuel for the race cars- even fuels that are supposed to be the same grade, will fluctuate in and out of the 'go-no-go" range. Different batches will vary slightly, so trying to get consistent results is often a bit tricky, because you don't have a base-line consistent fuel. If you were, say to purchase 30 gallons at one time, then keep in a controlled environment and use from the same batch after each adjustment, you could better document the change results. But that is a bit intricate for a daily driver.

Just my 2 cents an probably not worth half that!

Still a great truck, tho!

[Sharps40]

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[tincan1966]

Glad you aren't mad, because that was not my intent at all, was just wondering what the end result was. You found that already, too bad the hard way with some medium-well toasted pistons.

I do not know the correct formula, either, just I've always been told to tune to where you want it to run. To do that you need to find the rpm curve you drive at. WOT is irrelevant unless you drive that way all the time. Then, find YOUR midrange in that curve and adjust the "all-in" timing to pull into that range , typically about 34 degrees total timing, around 400-500 under your maximum shift point. Like I said this is NOT an exact procedure, just something that was relayed to me, and I've had decent success with it.
Of coarse now I mainly run computer controlled, but still I can set basic or static timing and allow the computer to pull in advance from there. My TBI is supposed to be timed at 0 at idle(600)rpm, and ends with around 32 @ 2200-2500. But I have found it really likes about 4 degrees initial and hits the 32 around 2000 with the lockup trans.

Now the turbo motor with the MSD 6AL digital control box and the boost timing control is a whole different animal I am trying to learn, because the 6AL will control timing and advance, but the boost timing control will take timing out as the turbo boost builds, to avoid detonation. Seems counter productive but it does work.

[AcampoDave]

Glad to help Sharps. Every time I see a book like that in a garage sale or a thrift store I buy it. (even if I already have it) I'm an old school guy and even though we have the internet now I still love those books. If you ever want me to look for something in them just ask, you know where to find me.