Crate engine swap advise please?

[73 C10]

Timing went up and down as they tried to meet pollution standards in different ways. Best performance and best mileage are when timing is as advanced as possible without detonation.

Suggestion is to keep the timing lower than optimum until you get the mixture straightened out and nail down the knocking thing.

Note that an adjustable vacuum advance with 20* on the crankshaft as the maximum is like saying "no one will ever want it higher than this" or the mfr would allow the adjustment to go higher. That suggests that most people would want it less, and in fact the factory spec is 15.

45 is hotter than 44. Hotter plug is better to burn off oil foiling, worse for detonation. The S is for "short", which helps get your wires in around the headers.

Thanks.

The AFR is ordered.

I'm going out to set the va to 12*-15*. I'm going to take anything in that range for now if I hit it since it's a PITA.

Back in a while.....

 

[MadOgre]

^^^ This.

I don't like that your tab and the delay timing light disagree. There's something goofy in all this.

Here's my recommendation, reviewing all of the above:

1) Find TDC and get an accurate set of marks on the timing wheel and polish up the tab so you can see WTF your timing really is.

2) Limit the vac advance to 12 to 15 degrees. 20 is too much. That may be the whole trouble, because it will knock when you get on it until the vac advance responds by backing off.

3) Set base timing for now to 8 degrees (ONCE YOU KNOW YOU HAVE AN ACCURATE READING).

4) Get the A/FR meter and set the needles/jets for cruise and power circuits first, then adjust the idle mixture. You should have something like 13 idle, 14.5 cruise, 13.5 power, 12.5 secondaries.

5) Now go back and set the base timing higher 2 degrees at a time, testing for knock each time. When/if you get to 16* BTDC base timing, stop there.

BTW, detonation (pre-ignition, knocking) sounds like you are shaking a 1# coffee can with a 1/4" steel ball bearing in it.

The reason our recommendations are all over the map is a lack of instrumentation: no reliable timing measurement, no A/FR readings.

You give us those, and MO and I will agree on everything.

I think all of us, Ceasar, You and Me are on the same page! LOL Just too many people posting at the same time using different words to say the same thing. lol

The only thing that is different that I am getting at is that the ??? x 052 rod in a 98 jet is actually leaner then the stock ??? x 047 in a 098 jet. So with a cam I would think that The Power mode is too lean for any cam especially given my experience with what a stock 350 wants. The only way this would make sense is if the cam somehow required a leaner fuel mixture to make power with? Which I have never seen. Or that the cam is actually stock and for some reason maybe he's at a 1000' and it likes it just a bit lean or his heads are quite restrictive?

I dunno this is the only thing that makes no sense to me. It does make sense that this leaner then stock jetting is contributing to his pre-ignition problem on top of too much timing. Or at the least that with this lean mixture he will be limited with how much total timing he can run.

Guys at 3000 feet have run the 1406 with out changing anything and have had good performance.

I just don't get how you would need to richen the cruise circuit by like 25-30% and then lean the power circuit 2-4% That makes no sense. I could see leaning the cruise by 2-4% and richening the power by 2-4% but not the other way around.

 

[MadOgre]

So now. I started by checking what I was at pre-drive. I unplugged the va and pluged the carb port. I zeroed the light. I read the timing on the tab at 10* @ 580 RPM. I adjusted the light 'till the TDC mark on the balancer lined up with the 0* on the tab and I had adjusted the light 12* from zero on the light. 2* difference. So go with what you want but there is an offset and I've been stating the light adjustment numbers so far. I set the light to 8 from 12 and set the distributor where the TDC on the balancer lined up with the 0* on the tab. I think that would be 8* BTDC @ 680 RPM. And would read 6* on the tab but I admit , I don't think I stopped to look for comparison.

I took a a spin with the va off and port plugged. It bogged taking off from a more labored sounding idle. Pulling out light footed was OK, but hammer down up to 45 was the rattling valve train sound. It lessens when letting of a bit with the foot.

Almost the same with the va plugged in. Bogged taking off.

If it bogs it is too lean!

That is the engine starving for fuel because its getting more air then fuel to make power to accelerate RPMs. If it bogs right off of idle then the You will have to step up 1 size on the primary jets and start working down with the rods again. If it only bogs when you open the 4 barrels probably going up 1 size with only the secondary jets may solve the issue.

 

[rich weyand]

I think all of us, Ceasar, You and Me are on the same page! LOL Just too many people posting at the same time using different words to say the same thing. lol

The only thing that is different that I am getting at is that the ??? x 052 rod in a 98 jet is actually leaner then the stock ??? x 047 in a 098 jet. So with a cam I would think that The Power mode is too lean for any cam especially given my experience with what a stock 350 wants. The only way this would make sense is if the cam somehow required a leaner fuel mixture to make power with? Which I have never seen. Or that the cam is actually stock and for some reason maybe he's at a 1000' and it likes it just a bit lean or his heads are quite restrictive?

I dunno this is the only thing that makes no sense to me. It does make sense that this leaner then stock jetting is contributing to his pre-ignition problem on top of too much timing. Or at the least that with this lean mixture he will be limited with how much total timing he can run.

Guys at 3000 feet have run the 1406 with out changing anything and have had good performance.

I just don't get how you would need to richen the cruise circuit by like 25-30% and then lean the power circuit 2-4% That makes no sense. I could see leaning the cruise by 2-4% and richening the power by 2-4% but not the other way around.

Beats hell out of me. Funny what you learn when you actually get the AFR numbers though. I would never in a million years have thought these needles would be right either, but that gives me the correct AFR across the range. I got the AFR meter after stumbling around with the chart and never getting the thing to run right, and just said, heck with it, I'm buying the meter.

I got it on this needle jet combination a couple years back and have never had to change it. And getting too frisky with it will break loose 31x10.5 BFGs on dry pavement on both sides (G80).

Bear in mind also that I have a very torquey cam with huge vacuum. Rather than it being "stock" or "more cam than stock", in some ways it is "less cam than stock" -- i.e. more toward torque and away from horsepower.

 

[rich weyand]

If it bogs it is to lean!

That is the engine starving for fuel because its getting more air then fuel to make power to accelerate RPMs. If it bogs right off of idle then the You will have to step up 1 size on the primary jets and start working down with the rods again. If it only bogs when you open the 4 barrels probably going up 1 size with only the secondary jets may solve the issue.

Wait for the meter! You can also bog too rich. Get the numbers first.

It'll also bog if his step-up springs are too light or the pistons are stuck.

 

[MadOgre]

I wish I could just go and look at it my self lol Then I would know in like 2 minutes whats going on lol

 

[MadOgre]

Wait for the meter! You can also bog too rich. Get the numbers first.

It'll also bog if his step-up springs are too light or the pistons are stuck.

I could see him being too rich on the cruise with 070 X ??? rods in a 098 jet. And then being too lean in the power with the ??? X 037 in the 098 jet. That would cause a hell of crappy running engine for sure!

Add too much timing and holy crap that would be a pain to figure out! lol

But according to the chart that is #19 which is about 12% rich in both directions. Only if you add a cam that required stock jetting for cruise and then more jetting for power would you have a problem.

 

[rich weyand]

I could see him being too rich on the cruise with 070 X ??? rods in a 098 jet. And then being too lean in the power with the ??? X 037 in the 098 jet. That would cause a hell of crappy running engine for sure!

Exactly. And that's exactly where I was before I got the meter, and getting 6mpg on top of it. Oh, I wasn't lean!

After I got the mixture sorted, I was surprised at how much timing it would take. And timing is like a horsepower adjustment right up to the knock limit. More is gooder.

Which is why modern cars have knock sensors. They run the timing right at the ragged edge.

 

[MadOgre]

Exactly. And that's exactly where I was before I got the meter, and getting 6mpg on top of it. Oh, I wasn't lean!

After I got the mixture sorted, I was surprised at how much timing it would take. And timing is like a horsepower adjustment right up to the knock limit. More is gooder.

Which is why modern cars have knock sensors. They run the timing right at the ragged edge.

Ya I hear you.

I had a rebuilt 305 that also had a really good stock 305 Q-jet on it. I ran that with 36* total timing and an Edelbrock 2101 intake. Ran a 2 1/2" Y pipe with a cherry bomb. In an 86' C10

You know people wouldn't believe me if I told them how much pep that little 305 had! It ran real good!

 

[73 C10]

OK

VA at 15*-16*

Without VA. Plugged. Sputtered taking off from stop with light foot. Hammer down to 45, no rattle. Instead, sever sputtering.

With VA. No sputter taking off from stop with light foot. Hammer down to 45, small rattle. And, sever sputtering.

For rod selection I have:

6252
6557
6857
7037
7337
7547
7342
7347

 

[73 C10]

It takes 9"-10" of hand pump vac to get the va to lift off the limiters fourth notch. This gave me 15*-16* of va.
It takes 17"-18" for full stroke.

Without the limiter, it takes 5" to lift off. This is why I asked about the limiters and choosing one that limits the top, not the bottom. So it would require the same 5" to get things started but limit it to 15*. I never got an opinion on this.

I have to think the difference in time it takes to build or drop from 9" to 5" to make a difference in the map.

 

[350runner]

Please post a link or pic to the limit device your using. The way your talking about it sounds backwards of what you need.

Sent from the dust in front of you!

 

[350runner]

You need a limiter that will limit the pull the vacuum can rod. The one you call a top limiter will keep you in an advanced state of some sort. Not good.

Sent from the dust in front of you!

 

[73 C10]

Please post a link or pic to the limit device your using. The way your talking about it sounds backwards of what you need.

Sent from the dust in front of you!

Here is the Crane type. It limits, what I'm calling the bottom of the stroke. No vacuum end:

http://m.summitracing.com/search/department/ignitions-electrical/section/ignition-components/part-type/distributor-replacement-parts?keyword=Limiter

This limits the top:

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[350runner]

So you have the top limiter correct?

Sent from the dust in front of you!