First real test drive today, after V8 swap.

[Road Trip]

Schurkey said:


Did you have the throttle opened at least somewhat during this testing?

I have never done that, ever. Don't see that it's going to make any difference with numbers like I've just posted.

I agree with Schurkey regarding the need to open the throttle while testing.

This removes a troubleshooting variable. While trying to diagnose this remotely
we are trying to match up your results to other 'known good' motors we've
worked on in the past. Sure, with the throttle sitting on the idle stops you
will get a reading.

But are your throttles barely cracked? Or where is your Idle Air Control valve
currently sitting? Has it moved since the last time we attempted a compression
test? Trying to quantify a compression test measurement with uncontrolled
variables, and you end up with squishy results that don't provide real insight
to the problem we're trying to figure out.

****

Another mistake I commonly see is performing a compression test by sequentially
removing the spark plugs one at a time, and when the results are reported, there
are skewed results. But what's not reported is that at the start of the compression
test the battery was full and the starter was cool. But by the end of the test
the engine was cranking over much slower, which *will* affect the observed results.

So, when I'm helping someone with a compression test, it looks like this:

* Make sure the battery is fully charged.
* Pull all the plugs. (Easier on the battery/starter, plus more consistent results between the first and last cylinders tested.
* Disable the fuel delivery.
* Disable the spark delivery.
* Have a known-good test setup like Schurkey described.
* Test each cylinder, writing down the results for each cylinder. (Which you did, good!)

My motivation is not to be pedantic or make you jump through hoops unnecessarily.
The clearer the picture we get while looking remotely into your engine bay, the more
valid our recommendations will be.

 

[DeCaff2007]

I agree with Schurkey regarding the need to open the throttle while testing.

This removes a troubleshooting variable. While trying to diagnose this remotely
we are trying to match up your results to other 'known good' motors we've
worked on in the past. Sure, with the throttle sitting on the idle stops you
will get a reading.

But are your throttles barely cracked? Or where is your Idle Air Control valve
currently sitting? Has it moved since the last time we attempted a compression
test? Trying to quantify a test measurement with uncontrolled variables, and
you end up with squishy results that don't provide real insight to the problem
we're trying to figure out.

****

Another mistake I commonly see is performing a compression test by sequentially
removing the spark plugs one at a time, and when the results are reported, there
are skewed results. But what's not reported is that at the start of the compression
test the battery was full and the starter was cool. But by the end of the test
the engine was cranking over much slower, which *will* affect the observed results.

So, when I'm helping someone with a compression test, it looks like this:

* Make sure the battery is fully charged.
* Pull all the plugs. (Easier on the battery/starter, plus more consistent results between the first and last cylinders tested.
* Disable the fuel delivery.
* Disable the spark delivery.
* Have a known-good test setup like Schurkey described.
* Test each cylinder, writing down the results for each cylinder. (Which you did, good!)

My motivation is not to be pendantic or make you jump through hoops unnecessarily.
The clearer the picture we get while looking remotely into your engine bay, the more
valid our recommendations will be.

Ok, a few things here. I do have all the spark plugs removed. I have the fuel pump relay unplugged, but I seem to still be getting a small amount of fuel somehow.

The battery is what it is. I know, that's the wrong answer, but guess what: EVERY battery I get from Advance is JUNK. They keep swapping them out for free batteries, so I'm not complaining. I've been meaning to get a decent charger for a long time, but could never justify the cost. Maybe it's time.

I know my gauge is good so thanks for that.

So, let's throw a scenario out there. Say I pony up for a charger (and use it). Say I crack the throttle open while testing (which I still believe is unnecessary). Say all other test parameters are good, and I still get numbers like I've just posted.

Then what?

 

[GrimsterGMC]

Ok, a few things here. I do have all the spark plugs removed. I have the fuel pump relay unplugged, but I seem to still be getting a small amount of fuel somehow.

The battery is what it is. I know, that's the wrong answer, but guess what: EVERY battery I get from Advance is JUNK. They keep swapping them out for free batteries, so I'm not complaining. I've been meaning to get a decent charger for a long time, but could never justify the cost. Maybe it's time.

I know my gauge is good so thanks for that.

So, let's throw a scenario out there. Say I pony up for a charger (and use it). Say I crack the throttle open while testing (which I still believe is unnecessary). Say all other test parameters are good, and I still get numbers like I've just posted.

Then what?

If you don't open the throttle plate while cranking it will create a vacuum in the manifold which will adversely effect your compression readings by up to 20 psi.

 

[Orpedcrow]

So, when I'm helping someone with a compression test, it looks like this:

* Make sure the battery is fully charged.
* Pull all the plugs. (Easier on the battery/starter, plus more consistent results between the first and last cylinders tested.
* Disable the fuel delivery.
* Disable the spark delivery.
* Have a known-good test setup like Schurkey described.
* Test each cylinder, writing down the results for each cylinder. (Which you did, good!)

If you don't open the throttle plate while cranking it will create a vacuum in the manifold which will adversely effect your compression readings by up to 20 psi.

Having chased my tail in circles many times, my experience has taught me these very same guidelines. This is THE way to perform a compression test.

 

[GrimsterGMC]

Ok, a few things here. I do have all the spark plugs removed. I have the fuel pump relay unplugged, but I seem to still be getting a small amount of fuel somehow.

The battery is what it is. I know, that's the wrong answer, but guess what: EVERY battery I get from Advance is JUNK. They keep swapping them out for free batteries, so I'm not complaining. I've been meaning to get a decent charger for a long time, but could never justify the cost. Maybe it's time.

I know my gauge is good so thanks for that.

So, let's throw a scenario out there. Say I pony up for a charger (and use it). Say I crack the throttle open while testing (which I still believe is unnecessary). Say all other test parameters are good, and I still get numbers like I've just posted.

Then what?

To stop the fuel you can just pull the fuse that supplies the injectors so they don't pulse.

 

[Road Trip]

To stop the fuel you can just pull the fuse that supplies the injectors so they don't pulse.

^^^^
Exactly as Grimster said.

And in case anybody wrenching on a TBI is wondering how:

You must be registered for see images attach

 

[DeCaff2007]

Alright well y'all have given me some insight. Looks like I have some re-testing to do. I'm going to have Advance Auto charge my battery up again. I guess I'll drop the dime on a battery charger . I wouldn't mind, but they are so damned expensive.

This may get done tomorrow, it may not. I have other things on my agenda tomorrow, so we'll see what happens.

.... let's continue to chase that wild goose and push that boulder uphill.

EDIT: Just an FYI, I'm nearing the point of tearing these junk aluminum heads OFF and putting the originals back on. I still have the push rods that go with the factory heads, so it SHOULD be a direct swap. That would mean non-angle spark plugs again , no difficult headers to deal with, and easy bolt-on parts again.

 

[Road Trip]

Alright well y'all have given me some insight. Looks like I have some re-testing to do. I'm going to have Advance Auto charge my battery up again. I guess I'll drop the dime on a battery charger . I wouldn't mind, but they are so damned expensive.

Hey Decaff2007,

No doubt you've got me pegged as a wild-eyed perfectionist type with a water-cooled credit card,
but the reality is that I'm a strict pay-as-you-go dude. Being extra careful with my
disposable income allows me to indulge in more than 1 hobby simultaneously.

Sounds like you have about as much excess money to burn as I do. :0) So when it
comes to all things having to do with batteries, having a battery charger at the
homestead *is* the cheapest way to go.

And as long as you stay on top of your battery health, the extra spendy battery
chargers with the 100+ amp boost are simply not necessary. As a matter of fact, my very
first 10/2 amp full manual battery charger I bought from Sears many, many moons ago will *still* get the job done:

(credit: 2/2/2024 eBay auction image -- my similar old soldier is currently BVR in deep storage)

You must be registered for see images attach

Currently in the shop my buddy & I have not 1 but 2 chargers available for use. He has a 'newer' Sears charger...but
it's still at least 12 years old. But still works like a champ. Took this action photo this evening:

You must be registered for see images attach

Meanwhile, while my original Sears charger was in deep storage, ~4 years ago I left a dome
light on, stranded myself, and was forced to buy my way out of a jam. Ergo, I ended up
with a new Schumacher. Another action photo from this evening:

You must be registered for see images attach

The takeaway from these photos?

* Old battery chargers (especially the simple ones) last a long time.
In this space, Used really does = Previously Enjoyed.

* Both chargers agree with each other, no discernible difference in how
well a battery works after being charged by either one.

* Thanks to a no-nonsense super cool local business (Battery World)
all I run are their load-tested 'blem' or '2nd' batteries. Normally these
batteries sat on some store shelf for a year, didn't sell, get returned,
and if they pass a load test after being topped off, they work as
advertised. (Normally $45-$60, the one in the photo was $60.)

Oh yeah, they give me a 12-month performance warranty on these
blem batteries. Been using these for years, and have yet to take
them up on their warranty. FWIW, the 454 in the chore truck has
a 15+ month old blem battery in it, always spins over with intent
and fires in <1 second.

The bottom line? A used flat tappet camshaft? I don't think so.

But how about purchasing a used battery charger? Absolutely.

Food for thought. Keeping it frugal.

 

[DeCaff2007]

No doubt you've got me pegged as a wild-eyed perfectionist type with a water-cooled credit card

Now that's funny!

Thanks for the info on the battery chargers. I'm looking at this one currently. NO start feature, though.

4Amp Fully Automatic Microprocessor-Controlled Battery Charger/Maintainer

Amazing deals on this 4Amp 12V High Freq Battery Charger/Maintainer at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

If I want to break out the deeper pockets (really DON'T want to, but it's DeWalt, just saying.....). This one HAS a start feature.

DeWalt DXAEC100 Professional 30 Amp Battery Charger 3 Amp Battery Maintainer for sale online | eBay

Find many great new & used options and get the best deals for DeWalt DXAEC100 Professional 30 Amp Battery Charger 3 Amp Battery Maintainer at the best online prices at eBay! Free shipping for many products!

www.ebay.com

With that I have a question: What's wrong with simply using jumper cables from a running vehicle to power the Heap while performing the compression test?

OH! Another question: Is it going to make any difference if I squirt some oil down each cylinder for the compression test? I've read about doing that. Never done it. Don't see the point. So, I'm asking.

 

[termite]

Now that's funny!

Thanks for the info on the battery chargers. I'm looking at this one currently. NO start feature, though.

4Amp Fully Automatic Microprocessor-Controlled Battery Charger/Maintainer

Amazing deals on this 4Amp 12V High Freq Battery Charger/Maintainer at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

If I want to break out the deeper pockets (really DON'T want to, but it's DeWalt, just saying.....). This one HAS a start feature.

DeWalt DXAEC100 Professional 30 Amp Battery Charger 3 Amp Battery Maintainer for sale online | eBay

Find many great new & used options and get the best deals for DeWalt DXAEC100 Professional 30 Amp Battery Charger 3 Amp Battery Maintainer at the best online prices at eBay! Free shipping for many products!

www.ebay.com

With that I have a question: What's wrong with simply using jumper cables from a running vehicle to power the Heap while performing the compression test?

OH! Another question: Is it going to make any difference if I squirt some oil down each cylinder for the compression test? I've read about doing that. Never done it. Don't see the point. So, I'm asking.

I'd atleast get a charger with a higher amp output. 4amp is going to be a slow charge, which is fine for recharging/maintenance but insufficient for keeping the battery hot during extended use, i.e. compression testing. Jumper cables woul help but you also encounter power loss over the length of the jumpers and connections.

Oil in each cylinder is to help diagnose worn rings, if I recall what my uncle taught me correctly. Dry comp low, with oil added increased compression indicates the rings are likely culprit not valves