2.76 open to 3.55 Sure Grip...expectations too high?

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Average 133
I'd say the Wallace is right on target
And I'd say there's your power problem.
Now, what to do about it.....
#7 cylinder is ~10% down from the average, but #6/8 are 5% higher. So Ima thinking you need to do a LeakDown test, cuz something is goin' on in there, in it can't be good. That is what I would do.
Looking at the plugs, what Timings are you running? Looks a hair lean to me, and a hair hot.
@yellow rose ?
Timing is 14 initial and 32-34 total. I played with it a bit, thinking the engine might not want that much advance, but 14 was right around where it seemed happiest. I do plan on revisiting the timing just to be sure, but I played around with the idle mixture when setting the timing, almost to the point to where I thought it might be on the rich end of things.

I’m still very much practicing and learning, so it’s sometimes confusing to me as to which I need to do first, and why. I.e. idle mixture vs. timing.
 
Detonation at WOT must be avoided at all cost.
yur Power-Timing is always first, but just to make sure it is not too much. And as long as the All-in, occurs after ~3200/3400 you should be safe, and it looks like you got that covered. Iron heads usually like ~36* at WOT, but not too soon, cuz they will rattle. But in your case at 133 psi, rattling may not be an issue.
Yur Idle-timing can be just about anything. But if it upsets your TransferSlot to Idle Discharge Port synchronization, you will get a tip-in hesitation. 14* is about right.
 
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32/34@3000 should be fine.
going to 36* I would slow it down to in the range of 3200/3400, cuz the onset of detonation can be awful hard to hear, and the difference of two degrees might be as little as 7hp at peak, so IMO not worth risking the engine for .
 
I just swapped rear ends. I went from a 7-1/4 2.76 open to an 8-3/4 3.55 Sure Grip. Now, I understand that I’m not driving a race car, but I was certainly expecting a more drastic change upon acceleration. Am I mistaken?


Depends on how much power and what rpm you make power at how effective gears are.
Below is a stock magnum "base" vs a modded one. The stock makes a pretty flat hp peak from 3700-5300 rpm at a relatively low rpm making easy for a high gear ratio to get you there and stay there. Say a 2.76 gear stays a high percentage of acceleration time around 4000 rpm your within 98% of peak hp more gear is not gonna give much more power since there would only be 2% "5hp" left, But the modded engine going from 4000 to 5800 rpm is a 134 hp gain not 5 hp so set of deeper gear giving a more average higher rpm time up in the 5400-5900 is gonna make a big difference.

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Depends on how much power and what rpm you make power at how effective gears are.
Below is a stock magnum "base" vs a modded one. The stock makes a pretty flat hp peak from 3700-5300 rpm at a relatively low rpm making easy for a high gear ratio to get you there and stay there. Say a 2.76 gear stays a high percentage of acceleration time around 4000 rpm your within 98% of peak hp more gear is not gonna give much more power since there would only be 2% "5hp" left, But the modded engine going from 4000 to 5800 rpm is a 134 hp gain not 5 hp so set of deeper gear giving a more average higher rpm time up in the 5400-5900 is gonna make a big difference.

View attachment 1715674895
Exactly. Too much "rule of thumb" info given as blanket statements. What you posted is where I was heading in my post on page 1. After reading the interwebs so many believe it's the same as adding 100 hp. A basically stock 318 will notice a "little" difference at the 0-25 punch, but it's not earth shattering on this type of gear change. Now take a car that doesn't have a good converter and a big cam, yep, the jump in gears will do wonders.
 
Okie dokie, here are the results of the leak down test. The initial numbers were not exactly what I was expecting judging by the compression test, so I conducted two tests per cylinder in hopes of some consistency.

CYLINDER DROP IN PSI @ 90 LOCATION OF LEAK
1- 10, 12 OIL DIPSTICK TUBE
2- 6, 6 OIL DIPSTICK TUBE
3- 3, 5 OIL DIPSTICK TUBE
4- 4, 4 OIL DIPSTICK TUBE
5- 5, 6 OIL DIPSTICK TUBE, CARB (?)
6- 4, 4 OIL DIPSTICK TUBE
7- 3, 4 OIL DIPSTICK TUBE, CARB (?)
8- 2, 3 OIL DIPSTICK TUBE

I'm not sure why #7 was only showing 3 and 4 psi leakage when the compression was so much lower than the rest of the cylinders. I'm also wondering why numbers 1 and 2 are leaking so much more than the rest. Then I got to thinking, when I rebuilt the engine, I had trouble with the rings on those cylinders (in other words, I damaged the rings upon installation). I removed those pistons, replaced the rings, and checked for damage to the cylinder walls. I didn't see anything that I thought was major, nothing I could feel with my fingernail, so I proceeded.

Is it possible for air to leak into the crankcase through a loose intake gasket, or would that ONLY result in air leaking out through the carb?

I'm also not 100% sure I heard air leaking through the carb on numbers 5 and 7, my shop air leaks like a sonuvabish.

Exactly. Too much "rule of thumb" info given as blanket statements. What you posted is where I was heading in my post on page 1. After reading the interwebs so many believe it's the same as adding 100 hp. A basically stock 318 will notice a "little" difference at the 0-25 punch, but it's not earth shattering on this type of gear change. Now take a car that doesn't have a good converter and a big cam, yep, the jump in gears will do wonders.
I trust what you say, and it makes sense. I think after listening to the input here, I'm past the gear ratio "problem" and headed down the rabbit hole of "where is my engine losing efficiency?"

These are good lessons, because I need to learn diagnostics like checking compression, etc.
 
To combine and summarize;
compression ............... LD@90psi
1 - 130, 133.................10/12CC
2 - 135, 134 ................ 6/6 CC
3 - 131, 129 ................ 3/5 CC
4 - 134, 133 ................ 4/4 CC
5 - 136, 136 ................ 5/6 carb
6 - 140, 139 ............... 4/4 CC
7 - 122, 120 ............... 3/4 carb
8 - 137, 137 ................ 2/3 CC

I'm struggling with #1.
11psi drop with 90psi injected is 79/90=87.8% so 12.2% leakage. But, that hole is right on the average as to pressure. And worse is that you say it is going into the CC. So I don't see that as being possible. I can't explain it except to say that I don't trust the LD number. Unless there is damage in the cylinder, right at the very top.
Number 7 is an anomaly; the top of the bore appears to seal very well, but the compression is low, pointing to a problem further down in the bore, or I might suspect that the test pressure is too high, and it is affecting the readings, by jamming the valves closed
Number 6 is also odd, it has the strongest compression, and about the best LD, so it represents what all the others should be aspiring to. I'm gonna go out on a limb and say that the pressure reading is not accurate. And that 133 to 137 as the others show, would be more correct.
The rest of the numbers are very good, if not exceptionally good

Leakage thru the carb usually means the intake valve is leaking. But in your case, the numbers are so very small, and nothing on the plug is helpful, and 90psi is a lotta test pressure. I typically test at 40psi, unless I'm looking for a particular problem.
I'm assuming that you are testing at TDC Compression on each cylinder. 90psi is kindof dangerous because the actual force on the top of the piston is 90 x the area, in your case 12.25 sq inches, so 1100 pounds of force. When that goes over the top, even just a couple of degrees, you cannot stop it. I pray it doesn't go over backwards.
I'm also assuming that you did NOT inject any oil into the cylinders. For the LD test, that will mess up the numbers, until the pressure blows it into the CC .

I would throw the #1 LD test out as an error. And #6 while peculiar, IMO, it is no big deal. But #7 is the black sheep; it is pointing to a problem on the cylinder wall that sorta goes away at the top. That means either a scratch/groove/rut, or an out of round cylinder.
So right now, you sorta have a 7 cylinder, unless #1 is accurate, then a 6 cylinder, and if 5 and 7 have leaky intake valves........... then that is gonna play havoc with intake until higher in the RPM band maybe 2200 or so.

If it was my engine,
I would redo the LD on #1, and
redo the compression test on 7, and
prove that the 5/7 intake runner is sealed on the valley side.
If it the intake to head interface was leaking, then ALL 8 cylinders should have leaked into the intake as well. But if you failed to remove the PCV and seal the valve covers, for the LD test, then you may just have been blowing pressure up the PCV hose. And besides, if the CC was blowing into the intake, there are at least 3 other cylinders with partially to fully open exhaust valves, so Ima thinking the air would just go out the tailpipe.
I would redo the LD on those two (5 and 7) as well, with the engine sealed, to prove that the intakes are actually leaking.

But before I would do anything, I would fix the leaks in the shop air,lol.
Done
 
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I cannot accurately express my level of annoyance at the leaks in my shop air, although I'm sure you understand. The compressor is back in the corner, where a leak lives, and a line is plumbed up and over to the hose reel, where another leak lives. So, I get to enjoy the sound of hissing in stereo whenever the system is charged. I always kinda just tuned it out and thought I'd deal with it "someday" until I actually needed to LISTEN for something, and that something just so happened to sound just like the shop air leaking. I will be addressing my list of priorities that is never-ending.

SO. I don't feel the need to say this was my first leak down test. I thought I was supposed to run pressure closest to the compression psi (~130), without exceeding the equipment limits (100psi), so I decided on 90. I'm going to run another test on all of the cylinders at a lower pressure and see what the results are. I did notice several times that the engine seemed to turn over backwards at about 40 or 50 psi, but then the pressure would hold once everything settled in place. Also, per the instructions, I merely disconnected the PCV hose from the valve, but did not seal the valve covers afterwards. I interpreted this as I was supposed to listen at the PCV valve for leaking.

Again, I'm going to have another go at this, hopefully with some better wisdom going into it. I also paid some attention to the intake and header bolts, since I seemed to have forgotten to visit them again after the initial break in. Needless (or not) to say, most (if not all), had a bit of tightening to do. I also noticed some oil accumulation near a couple of the intake bolts.
 
ome oil accumulation near a couple of the intake bolts.
That's pretty normal as the bolt-holes are open at the bottom. The factory bolts are pretty good at sealing, because the washer is tight-fitting and captive. But non-factory intake bolts will need a sealer on them.

All in all, yur doing pretty good. I look forward to your results.

If you heard air in the carb with the PCV flipped out, I'd be willing to bet a dollar the intake valve was not sealing. Redo the test and if same result, then;
To prove the intakes are leaking, you will need to remove the valve gear and redo the LD test with the pistons at the bottom.
With the air on the carb hissing, just bop the tips of the valvestems a lil with the handle-end of a hammer; Sometimes carbon gets trapped on the seat, and the bopping with airflow, usually blows it out. Your plugs are pretty clean, so I'm not expecting carbon.
By removing the valve gear, you can do this test with the pistons at the bottom, and there is no danger of the valves contacting the pistons. Furthermore, the valves cannot be held open by the lifters. So if bopping the valve stems does not cure the hissing, then the head will have to go to the machine shop. Either the valve is bent,burned or for whatever reason, not concentric with the seat. None of which you can fix in the garage...... at least I couldn't
But if the hissing goes away when you remove the valvegear, then you gotta look at your lifters and lifter preload.
You can get a visual, maybe, by removing the carb and covering the opening with a sheet of thin paper. I have not tried this, but the escaping air should at least disturb the paper....... I would imagine, unless it all goes out the tailpipes.

That just made me think of something. Going back to that hi-reading cylinder with normal LD, #6b IIRC, That could happen if the lobe is losing duration. So if the head comes off, you better check the cam lobes.
 
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you better check the cam lobes.
Oh boy, that's an ominous statement, considering I just lost a cam after my first rebuild. This is the second cam, and I've been hyper-vigilant in watching & listening for the same signs I saw before. I can't quite tell but I might be making myself think there's a tick near 6 or 8, but I can't nail it down. Even with a stethoscope.
 
Well maybe somebody else will come up with an alternative theory to the pressure being more than 5% higher than the average, while simultaneously having the same LD results as the average. IDK how else it can be except an earlier closing intake........... I'd love to be wrong.
 
Hell Yes you will feel a difference. I ran 3.55 in all my cars, but now i run 3.91s and EAT CHEVYS AND **** FORDS LOL.
 
Leak down test, round 2. This time I conducted the test at 40psi, instead of 90. I was also much more careful to find TDC in each cylinder. The first time I did the test, I though the piston just had to be coming up on the compression stroke, and not at TDC. The reason I thought this was because I thought all that had to happen was for both valves to be closed. I’ve learned that if the piston isn’t at the top of the stroke, it’s much easier for the air pressure to push the piston down in the cylinder. As always, anyone is welcome to correct any of this.

Here are the results:

CYLINDER PSI LOSS @40
1 - 5
2 - 4
3 - 5
4 - 5
5 - 4
6 - 2
7 - 2
8 - 2

Now, I also did another compression test prior to this second leak down, and most of the cylinders were all so close that I didn’t bother writing down the results. However, number 3 was low, around 120. I don’t know what the variable is here that’s making low pressure jump from cylinder to cylinder, but I’ll tell you that there were 2 things I didn’t trust about the leak down test as well - the gauges and me. I’m pretty sure I’m doing it right, but I’m also pretty sure I don’t trust the cheap *** gauge set I bought from you-know-where. The needles wouldn’t move smoothly, and the test gauge would sometimes take a couple seconds to “catch up” to the regulated air.

Next up is a vacuum test at the intake.
 
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