New engine issues

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Next time you have a valve cover off, there is a 7 digit number cast into the head on top of one of the intake runners.
Get that number, if for no other reason so that you know what you have.

If your heads are any of the “normal” passenger car 318 heads, the chambers would be smaller than 73 cc’s.
If they were more along the lines of what’s typical for 318 heads, like 64cc’s, then your motor would be closer to 10:1cr.

But, that doesn’t really jive with the 120psi....... which is part of the reason for the confusion(well...... at least my confusion).
 
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This engine has stock non adjustable rockers.
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Okay, but you said you took out the 3/8” pushrods because they were rubbing, and replaced them.
Did you check to see that the replacements were exactly the same length as what you took out?
 
I have to pull the drives side cover off to install the other 8 factory 5/16 push rods and take out the 3/8 comp cam push rods since they are too wide and rubbing against the push rod holes in the heads . I'll see what the casting number are
 
dazedand confused said:
The factory push rods are the same length but not width
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Just double check when you have both in your hand.
Not “kinda” the same length...... but the same length.

I would think in order to get any 318 pistons near zero deck height, a fair amount would have to be cut off the block........which would generally require shorter pushrods.
Maybe there’s some piston where that isn’t the case.

Can you ask the machinist how much was cut off the block?

Has anyone verified the lifter preload is correct?
 
I measured them side by side with a steel ruler / strait edge their the same length. Factory rod 5/16 wide
Comp cam rods 3/8 wide
 
PRH said:
Here’s a question regarding the on line cranking compression calculators......

Or something you can try when you’ve got the compression tester out.....

"Assuming you have an adjustable valvetrain........ how far can you crack the intake valve off the seat by removing any lash, and going a bit further...... before the compression tester shows “zero” compression?"

For example, if you tag a valve by over reving the engine and tweak it a little...... the compression reading is lower, but unless it’s severely bent, it’s not showing “zero”.
Yet, a bent valve never completely “closes”.

What’s the point of this?
My feeling is........ with cams that have extremely slow closing ramps, some compression starts to build before the valve is actually “seated”.
The valve is closing, the piston is ascending....... and if the piston is displacing more area than can squeeze through the small opening the almost seated valve has provided, some pressure will start to build.
So, if you tested two cams with the same exact actual closing points, but had radically different closing ramps(one really slow vs one that just slams the valve down), they would show different readings on the compression tester.
Although the calculation would say the cranking pressure would be the same.

It’s the same reason that a 292* cam could have 20* of vacuum.
The number of overlap degrees might be large, but the area under the overlap curve is still rather small because the valves aren’t open very far.

This 292/292-112 cam has the same overlap as the MP 484 cam, which is 284/284-108. Both have 68*.

Think that 484 cam would idle at 20” in this 318?
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"Assuming you have an adjustable valvetrain........ how far can you crack the intake valve off the seat by removing any lash, and going a bit further...... before the compression tester shows “zero” compression?"
I have done this test and at cranking speed the valves have to be on the seat and closed to begin making pressure.
As you surmised, Mopar cams are still not closed at the advertised numbers, AFAIK the intake is still .008 off the seat.So the actual seat to seat, closed, duration numbers could be quite a bit more and the measured cylinder pressure even lower than the calculators indicate.But it's the best we got.
Furthermore, it may be that at some higher than cranking speed, after the air is steadily moving into the cylinders, the .008 numbers give new an more accurate meaning.
What I mean is this; if the true seat closed to seat closed duration number of say the 284 cam was 300 degrees, and the calculator showed that the Scr needed to be 11.5/1(just guessing) to make decent pressure, and if we then built the engine to that Scr, we might find that at 3000 rpm(again guessing) and under some load,that the engine would be in some incurable detonation with full timing, at anything over say 50% throttle.
So,since the Wallace calculator spits out numbers that many here on FABO have proven to work,it would seem that we can safely ignore those numbers lurking in the shadows. And in fact, it may be best to. Unless of course you are a racer looking for that last little edge,I guess.

the 292/114cam,in at 110,closes the intake to it's adv'd number at 76* ABDC
the 284/108cam,in at 104,closes the intake to it's adv'd number at 66* ABDC

Here is the 292/114 cam in at 110, at 700ft, Ica of 76*
Static compression ratio of 9.0:1.
Effective stroke is 2.27 inches.
Your dynamic compression ratio is 6.48:1 .
Your dynamic cranking pressure is 120.14 PSI.
V/P (Volume to Pressure Index) is 79 ........................... 79


And the 284 offers plus10* of compression; and the new numbers are;
Static compression ratio of 9.0:1.
Effective stroke is 2.52 inches.
Your dynamic compression ratio is 7.08:1 .
Your dynamic cranking pressure is 135.60 PSI.
V/P (Volume to Pressure Index) is 99..................................... 99
this is a very significant pressure rise, translating to a higher VP.

Here is the same 284cam but with compression boosted
Static compression ratio of 10.:1.
Effective stroke is 2.52 inches.
Your dynamic compression ratio is 7.84:1 .
Your dynamic cranking pressure is 155.56 PSI.
V/P (Volume to Pressure Index) is 114 ................................ 114
again more pressure and vp

This is the factory engine, the yardstick to compare to from idle to 3000 or a bit beyond. I used 48* as the ICA and still at 700ft elevation
Static compression ratio of 8:1.
Effective stroke is 2.89 inches.
Your dynamic compression ratio is 7.10:1 .
Your dynamic cranking pressure is 136.12 PSI.
V/P (Volume to Pressure Index) is 113 ............................ 113
as you can see even the factory engine was pretty dismal

here is factory engine with Scr increased, no other changes
Static compression ratio of 9.0:1.
Effective stroke is 2.89 inches.
Your dynamic compression ratio is 7.97:1 .
Your dynamic cranking pressure is 159.01 PSI.
V/P (Volume to Pressure Index) is 132 .................................132
I have operated a 318 like this, and it was very nice

To make that 292 fly,with iron heads
Static compression ratio of 11.2:1.
Effective stroke is 2.27 inches.
Your dynamic compression ratio is 7.98:1 .
Your dynamic cranking pressure is 159.28 PSI.
V/P (Volume to Pressure Index) is 105 ............................. 105
This is as good as it gets, check the VP. This indicates a super-soft bottom end,requiring a clutch or a fairly hi stall TC, PLUS gears, to overcome and make into a streeter.And this at 11.2Scr.
This cam will begin to ramp up after 4500, and in a 318 will probably make full power around 5800. At 11.3Scr it will carry the power(with good heads) well into the mid 6000s, or beyond. It's a great cam if you have the heads for it,and buzz the engine up. However, with 3.55s and a 904, 4500rpm/first gear doesn't come around until 39mph, and the 105VP is just too soft to have fun with...... unless you have a pretty hi stall TC and get around it; or really skinny tires,and get them wound up.
I tried this cam in a 367 cube streeter, at 11.3Scr, and after advancing the cam twice, I yanked it and sold it to a racer. I had a clutch and 3.55s, and they had to stay. The manual trans locks the rpm into the soft zone to about 30 mph, and that was just too soft for me.
Believe it or not, the next cam was a 270/110 (three sizes smaller) and that was heaven.
 
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are you really running a fuel pressure regulator with just the stock mechanical pump? If so, no need for it and it is just a restriction to flow.
 
Stock pumps like mine have been known to put out more then 6 psi and edelbrock/Carter 4 barrel carbs should no more then 6 psi running through them even at high RPM
 
I’ve never tried the “crack the valve and see what happens”, but I’ll try it on something sometime.
But I have done numerous compression tests on motors with bent valves...... some of which were really quite bent...... and none of those showed “0” on the compression gauge.
And...... a bent valve is never really closed.
It’s that situation that made me wonder if you could get the tester to read anything with the valve not fully seated.

If the the “292” in this case is accurate enough to use for calculating the cranking pressure, then it should be behave accordingly in the motor....... which wouldn’t be 20” of vacuum in a 318 that cranks 120psi.

Like I stated earlier, the 292/292-12 cam and the MP 484 cam both have 68* overlap....... and I’m quite sure the MP 484 isn’t going to pull 20* in that 318.
More like 1/2 of that...... maybe.

Along those lines......
cam A, 284/296-110, 70* overlap
Cam B, 302/312-112, 83* overlap
Which has better idle quality, idle vacuum, and low end TQ?
(The answer is simple)

Anyway...... back to your regularly scheduled programming.
 
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PRH said:
If that info is correct, it’s only 9:1 if the heads are 73 cc’s.
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Yes, I agree with the numbers.... Here is one that looks pretty much 'at the top', but is actually down .016". So without measurements, or a piston PN and any info on the block being decked, we don't really know.

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I can' think of any 318 flat top piston that has a near zero deck height without valve reliefs; all the one with no reliefs are stock replacement types at stock CH. Perhaps the OP is just repeating the old Mopar advertising spec when the 9:1 is related??

The 120 psi cranking pressure says low SCR and/or late intake closing. The stock 318 readings would be closer to 130 psi.

PRH said:
My feeling is........ with cams that have extremely slow closing ramps, some compression starts to build before the valve is actually “seated”.
The valve is closing, the piston is ascending....... and if the piston is displacing more area than can squeeze through the small opening the almost seated valve has provided, some pressure will start to build.
So, if you tested two cams with the same exact actual closing points, but had radically different closing ramps(one really slow vs one that just slams the valve down), they would show different readings on the compression tester.
Although the calculation would say the cranking pressure would be the same.

It’s the same reason that a 292* cam could have 20* of vacuum.
The number of overlap degrees might be large, but the area under the overlap curve is still rather small because the valves aren’t open very far.

This 292/292-112 cam has the same overlap as the MP 484 cam, which is 284/284-108. Both have 68*.

Think that 484 cam would idle at 20” in this 318?
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Yes I agree with that thinking; I tend to adjust the numbers of advertised duration down a bit with some cams in an attempt to compensate for this. Not sure my 'adjustments' are exactly right LOL but it is in recognition of this factor. Yet, no, I would not expect the MP484 to idle at 20".....

These specs in the Erson catalog are the TQ20H cam.

(Edit to add: All questions answered above before reading the prior 2 posts.)
 
A little off topic, but for a mild cam upgrade to a basically stock 318, I like the “late model” 360 cam.
I’ve also seen it referred to as the “2bbl” cam.
203/203-109.5, .410/.410

Bigger than the stock 181/192-109, .373/.400 cam...... and works with all stock components, including the springs.
 
dazedand confused said:
This engine has stock non adjustable rockers. I bought a chrome gauge from a speed shop that works off of vaccum " fuel saver" with color coded face plate to adjust: distributor, idle, fuel/air screws on carb to get the maximum efficiency in performance and fuel economy. It was reading 20 while engine was running? I didn't know if this is the same vaccum test you guys where talking about?
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dazedand confused said:
Stock pumps like mine have been known to put out more then 6 psi and edelbrock/Carter 4 barrel carbs should no more then 6 psi running through them even at high RPM
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I run a BIG mechanical and a holley red electric with an edelbrock thunder AVS with the big needle and seats which is a copy of the Carter AVS. To much fuel pressure can sink the floats. The issue only shows up really at idle. My guess is it is not sinking the floats at idle. If not, the regulator is not needed and can create a host of problems especially if it is an inexpensive holley reg.
 
So without measurements, or a piston PN and any info on the block being decked, we don't really know.
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I agree.
From what I could find, the taller flat top, no valve pocket 318 pistons are basically 1.74ch...... which would require the block be cut .060 for zero deck height.
And, that could easily be enough to warrant a shorter pushrod, especially if the heads have been milled, valve job, etc.
On the other side, the cam has more lift, so the base circle should theoretically be lower...... which helps with the pushrod situation.

Lots of unknowns here.
 
So I messed up on one of my engine test: I was turning the engine over while doing a compression test with the throttle plates closed ? My bad! I'll recheck tomorrow the proper way and see what the correct compression is
 
To all : I screwed up on doing one of my engine tests! I was turning the engine over while doing a compression test with the throttle plates closed instead of being opened all the way . I will perform the test again tomorrow but the correct way plates open! Hopefully I will have a better compression results!
 
I think you'll get 5 psi more....And of course compression and vacuum gauges have been known to be off. Sorry, I'm not being much help am I LOL

PRH said:
I agree.
From what I could find, the taller flat top, no valve pocket 318 pistons are basically 1.74ch...... which would require the block be cut .060 for zero deck height.
And, that could easily be enough to warrant a shorter pushrod, especially if the heads have been milled, valve job, etc.
On the other side, the cam has more lift, so the base circle should theoretically be lower...... which helps with the pushrod situation.

Lots of unknowns here.
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Yes, those are the typical deck height numbers. A piston PN would go along way to clear things up. What is it we're trying to figure out again?
 
I messed up on my compression test. I checked it will carb was at the resting position . It was supposed to have the throttle plates wide open! I'll redo the test correctly
 
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