Flyinbrian72duster
Dart and duster
Ok so with this cam and a set of reman heads will the stock springs be good and stock lifters same pushrod
318 compression test results
- Thread starter Flyinbrian72duster
- Start date
-
Refresh the heads and short block. Then forget it. If you dont you will always have a question mark in the back of your mind when you run the engine. Ask me how I know.
Rat Bastid
Dunamis Metron
I don’t care what cam you use (RustyRatRod’s choice is about as good as it can get for your application IMO) but no matter what, degree the cam. If you don’t know how, learn. It’s valuable knowledge and inso doing you’ll learn a bunch about all the cam events.
Plus, you’ll know exactly where the cam is. Otherwise if you just do the dot to dot thing you won’t have a clue where it really is. And if something should happen that it doesn’t perform as it should, degreeing the cam all but eliminates that being wrong.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,937
- Reaction score
- 12,287
You said; engine was a 71. WIKI says elevation Cedar Lake In, is ~713ft
I said/say; Forget about the cam until AFTER the heads are done and installed, and you have done another compression test.
Your pressure, in a 71 engine, at a true 9.0 Scr, @713ft elevation; should be about 155psi,
Based on your compression test results, and based on 155psi being fresh, and
to the right of the dry results;
in red, I have calculated; the %pressure loss,
Also, to the right of that, in violet, is the %pressure loss based on 140psi being fresh.
Also, to the right of that, is a number in blue, that represents the %pressure difference between the wet and dry.
Here we go;
1-125dry/19.4/(10.7) (5.3) 132wet ..... 2-123dry/20.6/(12.1) (8.9) 134wet
3-114dry/26.5/(18.6) (3.5) 118wet ..... 4-138dry/11.0/(2.1) (10.9)153wet
5-134dry/13.5/ (4.3) (4.5) 140wet ...... 6-125dry/19.4/(10.7) (8.0) 135wet
7-137dry/11.6/ (2.1) (0.7) 138wet ...... 8-136dry/12.3/(2.9) (8.8) 148wet
>The smaller this blue number is, the more it tends to indicate a ring problem ( or no problem at all).
>The greater the blue number is, the more likely that the problem is valves. So your rightside head, at least, is toast, or it has really big chambers.
>#7 is a unique case, in that the wet/ dry results are much the same so would seem to indicate no problems at all; yet the 11.6% points to the engine NOT being a 9/1 engine, or the test was done at a much higher elevation than 700ft, or the gauge was Not accurate. Therefore, I added another column of numbers in violet, based on a normal of say 140psi@713ft; that is to say sorta normal for a low-compression engine. So now if you have a low-compression engine, the pressure loss is only 2.1%
Now, say after the valve job, the pressure by some miracle, in ALL the holes jumps up to 140. Every one. I mean I am talking a miracle. 140/155=10% pressure loss, so rings are still wore out. Except;
140psi is about what a low-compression Smoggerteen makes with the same 318 cam, when it is fresh.... at sealevel. I'll say it again;
With a stock sub-2000 stall convertor and typical street gears of 3.23s or less, forget installing a 340 type cam in that low-pressure (not low compression ratio) engine. If you do it anyway, your pressure is predicted to fall to less than 120psi,(in the 9/1 engine) and, so then, you will come back to FABO, moaning about what a totally lazy dog, your 318 has become, at typical stock stall and gears.
You shouldda at least have done the rings (assuming the holes are still round and straight with no taper,lol). But; if you do the rings only;
the pressure in a 9/1 engine with the 340 cam might rise to around 140; still doggy at stock stall.
If you replace the pistons and readjust the Scr to about 10.0, the pressure is predicted to rise to about 160 with that factory-spec 340 type cam. Now you got something to get excited about. (but I wouldn't run that or any other 114LSA cam in a 318)
Pressure makes heat, which makes power,especially low-rpm power.
Loss of pressure always equates to loss of low-rpm power.
Listen; I'm not telling you these things to make myself look smart.
I'm telling you these things so you don't make the same expensive mistakes I have made in my life since 1968, which in the beginning, mostly ended in disappointment.
Happy Hotrodding
Last edited:
I would. I think they are running low on cores.
Get a set of stock 340 springs OR Comp 901-16 springs and have them professionally set up on the heads when you have the heads done. I would go with the Comp 901.
Flyinbrian72duster
Dart and duster
I'm not looking to pull the motor to put a 318 back in it. I would build the 360 I have instead or buy a crate engine or buy a 340 block if I could find one for an obscene amount of money
Flyinbrian72duster
Dart and duster
Feels like peer pressure except that one person lol oh boy
I am going to go against the majority view here & say: just stick the cam in dot to dot. This is not some high horsepower race engine where every HP counts. Once you deviate [ ie, change cams ] from a proven combination, there is NO way of telling how a different cam will perform even after taking all the time to degree it to the recommended position. It might perform better [ or worse ] if it is either retarded or advanced from the setting on the cam card.
Install it & go. If you are happy, job done. Not happy, then you could adv or ret the cam. Advancing usually helps low end, retarding helps top end. Experimentation will be reqd.
Crane cams claims that when adv or ret a cam, a minimum of 4* [ crank degrees ] will be needed for the butt-meter to feel it.
Install it & go. If you are happy, job done. Not happy, then you could adv or ret the cam. Advancing usually helps low end, retarding helps top end. Experimentation will be reqd.
Crane cams claims that when adv or ret a cam, a minimum of 4* [ crank degrees ] will be needed for the butt-meter to feel it.
Dan the man
Well-Known Member
Compression goes up with the wet test, it's the rings. A wet compression test with bad valve's will not affect the results. Rebuild it or get a create engine. It's not a good idea to put rebuilt heads on a engine with those miles. Myself and others have done it only to have to rebuild the engine anyway.
Flyinbrian72duster
Dart and duster
Yes I see 100 min with a 40 variable ok so what are your thoughts. Thanks again for selling me that 8 3/4 housing and axles.
They look ok for the most part, but I think cylinder #3 has a valve issue... The other cylinders may have some blow-by on the rings since the wet test made them increase about 10 - 15 psi...
I would go with the stock 340 cam... .429/444 lift duration 268/276 overlap 44 centerline 114...
Our rule of thumb in the 80's was do not upgrade the cam in an engine with over 100 k on it... We knew a few people that did and ended up throwing a rod/spinning a rod bearing...
If you're going to replace the cam, get the Mancini Racing cam kit B for it with new rings, rod and main bearings, and a complete gasket kit for $205.... Thea
Clevite 77 Engine Kit - 318
However, I'm not sure if their rod bearings have the oil squirt hole in them, so I would ask them to verify or go to summit and get a set of rod bearings with the squirt hole capability to keep the cylinders oiled...
They look ok for the most part, but I think cylinder #3 has a valve issue... The other cylinders may have some blow-by on the rings since the wet test made them increase about 10 - 15 psi...
I would go with the stock 340 cam... .429/444 lift duration 268/276 overlap 44 centerline 114...
Our rule of thumb in the 80's was do not upgrade the cam in an engine with over 100 k on it... We knew a few people that did and ended up throwing a rod/spinning a rod bearing...
If you're going to replace the cam, get the Mancini Racing cam kit B for it with new rings, rod and main bearings, and a complete gasket kit....
Clevite 77 Engine Kit - 318
However, I'm not sure if their rod bearings have the oil squirt hole in them, so I would ask them to verify or go to summit and get a set of rod bearings with the squirt hole capability to keep the cylinders oiled...
DODGE Sealed Power 2130CP Sealed Power CP-Series Rod Bearings | Summit Racing
I would keep the 114 lobe center line for the stock 318 compression... It will have less overlap and a little higher cylinder pressures than the 108 LSA...
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,937
- Reaction score
- 12,287
You sure about that?
Less overlap yes but that has got nothing to do with cylinder pressure.
I get
268/276/114 in at split overlap (112) will have an Ica of 66*
268/276/108 in at split overlap (106) will have an Ica of 56*
That is a 10 degree difference, and the Wallace predicts an easy 10psi LOSS for the 114*
At 800ft elevation; in an 8/1 318;
115.56psi on the 66* compared to ............ 127.58psi on the 56*
Is the Wallace wrong?
The Wallace also predicts P/V s of;
84 for the 114*cam, which is what a stock slanty makes, compared to
101 for the 108*cam, which is a tiny bit more than an 8/1, 273 makes(97)
The stock 318cam is a 240/248/112 and in at split overlap(110*) will have an Ica of 50*, pressure predicted to be 134psi,@8.0 Scr/@800ft, with a P/V of 110; which is:
31% better than the Wide LSA 340cam, and
8.9% better than the 108LSA 340 cam.
Is my math bad?
read about P/V here; V/P Index Calculation
Flyinbrian72duster
Dart and duster
So you're saying pull it and refresh it
You already have a 360? If so and you like driving the car I would try to minimize down time and maximize performance per dollar spent. Head work and a camshaft will cost the same for 360 as a 318. You can drive the car with the 318 while you work on the 360. Get all your ducks in a row and when the 360 is done you can swap motors and not have all the down time waiting on machine work or parts to arrive. Plus the extra hp the 360 will produce without spending any more money than what you were already planning on spending on the 318. I don't have anything against 318's but if I were in your shoes that's what I would do.
Advantages as I see it.
1. Less down down time for car
2. Same budget
3. More performance
4. Easier to work on the motor out of the car.
5. Still have a running 318 if the 360 blows up. lol
I don't understand why you're still digging on this. You've verified it yourself that your cylinder pressure falls well in what's acceptable in the service manual. What are you wanting? You keep askin the same damn question a hundred times. DO you WANT to pull it and rebuild it? Then do it. The factory service manual itself says otherwise. But have at it. This is really gettin stupid.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 24,937
- Reaction score
- 12,287
OP
I don't care what the Service limit is;
90psi is low, even for a lawnmower, and
A 40 psi deviance is drag on the next cylinder.
Those 90/40 specs, if correct, are, IMO, conceived to fill a warranty agenda;
The same deviance can be had as a lobe falls off your cam, and who among us ignores that when it happens? Oh yeah great engine! it only has two cylinders at 120psi, compared to all the others at 160psi, so Ill just wait until they all drop to 90psi; Com'on; that's , dare I say it, retarded.
The 318 at full 135/140 is already a lo-po slug, but at 90psi, it is beyond my imagination to conceive that the factory spec could be that generous.
Just cuz an engine like that still runs is meaningless; the power and fuel consumption are already pathetic, not to mention oil-consumption if the rings are the cause of it. And if it might happen that an intake valve has gone down, then you have an engine-fire waiting to happen.
That's partly how the 318 went from being a strong runner before 1973, @150/155psi, to a pos bag-of-chit by the mid 80s, 130/135psi. Same cam-specs I might add. And that situation probably ushered in the Magnums, which with their new head designs, and slightly bigger cam, allowed the pressure to return, bringing back the power/economy . A Magnum is, at it's most basic, just a higher-compression 318 with better heads.
By the way; here is a list of cylinder pressures, to compression ratio equivalency, for a 318 operating at 800ft with an Ica of 48* . All C/R numbers are approximate.
at 90psi, it is 5.9 to 1 ..............
at 100 it is 6.4........ at 110 it is 6.9 ....... at 120 it is 7.3
at 130 it is 7.75 ..... at 135 it is 8.0 ..... at 140 it is 8.2
at 150 it is 8.6 ....... at 155 it is 8.85 ... at 160 it is 9.1
Now you know why the early 318s were so peppy, namely; close to or better than 155 psi
And at 8.0 they are slugs.
and at 90psi, they are only a little more powerful than a fresh 170 slanty.
Just so you know; my 1969FSM (the only one I have);
for the 9.2 rated engines;
the pressure is listed as 125 to 155, and
the maximum variation as 25psi
I'm assuming that the range of these numbers is partly to account for the elevation at which the test was done; the manual does not say, in addition to the usual factors such as cranking speed and degree of dryness on the ring-to-cylinder wall face.
end rant
I don't care what the Service limit is;
90psi is low, even for a lawnmower, and
A 40 psi deviance is drag on the next cylinder.
Those 90/40 specs, if correct, are, IMO, conceived to fill a warranty agenda;
The same deviance can be had as a lobe falls off your cam, and who among us ignores that when it happens? Oh yeah great engine! it only has two cylinders at 120psi, compared to all the others at 160psi, so Ill just wait until they all drop to 90psi; Com'on; that's , dare I say it, retarded.
The 318 at full 135/140 is already a lo-po slug, but at 90psi, it is beyond my imagination to conceive that the factory spec could be that generous.
Just cuz an engine like that still runs is meaningless; the power and fuel consumption are already pathetic, not to mention oil-consumption if the rings are the cause of it. And if it might happen that an intake valve has gone down, then you have an engine-fire waiting to happen.
That's partly how the 318 went from being a strong runner before 1973, @150/155psi, to a pos bag-of-chit by the mid 80s, 130/135psi. Same cam-specs I might add. And that situation probably ushered in the Magnums, which with their new head designs, and slightly bigger cam, allowed the pressure to return, bringing back the power/economy . A Magnum is, at it's most basic, just a higher-compression 318 with better heads.
By the way; here is a list of cylinder pressures, to compression ratio equivalency, for a 318 operating at 800ft with an Ica of 48* . All C/R numbers are approximate.
at 90psi, it is 5.9 to 1 ..............
at 100 it is 6.4........ at 110 it is 6.9 ....... at 120 it is 7.3
at 130 it is 7.75 ..... at 135 it is 8.0 ..... at 140 it is 8.2
at 150 it is 8.6 ....... at 155 it is 8.85 ... at 160 it is 9.1
Now you know why the early 318s were so peppy, namely; close to or better than 155 psi
And at 8.0 they are slugs.
and at 90psi, they are only a little more powerful than a fresh 170 slanty.
Just so you know; my 1969FSM (the only one I have);
for the 9.2 rated engines;
the pressure is listed as 125 to 155, and
the maximum variation as 25psi
I'm assuming that the range of these numbers is partly to account for the elevation at which the test was done; the manual does not say, in addition to the usual factors such as cranking speed and degree of dryness on the ring-to-cylinder wall face.
end rant
Flyinbrian72duster
Dart and duster
hmm I wonder if new heads would put my engine in the acceptable range
Where did any of your readings say 90 psi? Lowest one I saw was 114.
Flyinbrian72duster
Dart and duster
Flyinbrian72duster
Dart and duster
Exactly
PM sent.
We should all be so lucky.
What is your game plan so far?
This is what I have heard you discuss.
1. Rebuild/replace heads
2. replace camshaft / degree camshaft
3. Replace torque converter
All this work can be done with the motor in the car. Many have done this myself included. Now think about the steps involved to do that work with the motor in the car. Working over the fenders to do it all. Now picture yourself doing all the work with the motor out of the car, on a motor stand.
The transmission has to be separated from the engine. The exhaust unhooked. The radiator has to come out. Then while leaning over the fenders you are removing the whole front of the engine. Waterpump, fan, alternator, power steering, harmonic balancer, front cover and Possibly the grill. Not sure on a duster. Also removing the intake manifold distributor, associated wires, hoses, valve covers, rockers and pushrods, exhaust manifolds then cylinder heads.
What's left keeping the motor in the car? Starter wires and motor mount bolts? I'm probably forgetting somethings but you should get the idea.
Last edited:
-
