Dartfreak75
Restore it, Dont part it!
I'm just curious I have no intention of changing my plans haha
However I would like to learn more about it for future reference
Piston question
- Thread starter Dartfreak75
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However I would like to learn more about it for future reference
All things equal, you're talking about "maybe" a 20 HP difference with quench.
Don't you have to final hone those cylinder walls yet after boring to fit each piston to each bore ? That in itself may be enough to reduce your area of concern at the top ridge area.
I would take a .040 piston ring and slide it up and down in the bore by hand near the top of the stroke. Doubt it will be anywhere near catching on the low spot that did not clean up.
Those piston rings are round and they will ride over whatever low spot is left behind.
You may have to go back to the .040 piston plan yet if you can't find the .060 pistons.
A little extra hone on those 2 cylinders at the top to help clean them up, the new rings will expand out and and take care of the situation.
Steal from Peter to Pay Off Paul . . .
Then you are not cutting another .020 out of your bores to get to .060 and run the risk of getting into the water jacket.
Dartfreak75
Restore it, Dont part it!
He tried that. He thought that honing would take care of it and honestly it probably would run fine the way it is but he said he didnt really like it. He told me he has seen worse run just fine and he thought it would be ok but he didnt like it. And he wanted me to make the decision on sending it like that @40 or going 60 so I made the call to to 60. He said the walls had plenty of material to go 60 and he didnt think it would give me any trouble down the road at 60. I even brought up trying to find another block and he said that one would be fine. He said worse case we can sleeve those 2 cylinders
Dartfreak75
Restore it, Dont part it!
Ok well first off he didnt recommend low compression pistons. He just said he dont like kb and he would rather run a factory replacement piston than a kb. It's not like that.
2 yes it was sonic checked and he said the walls are have plenty of material there
3 yes he bored it over to 40 and it didnt get all the ring ridge out that's why I'm in the situation I'm in.
4 thanks for your opinion but I respectfully disagree. I think he has and is doing a fantastic job before I started this journey I called at least 6 machinist and none of them even had time to talk to me on the phone when they found out I wasn't building a 15k race engine. This guy not only took on the business but has helped me tremendously along the way.
While we're here. I done some research on quench last night. And for a street engine with steel rods up to 6000 rpm they recommend .038-.043 quench. With the kbs and a 1121 head gasket
(
(Kbs are .012 under the deck and a .028 gasket) that will put me at .040. So I'm in that quench range. Why is quench unobtainable with flat top pistons seems to me I would be there?
Wyrmrider
Well-Known Member
you got it freeking backwards
a race motor can avoid detonation because:
It's always running above peak torque
above BMEP
and it's always running good gas
now with tight quench
you are not as fuel sensitive
not as timing sensitive
not as compression sensitive
not as load sensitive
not having to shift down as much to keep from pinging
and 20 hp is huge
but the big gain is in low end and midrangewhere you can run more pressure wthot detonation
if you are going to run ft with the SMOG heads milled
run a thick gasket but they do not make one thick enough
run abig cam to blead off your torque
run low gears and a loose converter so you don''t load the engine
The more you lower your compression with ft the hotter it runs
you have to give it more gas to get the same power
the factory was chasing it's tail
go back to 67 not 73 and later
Use what they learned when the did the magnum - two quench pads
We did a LOT of dyno time developing that pston design with customm forged pstons- they work
I'd use ductile top rings either way
btw AJ can give you the details
a race motor can avoid detonation because:
It's always running above peak torque
above BMEP
and it's always running good gas
now with tight quench
you are not as fuel sensitive
not as timing sensitive
not as compression sensitive
not as load sensitive
not having to shift down as much to keep from pinging
and 20 hp is huge
but the big gain is in low end and midrangewhere you can run more pressure wthot detonation
if you are going to run ft with the SMOG heads milled
run a thick gasket but they do not make one thick enough
run abig cam to blead off your torque
run low gears and a loose converter so you don''t load the engine
The more you lower your compression with ft the hotter it runs
you have to give it more gas to get the same power
the factory was chasing it's tail
go back to 67 not 73 and later
Use what they learned when the did the magnum - two quench pads
We did a LOT of dyno time developing that pston design with customm forged pstons- they work
I'd use ductile top rings either way
btw AJ can give you the details
Dartfreak75
Restore it, Dont part it!
I'm doing some research on it. If I'm doing my math right i can obtain a .040 quench with the kb107 pistons and a .028 gasket. With the gaskets I got It will be around .062 which is over I know.
RAMM
Well-Known Member
Why don't you just go forged with a Icon or JE/SRP or Wiseco/Pro-Tru? Why stick with a Hyper-U and fret over piston integrity and ring gap? Those manufacturers I just listed are quality pistons at affordable prices. I wouldn't hesitate to use the 107's gapped at .026" just like they recommend either--but if youre going to wring your hands about piston quality then just move to a real GOOD forged piston and be done with it. J.Rob
Dartfreak75
Restore it, Dont part it!
Mainly the cost. I dont want to spend much more than 300 I will look into those you named and check them out. It's funny you said that because the machinist recommended me look into forged pistons and we looked up icons holy crap they was almost 700 a set I just cant afford that. But I will do some research on it while I'm looking.
I have a set of cast .060 pistons for an LA 360, If interested, PM me & I'll send pictures. I'm, asking 250.00 + actual shipping to your door.
Dartfreak75
Restore it, Dont part it!
I see what you are getting at it makes sense to me now. Ok so I been doing alot of research and I have a question. I gotta go look at me heads and see how much area there is there on the quench pad on the chamber but I'm pretty sure after he miiled them they are pretty much flat but I got to check. I was looking at the kb190 pistons they have a .050 dome with the same ch. So the piston will be .012 under still but the dome will be .038 above the deck with the thick gasket that will give me .012 plus how much (if any) is in the head obvious if the pad is even with the head surface what wont work but it it's anywhere around .025 that would work out perfectly. And give me a cr of 10.8 so here is my question. I'm now creeping up into the mid to high 10s can I still run pump gas in the high 10s or low 11 range?
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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You know that Quench, more correctly called Squish, is the distance between the piston and the top of the chamber, at the furthest from the sparkplug... right?
On a closed chamber head, with the pistond even with the top of the deck, then Q =gasket thickness, so it is easy to obtain and select-fit.
But when using a stock Mopar open chamber head with the pistons down in the hole, Q is impossibly huge.
On your heads, I have measured the chamber on the squish side as from .099 to .127, so if you milled to 65cc, that would be about .035 off the squish, so for arguments sake, lets say your heads started at .100. Therefore they would now be .065, right.
Now add the .012 that the pistons are down in the hole, and I wouldn't use anything but the .039 FelPro,
that adds up to ; .065 +.012 +.039=.116
Therefore, your Q is still impossibly huge to provide any benefit.
In order to get into the zone of .035 to .045, as you can see, with open-chamber heads, will require a specialty piston with a Quench-pad already on it, which you may have to adjust the height of, to work with your now shaved heads.
BTW
as to the KB107s
Between yrs 2000 and 2016, my 367 accumulated over 100,000 miles, on those,with no issues. I run a 4-speed, and the car never comes home to roost, that she hasn't been to 7000/7200 many many times. She was daily driver for many years. I have no problem recommending them, so long as the gaps are set right.
and I just gotta say this; mine also liked a skirt clearance of .0035, which I run at 205* minimum cooling temp. This is the set up that trapped 93 in the Eighth with a 230 cam. The Wallace calculator spits out 433hp at 3457 pounds and 930ft elevation. How much of that is due to the .034Q is not for me to say.
The thing is, I never built to that Q-spec for absolute power. Rather, I built it for Part-Throrrle torque and fuel economy...... because it was to be my DD, and I had heard it was worth about one cam size. In other words, I could run a 223 cam instead of a 230, and cash in on the higher cylinder pressure for hiway mpgs. And it worked.
The ugly zone for Q is said to be between .050 and .080. I have no experience with that.
Wyrmrider
Well-Known Member
Dart
.060 squish/ quench is a problem
look where the spark plug is
look at the small gap to get to the intake side of the chamber
how is the flame front supposed to navigate that gap
you go big like with unmilled heads and the piston down the hole still not good but better as the combustion can start all by itself at the back side
with tight quench- tight cold surfaces .030-.040 between them the flame front cannot travel so no light off - much less chance of detonation
plus the squish where you get turbulance to really light the fire
your build will be much more "crisp", responsive
try and get .040 or less or over 100 (the factory sogger way)
cheers
and no the compression you mentioned is not going to work on a street motor
unless maybe you get YR to tune it for you or e-85- or water injection, electronic ping detector, etc
learned a lot in the last 50 years- keep your eyes open
.060 squish/ quench is a problem
look where the spark plug is
look at the small gap to get to the intake side of the chamber
how is the flame front supposed to navigate that gap
you go big like with unmilled heads and the piston down the hole still not good but better as the combustion can start all by itself at the back side
with tight quench- tight cold surfaces .030-.040 between them the flame front cannot travel so no light off - much less chance of detonation
plus the squish where you get turbulance to really light the fire
your build will be much more "crisp", responsive
try and get .040 or less or over 100 (the factory sogger way)
cheers
and no the compression you mentioned is not going to work on a street motor
unless maybe you get YR to tune it for you or e-85- or water injection, electronic ping detector, etc
learned a lot in the last 50 years- keep your eyes open
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Compression ratio is not the enemy.
Cylinder pressure in a no-quench chamber is the trouble maker.
You can control the pressure with size and type of cam.
It is generally accepted that safe pump-gas pressure ceiling for cast iron heads is 160psi for open chambers and 165 for a tight-Q design.
If your engine comes in at 10.5, and you are at or near 800ft elevation, then for 160psi, your Ica (intake closing angle, will need to come in at around
Static compression ratio of 10.5:1.
Ica of 70*, 800ft
Effective stroke is 2.64 inches.
Your dynamic compression ratio is 8.01:1 .
Your dynamic cranking pressure is 159.55 PSI.
V/P (Volume to Pressure Index) is 131
Depending on
your tuning skills this will run on 91 gas at WOT with full timing.But notice the Ica is 70*; that's a pretty big cam, and the VP of just 131, is pointing it out. My math puts that 70*Ica on a cam of
284/292/110 (there are others)
Which would typically net to [email protected]. which IMO, is a lotta fun for a while, but not really a long-term thing.
Especially with a VP of just 131. That will make the bottom "soft", requiring a hi-stall TC and performance gears, and that takes away the cruise factor.
Read about VP here V/P Index Calculation
No, for a streeter, you want a VP well into the 140s, so you can run a more conservative stall and gears, so you can drive 65mph for more than just 30 minutes atta time.
So if I target 140 using the Wallace calculator, I get
Static compression ratio of 10:1.
Ica of 63*,800ft
Effective stroke is 2.81 inches.
Your dynamic compression ratio is 8.06:1 .
Your dynamic cranking pressure is 160.88 PSI.
V/P (Volume to Pressure Index) is 140
So notice
I had to drop the Scr to 10flat and selected a 63* Ica, which is ~2 cam sizes smaller. So my math gets
270/276/110.(there are others).
Ok from the earlier 284 to this 270 is 14* or 2 cam sizes, so I estimate 35hp or so lost at the top, traded for 140-131=9 points of VP or 9/131=6.9% more bottom end, In my opinion, a good trade, cuz it lets you run the same 6.9% less gear so say 3.55s instead of 3.73s. And you can run about 2 sizes less stall, or about 400 rpm; say 2600 instead of 3000.
But that 35hp is gone forever......... unless you set your engine up for a tight-Q and run the 5psi more pressure.
Lets try something
Static compression ratio of 10.2:1.
Ica of 63*, 800ft, tight-Q
Effective stroke is 2.81 inches.
Your dynamic compression ratio is 8.22:1 .
Your dynamic cranking pressure is 165.15 PSI.
V/P (Volume to Pressure Index) is 144
Check it out!
First notice that the only change I made was to increase the Scr from 10.0 to 10.2, which brought about 5 psi.
The 5 extra psi is good for I'm guessing one cam size in power, but notice the VP came along for the ride, posting another 4 points. 144 is a very good number for cast-iron heads.
Here it is for 89 gas
Static compression ratio of 9.8:1.
Ica of 63*,tight-Q, 800 ft
Effective stroke is 2.81 inches.
Your dynamic compression ratio is 7.91:1 .
Your dynamic cranking pressure is 156.89 PSI.
V/P (Volume to Pressure Index) is 137
Please note;
1) this is an exercise in explaining options; not a build recommendation.
2) 140Vp makes a real nice streeter.
3) a 270/276 cam is a great powerhouse for a streeter. I ran that in my alloy-headed 367, and would still be running it today,20 years later, had it not dropped lobes for lack of ZDDP.
4) For a streeter;Scr over 10/1 with iron heads,is treading on thin ice and requires best pump gas.
5) A more relaxed build would be to run 89 gas giving you some head-room for less than optimum tuning skills, and for the occasional tank of bad gas.
6) tight-Q, by itself, is not the Holy-Grail of a performance engine. But for a streeter, it can take an undriveable on 91 gas engine, right into the fun-zone, by helping to NOT-CREATE detonation in the first place, so you don't have to tune around it. Read @Wyrmriders posts#31&38 again and pay attention.
7) to get tight-Q in your 65cc iron-chambers, you may need a step-D cup WITH a raised Q-pad, to reduce your Scr enough to run a 270* type cam. Thank goodness they make those now, and you don't have to pay a machinist to build them for you.
8) because so far only the heads are written in stone, you are in a prime position to set yourself up with a long-term, no changes required, powerhouse street engine; if you take some time to co-ordinate all the components and cut specs. Take your time and do it just once.
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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What you really can't afford is a do-over. And that is what we are here for; in an effort to help you do it right the first time.
I remember in 1998 when I was planning my engine. Every big-name engine-builder I contacted recommended 9.5Scr as the max for my combo. I had already decided to use alloy heads, and 9.5 was still the recommended max.
But I was pretty sure with alloys I could go higher. So I figured out that the Ica was a huge player, and that it wasn't Scr that was the problem, cuz you know, racers were running 12/1 and more.
So I set mine up at 11.3/1 with a Dc 292/292/108 cam; and set about to tune that. And it worked. The key was the alloy heads, that let me run 180psi and more. That engine ran gangbusters strong.
It didn't take me long to figure out that pressure was king, but detonation was the achilles heal.
So you can't run 180psi with iron heads on the street. IDK if you can run 180 at all on pumpgas, but I would guess no.
IDK what exactly you can run.
But I can repeat what I have learned here on FABO. which I compiled and showed in a previous post.
And namely;
165psi with a tight-Q is about the limit on 91 gas.
For you, I would suggest 160 with tight-Q, to run 89 gas, giving you a degree of safety if you screw up on the tune.Or, lacking a tight-Q, I would suggest 155psi.
To achieve this, you need to know what cam you will be running, and that will be governed mostly by the application, which includes the rear gears and stall. And by the elevation at which this engine will be operated at.
If your budget is tight now, wait until you have to change both the gears and the stall because your pressure ends up too high! Or, if you install a way-too-big cam, and it drinks gas like a camel drinks water in the desert.
I was fortunate in that I had a lifetime of parts accumulated, to match my engine to the application..... but before the first summer was done, that 292 cam was already out and sold. It mightabin a great race cam, but it did not suit my application.
IMO;Application is everything.
No, you're not. You have to add in "however" deep your combustion chamber is......normally stock unmilled heads are "around" .095" deep. You have to add that into the equation.
See? This is what I meant when I said "geez". You should have just built your engine like you wanted originally. Now the waters are muddied up in the quest to get what? 20 more HP due to quench? God god almighty man.
Better get a Jones cam for it too or it'll run like ****. LOL
The old "Too Many Cooks Spoil the Stew" routine.
As "always".
In post# 7 where I mentioned I ran the 107s, that was a
j headed motor. It was a tad over 10:1. I ran 92 in it and it was fine, sometimes ran 89. It would rattle a little on 87, but I drive hard. Poor motor had no quench though...
And no I am not against quench, but a lot of SBMs, and BBMs have been built without it, and ran pretty good.
j headed motor. It was a tad over 10:1. I ran 92 in it and it was fine, sometimes ran 89. It would rattle a little on 87, but I drive hard. Poor motor had no quench though...
And no I am not against quench, but a lot of SBMs, and BBMs have been built without it, and ran pretty good.
Dartfreak75
Restore it, Dont part it!
Nothing has changed with the build Its the same pistons same heads same cam. I'm not changing anything. I'm just trying to learn something new.
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I just get tired of their same old bullshit.....not everybody wants builds with compression and quench on the ragged edge and a Jones cam. lol
mopowers
Well-Known Member
For a true "budget build" 360, don't discount good ol Speedpro H405CP's. It ain't rocket science to build a cruiser motor. For a simple reminder, check out RRR's budget 400 build.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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At 10.7, a Jones cam probably won't work; the Ica is likely to be too early, trapping too much pressure, and detonation is sure to occur. At 10.7, this engine will like a long slow lazy intake closing ramp.
Which, of course, will kill any chance at economy it might have had due to the hi compression ratio.
There is no better time than right now, to choose the right piston; it costs nothing to shop, and if the result of careful shopping yields 20 hp at peak, you know, in this case, that power-bulge extends all up and down the rpm range. And so, you can run a smaller cam to get the same absolute power, and simultaneously reap more torque at stall and less fuel-consumption at steady-state cruising. Since when did this become of no import to a streeter?
Shopping is free. A mistake in piston selection could be 20 years.
And tell me, who disdains 20hp at peak? That is pushing one cam size. that could easily be adjusted to 55/60 mph with gears, and make a tremendous difference in passing maneuvers.
A little time spent shopping, can mean decades of fuel savings.
Tight-Q is not all about absolute power. It's also about the fat low-rpm torque curve, the fuel-economy, the lightning throttle response, the reduction in stall and gears that can be employed, and about always having a lil extra torque for every occasion. It's more like adding 20 cubes by stroke,to your displacement.
Which, of course, will kill any chance at economy it might have had due to the hi compression ratio.
There is no better time than right now, to choose the right piston; it costs nothing to shop, and if the result of careful shopping yields 20 hp at peak, you know, in this case, that power-bulge extends all up and down the rpm range. And so, you can run a smaller cam to get the same absolute power, and simultaneously reap more torque at stall and less fuel-consumption at steady-state cruising. Since when did this become of no import to a streeter?
Shopping is free. A mistake in piston selection could be 20 years.
And tell me, who disdains 20hp at peak? That is pushing one cam size. that could easily be adjusted to 55/60 mph with gears, and make a tremendous difference in passing maneuvers.
A little time spent shopping, can mean decades of fuel savings.
Tight-Q is not all about absolute power. It's also about the fat low-rpm torque curve, the fuel-economy, the lightning throttle response, the reduction in stall and gears that can be employed, and about always having a lil extra torque for every occasion. It's more like adding 20 cubes by stroke,to your displacement.
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