Makes ya wonder
What's the REAL Compression Ratio for Stock 69 440 HP??
- Thread starter Jack Luckhowec
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I don't think so. The pistons look like the ones in my 11-69 casting 440. They put a notch at the edge of the piston to indicate FRONT. Aftermarket pistons usually have the word FRONT stamped into the piston.
The bearings were standard and dated July 1969. The head gaskets were steel. It is the numbers matching engine to this car:
The bearings were standard and dated July 1969. The head gaskets were steel. It is the numbers matching engine to this car:
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Maybe the pistons are different for 1971?
I have a 1974 360 that has dished pistons, The outer edge sits near zero deck but the middle is dished.
I have a 1974 360 that has dished pistons, The outer edge sits near zero deck but the middle is dished.
The earlier ones were dished.. maybe with a different head casting they changed that.
But I agree on the wimpy compression 383 problem. 516's milled .060 and steel headgaskets for this guy!
furious70
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What oem flat top piston was ever that far in the hole for a 383?
I've had a couple 383's that have those low CH flat top replacements.
I've had a couple 383's that have those low CH flat top replacements.
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Every 440 that I have tore down has had flat top, no valve relief type. I've only done one 1969 casting but several 74-78 engines.
This is the only 383 that I have done.
This is the only 383 that I have done.
66Satellite47
Well-Known Member
My '70 383 2bbl motor sure had factory flat tops, the dealer showed me my motor with heads off, during my warranty request prior to the 50,000 mile warranty expiration. No idea how far down the hole they were, but pistons were flat top, not dish.
wyrmrider
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nate
had lots of dyno sheets 58-78 but long gone we developed the quench dome piston to solve open chamber problems which were melting down motors in a very few miles
one motorhome with a new factory reman replacement did not even make it to vegas
we reduced egt by up to 800 degrees and that was with the non hp cam- hp cam was much worse
still know the formula
you can pick up torque below max torque
pick your rpm range which sets intake closing> duration
mopar not chevy profiles
9:1 256 @.006 460 lift intake closes about 53 abdc
9.4 262
9.7 264
10:1 268
go bigger than above you can get more top end but loose torque so more converter and gears
simple as that
had lots of dyno sheets 58-78 but long gone we developed the quench dome piston to solve open chamber problems which were melting down motors in a very few miles
one motorhome with a new factory reman replacement did not even make it to vegas
we reduced egt by up to 800 degrees and that was with the non hp cam- hp cam was much worse
still know the formula
you can pick up torque below max torque
pick your rpm range which sets intake closing> duration
mopar not chevy profiles
9:1 256 @.006 460 lift intake closes about 53 abdc
9.4 262
9.7 264
10:1 268
go bigger than above you can get more top end but loose torque so more converter and gears
simple as that
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I have a thread here titled "Lookie what $5000 buys you".
I plan to drive it ratty for awhile. It is being built like a 3/4 scale version of my red car. Smaller engine, smaller brakes, softer suspension, etc. Just a fun car for various stuff, even dirt roads!
451Mopar
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What "wyrmrider" said x2
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You write in a sort of abbreviated fashion so I'm trying to read between the lines on this.
Are you stating that the low compression, open chamber heads resulted in higher exhaust gas temperatures?
I'd like to understand this better. Were you asserting that the quench dome piston increased compression but by having some quench, it lowered the EGTs ? Can you explain it a little bit more?
wyrmrider
Well-Known Member
sure kern dog buddy
we started off working with the 67 and earlier old school wedge heads including max wedge - essentially a 265 chevy chamber with the spark plug low and as far to one side as you could get with no cooing around the plug and a hot spot between the center exhausts
the 413 truck had spark plugs angled like a sbm or FE ford- much better
there are many problems with the BBM chamber like flame travel when you wanted to run big doe pistons- we cut a lot of fire slots eventually angeling them from the plug to over toward the exhaust valve somewhat the burn pattern tells what to do
now the burn pattern with the open chamber is due to the big open area far from the plug whih either wants to iight off unevenly or wants to ight off all by itself
let me say right now you can make great hp with the open chamber with better than today's gas and eeping the revs above the torque/ BMEP peak- like a race car
The first thing we did was to weld up the chambers o ake the chamber as compact and as much an equal distence from the plug as possile This is too expensive for street but bus fleets could afford
Then Don Bass at TMS propane got some custom reverse popup into the back of the chamber with a dish to get whatever cr he wanted made up
Eureka moment especiall when matched with some custom cams from the late Bill Jenks at Potvin then Moon cams
still expensive but we met John ERB at trade show, got invited to the factory, showed him several designs and KB put them into production - much cheaper than the custom slugs from Nick Arias, Venolia etc
so why does it work?
you can run more advance due to the tihgter chambe and squish and quench
fact is advance does not make as much difference
you can get away with some bad gas
you can run more compression
now for the cam
I call the 68 up cams smog cam as they give an egr effect with exhaust dilution
they have long ramps on the open side and really long ramps on the close
without going to a really fast "race lobe" you can shorten the seat duration and keep or increase the .200 duration
too much overlap and your intake goes out the exaust more than you want it to
(header and rpm dependent and all that)
that's what heats up those stock exhaust manifolds cherry red even in a -say -cordoba going up a long hill. and melts down motorhomes, tow, stock rides with tall gears where's there's some load
Jenks hand calculator and file and stone finished master for the .904 lifter truck was 192 @ .050 with about the same lift and area as a standard 440 cam
Jones mopar cam from his best in class computer program is just as short on the seat but 205 ish @.050 264 @.004 256@.006
and about 248@.008 compared to say a 268 mopar cam--- that's 20 degrees
and jones cam is 50% bigger @.200 than the DC 260 @.275
now depending where you put your icl it's easy to close the intake 8 degrees earlier than stock, open the exhaust later and close the exhaust 10-12 dearees earlier ( remember the really long stock close sides-- and cuts the overlap
That's what picks up the dcr in a 73 and later 440 or say 9.5:1 motor esp with al heads
for shelf cams lunati voodoo or if you want to pay
you want more top end go bigger but there are tradeoffs more attention to detail then howard
actually all require attention to detail
we could go into quench and squish but the cmpact chamber is a big part of the combination
sort of like 67 915 or even better aftermarket heads with D dish pistons- but those also have the plugs moved and better chambers
we started off working with the 67 and earlier old school wedge heads including max wedge - essentially a 265 chevy chamber with the spark plug low and as far to one side as you could get with no cooing around the plug and a hot spot between the center exhausts
the 413 truck had spark plugs angled like a sbm or FE ford- much better
there are many problems with the BBM chamber like flame travel when you wanted to run big doe pistons- we cut a lot of fire slots eventually angeling them from the plug to over toward the exhaust valve somewhat the burn pattern tells what to do
now the burn pattern with the open chamber is due to the big open area far from the plug whih either wants to iight off unevenly or wants to ight off all by itself
let me say right now you can make great hp with the open chamber with better than today's gas and eeping the revs above the torque/ BMEP peak- like a race car
The first thing we did was to weld up the chambers o ake the chamber as compact and as much an equal distence from the plug as possile This is too expensive for street but bus fleets could afford
Then Don Bass at TMS propane got some custom reverse popup into the back of the chamber with a dish to get whatever cr he wanted made up
Eureka moment especiall when matched with some custom cams from the late Bill Jenks at Potvin then Moon cams
still expensive but we met John ERB at trade show, got invited to the factory, showed him several designs and KB put them into production - much cheaper than the custom slugs from Nick Arias, Venolia etc
so why does it work?
you can run more advance due to the tihgter chambe and squish and quench
fact is advance does not make as much difference
you can get away with some bad gas
you can run more compression
now for the cam
I call the 68 up cams smog cam as they give an egr effect with exhaust dilution
they have long ramps on the open side and really long ramps on the close
without going to a really fast "race lobe" you can shorten the seat duration and keep or increase the .200 duration
too much overlap and your intake goes out the exaust more than you want it to
(header and rpm dependent and all that)
that's what heats up those stock exhaust manifolds cherry red even in a -say -cordoba going up a long hill. and melts down motorhomes, tow, stock rides with tall gears where's there's some load
Jenks hand calculator and file and stone finished master for the .904 lifter truck was 192 @ .050 with about the same lift and area as a standard 440 cam
Jones mopar cam from his best in class computer program is just as short on the seat but 205 ish @.050 264 @.004 256@.006
and about 248@.008 compared to say a 268 mopar cam--- that's 20 degrees
and jones cam is 50% bigger @.200 than the DC 260 @.275
now depending where you put your icl it's easy to close the intake 8 degrees earlier than stock, open the exhaust later and close the exhaust 10-12 dearees earlier ( remember the really long stock close sides-- and cuts the overlap
That's what picks up the dcr in a 73 and later 440 or say 9.5:1 motor esp with al heads
for shelf cams lunati voodoo or if you want to pay
you want more top end go bigger but there are tradeoffs more attention to detail then howard
actually all require attention to detail
we could go into quench and squish but the cmpact chamber is a big part of the combination
sort of like 67 915 or even better aftermarket heads with D dish pistons- but those also have the plugs moved and better chambers
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Thank you for responding.
Okay, that is more information and while I think that I understand some of it, I'd probably have to talk face to face to fully grasp it.
The problem in learning for me, is that once an instructor steps outside of what I understand by using terms I've never heard, I get lost.
Some guys know their stuff so well, they don't know that they are leaving out some simple steps that some people need to know to understand.
Please understand that I am not criticizing you, I just am not as able to fill in some of the gaps.
For example:
"Jenks hand calculator and file and stone finished master for the .904 lifter truck was 192 @ .050 with about the same lift and area as a standard 440 cam"
I don't understand what the first half of the sentence means.
What I think that I understand is that the low compression big blocks with no quench and "EGR effect" cams had problems with high exhaust gas temperatures. You helped develop a fix for it, including pistons with a "Pop up" section to induce quench. This, along with changing some cam timing events resulted in better power and durability?
Okay, that is more information and while I think that I understand some of it, I'd probably have to talk face to face to fully grasp it.
The problem in learning for me, is that once an instructor steps outside of what I understand by using terms I've never heard, I get lost.
Some guys know their stuff so well, they don't know that they are leaving out some simple steps that some people need to know to understand.
Please understand that I am not criticizing you, I just am not as able to fill in some of the gaps.
For example:
"Jenks hand calculator and file and stone finished master for the .904 lifter truck was 192 @ .050 with about the same lift and area as a standard 440 cam"
I don't understand what the first half of the sentence means.
What I think that I understand is that the low compression big blocks with no quench and "EGR effect" cams had problems with high exhaust gas temperatures. You helped develop a fix for it, including pistons with a "Pop up" section to induce quench. This, along with changing some cam timing events resulted in better power and durability?
wyrmrider
Well-Known Member
jenks did the lift table for that cam on a hand calculatornand not every millionth of a degree and not to every millionth lift --then roughed it out on a mill
cut turn cut turn
then smoothed the between cuts with a file while checking his lifts
then used a stone and checking refraction lo light off the cealing where you could see the flats
before the days of UD harold and his 8 bit computer, or Isky and others including Harold early on, with time on a mainframe and Polly the Polydyne parrot
Now you do not even have to make a master
just compute the lift table and feed it directly into a CNC grinder
but you still have to know what you are doing to prevent valve bounce and take up the initial without hitting it with a hammer -it's all important
cut turn cut turn
then smoothed the between cuts with a file while checking his lifts
then used a stone and checking refraction lo light off the cealing where you could see the flats
before the days of UD harold and his 8 bit computer, or Isky and others including Harold early on, with time on a mainframe and Polly the Polydyne parrot
Now you do not even have to make a master
just compute the lift table and feed it directly into a CNC grinder
but you still have to know what you are doing to prevent valve bounce and take up the initial without hitting it with a hammer -it's all important
Cam grindin' ain't easy!
66Satellite47
Well-Known Member
wyrmrider, I think I'm starting to understand your comments/suggestions. Seems like you were attempting to correct the negative effects of the "emission" designs started in '68 with the 906 heads and the the continued decrease in static CR. I understand the emission designs were intended to raise the exhaust gas temps to continue combustion out the exhaust system, reducing unburned hydrocarbons. Since my thinking has been focused on my drag racing applications, I didn't quite understand some of your posts. Now I'm starting to get it. Thanks. I also wasn't thinking about all the differences that a cam design would make on a "street" cam compared to a drag race cam. Thanks again, that fits very well with my approach to what does work for both a drag car & a real street car.
Nate S
Well-Known Member
I think Wyrmrider has a good and valid perspective on this but it's not the only one and reflects a set of experiences that aren't universal. It's easy to find alternate views in regards to the cam and heads. There's a '68 roadrunner article where they praise the new heads because for the same compression ratio there's much less knock than the previous year. Mopars never had quench that was meaningful from the factory, only aftermarket pistons have allowed that. I've run both open and closed chambers with similar compression ratios and found little difference myself. As for the cam, yeah there are faster ramp ones than the factory magnum but for the specs it performs very similarly to others of similar design. Comp cams 262 is nearly identical, no special loss of low end power on the magnum because of the largely non-functional end-ramp. Not much air flows through a valve that's open .008" or less, that's why everyone looks at .050 figures.
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