Demonic
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Measure the size of the actual opening on that, if it didn't leave with the motor.. If it is around 1 1/8", the EMP-Robertshaw high flow thermostats are around 1 7/16" More flow= heat out of the heads quicker.
Need some engine advice....
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Measure the size of the actual opening on that, if it didn't leave with the motor.. If it is around 1 1/8", the EMP-Robertshaw high flow thermostats are around 1 7/16" More flow= heat out of the heads quicker.
wyrmrider
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those "10.5" 6 pack pistons- more like 9.5 with stockheads and replacemrnt gasket
and they still rattled
I agree on the d dish pistons and tigt quench
EMM build was more like a race motor
does not work well on the street
(being generous here
and they still rattled
I agree on the d dish pistons and tigt quench
EMM build was more like a race motor
does not work well on the street
(being generous here
IQ52
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I liked the read. It is however a great deal of talk with no specific test results. More like a Cometic sales pitch.
Noticed in that article that they are saying a flat top piston is fine to use in a quench build. So do you think that would work on my motor? Leave the pistons I have at .010" down with something like a .040 head gasket. Then replace the cam with something that bleeds off pressure better. Kind of contradicts what is being recommended in this thread about using a dish piston.
wyrmrider
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pick your rpm range, your torque curve then pick the cam, pistons etc
I do not like .050 quench go for 30-40
now pick your compression that works with your cam duration and intake close
doing the way in post 144 can end up with too big a cam with no low end
I do not like .050 quench go for 30-40
now pick your compression that works with your cam duration and intake close
doing the way in post 144 can end up with too big a cam with no low end
451Mopar
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My 500" stroked 400 has flat top pistons and quench head design, it is also 12.4:1 compression.
The dish is used to add volume to lower the compression ratio. The D-Dish or "quench dome" for open chamber heads sore of pinches the cylinder chamber down in diameter, with the air/fuel pushed more towards the sparkplug side of the chamber. The turblance and reduced diameter (smaller surface area against the hot head) helps prevent un-intended ignition (detonation.)
Quench distance is important, and the block needs to be true so the pistons all have the same deck height. 0.040" is a safe quench distance (steel rods.) Lower RPM, Steel Rod engine can go smaller, but below 0.030" you can bang the piston off the head at high RPM.
Seen that. My Friends Brother (I know, 3-Hand..etc, but I seen the damage.) bought a car with more of a race engine, and it appeared during the last freshen to get more compression, a 0.020" head gasket was used when the piston was zero deck or maybe even slightly above? He drove it crusing and such and did not have a problem, but when it was reved hard, the piston hit the head and pinched the ring groove to where the rings stopped moving, then a really bad damage happened.
PRHeads
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It was really just something I grabbed quick to help explain some of the theory behind quench.
Like I said earlier, every shop has their own way of doing things.
When a customer tells me the motor absolutely positively has to run on pump gas....... I don’t push the CR envelope...... and it gets built with effective quench.
For a fairly straight forward street/strip build, with a very reasonable hp goal....... I don’t see any reason to not build it that way.
IQ52
Well-Known Member
I don't design engines for others anymore. But when you are starting with a clean slate, only a knucklehead would do something other than what you describe.
Oh, I don't intend on apologizing to any offended knuckleheads out there. Not sorry.
451Mopar
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FWIW, my compression ratio numbers may be a bit high compared to the Wallace Racing calculator, and I round them to 1 or 2 decimal places.
I don't account for the piston to wall clearance volume above the top piston ring.
That might be 0.100cc, and lower the compression by 0.0067 of a point of compression.
PRHeads
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There is usually closer to 1cc of area above the top ring.
SRP piston I have in the shop.....
Piston is for a 4.350 bore.
Area above top ring is 4.310.
Top ring down measures .255
Area above the top ring is 1.137cc
On a typical flat top 10:1 446 that changes the CR by .1
10.144 down to 10.044
As the CR goes up, each CC has more affect on the net result.
If the CR for that 446 was calculated at 13.87 without that area above the rings being factored in...... then you added in the 1.1cc that’s actually there...... the number drops to 13.67.
SRP piston I have in the shop.....
Piston is for a 4.350 bore.
Area above top ring is 4.310.
Top ring down measures .255
Area above the top ring is 1.137cc
On a typical flat top 10:1 446 that changes the CR by .1
10.144 down to 10.044
As the CR goes up, each CC has more affect on the net result.
If the CR for that 446 was calculated at 13.87 without that area above the rings being factored in...... then you added in the 1.1cc that’s actually there...... the number drops to 13.67.
Last edited:
451Mopar
Well-Known Member
Your right, it all adds up. The higher the compression ratio and the larger the bore size, the effect on compression ratio becomes greater.
I was just saying my compression ratio calculation was slightly off because I did not include that extra volume above the ring, and I don't have the top ring down measurement anyway, so just guessing around 0.2"?
I will have to add that into the excel spreadsheet to make it more accurate.
When you don't have the actual parts, most of these numbers are checking if the numbers are in the ball park.
Seems the block heights are taller than "spec" and can change front to back and side to side making the compression ratio different in each cylinder unless the block is cut to square it up and the cylinder head chambers equalized.
This is where my "quench" dome KB pistons got interesting. on the two heads I had, the flat part of the chamber was about 0.010" different, and both too deep to get the correct quench distance. I think one head was cut 0.040", and the other 0.050" to get the quench distance correct, then had to measure and equalize all the chamber volumes.
joemish
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What is the ideal quench height?
Quench should be as tight as possible without the piston actually contacting the head. This, in turn, is largely dependent on the type of connecting rods and the engine's peak rpm. A good rule of thumb is that you can run as little as 0.038 to 0.043 inch with steel connecting rods.
What Is The Ideal Quench Height? - Hot Rod Network
www.hotrod.com/articles/ideal-quench-height/
Quench should be as tight as possible without the piston actually contacting the head. This, in turn, is largely dependent on the type of connecting rods and the engine's peak rpm. A good rule of thumb is that you can run as little as 0.038 to 0.043 inch with steel connecting rods.
What Is The Ideal Quench Height? - Hot Rod Network
www.hotrod.com/articles/ideal-quench-height/
Splangj
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My poorly built 4.125” 440 has at least -060” down in the hole flat top pistons, with open chamber Edelbrock rpms, to achieve around 10.3 cp. it runs well until it’s over 80 degrees, then it will detonate. This is with an aggressive timing curve. My Dart, also with a good timing curve will not detonate. I’ve even timed it too advanced and it didn’t ping, just lost power. MM built that 408 with zero deck dished pistons. It’s got closed chamber Edelbrock heads and a 040 head gasket.
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I didn’t read the whole thread. Did the op ever contact Brian at IMM? That’s where I’d start. He has many awesome builds. And customer satisfaction is top priority. Kim
The motor made it back to Brian in CA and last I heard was scheduled to be taken apart today.
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Ur on the right track. Kim
Thought I would get this thread up to date. Motor was finally taken apart last week. Bearings were not terrible but did show signs of the detonation, they are being replaced however since it is at this stage. Couple of other things were learned upon disassembly. Instead of the block supposedly being bored .010 as per his sheet, it was actually bored .020". Also the pistons were .030" down in the hole instead of the .010" that he wrote down on the spec sheet. With these measurements, he is coming up at 10.1:1 compression. Brian has no idea how these measurements were not recorded correctly. I believe they had 2 of the same type builds going on at the same time and measurements were not following the correct build. He still has no idea why this motor was detonating because he has put together quite a few the exact same as this one with the exception of the intake manifold. We used the short Weiand Action + for Ramcharger ductwork clearance. He doesn't think that is the issue, but who knows.
So Monday he is ordering CP full dish 30cc pistons with some swirly cuts and will use a .040 or so head gasket to get a compression ratio of 9.7:1. Also is ordering a different cam to drop the cranking compression down to 170ish. So what is everybody thoughts on this plan?
One other question. He said he will be able to order the new pistons the same weight as the old ones, so won't have to rebalance. Is that common practice and wise to do?
So Monday he is ordering CP full dish 30cc pistons with some swirly cuts and will use a .040 or so head gasket to get a compression ratio of 9.7:1. Also is ordering a different cam to drop the cranking compression down to 170ish. So what is everybody thoughts on this plan?
One other question. He said he will be able to order the new pistons the same weight as the old ones, so won't have to rebalance. Is that common practice and wise to do?
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Balance is based on the combined weight of the piston, rings, rod. With all you've been through, I recommend you request the shop check/balance the assembly. Otherwise, it sounds like a good design.
wyrmrider
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so what was the quench with the old build and cr?
are the 30 cc dish pistons designed for 0 deck?
if 0 deck .040 gasket is sorta ok
if they are down .010 then NO
.030 quench works better
post specs on both cams
170 is ok but 185 can be made to work
glad you may have found a cuse
are the 30 cc dish pistons designed for 0 deck?
if 0 deck .040 gasket is sorta ok
if they are down .010 then NO
.030 quench works better
post specs on both cams
170 is ok but 185 can be made to work
glad you may have found a cuse
There was no quench on the first build. CP doesn't make a d-dish piston for this stroke motor. Something to with not enough room to the pin. So they make this full dish with some kind of swirly cuts in the dish which has about a .40" flat around the perimeter, which will be at 0 deck. Brian thought the cam in the motor now would work as well, but wants to be absolute certain we are not right on the edge of detonation. He is going to dyno it on 87 octane just to be sure as well.
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