High compression on pump gas tricks???

Instead of cooling the fuel, keep it warm so it evaporates better/easier. Warm and under pressure.

I had ceramic long tube headers on my 99 dakota R/T with around 12 to 1 iron head 410CID and those headers you could still hold your fingers on for a couple seconds immediately after getting back from running hard down the highway even before shutting off the engine, most headers I have seen will melt your skin instantly on contact after somethign like that. Under hood temps were much lower than most other header equipped cars. Something else I did on that one was I ran an airgap style intake but it would not have much access to cool air to flow under it so I removed all the webbing I could from the huge AC/Alternator bracket and ran a big mechanical fan (I normally run electric fans) to keep a steady stream of air flowing through there. I even glued a phenolic resin type plate to the bottom of the intake to keep the hot cam oil from heating the intake.

Other things I have thought about as far as ways to keep the air cool is to use plastic ducting instead of metal (Aluminum dryer ducting), you could strip all the paint off a metal air cleaner and ceramic coat that, obviously make sure you suck air from in front of the radiator not behind it.

Sometimes lots of little things add up to make a pretty significant difference.

I always wonder why nobody makes phenolic resin intake manifold gaskets for old motors, it would be a nice way to help keep heat out of the intake manifold when plastic intakes are not available.

Has anyone come up with a good way to run reverse cooling on a mopar engine yet?

I am gonna see if my local machine shop can put copper beryllium exhaust seats in an iron magnum head I am getting ready to put in my next MPG project... I had not thought about doing that.

What are everyone's tricks for safely running the highest compression possible on pump gas? Also what is the most compression you have seen run safely on pump gas?

I will share a few tricks that work for me

Coolest intake air possible
Keep as much heat as possible out of engine compartment, wrap headers, minimize restriction of air flow out of the engine compartment from the radiator
Keep fuel as cool as possible, heat wrap lines near exhaust, keep lines as far as possible from exhaust, phenolic carb or phenolic carb spacer
Very tight quench
Aluminum heads when possible
Sharp angle on intake valve to help break up fuel droplets
Fully radius and polish exhaust valve head to keep it from getting hotter than nessacary and keep it from heating the air in the chamber
Don't be afraid of ethanol fuel
Coolest plug that don't foul out
Very careful control of timing, tight distributor bushing, carefully curved distributor
Late intake valve timing or at least not too early
Coolest engine temp that is reasonable, usually 180* on the street for me
Slightly loose converter
EFI with return line
Smooth out or round off any sharp edges in the combustion chamber
Find injectors with as many spray holes as possible for the given flow rate needed
Plastic intake manifold if I can find one for the application to keep the air cool (no 6.1 or eddy intake for my hemi)
On the new hemi 6.4 I run the piston squirters and stick a bunch of computer heat sinks on the oil pan and filter to keep that oil cooler to keep the chamber cooler

No love for thermal barrier coatings ?
With high compression and low octane , combustion chamber heat can be reduced by coating the piston and chamber.
I have read some interesting results from this.

I am still undecided about coatings, here is why.

We know running aluminum heads can allow you around another full point of compression vs an otherwise identical iron head, the reason is it conducts the heat away from any hot spot faster so the hottest point in the chamber is no longer as hot and no longer as likely to pre-ignite the fuel. Same with the piston, the heat can spread out faster from any given point. Now we would add a ceramic coating that does the exact opposite...? It is possible I am missing something, maybe just keeping the heat from being absorbed in the first place outweighs it but my though is that it would just have a hot spot with the piston behind it still trying to transfer heat evenly through out but the surface could more easily develop a hot spot, sort of an in between of the properties of aluminum and iron...

One other thing I like to do that seems to work really well for me is running as flat a piston as possible, for example a 318 with stock flat top pistons, no valve reliefs set with a real tight quench and magnum heads let me get away with very high compression, lowest surface area possible for a piston to keep it from absorbing heat... it may be worthwhile to run a head with a bigger chamber so you can run less or no dish in the piston. I always prefer a perfectly flat piston if possible.

I am still undecided about coatings, here is why.

We know running aluminum heads can allow you around another full point of compression vs an otherwise identical iron head, the reason is it conducts the heat away from any hot spot faster so the hottest point in the chamber is no longer as hot and no longer as likely to pre-ignite the fuel. Same with the piston, the heat can spread out faster from any given point. Now we would add a ceramic coating that does the exact opposite...? It is possible I am missing something, maybe just keeping the heat from being absorbed in the first place outweighs it but my though is that it would just have a hot spot with the piston behind it still trying to transfer heat evenly through out but the surface could more easily develop a hot spot, sort of an in between of the properties of aluminum and iron...

One other thing I like to do that seems to work really well for me is running as flat a piston as possible, for example a 318 with stock flat top pistons, no valve reliefs set with a real tight quench and magnum heads let me get away with very high compression, lowest surface area possible for a piston to keep it from absorbing heat... it may be worthwhile to run a head with a bigger chamber so you can run less or no dish in the piston. I always prefer a perfectly flat piston if possible.

You're not going to like my suggestion...Run a functional EGR valve. You'll lower the combustion temperarture and increase fuel economy for cruise and highway.

There is ZERO truth to the oft repeated nonsense that aluminum heads can use a point more compression than iron. None. Guys running iron heads can run the same compression as guys running aluminum heads. It’s ridiculous to keep saying that falsehood. There is no possible way in hell that running along at a cruise and running into tip in rattle will stop if you switch to aluminum. Common sense says the increase in heat load happens so fast it wouldn’t matter if the heads were made of unobtainimum it wouldn’t matter.

There are no “tricks” to running more compression than the “orthodox” standards we have been lead to believe. Common sense engine building, cam selection and chassis isnt trickeration. It’s common sense.

You're not going to like my suggestion...Run a functional EGR valve. You'll lower the combustion temperature and increase fuel economy for cruise and highway.

Aluminum helps reduce detonation not just because of what happens over the course of one particular engine cycle, it helps because over the last several thousand cycles previous to that one particular cycle the heat has spread out more evenly throughout the cylinder head instead of staying more in one spot like it would have if the heads were iron. You can experience the same phenomenon when heating a head to remove a broken exhaust bolt, you put the heat on a broken bolt in an iron head and it will very quickly heat up the area the bolt is in and the rest of the head temp barely changes temps if at all and that spot will stay hotter much longer than if you do the same thing on an aluminum head, that hot spot around the broken bolt cools off waaaaay faster and the heat is much more quickly spread out through out the rest of the head. The aluminum spreads out the heat over time and prevents hot spots much more effectively than iron. You are ignoring the heat dissipation over time and focusing on one small slice of time where both heads are perfectly exact temp through out but over running time that is far from what is happening inside the engine.

There is no way that the aluminum head can dissipate heat so fast as to reduce local combustion temperature to reduce detonation.

Aluminum, thermal conductivity 136 btu/hr

Cast iron, thermal conductivity 46 btu/hr

So, aluminum triple thermal conductivity as cast iron, but no difference in operation?

That would be a no.

Don't get me wrong, you are stating the advantages of an aluminum head over an iron head is....?

And I agree in terms out output, iron comes out ahead everything else equal because of thermal efficiency, but it would also put a specific combination closer to detonation on a specific fuel.

Can't have it both ways. Thermal efficiency is keeping heat in the chamber (=power) but that can aggravate detonation sensitivity on pump fuel as well.

A general thought of a point in compression is not the definition of working miracles, it's general understanding of thermal conductivity between two different metals.





What I’m saying is you can run the same compression ratio with iron heads as you can with aluminum. It’s as simple as that. While aluminum rejects heat faster than iron, it still can’t react fast enough to allow more compression. It’s physically impossible.

I disagree. (Or would say, I'm ok with agreeing to disagree).

A few others thoughts on the matter-



But could the thermal properties of iron offer a power advantage over aluminum? That question gets complicated.

“Thermal conductivity has been debated for many years,” said Kevin Feeney of RHS, Memphis, Tennessee. “Historically, an iron head was considered more durable, and able to make more power due to the fact that it would not dissipate the combustion heat as quickly. With everything else remaining equal, there exists some merit to this argument.”

Mike Downs of Trick Flow Specialties, Tallmadge, Ohio, pointed out that the thermal conductivity of aluminum is “four or five times that of iron. This means an iron head will usually operate hotter. On the positive side, this means the fuel is pre-heated in the intake runner and easier to ignite in the cylinder.

On the negative side, it means the preheated air/fuel mixture will expand, reducing the effective flow into the engine and increasing the risk of pre-ignition. A properly designed aluminum head will transfer heat more quickly to the coolant, leaving the intake runner cooler and therefore able to flow more air-fuel mixture into the cylinder. High-energy ignition systems easily compensate for the cooler intake charge and help achieve maximum fuel burn.”

“The greater thermal conductivity of aluminum is a great advantage,” agreed Chris Frank of Frankenstein Racing Heads, Joshua, Texas, “especially in power-adder applications. That ability to dissipate heat quickly allows for more aggressive tune-ups.”

“Aluminum heads dissipate heat quicker than cast iron,” echoed Torrance, California-based Edelbrock’s Smitty Smith. “This can be an advantage in elimination-style drag racing, keeping the head temperature consistent round after round.”

With aluminum, Tony Mamo of AFR (Air Flow Research), Valencia, California, concurred, “detonation is less likely in an engine on the ragged edge, as it won’t hold as much heat. But that also firms up the argument that a cast iron head on an engine without detonation issues would make more power for the very same reason!”

“You need to build more heat with aluminum to make the same power,” agreed Bill Mitchell Jr. of Bill Mitchell Products, Ronkonkoma, New York, “or compensate by coating the chambers to keep more heat in the cylinders.”

I would love to contribute to this analysis, but I would have to dig out my thermodynamics books again.

Part of this discussion needs to separate out steady state equilibrium conditions VS transient conditions.

It's not about the temperature of the head, if it was you could just make up the difference by altering the coolant temperature.

It's about how quickly heat is conducted away from the chamber and into the cooling system. Just some numbers as an example but lets say you have peak cylinder pressure of 1200psi and peak combustion temperature of 4000 deg F, obviously that's a huge delta between say 200 degree coolant. How could a material separating those 2 one of which multiple times more thermally conductive -NOT- drop peak temperatures and therefore pressure?

Combustion heat/energy that could be pushing the piston down is lost to the cooling system which is then dissipated by the radiator.

As long as the cooling system isn't on the brink of being overloaded you could easily have more combustion heat being wicked into the system (by a head with much greater thermal conductivity) while maintaining the same coolant temp.

If that was not possible you would have a very large swing in coolant temp at say idle vs high rpm wide open throttle.

Hey, at least we agree that HP is king

I have no idea what video you are referencing.

The problem with cast iron is one spot can be significantly hotter than another spot, a ridge in the combustion chamber for example, you may have a 200 degree coolant temp but a hot spot that is 300 degrees because the heat is not transfered away very fast and the rest of the iron just slightly above the coolant temp perhaps 220 degrees. Aluminum on the other hand can also have the 200 degree coolant temp but the same thickness aluminum as the steel was but that one spot won't get as hot, the heat can move away from that area into the surrounding area quicker so you have a more consistent temp of the aluminum in the actual chamber, the temp in the same hot spot might get to 250 and the rest of the aluminum perhaps running 225 degrees so the average heat of the chamber is about equal but there are not as dramatic of hot and cool parts. That is why I brought up about the heating broken bolts, the aluminum head needs more heat applied to that spot to get it hot enough to remove the bolt and that entire aluminum head will get warm and the iron head will not but look out because that one spot you heated will burn your finger for several minutes. There is not a significant heat transfer from just one split second of heat but after thousands and thousands of those flashes of heat there are going to be hotter areas in the iron head than an identical aluminum head would have achieved.

Maybe a better analogy for you would be a well insulated and sealed up house with the thermostat set to 70, the entire house is close to that 70 degrees but then you got a drafty old house where you may achive 70 right there at the thermostat but there are much hotter and colder places in the house.

I don't understand how someone can claim the heat transfer is enough to make a difference in efficiency because less heat is absorbed by the iron, but on the other hand not understand how in one isolated part of the chambers temperature enough to make a hot spot that can start preignition when the fuel and air mix is squeezed to 250PSI against one spot that is already hot because it can't transfer it to the coolant fast enough...

You certainly CAN reduce detonation with coolant temperature. An engine at 190 degrees is much more detonation prone than one running at 160. It IS as simple as that.

A few more bits of info from engine builders-



From Darin Morgan (was at Reher-Morrison now I believe BES)

"A cast iron block with cast iron heads will make more power than any other combination.
A cast iron block with aluminum heads will make less power.
An aluminum block with aluminum heads will make even less power."



From Larry Meaux (pipemax creator)

"a back-to-back Dyno test on SBC
cast-iron Bowtie Block -vs- alum Block
everything exactly the same, just blocks were swapped
there was 30 HP difference at 600 rpm/sec

another back-to-back Big Block Chevy test = approx 40 HP

another back-to-back SS Hemi test on Cylinder Heads only
with cast-iron -vs- aluminum = 12 HP more w/cast-iron
same flow numbers + port vol CC's

i did another similar test with my own personal SBC dyno test engine
..on the small block Chevy, it was a solid 8+ HP gain with
cast-iron over aluminum head.

the above were actual Dyno tests,
for theoretical HP/TQ differences between alum -vs- iron Blocks
by using FlowBench CFM Numbers -vs- what HP the different
block materials made on the Dyno =>

the results were=> for the same Flow CFM numbers,
i have yet to see an aluminum block engine make
the same HP/TQ that the cast-iron Block engine makes.

so far in all my Data,
the cast-iron Block always 100.0 % PerCent of time
makes more HP/TQ than an aluminum block

since Heat=HP/TQ
i think most of it might have been lost
to aluminum block acting like one big Heat-Sink
and some of it to ring blowby cfm w/alum.

very good discussion guys ! i am learning things as well as confirming things i have thought about for many years.
i have always liked higher engine temperatures [200-205f] than most, but sometimes i have difficulty getting the correct distributor curves [mechanical as well as vacuum advance] for the particular application.
having said that, i realize today's factory high horsepower is all fuel injection computer controlled, as well as using higher engine temperatures, but if using carburetor[s], a knock sensor [or two] plus a retard box is the correct way to go, correct ?
please help me understand how these retard boxes work with knock sensors. the only one i'm even slightly familiar with is the MSD box with the dial on the face, and as i understand it, that unit just pulls timing at a preset rpm ? can it even work with knock sensors ?
my foggy old brain needs some assistance here. TIA !

I don’t disagree with any of that. In fact, I whole heartedly agree that an aluminum block won’t make the power an iron one will. I know this from back to back testing and found it the same every time. I’ve never tested the same with heads, but Morgan and Meaux are two of the smartest, most experienced guys in the field, so I don’t doubt their results with head materiel changes.

What I’m not seeing is how this relates to detonation resistance. IMO it doesn’t, because the transient response time for detonation to occur is so fast the head materiel is of no consequence. I was running higher than orthodox pump gas compression ratios clear back in 1984. And never have I seen an aluminum headed engine take more compression (or an iron head taking less compression) before detonation sets in.

Yes and it was mentioned but just to reiterate, I also don't think all of the power loss from iron to aluminum block is solely from thermal loss but also to a great extent stability/ring seal. (which they also touched on)

[/color]I agree. Some of that power loss is ring seal.


As far as detonation resistance, I think we need to look at it in terms of the title of this thread for starters. The engine masters video was an attempt but I don't think really getting down to where it matters. I think you would need to start with an aluminum headed engine on the edge of pump gas usable then switch to iron to see if it will take the same ignition lead on the same fuel then compare power. At a more realistic/stable coolant temp if we are trying to figure this out for street driven vehicles vs just a drag car. (and I would think that would be the goal)

[color:#FF6600] I agree. As long as the chambers between the two heads are the same, as well as quench etc. then that would be a good test. Who knows, when I get my dyno up and running I may try it if someone wants to pay to do it. As far as coolant temperature I keep all my street/strip stuff at no hotter than 180 and prefer 160. If you can get it down below 160 (which is near impossible in a street car) you won’t have much of a heater/defrost. At that point, you no longer have a real street/strip pump gas deal. But 160 is easily doable and it reduces detonation tendencies by an order of magnitude.


When they start with an under 10 to 1 engine and high 130's coolant temp and a decent bit of cam, you're miles away from being detonation sensitive no matter what the head is made of.

[/color] I agree.

Yes of course you can transition into detonation instantaneously, I just have a different viewpoint of how heat conduction can affect this, regardless of how fast this can occur.

As a different example, I've calibrated hundreds if not thousands of supercharged GM vehicles with factory piston squirters. Replacement engines that delete these are notably more sensitive to detonation at both part and WOT and do not take as much lead at WOT compared to a stock shortblock. That being said, I don't think the amount of heat squirters could pull out of the piston compares to how much heat a combustion chamber could transfer, especially if we are comparing a material multiples more effective at doing so. (and transferring to a much larger completely surrounded volume of coolant much more efficient itself in heat transfer than oil)

[color:#FF9900] I don’t disagree with this. I think piston oilers are a big deal. I think every engine can use them, but most of the old junk I work on/with doesn’t lend itself to retrofitting piston oilers. If I could do piston oilers I would.

To that example, if the idea that everything is happening too fast for it to matter was true, I don't think you would see much difference with piston squirters, nor do I think manufacturers would bother spending money on them, if they didn't matter.

If you're on board with the idea that when approaching the edge of detonation on a particular combo, that heat can push it either way (safer or over the edge) and also don't dispute Morgan and Meaux's observations on HP output vs material differences, I think it's fair to conclude that if you had an aluminum headed engine on the edge of detonation on a particular fuel that switching to an equally capable iron head may put it over the edge due to it's lesser ability to transfer heat as efficiently.

[/color] I’m not sure about this one. There certainly is some power loss because you lose some heat through the aluminum, but IMO crap ring seal is the big power loss. I just cringed when a guy came in with a NA program and he was dead set on switching to an aluminum block. I knew it would lose power and I knew ring seal would be garbage after 5 or so heat cycles. The difference in surface area between a pair of heads and a block is huge. I’m sure someone on here who is good with math could calculate the number of BTU’s it takes to get an aluminum block from ambient to operating temperature, but I’d bet it’s significant. And then they could calculate how many BTU’s is required to keep an iron and aluminum block at the same operating temperature. Again, I’d bet it would take a significant of heat (power) just to maintain that temperature. And again, it would take less heat (power) to keep the iron block at temperature than the aluminum block. And that is a power loss.


Otherwise what would account for the power difference?

[color:#FF6600] Ring seal and the amount of heat it takes to retain operating temperature.

Just speculation but as far as your observations of never seeing a difference in what engine would take more compression (vs head material), is it possible that like the engine masters comparison, that the engine, whatever it was, was not on the brink of detonation vs the fuel used, with either cylinder head?

[/color] It depends on who you ask, but most would tell you I run everything on the edge of detonation. I spent the last weekend working with 4 different pairs of tunnel ram carbs, and according to the “gurus” standing around, I was going to send every one of them into detonation. The plugs agreed with me, and all four of the owners are happy today with how their tunnel rammed engines are performing on the street. As a reference, one of them is a 632 Chevy with Big Chief heads and a pair of 1600 CFM Twin Blade Dominators on it. A quick shout out to Trevor at Get’M Performance. A super sharp guy and he is willing to help. He pulled my chestnuts out of the fire twice last weekend.

Lastly, again, not trying to say there's a miraculous/huge difference, just in cyl head material difference, but I do think it's notable and measurable, for good reason. At least something to be considered, when planning a combination, including vehicle weight, trans type/converter/gearing, intended use (what kind of load it will see)/fuel/etc.

[color:#FF6600] I can’t disagree with this either. I think one mistake some guys make is they don’t think in terms of combination. Your last sentence sums it up pretty well, but one metric you didn’t mention was the driver. One guy I worked with last weekend didn’t drive in a manner that would cause me to build him an engine with more than about 10.5:1 ever. He had a 4 speed and he didn’t downshift near enough to warrant another point of compression regardless of what the heads are made of. He drives his street/strip car like he’s driving a Prius. In a corner where were I were driving I would have dropped all the way to first gear he just lugged it out of the corner in third. It doesn’t matter what you do, if you build an engine for a guy like that with unorthodox compression ratios he will drive it into detonation no matter what you do. You have to build and tune for the end user and how they drive. If you don’t, you can end up eating a poo sandwhich.

Drop your coolant temp 40 degrees, block of any heat to the intake manifold, use a quality annular booster and a relatively high compression pump gas engine will make way more power.

heat is always blocked no matter what intake is used. i have experimented with coolant temperatures between 180-210f, and it doesn't seem to be much difference. what i have noticed, however, is gas mileage is noticeably better at 205 than at 180. these are street/some strip engines. i know mileage means nothing in this discussion, but could that mean a better combustion process at elevated temperatures due to me NOT correctly putting a package together, or choosing wrong components ?
i have never asked anyone about choosing a cam, although i like around 240-270 duration @.050. just because that's the way i have always done it. also 3.90 to 4.30 gear sets with a 3000-4000 converter stall so the engine doesn't lug.
it now comes down to ignition timing, carb tuning, and exhaust experimentation. i realize when a guy can hear a "ping" inside, there is more happening inside the engine that is not good. this now brings this "old duma$$" to think about knock sensors, retard timing, and coolant temperatures.
thank you mr. mad scientist, for taking the time to help me get my head around the items i have been screwing up all these past years !