Best Head Gasket?

#1
I've been running the 0.009" single layer viton-coated steel head gasket for about 15 hours and then I started blowing side cover gaskets, losing power, and burning a little oil. It ended up being that my head gasket blew into the oil passage right next to the cylinder:

Pic-02202019-001.jpg

I've had this happen to the old head, in the same spot, but I caught it before it got bad like this.

This engine with the old head had 9.9:1 compression at 29* timing. Now with the new head it has 10.6:1 and 32* timing. It runs 87 and 89 octane and never detonates.

I was thinking about trying one of the copper head gaskets from NRR. I'm not sure what the advantage to an MLS gasket is unless you need to run a thicker gasket than stock for squish clearance or to lower compression. I do not need a thick gasket but I can mill the head more if necessary.

Is this a normal failure on a modified engine? Am I using the wrong head gasket? Is it possible the deck surface is warped?
 
#2
Time to get out the Starret straight edge. I'm running the steel/tin versions from OMB, I did though spray both sides of them with copper coating, have not seen a failure yet. 3 years on the hemi, and going on 2 on the non. Both built with all the goodies, and still using head bolts.
 

65ShelbyClone

Well-Known Member
#7
Now with the new head it has 10.6:1 and 32* timing. It runs 87 and 89 octane and never detonates.
Not that you can hear anyway. IMO you need to be running better gas than that.

What cam is in there? Water-cooled car engines with lower head temps would gladly ping on your combination of compression/fuel/timing.
 
#8
The cam is the definitely an important factor when it comes to detonation resistance. Specifically, the intake valve closing event, degrees ABDC. A larger number here will reduce the dynamic compression ratio and reduce the cylinder pressure on the compression stroke, thus increasing detonation resistance and reducing the fuel octane requirement. My particular setup has resulted in a 10.6:1 static compression ratio and an 8.1:1 dynamic compression ratio. The intake valve closing event is at 71 degrees ABDC, measured at ~0,001" lift. This engine seems to be happy running 92 octane pump premium. The stock cam would not hold the intake valve open as long and that would result in a greater dynamic compression ratio and higher compression stroke cylinder pressures, which would decrease detonation resistance and increase the fuel octane requirement. An old-school car guy rule of thumb stated that you want to keep compression stroke pressure below 180 psi in order to run pump premium fuel. Between 180 and 200 psi you should consider octane boosters or a blend with race gas. Above 200 psi and race fuel is required. Car engine technology has changed since this rule of thumb was devised. It's not the `70's anymore. We use CFD to model and optimize air flows and combustion. Add in SEFI and now DFI and you can have a high compression engine that can live detonation free on 87 octane. Unfortunately, that is not our carbureted Honda/clone engines, so we should probably stick with the old school rules of thumb for our application.

With all that said, I'm running a three layer 0.027 MLS head gasket without any type of additional sealer and have had no problems. Certainly put a straight edge on your block deck surface and the cylinder head. If everything is flat, consider increasing the cylinder head stud torque slightly since the aftermarket studs are stronger than the stock bolts and require more torque for proper stretch.

-Ray
 
#9
Not that you can hear anyway. IMO you need to be running better gas than that.

What cam is in there? Water-cooled car engines with lower head temps would gladly ping on your combination of compression/fuel/timing.
I have a MOD2 cam with 1.3:1 rockers and 27/25mm valves. The head is a milled 22cc with a total 0.028" squish clearance. I understand I probably don't hear when it pings but the piston crown and head look spotless compared to other engines that I've seen that detonated. I would have ran lower timing but it seemed to really like it. I'm not going over 32* though. Can't get too greedy...

The cam is the definitely an important factor when it comes to detonation resistance. Specifically, the intake valve closing event, degrees ABDC. A larger number here will reduce the dynamic compression ratio and reduce the cylinder pressure on the compression stroke, thus increasing detonation resistance and reducing the fuel octane requirement. My particular setup has resulted in a 10.6:1 static compression ratio and an 8.1:1 dynamic compression ratio. The intake valve closing event is at 71 degrees ABDC, measured at ~0,001" lift. This engine seems to be happy running 92 octane pump premium. The stock cam would not hold the intake valve open as long and that would result in a greater dynamic compression ratio and higher compression stroke cylinder pressures, which would decrease detonation resistance and increase the fuel octane requirement. An old-school car guy rule of thumb stated that you want to keep compression stroke pressure below 180 psi in order to run pump premium fuel. Between 180 and 200 psi you should consider octane boosters or a blend with race gas. Above 200 psi and race fuel is required. Car engine technology has changed since this rule of thumb was devised. It's not the `70's anymore. We use CFD to model and optimize air flows and combustion. Add in SEFI and now DFI and you can have a high compression engine that can live detonation free on 87 octane. Unfortunately, that is not our carbureted Honda/clone engines, so we should probably stick with the old school rules of thumb for our application.

With all that said, I'm running a three layer 0.027 MLS head gasket without any type of additional sealer and have had no problems. Certainly put a straight edge on your block deck surface and the cylinder head. If everything is flat, consider increasing the cylinder head stud torque slightly since the aftermarket studs are stronger than the stock bolts and require more torque for proper stretch.

-Ray
That is some great information there! I checked compression after the first few trips and it always came up about 110psi. Probably the compression release working there. Maybe I should turn it over with a drill next time I check?
 
#10
I use a whetstone on the head and deck, at least. Some 300-ish on a flat counter isn't bad, to see any high spots. Those coated steel gaskets should be fine. Accurate torque on the head?
 
#11
I use a whetstone on the head and deck, at least. Some 300-ish on a flat counter isn't bad, to see any high spots. Those coated steel gaskets should be fine. Accurate torque on the head?
After I milled it, I sanded the head on 300, 800, and 1500 sand paper clamped onto the table for my vertical bandsaw, then I ran it on the lapping plate for awhile. I can't really (well I can but I'm lazy) sand the deck surface on a table but I can hold the lapping plate to it.

The head has studs and I torque them to 20 ft-lbs with a clicker every time.
 
#12
That is some great information there! I checked compression after the first few trips and it always came up about 110psi. Probably the compression release working there. Maybe I should turn it over with a drill next time I check?
Yeah you probably want to turn it over with some sort of motor. Remember air has mass and all cylinders leak past the rings/through the ring gaps. The faster you turn the engine, the less time the air has to leak past the rings, so less volume of air leaks and you have more pressure.

The head has studs and I torque them to 20 ft-lbs with a clicker every time.
I think that 3 lb-ft over the stock bolts. I torqued mine (Burris Racing head studs) to 20 as well. Perhaps try 22 lb-ft and be sure to use a cris-cross pattern working up to it in 5 or so lb-ft increments.

-Ray
 
#13
Yeah you probably want to turn it over with some sort of motor. Remember air has mass and all cylinders leak past the rings/through the ring gaps. The faster you turn the engine, the less time the air has to leak past the rings, so less volume of air leaks and you have more pressure.
Also true. Great point!

I think that 3 lb-ft over the stock bolts. I torqued mine (Burris Racing head studs) to 20 as well. Perhaps try 22 lb-ft and be sure to use a cris-cross pattern working up to it in 5 or so lb-ft increments.
Yeah, since I'm not wearing on the block's aluminum threads as I tighten them, plus the studs can reach all of the threads in the block, I though an even 20 was a good compromise. I usually do a staggered pattern like tightening lug nuts in hand tight, 8, 12, 16, 20 steps. I always want to make sure I crush the gasket evenly.
 
#14
After closer inspection tonight, I found the head and deck surface are indeed warped. The head was about 0.0004" (0.4 thousandths) out of plane and the deck was 0.0011" (1.1 thousandths) out of plane. I'm currently getting a blast of an arm workout throwing a 10 pound lapping plate around on the deck. I'm taking pictures along the way for a later post.

Thanks for the input!;)
 

65ShelbyClone

Well-Known Member
#15
How did you measure down to 1/10,000 of an inch? Was it out of plane or out of flatness?

Being an aircooled aluminum engine with cast-in (I think?) iron sleeve, I would have called the deck good at just 0.001 out of flatness. The head needed attention though.
 
#16
How did you measure down to 1/10,000 of an inch? Was it out of plane or out of flatness?

Being an aircooled aluminum engine with cast-in (I think?) iron sleeve, I would have called the deck good at just 0.001 out of flatness. The head needed attention though.
It was warped so I guess I should have said out-of-flatness. The deck was worse than the head. The head's high spots were right around the bolt holes so the clamping force is what seems to have done that. The block was concave with the top and bottom as the high spots.

I measured it with a vernier depth gauge. I made sure it read zero by setting it on a surface plate, then I bridged it across the high spots on the head and deck surface and measured the depth of the low spots.
 
#17
the clone karting guys claim the yellow graphite head gasket seals the best and i also seen it on arc website i am running a .000 deck so i need atleast .035 piston to head
 
#18
the clone karting guys claim the yellow graphite head gasket seals the best and i also seen it on arc website i am running a .000 deck so i need atleast .035 piston to head
I'd have a ton of milling to do to run a 0.035" gasket. I already took 0.040" off the head. I am about 0.018" in the hole.
 

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