What head gasket for boost? MLS leaking oil

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maca

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Hey guys
I am running 10 psi on my wifes 360 magnum through a supercharger. I fitted some MLS gaskets but they leaked oil as I only machined the heads. So i pulled the engine and machined the block and the heads and fitted a new set of gaskets with a special spray to seal it. They still leaked oil. So i fitted a set of thin graphite gaskets and tonight i just blew them out.

What are my head gasket options. I may just blow other gaskets out. Even if i use thicker ones but if i use the mls gaskets they will leak oil. Very frustrating. The mls gaskets i used were for a LA 360. Are they different to the magnum mls gaskets?
 
question... are you doing.. iron head to iron block, or aluminum head? the RA finish has to be pretty smooth for the MLS gasket to seal up right. cometic has detailed instructions for the finish requirements on both surfaces. I've seen heads and blocks ( all brands ) get surfaced or decked and leak out the corners. make sure the shop that does it sharpens the stones if it is a quik way surfacing bed, if thats what they use (old school, but works great ).
 
moper said:
What fasteners are you using on the heads?
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Are you using bolts or studs? If bolts are you re-using them? Did you re-torque the heads after the first heat cycle? This is important with mls gaskets and boost.
 
brian6pac said:
Where exactly are they leaking oil ?
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Yes where is this leaking? Between cylinders 6 & 8 and between cylinders 1&3?
10 psi is not a lot of boost. I've run 14-15 psi racing and had no problem with standard Felpro Permatorque head gaskets. (Mitsu 2.6L, iron block, AL head).

Something is not sounding right. Maybe time to use ARP bolts; clamping force is a lot higher, maybe 50% or so.

Do you have a boost gauge on this car to verify peak boost? Is there any boost relief on the system, or is this just counting on the gearing and belt ratios to control boost levels?

Also, examine the pistons for any signs of detonation. That can blow out gaskets. (But I am not sure how it would cause leaking oil.)
 
Hey guys thanks for the replies.
I'm using Edelbrock aluminium heads and arp head studs torque down to the factory torque settings. I did ask for the Finish they recommend on both services.
The first time that leaked from right across the whole gasket. The second time both surfaces were machined and it was built from a Chevy shop who use these gaskets on all their engines. But they used la gaskets. That's why I was asking if the la and magnum ones are different. The second time they leaked out of the corners. They said it had never happen to them before and the only think I could do differently was to drill the rivets out and spray in between each layer.
Rather than pulling the whole engine out again and machining it all again I would rather try a better head gasket. I am pulling the aluminium heads off and putting on iron engine quest heads this week.
Maybe i should try Felpro Permatorque gaskets
 
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OK on the ARP's. When you say factory torque settings, that is something to pause over..... You don't torque ARP's to the factory torque; you torque them to a significantly higher torque and make sure you use the thread lube every time. Those 2 things together (higher torque AND thread lube) are how the ARP clamping force gets so much higher than standard factory head bolts. The ARP's should have instructions as to the torque to use; and that should be online too.

BTW, do these ARP's have the washer under the nuts too?

I never thought there was a difference between Magnum and LA around the bores; just up around the pushrods. Maybe someone can say better.

Is this a very early Magnum block perchance that still had the oil passages up from the cam bearing #'s 2 & 4? What it perplexing is how the oil in a Magnum could get anywhere around the head gasket except from the lifter valley area, and the drain holes in the heads.

Have you put a pressure gauge on the crankcase and see if you are getting a lot of positive pressure in the crankcase? Intake leaks or ring blowby could be pressurizing the crankcase a bunch.
 
Thanks, I will look up the arp torque down procedure's. Yes they do have washers under the nuts.
I know the oil holes your talking about. They don't have them in my block. I am also puzzled to how so much oil can pass through the layers of the gasket. It can only come from the valley area.

The blowby was fine until last night when i blew the gaskets out.lol
 
Oil leaking into the supercharger might push out through the layered gasket. But you ought to see it on the plugs and all over the place.

And pressure in the crankcase oughta blow out the valve covers 1st!
 
My thought was the crankcase pressure is to high, intake gaskets leaking from the boost? What intake gaskets are you using, I know a friend had that problem with a chevy motor. I can't see oil leaking from the head gasket other than the valley.
 
Boost and blowby will try to force oil out, but the head gaskets are not where I'd expect to see it. How much oil are we talking about here? Is it burning it too or are these only external leaks?
 
Hey guys thanks for the replies
I have stripped the heads off and I have blown both head gaskets out Into the valley. I think it was must have been timing that's caused it and poor head gaskets. The heads were machine but the deck wasn't. I don't really want to pull the engine completely down and get the decks machined. Some I'm looking for a head gasket that will handle just over 10 pounds of boost. The mls gaskets will leak oil if i use them
 
Sounds like detonation blew them out. Ten psi isn't that big a deal in terms of stress. "If" the decks are truly flat, and the proper cleaning ans torquing is done, I don't think a special gasket would be needed at all. Especially given the use of the head studs. Denonation on the other hand, can get through anything. You alreadu know the MLS needs the ultra smooth surface and there's no way the factory deck is there, so I'd just run s standard replacement gasket, and fix your tuning issue that's blowing them out. If you list the rest of the combo we might be able to give you a starting point for tuning.
 
maca said:
The mls gaskets will leak oil if i use them
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Do you really know that for certain? If the factory torque specs on the head studs have been used instead of the much higher torque specs of the ARP's, then you really did not install either gasket as well as they could be installed.

Do you have a boost gauge on the car? Like Moper, some info on the setup might be helpful.
 
Hey guys
Yes I have a boost gauge:). Sorry mike I don't know the brand of the mls and there is nothing written on them.
I built the engine and used the factory bolts and factory torque settings with these thin gaskets.
https://www.summitracing.com/int/parts/dcc-4120094/overview/
They compress pretty thin.
If I use 1008s then should I use studs too? I can buy some of these but I also have these head gaskets here in my garage.
These say good for up to 12-1 comp
https://www.summitracing.com/int/parts/dcc-4876048/overview/

but these say only for stock engines
https://www.summitracing.com/int/parts/fel-9898pt/overview/

Some built info
Stock magnum bottom end. Engine quest heads and the cam below
https://www.summitracing.com/int/parts/cca-20-746-9/overview/
 
MRL Performance said:
Need to get cometics and Arp studs and torque them to Arp specs
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Yeh you are right. I guess I am looking for an easier option so I don't have to strip the engine and deck the block and machine the heads as I wanted to run this engine in a track day very soon.
But I guess I could just blow the 1008s out too
Should I use the cometic for magnum or are the LA ones ok too and what thickness should I run
 
The Cometics are the best solution. Thickness is set by the compression ratio that you want and any quench gap you want. Are your pistons 'down in the hole"? I.e., is there some height to the deck from the top edges of the pistons at TDC? With a stock Magnum bottom end, there should be. In that case, there is no quench gap to set and so you use the Cometic thickness just to set static CR. And the static CR needs to be computed so that with the 10 psi boost you don't over do the overall cylinder pressure.

Hmmmmm. It just occurred to me that your static CR might be too high to start with. That would explain the head gaskets going and the detonation. With the stock Magnum bottom end and 63 cc head chambers and the thin .025" head gaskets, it looks like you had a static CR of around 9.0 or 9.1. Okaaaay, I think THAT might be the problem. Your cam looks to be for pressurized engines (wide LSA) but I suspect the resulting dynamic CR of around 7.4 is still too much for 10 psi boost. Detonation will result and the head gaskets will keep going.. if not worse. Maybe it is fortunate that your head gaskets weren't clamped down hard, as they could blow rather than a piston top or ring or ring land! (Dang... maybe this thing DOES need to come apart... for inspection of the rings....)

I suspect that the static CR needs to be brought down to the low 8:1 range to be OK with 10 psi boost. It's gonna take a lot thicker gasket than any discussed so far. I can do some research but it will take me some time to get to the data.

Can you post a pix of the piston tops so we can all be sure what pistons you have? (There are a few Magnum piston tops....) Then a clear picture of the static CR can be had. Ideally, you would also give us a measurement of how far the top edge of the piston is down from the deck with the piston at TDC, so we can be sure.
 
YOu said above you had ARP studs. Now you've got stock stuff? You need to talk about your tune before you spend more on hardware or gaskets. Detonation won't let anything live.
 
I assumed he meant that took out the ARP's and put in the factory head bolts on the lat go-round with head gaskets.
 
Hey guys
Sorry for the confusion. I have 2 engines. The one that currently has MLS gaskets and studs is leaking oil. The second engine is the one where I blew the gaskets out and wanting to fix this one. My compression rate is 9.0 to 1. I have run this combo for years on low boost but this is the 1st time I have run 11 psi. I would like to run studs in this engine too but I have just read that the arp studs 144-4005 are for edelbrock heads only and I am using engine quest heads. Anyone know what ones I need for engine quest heads? Or do I need to use the arp bolts that are for the magnum
thanks
ARP - The Official Site | Chrysler - Small Block Kits
I just found a kit 144-4003 that apparently fit magnum and engine quest heads.

I'm not really up to date with cylinder pressures. I have run this combo in the past but with less boost. I have run more boost but the lsa on the cam was 112 not 114. So if I run this set up will keeping the timing really safe help with the cylinder pressure issue as it will help with the detonation
 
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