Closed chambers gone bad… that’s a wrap

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madhatta360

madhatta360

1973 Duster 340 H-code TX9
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Unfortunately pistons kissed the the 65cc SM heads luckily not enough to damage the heads.

These were the old speed pro high compression 340 style poking out the deck, ran the stock .053 head gaskets but just wasn’t enough. At this point I’m thinking of just having the lower end redone, going stroker route and starting fresh using the heads and 1.6 rockers I bought.

Luckily piston walls are good no scoring from what I was able to see but certainly will have it checked. Been a great learning curve not the outcome I was going for but **** happens.

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I'm not seeing valve witness marks. Can you be more specific?
 
Are you talking about the clean spots opposite the valve reliefs?
 
I believe what he's concerned with is this...

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It is damn close but doesn't look like it hurt anything.... Probably due to piston rock on cold start up.... Back in the early 90's Ford had an issue with the Probe, they were rattling on cold start, I tore a few down, you could see the piston part number stamped into the top of the piston transferred to the aluminum cylinder head... Didn't hurt a thing, we would put it back together with a .010 thicker head gasket...
 
What heads where you running? If it didn't pinch the ring lands, it should be easy enough to get the pistons milled enough (maybe even use a piece of glass with stick on 180 grit and clean the witness marks off the quench pads) to make clearance and run a Felpro 521SD .060 thick compressed gasket.
 
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How far out of the hole are the slugs?
If the clearance is super tight on a certain area of a piston, no deposits will collect.
 
haven’t measure each piston yet, these speed pro supposedly install .020 above top deck. Not sure if the PO had the deck milled, I’m assuming they did cuz he told me bottom end was redone and used .030 over pistons. That’s the only thing he didn’t have paperwork for.

These heads are the SM 65cc closed chamber ones 2.02/1.6 valves, running hughes 1.6 rockers bringing cam to .512 lift. 7.775 pushrod length, thing was hammering but not a bottom end noise thought maybe it was rockers/valve adjustment. Then I used the camera scopes the spark plug holes and saw the piston hitting when spinning over by hand, ever so close.

To me on the one pic (cyc2) it looks like the valve relief area actually hit the bottom of head, not worried about valves they are okay, but I think it damaged that piston.

Not sure where to go with this yet, def thought about running slight thicker gasket- I was making 170-180psi in all holes so compression was spot on.

iCloud
 
In my experience, those pistons run .018 above deck, but a 9.595 (-.005 deck cut) will cause problems when you start running a loose fitting forging at .028 piston to head. These flat tops sit .036 lower than what you've got right now.
DODGE Ross Pistons 99625 Ross Racing Forged Pistons | Summit Racing
It would possibly play pretty nicely with a set of these gaskets, but they're .014 thinner, which affords a total of .022 extra clearance. I would install the pistons and measure if they come above deck first.
DODGE SCE Gaskets M691239 SCE MLS Spartan Head Gaskets | Summit Racing
But... before trying to re run what you got, you want to invest in one of these and tell us what you presently have at each corner of the block. I would check each hole "just in case"... Sometimes, things get bent when pistons start kissing the heads.
DIAL INDICATOR STAND TDC FINDER LS1 LS2 LS3 LS6 LSX LQ4 LQ9 4.8 5.3 5.7 6.0 6.2 | eBay
 
My two cents- take it apart and go over everything with a fine tooth comb before spending any money. Pistons do not appear to be hurt. Some race engines have been purposely designed to barely kiss the head chamber similar to what you think yours is doing. Rod bearings, ring lands, and piston crowns will tell the tail once torn down and cleaned up.

Now if you are looking for an excuse to go stroker then by all means go for it. Regardless when you mock up bottom end this time you must measure how far out of the bore the piston is by rocking the piston in the bore both against the thrust side and opposite side. The looser the bore the more piston rock can happen. Get your deck bridge and dial indicator out. I would also measure the head gasket after compressing it by pulling the heads again.
 
madhatta360 said:
haven’t measure each piston yet, these speed pro supposedly install .020 above top deck. Not sure if the PO had the deck milled, I’m assuming they did cuz he told me bottom end was redone and used .030 over pistons. That’s the only thing he didn’t have paperwork for.

These heads are the SM 65cc closed chamber ones 2.02/1.6 valves, running hughes 1.6 rockers bringing cam to .512 lift. 7.775 pushrod length, thing was hammering but not a bottom end noise thought maybe it was rockers/valve adjustment. Then I used the camera scopes the spark plug holes and saw the piston hitting when spinning over by hand, ever so close.

To me on the one pic (cyc2) it looks like the valve relief area actually hit the bottom of head, not worried about valves they are okay, but I think it damaged that piston.

Not sure where to go with this yet, def thought about running slight thicker gasket- I was making 170-180psi in all holes so compression was spot on.

iCloud
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What "I" would do is get that #2 up to TDC, put some clay on that piston put the head back on and torque it to spec. Use the same head gasket. See what you come up with. They might just be "clean" in those areas because of good quench.
 
Heck, if all else fails, and they are actually hitting, run a thicker head gasket. It's not like you're gonna lose quench. LOL
 
RustyRatRod said:
Heck, if all else fails, and they are actually hitting, run a thicker head gasket. It's not like you're gonna lose quench. LOL
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Bingo!!!! I asked where they sit out of the hole.

Cometic will make what you need. Pricey, yes, worth it, absolutely! If your slugs were, let’s just say…. .030 positive, above deck, have Cometic make a .070 gasket for .040 clearance.

Now redo the math with your numbers…. Call Summit or Cometic.
 
If you're short on cash you can take it apart and shave .010" of the domes with a flat file in just a few strokes. I guessing it didn't hurt anything. If the bearings still look okay run a hone through it, put a new set of rings in, and run it. Now if want a 408" kit I can take care of you on that.

Tom
 
Or even a HF stationary belt sander. It may sound rough but it works, lol! If I could swing that stroker kit, though, I would get all over that business. A 390 inch 318 stroker is amazing in its own right, but the 416 incher is a whole ‘nother animal.
 
I wouldn't waste money machining anything when a thicker head gasket will solve the problem.
 
madhatta360 said:
Unfortunately pistons kissed the the 65cc SM heads luckily not enough to damage the heads.

These were the old speed pro high compression 340 style poking out the deck, ran the stock .053 head gaskets but just wasn’t enough. At this point I’m thinking of just having the lower end redone, going stroker route and starting fresh using the heads and 1.6 rockers I bought.

Luckily piston walls are good no scoring from what I was able to see but certainly will have it checked. Been a great learning curve not the outcome I was going for but **** happens.

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Haven't seen you post in a while good to see you again. Those are the PT 8553s and compressed they're actually around .046 to .048 ime.
You would want to use the 521 SD or 519 SD , whichever one is for the LA engine.. I forget... or if you end up with the Magnum version.. you just cut the captured push rod hold portions off with some cutters.
Those when compressed are .054-.056

Otherwise have the heads chamber milled
 
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measure each piston at TDC with a bridge, you can even rock the piston while measuring. The older the build the bigger the rock. An uneven deck will get you in trouble as well. With those heavy pistons I would run a minimum .040 clearance to account for rod stretch at high rpm. I run a .060 thick gasket .020 above deck piston and spin to 6800 every pass.
 
mderoy340 said:
measure each piston at TDC with a bridge, you can even rock the piston while measuring. The older the build the bigger the rock. An uneven deck will get you in trouble as well. With those heavy pistons I would run a minimum .040 clearance to account for rod stretch at high rpm. I run a .060 thick gasket .020 above deck piston and spin to 6800 every pass.
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Yes I’m thinking if i had at least a .060 I’d be in the clear, actually pulled both heads today and wiped down the pistons was just carbon. I have a nice deck bridge and just bought a good digital dial indicator so I’ll check and measure each piston. For the season I’m thinking I can get a proper head gasket that will give me .040 quench and I’ll run it and then send it out over winter for a stroker build. I’ll post up some photos later
 
Pulled the oil filter cut it open and drained the oil didn’t see any brass or indications of metal. Bought a good digital dial indicator for my deck bridge, going to measure each piston at TDC and determine what thickness gasket and put it back together. Run it for the season and pull it for winter, time to send it boys!

Also did a water test on the heads to check valves, all is good with the heads, think it’ll be good, we shall see I’ll keep y’all updated
 
If you get everything fixed with just a head gasket run it and get another block for your stroker build. It’s always nice having a dependable “spare” shortblock sitting there available. That way you can take your time on your next build and possibly for a few deals. That code is good all year so if you need a spare let me know.
 
pittsburghracer said:
If you get everything fixed with just a head gasket run it and get another block for your stroker build. It’s always nice having a dependable “spare” shortblock sitting there available. That way you can take your time on your next build and possibly for a few deals. That code is good all year so if you need a spare let me know.
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Thanks John, you’re the best appreciate everything, I’ll keep you posted.
 
I had great phone conversations with John.
We laughed a good bit and rambled on with tech talk.
Big thumbs up to John!

:thumbsup:
 
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