What are these Pistons and what's up with my block

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YWGScamp72

YWGScamp72

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So I pulled the heads on my 318 to prep for my 268 cam and speedmaster heads. The pistons are Gold and it looks like it's been sleeved. Pistons sit very flat at TDC and have 4 vlave relief cuts. Bore is just a hair under 4. Let me know what you think will this help with my compression with the addition of my heads and skinny gasket. Gasket that came off looked like a thick composite one.

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Yup, most likely not sleeved. The clean spot is where the fire ring of the head Gasket was. It's metal, so it won't leave as much crud behind.

The yellow/gold is likely from gas pissing down the intake. Either percolating after shutdown, or other carb/tuning issues. Either way it's where the gas has washed the carbon off the top of the piston.

The pistons are sitting down in the bore like a normal 318. "even with the deck" would be just that. The 4 reliefs are normal.

Your compression isn't likely to be much over 9, if that, no matter how thin your Gasket is because of how low the 318 pistons sit. You'll have to measure actual bore, how far down the pistons are, and cc the heads to get an accurate figure.
 
Hard to tell if that is a sleeve from the picture, but sleeves are OK. At
040 over, roughly 8 cu in. Pistons are aluminum in color, that gold is from combustion, not sure from the picture if it's an intake, where the clean area is, but intake I think. Fuel is cleaning the area.
Someone else can zero you in on gasket thickness. That piston is pretty much a stock replacement.
 
Okay, I just ran the numbers, I was off 1 1/2 cu in, it's 324 1/2 cu in.
 
@ a .060 overbore, 3.97 x 3.31= 327.79 (Like!)
@ a .090 overbore, 4.00 x 3.31 = 332.76 (Even better!)

Everything is just a sonic check away from being able to do this. The bigger bore helps with compression and better breathing from the cylinder head. A piston greater than 3.97 (.060 over sized) is probably going to be a custom piston. You’ll also need a dome to get any type of reasonable ratio. It might be a bit hard to get over a 10.5-1 ratio.
 
Thanks all plan is the do the aluminum heads, xe268h cam, air gap, and 750 Holley. Just wanted to make sure there were no abnormalities
 
YWGScamp72 said:
Thanks all plan is the do the aluminum heads, xe268h cam, air gap, and 750 Holley. Just wanted to make sure there were no abnormalities
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What heads? If you're talking Speedmaster, they have 65cc combustion chambers (claimed). Those pistons look about 1/10 down the hole, so say .090 - that's another 18cc. Assuming .039 for the gasket and a couple cc for the valve reliefs, your compression ratio is about 7.9 to 1. With compression that low, I'd think about calling Hughes and asking about their Whiplash cam that they claim is designed to build cylinder pressure in low cr engines. If the bores are good you could replace the pistons with ones that run at zero deck, that would raise the cr to about 9.5 to 1 assuming everything else stays the same.
I have the XE268 in a 318 with KB flat tops and 302 casting heads with bigger valves (1.88/1.60) and mild porting, runs really strong. My calculated cr is about 9.8 - runs really nice at that cr but I have no idea how it would run down around 8.
 
I have Mr. Gasket head gaskets on my 318, bored .030 over. Part number 1121G, compress to around .028. My engine is stock. Do not believe you can get much thinner than that, at least I couldn't find any.
 
kdeboy said:
What heads? If you're talking Speedmaster, they have 65cc combustion chambers (claimed). Those pistons look about 1/10 down the hole, so say .090 - that's another 18cc. Assuming .039 for the gasket and a couple cc for the valve reliefs, your compression ratio is about 7.9 to 1. With compression that low, I'd think about calling Hughes and asking about their Whiplash cam that they claim is designed to build cylinder pressure in low cr engines. If the bores are good you could replace the pistons with ones that run at zero deck, that would raise the cr to about 9.5 to 1 assuming everything else stays the same.
I have the XE268 in a 318 with KB flat tops and 302 casting heads with bigger valves (1.88/1.60) and mild porting, runs really strong. My calculated cr is about 9.8 - runs really nice at that cr but I have no idea how it would run down around 8.
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I know they say this not the most accurate indicator, but before I tore the heads off my compression test revealed 160+psi across all cylinders. I have the Mr gaskets 1121g gasket for when I put the 65cc speedmasters on and the pistons are currently sitting 1/16th (.0625) in the hole .040 over bore. Hopefully that should change these calculations to a more desirable number.
 
I did a calculation with a couple different numbers and couldn't get less than 8.8cr on the low end and 8.88 on the high end. But I guess we'll see when it's all out together this Feb. Thanks for the replies everybody.
 
CRUZE 418 said:
I have Mr. Gasket head gaskets on my 318, bored .030 over. Part number 1121G, compress to around .028. My engine is stock. Do not believe you can get much thinner than that, at least I couldn't find any.
Click to expand...
YWGScamp72 said:
Thanks all plan is the do the aluminum heads, xe268h cam, air gap, and 750 Holley. Just wanted to make sure there were no abnormalities
Click to expand...
Where are the "clean" spots on the pistons? All by the intake valve, so one cylinder it is on the left and the next on the right?
If you are running an AirGap intake, there is little heat to aid fuel vapourization. This lets fuel droplets from a standard booster carb get into the cylinder. This is wasted fuel, higher emissions and the fuel on the cylinder wall washes the oil off and into the oil pan. Cylinder wall and ring wear go up. Look for a carb with annular boosters in the primary side, for the much better atomization characteristic. On a Holley the boosters may be replaceable, but require knocking the originals out and staking the annular in. There is a company that manufactures a variety they call shear boosters. The new Edelbrock AVS2 carbs have annular primary boosters.
If that "clean spot" went all around the piston it would indicate oil coming up past rings not doing their job. Concentrated where it is, I concur with the other guys on fuel. Between the AirGap, standard boosters and possibly a bit rich fuel mixture explains that.
For a 318 that is mostly street driven, I would recommend changing to an Edelbrock AVS2 650 cfm carb. If you are used to tuning a Holley the Carter/Edelbrock and Rochester carbs take a bit of getting used to. A new carb will come with a tuning manual with a jet/metering rod chart. Once you get it tuned, for serious racing, to adjust for weather conditions you generally just change the metering rods. No spilled fuel.
For head gaskets, Cometic and probably some others, you can get thin MLS gaskets that will aid getting some more static compression. Block deck and head surface finish is critical. I want to use thin MLS gaskets for my Ford 289. The machinist that hot tanked them said the heads had been milled with old technology, probably in the mid to late '70's when the engine was rebuilt to put in the 40 Fordor. To run MLS he will need to skim the heads and possibly the block.
 
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What is MLS? Guessing it is a steel shim, .017 or so?
 
CRUZE 418 said:
What is MLS? Guessing it is a steel shim, .017 or so?
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MultiLayerSteel. Kind of like stacking steel shim gaskets that were somewhat common 60 or so years ago. I know GM used shim gaskets on small blocks about 0.015 thick. Each layer of MLS is thinner.
If I remember correctly for the Ford I could get down to 0.019". Not good to use on a zero deck piston height. Depending on the block, rods and intended RPM, you can run with as little as 0.025 to 0.030 piston to head clearance. That is pushing it a bit. 0.030 to 0.035 would be safer.
 
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Those pistons look like they have the bevel/chamfer around the outside. Sold under a few names.
 
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