Closed chamber with flat tops

[Cudaroy]

Hi all,
I recently bought a 318 that had been rebuilt 5K ago. It has flat top pistons without reliefs and is running closed chamber 53005714 heads.
When I saw the ad It was still in the car and I wanted to hear it run so I went to hear it and it had a mild knock ( disclosed by seller). I bought the long block for $100 and a week later brought it home. I discovered that the #4 rod bearing was smoked as well as the crank journal. I have 2 other engines (68 and 69 318's) that I hope has a usable crank.
When I pulled the pan I saw what I first thought was a wrist pin retainer ring. I yanked the heads and removed the pistons to find that the wrist pins are non floating so it wasn't that. I then discovered the wire retainer was for the #2 intake lifter. Never saw that before.
I noticed that two pistons had slight contact marks from the valves but was told that they were running 1.6 rockers before going back to the 1.5 273 rockers. The marks were not "fresh" and it did not run bad like a bent valve scenario.
It has a comp cams 340 HP replacement cam- [email protected] lift.
Is this too big of a cam with flat tops without reliefs with the closed chamber heads?

 

[moper]

Sounds more like it was overreved. The lifter clips do ocasionally come out. I've seen it on several brands although the most consistently are the ones from Edelbrock that use a flat steel rather than round wre clip.
I would have the valve springs checked - if it's a 340 replacement cam and they left the 318 springs there's your reason for the clips popping and piston "eyebrows". If should fit with no problem, but like any cam, the valve springs have to be upgraded to match the cam and they need to be set up properly to give the right pressures.

 

[Cudaroy]

Thanks for the quick reply........the springs were replaced with the recomended ones from Comp cams........over revving? Most certainly.
My biggest concern is the use of non relief flat tops with closed chamber heads. I did not measure how far down the hole the pistons are but it isn't much. I can not find any info on the heads but know they are small valve. The block is a '90 LA 318 and assume the heads are also '90 vintage.
Just wondering if anybody has had a similar setup and had any issues with clearance.

 

[moper]

That's whay I'm talking about tho - there is no difference in distance from valve to piston between open or closed chamber head designs. To me, the fact that it's only one or two cylinders says it's not a consistent issue. Chances are they are at least .040 down, and the gasket is the same thickness. The cam is not lifting the valve much - the "normal" max for a small block is around .520 lift. Even with 1.6s I don;t think you're there.
Regardless - if it's apart get yourself a dial indicator and some play dough and measure how close they get on a few holes.

 

[Cudaroy]

That's what I wanna hear. I realize it is by no means a radical cam and should not see clearance issues and didn't know about the open/closed valve height...thanks.
Just want to build a dependable little 318 for the 68 Fastback I just picked up. Going for a vintage type build with a '68 LD4B intake, old '61 413 600cfm carb, etc.

 

[Cudafever]

That's what I wanna hear. I realize it is by no means a radical cam and should not see clearance issues and didn't know about the open/closed valve height...thanks.

The exception to the Rule!..... if these heads were an open chamber head that was cut down to create a closed chamber, Your Valve to Piston clearance is a lot closer now.
What is the part ## on these heads.

How many thousandth is the piston in the hole at TDC.

 

[Cudaroy]

Part #53005714 on the heads........These were never open chambered I am sure. If they were milled THAT much I'm sure we would probably have 3 sided ports LOL! All I know about the heads is they are 1.78-1.5 valves.
I haven't measured how deep in the hole they are yet........kinda a moot point after Moper's schooling of me.
Thanks.