Valve to piston tolerances

ckessel · Thursday at 8:30 AM

Have. question for those who are more in the know than I. When running the 66-71 flat top piston, L2266F Speed Pro or the cast version 350P30 that have the 1.990 compression distance, what's the limits on lift/duration before you need to notch?

69L48Z27 · Thursday at 7:19 PM

P to V clearance guidance I always got was .100” exhaust and up to 20 thou less for intake. Put it together and measure.

ckessel · Thursday at 10:03 PM

That part I remember but I also remember there being a rule of thumb that if you kept less than a certain duration @.050, you were good to go. My info quest is for a future rebuild on a 440 for my wagon. I'm going to run the L2266F, or cast equivalent units, when I put it back together. It's currently the low compression, it's a 75, engine. Since I have to do a full build, I'm pre planning for cam possibilities. Figuring on less than 220* @.050 with a 112-114* lobe center.

1 Wild R/T · Thursday at 11:00 PM

ckessel said:
That part I remember but I also remember there being a rule of thumb that if you kept less than a certain duration @.050, you were good to go. My info quest is for a future rebuild on a 440 for my wagon. I'm going to run the L2266F, or cast equivalent units, when I put it back together. It's currently the low compression, it's a 75, engine. Since I have to do a full build, I'm pre planning for cam possibilities. Figuring on less than 220* @.050 with a 112-114* lobe center.

Back in the 80's I ran a DC 509 ([email protected]) with L2266F pistons & per the clay test had over .120 on both intake & exhaust... It was a pig, not enough cylinder pressure for the cam... But it sounded nasty as hell.....

Everyone said the .509 was the cam to run... I learned a lot... Rhoades lifters gave me back my bottom end but the valve clatter sounded like my buddies pickle fork hydro...

Geoff 2 · Friday at 1:31 AM

Wider LSA gives more P to V clearance....but it should be measured at TDC, & 8-10* BTDC for the exh....& 8-10* ATDC for the intake.

ckessel · Friday at 9:37 AM

The 509 is what my 65 had in it when the 440 was in. I wish I hadn't set that engine packing when I pulled it out to start the 65 project. Could have used that for the wagon. Do a better bump stick more suited to the car, reseal it and done. I had limited space and didn't want to store it. Prior to that I learned an expensive lesson. Had an old turkey barn I was using as my shop. Had my 70 Challenger in it, several big blocks, trannies, stuff. Never got around to bringing that stuff down, after booting some, to my new garage. Had to evacuate due to a wildfire and lost everything in that barn. But I still had a house to live in. Since then, I try not to hoard.

PRHeads · Friday at 9:44 AM

Figuring on less than 220* @.050 with a 112-114* lobe center.

With the proposed short block, that’ll have plenty of clearance.
Might possibly be iffy if you milled the heads .100” or so.

ckessel · Friday at 10:14 AM

Thanks for that Dwayne. I don't plan on having that much shaved. Just enough on them and the decks to get them all trued up.

ckessel · Friday at 3:26 PM

Just to throw it out there, the heads are 902 castings. I'm assuming mid 70's smoggers, like 452's, with hardened seats.

BSB67 · Friday at 3:39 PM

Rule of thumb from the 70s-80s is that the MP 509 will clear the 68-69 pistons (2.030”). Won’t clear 383 w/ 1.932” piston.

Rules change with block or head milling, and oversize thick margin SS valves.

Valve to piston tolerances

ckessel

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69L48Z27

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ckessel

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1 Wild R/T

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Geoff 2

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ckessel

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PRHeads

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ckessel

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ckessel

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BSB67

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