Safe Valve Pocket Depth

[Red_Duster]

Hey all. Getting ready to put my 383 together for the ‘68 dart. Nothing fancy, we all have a budget, right? The build is a fresh short block, .030 over with Speed Pro L2315 flat tops .014 in the hole. Cam is the Lunati Bracket Master II with 230@.050 and .480 lift with 2 degrees advance (over the 2 ground in) Stealth Heads, Lunati springs, Comp 1.5 rockers, Edelbrock RPM and TTIs in front a 2500 stall and 3.55s. I have cometic .027s to keep the static compression around 9.9:1. Dynamic should be around 8.9 to 1. Holley sniper on top.

My question is, (hopefully PRH will chime in) I have access to the Lindy pocket cutter and a junk set of 906s. I was thinking about adding valve reliefs before I put everything together and put it in the car in case I ever want to go with 1.6s for more lift. What is a “safe” depth to cut? I was thinking .040 but I don’t want to risk burning through.

I know someone is going to say take them out and to a machine shop, but I think I can tackle this, and have to save for a wedding in October (but she wants the car there!)

 

[RustyRatRod]

Why not call Speed Pro and see if they can tell you the nominal thickness of the piston head? I bet they can.

 

[Red_Duster]

Why not call Speed Pro and see if they can tell you the nominal thickness of the piston head? I bet they can.

Well, I didn’t know the proper terminology to start, so thank you RRR!

But I do remember seeing that folks on here have done it, so I figured I’d ask.

 

[Rat Bastid]

Measure how much piston to valve clearance you have now.

You need piston to head clearance plus .010 for the intake valve and intake valve clearance times 1.6-2.0 and send it.

So, if you have .040 piston to head clearance you need .050 intake piston to valve clearance.

For the exhaust you need that .050 (intake P/V) times 1.6-2.0 which would be .080-.100 exhaust P/V.

Any more than that and you are pissing away compression ratio.

 

[RustyRatRod]

Well, I didn’t know the proper terminology to start, so thank you RRR!

But I do remember seeing that folks on here have done it, so I figured I’d ask.

I have no doubt they can stand .040" but it would be good to know to be sure.

 

[Red_Duster]

Measure how much piston to valve clearance you have now.

You need piston to head clearance plus .010 for the intake valve and intake valve clearance times 1.6-2.0 and send it.

So, if you have .040 piston to head clearance you need .050 intake piston to valve clearance.

For the exhaust you need that .050 (intake P/V) times 1.6-2.0 which would be .080-.100 exhaust P/V.

Any more than that and you are pissing away compression ratio.

Checking springs should be here tonight, but I haven’t ordered pushrods yet. Once there are here, can I mock up without gaskets at measure valve drop at 10 BTDC and 10 ATDC and add the compressed gasket thickness? I don’t have any compressed gaskets and I don’t want to booger those cometics at $90 a pop.

 

[Red_Duster]

Since that cutter runs through the guide (15 degrees?) it’s really cutting an eyebrow more than a true pocket. I wouldn’t think that would have a huge impact on compression and balance? The lock collar should get them all the same on depth if I set it with a feeler gauge, or at least that’s the plan l.

 

[MOPARMAGA]

Hey all. Getting ready to put my 383 together for the ‘68 dart. Nothing fancy, we all have a budget, right? The build is a fresh short block, .030 over with Speed Pro L2315 flat tops .014 in the hole. Cam is the Lunati Bracket Master II with 230@.050 and .480 lift with 2 degrees advance (over the 2 ground in) Stealth Heads, Lunati springs, Comp 1.5 rockers, Edelbrock RPM and TTIs in front a 2500 stall and 3.55s. I have cometic .027s to keep the static compression around 9.9:1. Dynamic should be around 8.9 to 1. Holley sniper on top.

My question is, (hopefully PRH will chime in) I have access to the Lindy pocket cutter and a junk set of 906s. I was thinking about adding valve reliefs before I put everything together and put it in the car in case I ever want to go with 1.6s for more lift. What is a “safe” depth to cut? I was thinking .040 but I don’t want to risk burning through.

I know someone is going to say take them out and to a machine shop, but I think I can tackle this, and have to save for a wedding in October (but she wants the car there!)

What size cutter do you have and stem diameter of the cutter ?
You can clay your pistons with no gaskets between your head and block, just add that thickness to your clearance.
And then everything rat bastid said too

 

[Red_Duster]

What size cutter do you have and stem diameter of the cutter ?
You can clay your pistons with no gaskets between your head and block, just add that thickness to your clearance.
And then everything rat bastid said too

It’s a buddy from work, so I’d have to confirm. He’s a big block Chevy guy and 454 intakes are 2.19, so at least. Probably 11/32 guide for the cutter, but hoping he has a 3/8th.

I’ve see where people make a fly cutter out of an old valve, and I have plenty of stock 906 valves, but the are smaller than what’s in the stealth heads.

 

[MOPARMAGA]

It’s a buddy from work, so I’d have to confirm. He’s a big block Chevy guy and 454 intakes are 2.19, so at least. Probably 11/32 guide for the cutter, but hoping he has a 3/8th.

I’ve see where people make a fly cutter out of an old valve, and I have plenty of stock 906 valves, but the are smaller than what’s in the stealth heads.

Yep you'd definitely want 2.19 for the 2.14s In the stealth .
Hopefully it all works out, good luck!!!

 

[1968rt]

Flat top speed pros have almost 1/2" of aluminum on top. Plenty of room to notch them.

 

[1WildRT]

Flat top speed pros have almost 1/2" of aluminum on top. Plenty of room to notch them.

I recently checked a set of Speed Pro's for a BB Chevy, they were right at .300 & Speed Pro said no thinner than .240.... Obviously not the one I took a picture of.... But that's my mill & my piston vise... And a piston from a engine I sold many years ago...