Don Terrill’s Speed-Talk

I have a set of older non used flat top (just valve reliefs) JE pistons with 5/64 ring grooves. When I bought them, thin rings were not really common yet. I was planning to use a set of Brodix Track 1 heads with standard valve spacing. The project has mushroomed and I'm going for more HP and higher rpms, and I'm going to AFR Eliminator 227s with 60/40 valve split. Have also increased the lift, duration, and tightened the LSA with the new cam. Motor is a 400 cid SBC.

Two questions:
Will I likely have to cut the pistons to have enough radial valve clearance if they were originally cut for standard valve spacing? Will the valve reliefs be deep enough for more duration, and tighter LSA? (of course will check all this during assembly, but want to get an idea of what I might be in for)

Aside from the obvious extra drag and hp loss that fat 5/64 rings will have, will they work and live at up to 7000-7500 rpm in a road racing application?

Thanks for any help in advance.

~~fast freddie

Save yourself headaches and buy new pistons. The valve pocket depth would be a guess, the radial clearance would more than likely be off because of the 60/40 valve movement. The biggest I believe would be the ring package. 5/64 rings will not like 7500 probably would start to lose good seal way before that. Dan

If your really hung up on using those pistons Total seal may have a spacer that will take your compression rings down to far better and power producing 1.2mm size.

It all hinges on how deep your 5/64” ring groove is for them to have the needed spacer or not.

Then you just have to deal with getting the valve notches set up right.

I am going to take a guess that once you get those notches in the right place and deep enough that you will have about 12 CCs of total notch volume you may have to make up for depending on the compression your shooting for.

This may be the make or break factor for using these pistons assume you can notch them deep enough in the first place for a cam lift you have in mind.

I have not check personally on the spacers and narrow rings but have heard that they cost more than new pistons would. they were developed for classes having to use stock size ring grooves. then there is the cost and time of machining the valve pockets. Dan

mag2555 wrote: ↑Tue Jan 24, 2023 5:17 pm If your really hung up on using those pistons Total seal may have a spacer that will take your compression rings down to far better and power producing 1.2mm size.

It all hinges on how deep your 5/64” ring groove is for them to have the needed spacer or not.

Then you just have to deal with getting the valve notches set up right.

I am going to take a guess that once you get those notches in the right place and deep enough that you will have about 12 CCs of total notch volume you may have to make up for depending on the compression your shooting for.

This may be the make or break factor for using these pistons assume you can notch them deep enough in the first place for a cam lift you have in mind.

How much HP are you talking about? He never stated they will see 8000 and will be fine below.
Should be plenty of material to make the pistons work.

af2 wrote: ↑Tue Jan 24, 2023 5:45 pm

mag2555 wrote: ↑Tue Jan 24, 2023 5:17 pm If your really hung up on using those pistons Total seal may have a spacer that will take your compression rings down to far better and power producing 1.2mm size.

It all hinges on how deep your 5/64” ring groove is for them to have the needed spacer or not.

Then you just have to deal with getting the valve notches set up right.

I am going to take a guess that once you get those notches in the right place and deep enough that you will have about 12 CCs of total notch volume you may have to make up for depending on the compression your shooting for.

This may be the make or break factor for using these pistons assume you can notch them deep enough in the first place for a cam lift you have in mind.

How much HP are you talking about? He never stated they will see 8000 and will be fine below.
Should be plenty of material to make the pistons work.

target hp is 650-675, with redline no more than 7500. HP peak around 7K.

Many times people have used standard valve spacing pistons with these heads. It’s just something that has to be measured upon assembly. I have new JE pistons in the box. They say small block chevrolet 20/30 shift on the box. I asked them about it. They sad that meant standard spacing

The mass of 5/64" rings and there sealing abilities start to get very comprised above 6000 rpm and a lot of where they start to go South in there sealing abilitie hinges on the the stroke / piston speed of the motor.

Even a barrel face 5/64" with its minimal contact area starts to get comprised around 6000 rpm.

If your seriously looking for your motor to make peak hp at 7K and above and not have the rings fatigue in just 20 passes then get new Pistons and leave the thought behind of running what you have sitting there now!

5/64 = too much drag/tension ? How about lightening and reducing tension ? How about a skilled design, groove on the back side ?
I know a machinist who works cheap/lol. Art.

Can't help much on cast ring ring mods- it sound like grinding sawed silicon wafers flat prior to printing and cutting computer chips off them. But a few companies make steel ring-spacers to go from your last-century 0.078" ring grooves to modern thin rings. Some spacers are even grooved for gas pressure applications. Didn't keep the names though so you'll have to do some legwork.