Hastings Ring Gap?

[HTMLmopars]

I'm actually starting to put together the bottom end of my .020" over 318 after way too many months (whoever it was on here that told me to pay them to build my motor was probably right), I'm finally measuring ring gap for the motor. Basically it's just going to be a mild street/strip motor, I don't want to baby the thing, but it's only getting 9.4:1 compression and is essentially destined for a lot of street driving.
Now the question, I'm trying to get my ring gap dialed in accurately. I have a set of Hastings rings going on some KB 167 pistons and according to the Hastings webiste, I should have between .012" and .022" ring gap. From the research I've done, it seems like .020" to .030" is pretty reasonable. I measured one ring at .019" before I decided to get a better target.
Obviously I don't want the gap to be too big, but is it worth the time to open the rings up to closer to .025"? This is my first engine build and so I'd rather go on the cautious side rather than the more aggressive side.

 

[1WildRT]

The key to your puzzle is this..... KB 167 pistons.... Hastings didn't make the piston... So they don't know your running a Hyperutectic piston which needs a wider ring gap than a standard cast piston or a forged piston.... Go the the KB piston website & see what they have to say...

Or....

 

[MOPAROFFICIAL]

.028-.030 will be fine with a good tune.
.032 would add insurance for a bad tune

I would use .030 gap on the top ring and watch the timing during break in 'keep it around 28-32 total'.
That's on the cautious side, not that it necessarily need that little.
Jmo.

The dynamic or cylinder pressure/cranking is what will really impact it.

 

[RustyRatRod]

I agree with Justin's post #3. A bit wider is what you will be safe with. Trust me, you don't want them under .020". No way. I would go .030 in a heartbeat.

 

[Bakerlite]

Ah!! The old KB trap!!!

 

[golden boy]

all the engine builders i talk to won't build an engine with KB pistons unless they gap the top rings @ .030+ (4"bore). i, of course found out the hard way.

 

[MOPAROFFICIAL]

all the engine builders i talk to won't build an engine with KB pistons unless they gap the top rings @ .030+ (4"bore). i, of course found out the hard way.

Pretty much. Only if you build a 9.5 comp or sub 170lb dynamic/cranking motor can you run .028 or .029 and survive.
I'll be running .034 or .035 on my next stroker incarnation.

 

[RustyRatRod]

Pretty much. Only if you build a 9.5 comp or sub 170lb dynamic/cranking motor can you run .028 or .029 and survive.
I'll be running .034 or .035 on my next stroker incarnation.

I remember talking to Marco YEARS ago when I was wanting some ring gap advice. He said "don't be afraid to give enough gap to drive a bus through it". LOL

 

[HTMLmopars]

Thanks for all the info! I kinda picked up someone's unbuilt motor, so it's not like I researched and bought all of the parts. Little bit of detective work for me, but it's getting closer.
Looks like .032" is probably a good target for me, and the image above says 2nd ring is fine to be gapped normally, so those will be .020" target gap?

 

[MOPAROFFICIAL]

I remember talking to Marco YEARS ago when I was wanting some ring gap advice. He said "don't be afraid to give enough gap to drive a bus through it". LOL

In my early years of learning I literally gapped the top ring .075 on my 340 w/kyb.
Pulled hard LOL

 

[RustyRatRod]

In my early years of learning I literally gapped the top ring .075 on my 340 w/kyb.
Pulled hard LOL

I'm sure. lol

What's your opinion on the 2nd ring gap? I've always gapped them to the top ring spec. I mean.......look at the consequences. LOL

 

[MOPAROFFICIAL]

Thanks for all the info! I kinda picked up someone's unbuilt motor, so it's not like I researched and bought all of the parts. Little bit of detective work for me, but it's getting closer.
Looks like .032" is probably a good target for me, and the image above says 2nd ring is fine to be gapped normally, so those will be .020" target gap?

.024

 

[MOPAROFFICIAL]

I'm sure. lol

What's your opinion on the 2nd ring gap? I've always gapped them to the top ring spec. I mean.......look at the consequences. LOL

For all my years I've left them stocks back I've never really paid attention so I think it was like .018-.020, but with higher compression 'ragged edge' I'd add some to it as well. A spread of .008-.010 ex .034 top and .024-.026 second.
Again... I've left them to stock spec too.

 

[AJ/FormS]

i, of course found out the hard way.

Hyup; as did I. I fought what I thought was an overheating issue, for months. Finally I took the engine out and apart and opened up that top gap; and presto! the engine got a whole new personality.

To the OP:
Here's a tip for you;
The ring gap changes by .0031416 inch per .0010 bore change.
You can use this tidbit of information to measure all your bores, using the same ring, to find the hole-size variation. Mark the holes from smallest to largest. Then, in the smallest hole fit each top ring to find the tightest or loosest rings by the size of the gaps. Then match-fit each ring to each hole, so that your ring-gaps are all the same and you don't have one or two cylinders with tighter gaps.
This is especially useful if you are file-fitting your rings.
By starting in the smallest cylinder, if you file too big a gap, just move the ring to a bigger hole.
What? you think 20-over means something?
Well, around here it doesn't seem to. My 40-over holes varied enough to, by using the same ring, the gaps varied over .003 inch. After I had a different machine-shop straighten and equalize the bores, what was originally supposed to be a 4.040 bore, they ended up mostly at 4.045.... and my KB107s were did nuts all the same to about 4 decimal places. For my street application, KB listed the skirt clearance at .0015 to .0020;
Yeah so the pistons ended up being a lil baggy, which really disappointed me. As it turns out tho, after some experimentation with the minimum running temperature (I ended up at 207*F in compensation), that is just what this combo needed; she turned into a wicked sweet engine.
OP I wish you all the best.

Now; as to your 9.4 Scr; you said;

Basically it's just going to be a mild street/strip motor, I don't want to baby the thing, but it's only getting 9.4:1 compression and is essentially destined for a lot of street driving.

I googled Skaget and get elevations ranging from zero to 5740 ft. but typically 3400ft.
If this is correct;
then you are gonna have to be careful with cam selection, so as to get an altitude-compatible cylinder pressure, at 9.4Scr.
That is to say, the stock 318 cam has an Ica of about 50*, and is predicted to make around 152psi@3400ft which is great. But; If you take that car down to sealevel, the pressure is predicted to rise to over 170, but at 5700ft is just 140. That 170psi in an open chamber iron head design, is usually iffy to operate even with 91 octane gas.
The smallest performance cam that you might consider is likely to be around 262 advertised, which you might install at an Ica of say 59*. This is predicted to drop your pressure to 140psi@3400, 158psi@sealevel, but just 128@5700
So keep those things in mind. Or maybe you already have......... IDK.

You can mitigate some of that gross pressure difference by
1) not taking the car too far from it's home base, or
2) using a solid-lifter cam-design with fast ramps. Also,
3) alloy heads will like more pressure.

 

[HTMLmopars]

Now; as to your 9.4 Scr; you said;

I googled Skaget and get elevations ranging from zero to 5740 ft. but typically 3400ft.
If this is correct;
then you are gonna have to be careful with cam selection, so as to get an altitude-compatible cylinder pressure, at 9.4Scr.
That is to say, the stock 318 cam has an Ica of about 50*, and is predicted to make around 152psi@3400ft which is great. But; If you take that car down to sealevel, the pressure is predicted to rise to over 170, but at 5700ft is just 140. That 170psi in an open chamber iron head design, is usually iffy to operate even with 91 octane gas.
The smallest performance cam that you might consider is likely to be around 262 advertised, which you might install at an Ica of say 59*. This is predicted to drop your pressure to 140psi@3400, 158psi@sealevel, but just 128@5700
So keep those things in mind. Or maybe you already have......... IDK.

You can mitigate some of that gross pressure difference by
1) not taking the car too far from it's home base, or
2) using a solid-lifter cam-design with fast ramps. Also,
3) alloy heads will like more pressure.

The car is going to pretty much live at and around sea level, so setting it up for dense air is more important than performance at high altitude.
To note, I had the 9.4 number in my head and didn't check my notes, that was my potential highest number with some pretty big work to get there. Sorry for throwing that out there. The real number is right in the neighborhood of 9.0:1 depending on what head gasket I use.
I'm planning on running a Hughes hydraulic roller conversion cam, primarily because I got into this project by installing a flat tappet cam and then not breaking it in correctly/poor metallurgy causing it to go flat. Plugging in the numbers on the Hughes cam using the online calculator I found (which must be 100% accurate), I was getting a touch under 170psi @1000ft. A couple other calculators were giving me lower dcr numbers, but no psi to reference and no altitude input

 

[crackedback]

I remember talking to Marco YEARS ago when I was wanting some ring gap advice. He said "don't be afraid to give enough gap to drive a bus through it". LOL

Marko at UEM. I worked with him in 1982-1985 for a while before he went to Mallory then on to UEM. He had a rally nice 55 Chevy. the plate FSTRNU

 

[RustyRatRod]

Marko at UEM. I worked with him in 1982-1985 for a while before he went to Mallory then on to UEM. He had a rally nice 55 Chevy. the plate FSTRNU

That's funny. Always liked him. Spoke with many times back when I was really building a lot of engines. Really a big help.