Head porting question

[6spdYJ]

Hi all, I've been lurking for a few years and finally had all of the components come together so my build is getting started. I want to do the head work before it all goes to get bored, decked, and the valve job. I'm keeping stock size valves because I'm aiming at a low-end torquer.

1996 NVH block .030, 7120 head, 258 12CW crankshaft, KB10177-030 pistons.

The gist of this post is a few questions about chamber wall angles and exhaust valve guide boss shaping. I've been searching and can't find exactly what I'm looking for. So, on the spark plug side of the chamber, what is a good angle for that wall? It looks like i can bring the bottom of the wall out and make it more vertical to get some more Cc's. I've seen the spark plug wall described as 9*. It's far from 9* according to my eyecrometer. According to the compression calculator I'm aiming for 61.7 Cc's. Would this be a good approach to gain some volume and possibly assist swirl?

The next question is about the exhaust valve guide boss. I haven't seen any pictures posted online that show any shaping to the flat milled surface. I looked as close as I could and saw that the flat nearly lines up with the floor of the port into the header. My thought was to just round the sharp edges and polish it because I can imagine the exhaust stream smashing into the flat and causing turbulence before it leaves the head. Is this left alone for guiding flow to the port?

Thank you all for the shared knowledge and experience!

[mpgMike]

I first sit the head on the bare block and from the bottom, mark the cylinder bore around the exhaust valve. I grind that area out to the cylinder bore to enhance flow through the exhaust valve. Next, I radius the sharp transitions from open chamber to squish pad. In the exhaust port, I bullet-shape the guide boss and smooth transitions from seat to pocket. Intake side I try to open up the area around the guide ON THE CYLINDER WALL SIDE. This promotes a swirl as the charge enters the cylinder. Of course, blending away factory machined sharp transitions. For low-end torque, you don't want to open the ports larger, they're plenty big.

CC1.png

CC1Txt.png

[6spdYJ]

I made a set of go/no go gauges for both valves. The intake 80% gauge fell in. It's only getting blended in the throat. I checked the exhaust at 80% and it almost passes down to the bowl. The 85% gauge sits just below the valve seat. On the exhaust side, would you recommend 80% (1.20") or 85% (1.275")?

[eugenebuilt]

1996 NVH block .030, 7120 head, 258 12CW crankshaft, KB10177-030 pistons.

According to the compression calculator I'm aiming for 61.7 Cc's.

I can’t answer your question directly, but curious about a couple things in your post.

1. How did you source those pistons, directly from UEM or from a dealer? Which dealer?

2. Your 61.7cc target is interesting, help me understand why so much effort to work greater volume from the head side instead of using a piston with a greater dish? Just working with what you have, or is there a more specific reason?

I’m a student here and in the middle of my own build, my questions are genuine curiosity - no judgement.

I have questions for mpgMike about that head work in his image but I’ll post in his project page

[6spdYJ]

I ended up getting them from a local wholesaler. Maybe it's just my luck but they were tough to find. I was originally looking for the KB438C and called UEM directly to find out those are discontinued. The KB10177 is the same piston but with the metric ring pack. They matched Summit's price and had local pickup. The one thing I missed when I ordered them was the height of 1.363 instead of 1.353. I'll just measure and deck it for. 008" above deck like Russ does. I bought my rods from him. Shout out to Russ!
Getting 61.7cc from a 58cc chamber isn't really a lot of material removal compared to guys that open them out to 66 or so. My target is 9.5 static and 8.5 dynamic cr with. 035 quench. I'm probably going to have to act like a mature adult when I get it done because I'm certain it's going to easily deliver more torque than my transmission is rated for.

[eugenebuilt]

I ended up getting them from a local wholesaler. Maybe it's just my luck but they were tough to find. I was originally looking for the KB438C and called UEM directly to find out those are discontinued. The KB10177 is the same piston but with the metric ring pack. They matched Summit's price and had local pickup. The one thing I missed when I ordered them was the height of 1.363 instead of 1.353. I'll just measure and deck it for. 008" above deck like Russ does. I bought my rods from him. Shout out to Russ!
Getting 61.7cc from a 58cc chamber isn't really a lot of material removal compared to guys that open them out to 66 or so. My target is 9.5 static and 8.5 dynamic cr with. 035 quench. I'm probably going to have to act like a mature adult when I get it done because I'm certain it's going to easily deliver more torque than my transmission is rated for.

Thanks for your reply.

Yes, looks like the legacy 1.353 Icon and KB series are elusive across the board potentially replaced by the 1.363 variety which are also elusive at dealers because dealer catalogs don’t yet reflect UEM catalog. I had a bit of luck myself finding the last set of IC944.030 from UEM after about 20 phone calls and 3 weeks of waiting.

I get you on the CC work, wondering if I should consider similar on my project while head is still at machine shop (I’m not comfortable doing this myself). They’re already replacing valve seats and guides to match the LS valve kit I got from Russ. Before I took it to machine shop I measured 0331 TUPY head at 55.9cc which would net me 10:1 SCR and 8.6:1 DCR with my cam recommendation from Russ if CC volume is unchanged which should be ok for 91 octane but wouldn’t mind it lowered a bit. I’ll see where it measures after valve work.

Following your handle in case you post build updates

[6spdYJ]

I wanted a D dish hypereutectic and Kb438c was about all that came up. I couldn't find them so I called UEM. They said they had 37 sets on the shelf. Nobody could get them. Out of near desperation I called the wholesaler and the salesman was so cool, he called UEM and kept on it until he got the part number for the KB10177. And then he matched Summit's price for the KB438C. Being a wholesaler, he didn't even have to give me the time of day. Awesome guy!

[eugenebuilt]

I wanted a D dish hypereutectic and Kb438c was about all that came up. I couldn't find them so I called UEM. They said they had 37 sets on the shelf. Nobody could get them. Out of near desperation I called the wholesaler and the salesman was so cool, he called UEM and kept on it until he got the part number for the KB10177. And then he matched Summit's price for the KB438C. Being a wholesaler, he didn't even have to give me the time of day. Awesome guy!

37 on the shelf and nobody can place an order. That’s nuts.

You helped me fill in a blank with the KB438c part # on my write up about the superseded part #s here: viewtopic.php?t=6894

Good to know these exist and sitting at UEM. In case you try again on a different project in the future you could try this: ask UEM which warehouse those KB438C are sitting and then order through a dealer by phone with drop ship instructions to that UEM warehouse. This will prompt a superseded notice in favor of the new part but you could call the dealer and insist they push the order with original part to UEM warehouse as requested. Then call UEM referencing your dealer order number and explain the situation and request assistance fulfilling the original part from the warehouse holding the part. This is exactly how I got ahold of my IC944, with a touch of patience.

[6spdYJ]

I went to UEM's website and checked their retailers list and checked to see if any were in my area. Summit would have been an option but going local pickup was a 100% safeguard against porch pirates.

I'm still open to opinions about opening the exhaust port under the valve seat. I'm leaning toward 85% (1.275") to let it breathe. I can't help but think it'll help the short radius be less of an overhang and help laminar flow. 80% (1.2") might help velocity. I would really appreciate anyone's voice of experience.

At the exhaust port, I'm looking to only polish the floor and leave the step to fight reversion, but raise the roof to match the header tube.

[mpgMike]

If the exhaust port in the head is slightly smaller than the port in the header, that becomes an anti-reversion mechanism. Perhaps reconsider opening out the exhaust port in the head.

[6spdYJ]

So far I've accomplished absolutely nothing. One thing I found is that I can get a Victor/Rines head gasket in .028" thickness. If I use this, I can have the piston .007" down in the bore instead of. 008" above deck. If I do this, it still allows using the. 043" head gasket as an option. I see the thinner gasket as less likely to fail (in a very unlikely failure point). It will also reduce the milling needed for the deck height.