CNC heads clarification
CNC heads clarification I just received a set of new 821 heads that have been CNC ported. I think they came from an individual that works at a sponsor, regardless. The intake port has a hole in it, where the rocker bolt comes in. I questioned this, and the reply was, that's common with big port heads. That PRC.and Mast have produced the same, at some point. Is this valid?
Also, on the same heads, in the combustion chamber the area between the valves varys. One head in particular. One end is tight, the other end is a shoulder of 3/16 inch. ?
Looking to the experience of you all for clarity.
My background, playing with hp on a small scale for years. The last five years I dove right in! I have 30k plus in LS engines and parts on the shelf!
Also, on the same heads, in the combustion chamber the area between the valves varys. One head in particular. One end is tight, the other end is a shoulder of 3/16 inch. ?
Looking to the experience of you all for clarity.
My background, playing with hp on a small scale for years. The last five years I dove right in! I have 30k plus in LS engines and parts on the shelf!
How about the shoulder between the valves? Seems to me something isn't in line?
TECH Addict
Joined: Dec 2017
Posts: 2,190
Likes: 976
The rocker bolt hole becoming exposed by porting is BEYOND "common". It's rare that it DOESN'T happen. Even in a mild minimal CNC program like that one.
As said, just put thread sealer on the bolts. Use the Permatex/Loctite "automotive thread sealant with PTFE"; NOT any kind of RTV. Gasoline will dissolve silicone.
You can add a washer under the bolt heads to keep them from protruding into the ports. You can also Heli-Coil the threads, which makes them MUCH more robust than just the aluminum by itself is.
As far as the variation in the space between valves, yes of course, that's pretty sloppy. Typical factory machine work. OTOH, THIMK for a minute about what you'd have to do to change it. You'd have to replace the guides to re-orient the valves, remove the existing seats, cut in new counterbores for them, and install new seats, which most likely would have to be larger than the OE. At some point, all that machine work gets PROHIBITIVELY expensive; i.e. not worth it. Since those look to be a "Stage 1" kind of port job, not what could be considered "max effort" or whatever, part of what you're NOT paying for in those, is that much machine work.
As said, just put thread sealer on the bolts. Use the Permatex/Loctite "automotive thread sealant with PTFE"; NOT any kind of RTV. Gasoline will dissolve silicone.
You can add a washer under the bolt heads to keep them from protruding into the ports. You can also Heli-Coil the threads, which makes them MUCH more robust than just the aluminum by itself is.
As far as the variation in the space between valves, yes of course, that's pretty sloppy. Typical factory machine work. OTOH, THIMK for a minute about what you'd have to do to change it. You'd have to replace the guides to re-orient the valves, remove the existing seats, cut in new counterbores for them, and install new seats, which most likely would have to be larger than the OE. At some point, all that machine work gets PROHIBITIVELY expensive; i.e. not worth it. Since those look to be a "Stage 1" kind of port job, not what could be considered "max effort" or whatever, part of what you're NOT paying for in those, is that much machine work.
The rocker bolt hole becoming exposed by porting is BEYOND "common". It's rare that it DOESN'T happen. Even in a mild minimal CNC program like that one.
As said, just put thread sealer on the bolts. Use the Permatex/Loctite "automotive thread sealant with PTFE"; NOT any kind of RTV. Gasoline will dissolve silicone.
You can add a washer under the bolt heads to keep them from protruding into the ports. You can also Heli-Coil the threads, which makes them MUCH more robust than just the aluminum by itself is.
As far as the variation in the space between valves, yes of course, that's pretty sloppy. Typical factory machine work. OTOH, THIMK for a minute about what you'd have to do to change it. You'd have to replace the guides to re-orient the valves, remove the existing seats, cut in new counterbores for them, and install new seats, which most likely would have to be larger than the OE. At some point, all that machine work gets PROHIBITIVELY expensive; i.e. not worth it. Since those look to be a "Stage 1" kind of port job, not what could be considered "max effort" or whatever, part of what you're NOT paying for in those, is that much machine work.
As said, just put thread sealer on the bolts. Use the Permatex/Loctite "automotive thread sealant with PTFE"; NOT any kind of RTV. Gasoline will dissolve silicone.
You can add a washer under the bolt heads to keep them from protruding into the ports. You can also Heli-Coil the threads, which makes them MUCH more robust than just the aluminum by itself is.
As far as the variation in the space between valves, yes of course, that's pretty sloppy. Typical factory machine work. OTOH, THIMK for a minute about what you'd have to do to change it. You'd have to replace the guides to re-orient the valves, remove the existing seats, cut in new counterbores for them, and install new seats, which most likely would have to be larger than the OE. At some point, all that machine work gets PROHIBITIVELY expensive; i.e. not worth it. Since those look to be a "Stage 1" kind of port job, not what could be considered "max effort" or whatever, part of what you're NOT paying for in those, is that much machine work.
TECH Addict
Joined: Dec 2017
Posts: 2,190
Likes: 976
I`m disappointed at the workmanship out there
I`m disappointed at ... the clarity of sellers disclosure
Q: How can you tell a used car seller is lying?
A: His lips are moving
Q: How can you tell a used car seller is stabbing you in the back?
A: He's smiling
And so on...
Trending Topics
My AFR 225 cathedrals had the same problem. As stated, most intake ports have this issue. Make sure you not only seal the threads, but also make sure none of the rocker bolts/studs are long enough to protrude into the port. This would obstruct airflow, and kinda hinder the CNC porting. I experienced this, and shortened the bolts just a tiny bit.....
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
