Opinion: Walnut blasting ceramic ports
#1
Instructor
Thread Starter
Opinion: Walnut blasting ceramic ports
I was looking for your experiences and opinions on using walnut blasting to clean carbon on ceramic exhaust ports.
1) Too aggressive and more damage than good.
2) Good idea thoroughly clean carbon.
3) What the hell, give it a shot. This is commonly suggested by people trying to sell a used head.
My thought is this is a common cleaning idea used on intake ports for direct injection engines and not sure how it would be for ceramic on exhausts.
Here’s a gratuitous picture taken from a google search.
1) Too aggressive and more damage than good.
2) Good idea thoroughly clean carbon.
3) What the hell, give it a shot. This is commonly suggested by people trying to sell a used head.
My thought is this is a common cleaning idea used on intake ports for direct injection engines and not sure how it would be for ceramic on exhausts.
Here’s a gratuitous picture taken from a google search.
#2
Rainman
Rennlist Member
Rennlist Member
Walnut blasting is to clean the carbon **** out of ports and valves on DI engines that don't have the constant mist of excellent solvent (gasoline) raining down on everything.
Your exhaust ports probably have some carbon on them making them black as a result of combustion. It would only be really heavy if you had a serious oil burner on your hands.
It's like when guys pull the head on their engine and spend all kinds of time cleaning the pistons...it's all going to be "dirty" again in about 10 minutes of running, so why bother?
Your exhaust ports probably have some carbon on them making them black as a result of combustion. It would only be really heavy if you had a serious oil burner on your hands.
It's like when guys pull the head on their engine and spend all kinds of time cleaning the pistons...it's all going to be "dirty" again in about 10 minutes of running, so why bother?
#3
Three Wheelin'
I work at a shop that specializes in Porsche and BMW/Mini, and we also do some Audi work. Porsche tends to design effective breather systems, so we do not see too much of an issue with carbon buildup on the intake valves/ports of their DFI engines. However, on the DFI BMW N54 engines, Mini N14 engines and anything VW/Audi we see lots of carbon buildup, and do a fair amount of walnut shell blasting (which works as well as pictured above).
I remember seeing BMW literature from the 1980s advocating the use of walnut shells to remove hard carbon deposits from intake valves, which tended to form as a result of the poor early formulations of the unleaded gasoline of that period (the oil-based carbon the builds up on the valves/ports of DFI engines tends to be softer and gummier, much of it can be manually removed with pick tools).
Anyway, the main reason for using walnut shells is that it can safely performed on an engine installed in the car. During the service, the engine is turned over until the valves of the intake port being worked on are closed; the goal is to vacuum out as much of the walnut media as possible, but if a small amount end up in the combustion chamber, it is not the end of the world as the shells will quickly burn up.
As for a 944 head that is disassembled and removed from the car, simply use a soda blasting cabinet. I have one at my shop and use it all the time on aluminum cylinder heads. It instantly blasts off any hard carbon buildup. I understand that your concern may be the delicate nature of the ceramic exhaust ports used in the Porsche 951 heads (also used on the 964/993 heads). Walnut shells might be "softer" than grains of baking soda, but there are other variables such as air pressure, duration of blasting, etc. The bottom line is that 30+ year old ceramic port liners are susceptible to cracking no matter what, but if there is heavy carbon buildup, you will need to blast them anyway to find out!
Hope this helps, good luck with whatever you decide.
I remember seeing BMW literature from the 1980s advocating the use of walnut shells to remove hard carbon deposits from intake valves, which tended to form as a result of the poor early formulations of the unleaded gasoline of that period (the oil-based carbon the builds up on the valves/ports of DFI engines tends to be softer and gummier, much of it can be manually removed with pick tools).
Anyway, the main reason for using walnut shells is that it can safely performed on an engine installed in the car. During the service, the engine is turned over until the valves of the intake port being worked on are closed; the goal is to vacuum out as much of the walnut media as possible, but if a small amount end up in the combustion chamber, it is not the end of the world as the shells will quickly burn up.
As for a 944 head that is disassembled and removed from the car, simply use a soda blasting cabinet. I have one at my shop and use it all the time on aluminum cylinder heads. It instantly blasts off any hard carbon buildup. I understand that your concern may be the delicate nature of the ceramic exhaust ports used in the Porsche 951 heads (also used on the 964/993 heads). Walnut shells might be "softer" than grains of baking soda, but there are other variables such as air pressure, duration of blasting, etc. The bottom line is that 30+ year old ceramic port liners are susceptible to cracking no matter what, but if there is heavy carbon buildup, you will need to blast them anyway to find out!
Hope this helps, good luck with whatever you decide.
#4
Three Wheelin'
Walnut blasting is to clean the carbon **** out of ports and valves on DI engines that don't have the constant mist of excellent solvent (gasoline) raining down on everything.
Your exhaust ports probably have some carbon on them making them black as a result of combustion. It would only be really heavy if you had a serious oil burner on your hands.
It's like when guys pull the head on their engine and spend all kinds of time cleaning the pistons...it's all going to be "dirty" again in about 10 minutes of running, so why bother?
Your exhaust ports probably have some carbon on them making them black as a result of combustion. It would only be really heavy if you had a serious oil burner on your hands.
It's like when guys pull the head on their engine and spend all kinds of time cleaning the pistons...it's all going to be "dirty" again in about 10 minutes of running, so why bother?
So, a bit of time spent cleaning each piston top (while at TDC and by hand/solvent, NOT with any kind of air tool or grinder!) is worth it.
Now, if said carbon buildup is due to excessive blow-by from worn out piston rings/bores, then the whole thing needs to come apart and be cleaned and/or replaced!