Waldi Posted March 31, 2018 Report Share Posted March 31, 2018 My CP engine has 2 core plugs on the front side. The parts manuals only show one plug. I replaced one, but am not sure about the other: is it the flat spherical type as currently installed or the cup type? Thanks, Waldi Quote Link to post Share on other sites
ed_h Posted March 31, 2018 Report Share Posted March 31, 2018 Waldi-- I'm pretty sure mine was originally a cup type. I replaced it with a cup type, but I'm not sure it really matters. Ed Quote Link to post Share on other sites
Waldi Posted March 31, 2018 Author Report Share Posted March 31, 2018 Thanks Ed. I prefer the cup type, as it provides a larger seal area, especially when the bore is not 100%. Will go with that. Regards, Waldi Quote Link to post Share on other sites
Fireman049 Posted March 31, 2018 Report Share Posted March 31, 2018 Hi Waldi ~ In days of old when I was an apprentice mechanic we used to cover the back of the cup type core plugs with a coating of solder to prevent corrosion taking place. (This was in respect of core plugs fitted in the cooling system). Tom. Quote Link to post Share on other sites
Waldi Posted March 31, 2018 Author Report Share Posted March 31, 2018 (edited) Hi Tom, That would have been a good approach especially in the days where more water was added and corrosion inhibitors as in modern coolants not as common as today. Basically it provided cathodic protection, as long as it was not covered with chalk (CaCO3). Regards, Waldi Edited March 31, 2018 by Waldi Quote Link to post Share on other sites
astontr6 Posted March 31, 2018 Report Share Posted March 31, 2018 Hi Tom, That would have been a good approach especially in the days where more water was added and corrosion inhibitors as in modern coolants not as common as today. Basically it provided cathodic protection, as long as it was not covered with chalk (CaCO3). Regards, Waldi When I re-built my engine after 44 years of use and came to remove the old core plugs. I was surprised at how thin they were caused by corrosion. They would not have lasted much longer before leaking even though I had used Distilled water since new and quality anti-freeze with tri-annual changes. Therefore if you have the block out, change the lot in my view, especially if they have been in for a good few years. I am also not certain as to the quality of my replacements as 2 of them have leaked from the inside edge through cracking but luckily they were the easy to get at ones! Bruce. Bruce. Quote Link to post Share on other sites
Waldi Posted April 3, 2018 Author Report Share Posted April 3, 2018 Just to complete the story: I removed the old dished core plug, to find the bore had a recess, so only a dished plug will fit. It was, as expected, pretty corroded. So I guess on the front of a CP engine (and maybe also on others), there is one (deep) cup type core plug and one dished ("flat") plug. All plugs I needed for block and head were in the set I bought from Moss, all fitted well. Regards, Waldi Quote Link to post Share on other sites
ed_h Posted April 3, 2018 Report Share Posted April 3, 2018 My 74 CF block must not have had that stepped bore, or possibly the step was much deeper. You can se in my pic above that a cup type plug went full depth. Ed Quote Link to post Share on other sites
Waldi Posted April 3, 2018 Author Report Share Posted April 3, 2018 Hi Ed, I technically prefer the cup type, the likelihood for leakage is smaller since it does not have a line contact but a wider band. All other plugs in my engine are cup type, not sure why this one is not. As always, there probably is a reason for it. Regards, Waldi Quote Link to post Share on other sites
M. Pied Lourd Posted August 6, 2020 Report Share Posted August 6, 2020 Thank you for this thread...I’m just encountering the same problem on my TR250 engine build. I have the cup type and also have the recess...I’m thinking of carefully grinding down the lip of the cup one the ensure it is flush (or slightly below) the face of the block so the gasket and front engine plate fit correctly over it...it is the right diameter plug but not the right depth. Any thought on this approach? Don’t think I want to wait 2 weeks for a new dished one... Cheers Tush Quote Link to post Share on other sites
Waldi Posted August 6, 2020 Author Report Share Posted August 6, 2020 Hi Tush, I would not cut the plug, it’s sealing principle relies on the elastic behaviour, which the “skirt” provides, like a very stiff spring. Also not worth taking chances given the amount of rework needed if it starts leaking. Just my 2cts. Best regards, Waldi PS: good to see you on the forum every now and then, I watched several of your video’s when I was wondering “how others did it”, so thanks for that effort! Quote Link to post Share on other sites
M. Pied Lourd Posted August 6, 2020 Report Share Posted August 6, 2020 (edited) Thank You for the reply. I'll see how long it will take to get the other style to me.... I figured it could work as there will be at least 1/2 of the edge of the cup to still seal along with a little RTV around the edge....plus the plug would be held in with the gasket and front engine plate....you are right though, I would hate to have to take it back out again. I am planning on doing my engine break in prior to putting the body back on but I am not sure a 20 minute break in time would be sufficient to know if it was leaking or not.... As an aside, I have sent the Vendor I purchased this plug kit from to see if anyone else has reported issues with the fitment....this kit was marketed as a TR250 kit so I don't want others to run into the same issues... Cheers Tush Edited August 6, 2020 by M. Pied Lourd Quote Link to post Share on other sites
Graham J Posted August 7, 2020 Report Share Posted August 7, 2020 10 hours ago, M. Pied Lourd said: Thank You for the reply. I'll see how long it will take to get the other style to me.... I figured it could work as there will be at least 1/2 of the edge of the cup to still seal along with a little RTV around the edge....plus the plug would be held in with the gasket and front engine plate....you are right though, I would hate to have to take it back out again. I am planning on doing my engine break in prior to putting the body back on but I am not sure a 20 minute break in time would be sufficient to know if it was leaking or not.... As an aside, I have sent the Vendor I purchased this plug kit from to see if anyone else has reported issues with the fitment....this kit was marketed as a TR250 kit so I don't want others to run into the same issues... Cheers Tush I sense a YouTube video on engine build coming this week! Quote Link to post Share on other sites
M. Pied Lourd Posted August 8, 2020 Report Share Posted August 8, 2020 Stay tuned Cheers Tush Quote Link to post Share on other sites
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