Chapter 3, Reassembly preps, painting and final cleaning
For main reference and guidance during the engine reassembly process, I will be mostly following the sequence of steps as Miles Wilkins outlined in his book “LOTUS Twin-Cam Engine”. For general automotive good operating practices and procedures not covered by Wilkins, I will reference Tim Gilles text book, “AUTOMOTIVE ENGINES - Diagnosis,Repair, and Rebuilding” 7th edition, used in my engine rebuilding class. An additional reference consulted was “Tuning Twin Cam Fords” by David Vizard.
These are the sequence of steps I used in prepping my engine block for reassembly. There are more detailed explanations for each section.
- Install the core plugs and coolant jacket drain plug. Core plugs should be installed before the block is mounted to a universal engine stand. This is especially important for the rear plug since the mounting plate for the stand will restrict access to the rear of the block.
- Install the oil gallery plugs.
- Paint the block at this time since there is less stuff to mask off.
- Do a final cleaning of the crankcase surfaces.
Plugging the holes:
Who would have thought that after watching multiple Youtube videos, installing core plugs could be so difficult. Ideally, in watching Youtube videos, pounding in core plugs is simply smearing sealant on the plug or hole (sealant use seems to be optional with some guys) and pounding the plug in with a socket using a few hammer blows. Unfortunately in my case, it didn’t work out that way and a detailed step by step sequence of the painful experience follows.
There are three core plugs on the TC engine block, two 1-⅝” diameter plugs on the exhaust/left side and a larger 2” plug at the rear. I had ordered core plugs from one of the Lotus vendors but didn’t ask if they supplied steel or brass. I was sent a set of stainless steel plugs. Wilkins in his book vaguely mentions using a “suitable drift” by which he means sockets for core plug installation .For the 1-⅝” plug, I found that a 1-¼” or a 30mm socket will fit perfectly on the plug outer rim and a 1-⅛” socket will give a good fit inside the 1-⅝” plug. For the 2” plug, a 1-½” socket will fit on the plug outer rim but unfortunately I didn’t have a socket that will give a good close fit inside the 2” plug. All of the sockets I used were the standard short non impact style which will in the end turn out to be one of the problems contributing to my failure (Pic 1). A set of deep well impact sockets would have been a better choice.
For sealants, Wilkins mentions using Wellseal. Most of us probably don’t have a tube of Wellseal available so a search for an equivalent sealant is required. The purpose of the sealant is to seal against tiny gaps in the metal to metal interference fit between core plug and casting. In a low pressure, moderate temperature application such as a car coolant system, I believe any gasket type sealer should be more than adequate. A search of the internet shows that Permatex Aviation Form- A Gasket Sealant Liquid, Permatex Grey, Hondabond/Yamabond/Kawabond/Threebond sealants and various Loctite products are equivalents used by the British car community. I should mention that Permatex Indian Head Gasket Shellac used by some appears to be very similar looking to Wellseal. For my use, I chose Hondabond 4 due to its availability at my local Honda motorcycle dealer.
The final item to consider is the hammer. It has to be heavy enough but still be controllable when swinging. All I had available was a 2 lb dead blow hammer which gave underwhelming results .A heavier dead blow hammer would have been better from the start. I also used a 5 lb mini sledge hammer at the latter stages in desperation.
With all of my tools and plugs assembled, I started my preparations for the first plug which was the 2” stainless steel. Because the Kent block is relatively light, it is important to have the block resting on a solid surface such as a concrete floor or a heavy work table to take the impact of the hammer blows. After a quick visual check of the holes in the casting for any damage or imperfections to the hole surface before proceeding, I performed a light touchup of the sealing surfaces to remove any corrosion with fine sandpaper, and a final wipe down with alcohol of both the plug and the hole edge. A light coat of sealant is then applied evenly to the plug edge. The plug is squarely aligned to the hole, and the socket is placed evenly on the plug rim. Because the socket is a standard short socket there is no way to safely hold the socket in place during the hammer strike. As a result the socket would skate off the plug and the plug bouncing off the block after every hammer strike. After a few more attempts with the same result, I decided to stop and regroup. My next brilliant idea was to try to shrink freeze the plug with canned air. Using a half can of Dust Off to freeze this time, the smaller 1-⅝” stainless steel plug, got the same result using both the 1-¼” and the inside the plug 1-⅛” socket. The plug would not go in. At this point, I decided to give up on using sockets and decided to rent a bearing/ seal driver kit from my local Advanced Auto parts store. I also decided to give up on using the stainless steel and use brass plugs for my next attempt. So again starting with the smaller 1-⅝” brass plug and using the adapter disc with flat side down against the plug and my steel 5 lb mini sledge hammer, I successfully drove in the plug with about three moderate blows. I completed the job with the remaining two plugs. The last hole in the water jacket is for a threaded ¼” threaded drain plug, guessing possibly BSP threads, just behind the rear 1-⅝” core plug (Pic 2). Apply a bit of thread sealant and tighten snugly with a 9/16” socket.
I should explain that the decision to abandon the stainless steel core plugs was not to malign the plug itself but that I didn’t want to cause possible damage to the rented tool with the potentially harder SS plug. The cheap bearing/seal driver set that I rented was all aluminum, both the adapters and the driver/handle. I felt that the harder stainless would form dents in the adapter face and I didn’t want to pay for any damages. I plan on another attempt using the SS plugs for my next rebuild with the right tools in hand. This will include correct size deep well impact sockets and/or steel adapters of the correct sizes, a steel handle/driver and a 4 lb or heavier dead blow hammer. For those wanting to use brass plugs, a rented seal/bearing driver kit will work as well.
One last caution for those wanting to buy the plugs from other sources, be aware that the plugs come in different depths. The 1-⅝” plugs used in the Lotus Twin Cams are also used in older small block Chevys. The ones supplied for the SBCs are about twice as wide in depth and if used in the Lotus will protrude further into the water jacket. Plug depth is especially critical for the 2” plug which has only has about ⅓” of clearance between the #4 cylinder and the rear casting wall.
With the water jacket sealed up, it's time to seal off the oil galleries holes. You trust that the machine shop did their job of cleaning the block but it doesn’t hurt to verify. Before screwing in the threaded plugs, I ran a brush through both sides of the high pressure oil galleries and blew out the holes with compressed air. A tiny bit of fine dust blew out, possibly some left over corrosion. There are three ¼” pipe threaded holes for the high pressure oil supply side galleries. One threaded hole and one small unthreaded hole at the rear of the block (Pic 3), two threaded holes at the front of the block (Pic 4) and one tiny (possibly 1/16” pipe) threaded hole also for the high pressure supply side on the right side of the block (Pic 5). All have pipe sealant applied to the threads and gasket sealant to the small plug before installing. Depending on the source, the oil gallery plug pipe threads are either NPT, BSP, or NPTF depending on who you want to believe. I have not personally verified the thread type.
Installing this small approximately 7/16” push in oil gallery plug (Pic 3) was the final stumbling block to overcome in completing the block plug installation. As with the coolant core plugs, I had a difficult time installing this plug which is not normally removed by most engine builders since it doesn’t plug a pressure side oil gallery. It plugs a hole in the oil drain from the head back to the sump and is not pressurized. In my case the machine shop removed the plug as is their practice for block cleaning. This is not a problem since there are replacement plugs for that hole; the problem I had was getting the correct sized plug from the vendors. I measured the oil return hole on my block at 0.423”. It is possible that this particular hole size may not be standardised for all Kent blocks, thus the variation in the plug sizes supplied by the various vendors.
These were the plugs supplied by the two Lotus vendors:
Dave Bean - EP0461, Soft Plug 29/64” (0.453”). As delivered, the plugs were measured at 0.480”.
RD Ent - A026 E 6034, Core Plug 7/16” (0.437”). As delivered, the plugs were measured at 0.452”.
Burton lists a 7/16” plug in their catalog
My first attempt in trying to drive in the plug was with the ones supplied by Dave Bean. I used a small socket on the outside edge of the plug which resulted in a totally destroyed plug. With the second plug, I used a steel rod on the inside cup of the plug. This resulted in the steel rod punching a hole in the plug after a couple of hammer blows..
Knowing that the plugs supplied by Dave Bean had fitment issues, I ordered two plugs from RD Enterprises. I measured the plugs when they arrived and saw that they were smaller in diameter than the ones supplied by Dave Bean and initially thought that they may fit. There is no chamfer around the hole in the rear of the block so getting the plug centered and straight is a bit difficult. For the first RD Ent plug I used the head of a ½” bolt about 5” long against the outside edge of the plug to hammer the plug into the hole. As with the Dave Bean plug, the edge of the plug started to deform before the plug would start to go in.
With three plugs destroyed I decided to regroup and do additional research on the internet. I found a company in the UK that supplies core plugs and has a core plug conversion chart that gives dimensions of holes in fractions and decimals. According to the chart, there should be a 0.010”-0.015” interference fit between the hole and plug. Their plugs are automatically oversized for the holes for proper interference fit,
https://enginecoreplugs.com/conversion-chart/.
From my measurements of the plugs received from Dave Bean and RD Enterprises, both of their plugs are grossly oversized for my hole and the reason I had problems trying to install them. With my oil gallery hole measured at 0.423”, the plug that should be a match will be for a 27/64” (0.422”) hole. I found a company in the US supplying all sizes of core plugs and ordered a batch of 27/64” plugs in brass.
https://freezeplugfactory.com/When the 27/64” plugs arrived, I measured the plug diameter as 0.427” which gives a 0.004” interference fit. Even though less than optimal, I decided to use these plugs since the plug will be under almost no pressure from the oiling system. The plug drove in fairly easily with a few moderate taps of the hammer. I’m wondering if the steel version of these plugs may give a tighter fit. With the last plug installed, this completes the block prep. Next step, painting the block.
Finally ,what are these three left over open holes on the block(Pic 3 & 4)? There are three holes still left unplugged at this stage of the bottom end reassembly process. The first one previously mentioned is the hole for the oil pressure gauge fitting at the front right side of the block which will be fitted after the engine is put back into the car. The second and third holes are at the front of the block. The second hole is for the head oil drain gallery back to the sump. This hole is normally not plugged and will be blocked when the timing cover backing plate and gasket are installed. The third hole is for the coolant bypass passage from the head back to the water pump suction. This hole aligns with a corresponding hole in the backing plate and the timing chest cover.
Pic 1 - These are the sockets I initially used in my initial attempts.The biggest problem in using the shallow standard style sockets is the inability to control the sockets in place on the plug when striking directly with a hammer plus the possibility of shattering on impact. A safer and better method would have been to use an extra long deep well impact socket that fits snugly inside the plug well without being too tight. An alternative would be to fabricate a steel or aluminum handle/driver to fit inside the plug well.
Pic 2 Left side view of block
(2) 1-⅝” core plugs
(1) block coolant drain plug
(0) oil gallery plugs
Pic 3 Rear view of block
(1) 2” core plug
(1) supply side oil gallery plug
(1) 27/64” oil drain plug
Pic 4 Front view of block
(2) supply side oil gallery plugs
(1) head oil drain opening
coolant bypass passage
Pic 5 Right side view of block
Supply side oil gallery plug to opposite side oil gallery
Oil pressure gauge threaded connection
