glazed bores and slick50

[bengalcharlie]

hi all

Happy 2022!! wow another year gone by!

I have taken my engine apart and all is fine but the bores are very shiny and glazed so that might explain my low compression. I am considering honing the cylinder walls but I have used slick 50 in the past and wondered if someone her can tell me that might cause problems? could one remove the slick50 coating by honing or not?

Secondly I noticed that some of the coolant holes in the head gasket are tiny and restrict the water flow through the head. Is that common or can I ream these holes bigger to allow more coolant flow through the block and head?

Cheers Robin

[rgh0]

Proper honing will remove the bore glaze and restore the cross hatch pattern required to hold oil and lubricate the bore. This is best done by a professional engine rebuilder with the right equipment. The bores and pistons will need to be carefully measured before hand to determine if the existing pistons can be used in honed bores with just new rings or whether you need to go to oversize pistons and a rebore.

The coolant holes are designed to control the amount and direction of flow through the block and head for best cooling. Unfortunately different suppliers seem to have variations in the hole pattern and I have never been able to determine what was the original Lotus factory pattern. However it does not seem to be that critical as they all appear to work OK

cheers
Rohan

[bengalcharlie]

hi Rohan

Thank you for your reply. I am glad you replied! Yes I will take your advice and go from there. Cleaning up my garage today so I can concentrate on the task at hand. I have not been on this forum for years and I am happy to see it is still going strong with people like yourself still online and helping others!
I have been playing with another lotus so my plus 2 has been lingering in the garage for a few years now.
Time to get her going again.
Cheers Robin

[Mike Ostrov]

Hi, Robin. Follow Rohan's detailed recommendations. This is how I have de glazed both Coventry Climax and Lotus Twin Cam cylinder bores. If there is no measurable excess wear and you are certain a de glaze is required due to lack of power, over heating, a compression and leak down test, I use a flex ball sized to the bore with a reversible drill to de glaze and create a 45 degree cross hatch pattern. A suitable lubricant and a through cleaning are necessary. So, often best left to a competent machine facility. Cheers. Mike.

[2cams70]

I beg to differ on this one. Glazed bores are 100% normal on these engines after they have done 30,000 - 40,000 miles or so. The nice fresh cross hatch pattern quickly disappears during use unlike modern engines running fuel injection and hardened liners and it normally causes no serious issues. Best to measure the bores to see if they are within spec. If they aren't then you require a rebore and new oversize pistons. A deglaze won't work.

Deglazing = removing metal. Something you don't want to do unless necessary. If however you do want to deglaze the bores it is best to have it done professionally. Both the cross hatch angle and depth is critical. You are unlikely to get it correct doing it by hand.

It's OK to clean up coolant holes filled with gunk but it is not OK to enlarge them. The flow of coolant around the engine is regulated and these holes are part of that regulation system. Too big and the flow of coolant will be too fast to allow correct transfer of heat to the coolant for an even temperature distribution.

[tonyabacus]

Robin
There is a series of articles that you may like to read on the subject of honing and honing angles and their effects. I have listed them below, they are from a US piston/ring manufacturer but very informative, the first is a quick explanation and the second a more detailed presentation that you will need a cup of coffee and a spare hour to watch, but worth it if you really want to get into the detail.

It is a subject that raises many questions and issues over time and often gives rise to bad information being bandied around especially when it comes to some of the You Tube videos of home techniques people use. These articles from Total Seal whilst very technical in parts explains precisely why the job is really for the professionals. I seem to recall there has been some fairly recent discussions on one of the Forums about crankcase compression with oil being blown out from different places on some members engines. Watching these couple of videos may go some way to explaining why that can happen (for the benefit of those that may be suffering from this type of problem and are perhaps reading this).

Piston ring sealing in the bore is far more than just getting the honing right or the ring gap right as explained in the third link below. What is happening above, below and behind the piston rings also has quite an effect, speak to Dave Powell (below) if you want a fuller explanation of what is happening in this area of engine build relative to performance (I have no connection to Dave but know from his reputation that he has a better understanding of some of these aspects of engine building than some I have come across).

Whilst the gauge they talk about in the first video would be useful, you can easily make up your own either using a piece of clear plastic or just a piece of good card cut to 22 1/2 degrees. This is the included angle for the 45 degrees needed for most road car engines.

The company (Total Seal) is represented in the UK by Performance Unlimited near York, where Dave Powell has over 40 years experience building literally nothing but race engines and in himself is a mine of information and a very helpful guy. I have listed his contact details also.

Hope this helps with your thinking on best way forward
Tony

https://www.youtube.com/watch?v=cRINK2O63GM
https://www.youtube.com/watch?v=LIfbYd9cqcs
http://blog.wiseco.com/ring-grooves
http://www.performanceunlimited.co.uk/

[512BB]

Here is one I did earlier, and I am just a humble twin cam engine builder lol.

Sometimes I think people read far to much into these things. Its not rocket science, just takes a bit of practice.

Leslie

[tonyabacus]

Leslie
Without prejudice to your own skills and knowledge, in responding to Robin's question I was trying to point him towards information that may help him and others understand what is involved and why companies have invested millions of pounds over the years looking into and resolving issues connected to rings, bore wear and honing and what can emanate from getting it wrong.

It would seem from your own response that you have more experience in this from carrying out a number of engine rebuilds and whilst I accept that there are perhaps some who are capable of doing this themselves, there have been many that have ruined a good engine in the process.

Robin you may recall was questioning low compression and therefore the links may give him some further knowledge to help him find the reasons for that issue, hence also my suggestion to contact Dave Powell to talk through his particular problem. One of the topics discussed in the links, is how the honing angle can affect oil flow either up or down the bores and also how it can affect ring rotation to a point allowing blow by, which may of course be part of Robin's low compression problem.

Perhaps to help those wishing to have a go themselves, you could explain how to go about it, what types of kit to use and what pitfalls to look out for, so those that are confident enough can have a go.
Tony