Boredom has set in.
For the first time in about 10 years I am not restoring a Triumph, and I needed something to do.
Since I finished my Stag project, it has left my Stag engine TR feeling a little sluggish, even if this is a false feeling with the TR weighing about a quarter of a ton less than the Stag.
I decided the solution would be to build it another engine, and recycle the old one through one of my other Triumphs.
I never expected to get the 246bhp I achieved with the Stag project, and I also never expected it to be quite happy on regular unleaded with a 10.5 : 1 compression ratio, especially since I am running a maximum advance of 31 degrees.
This gives the possibility of squeezing a bit more out of the Stag engine.
To this end I have been slowly accumulating bits over the last 12 months with the intention of starting when I ran out of other things to do, which has now happened.
The idea is to build this engine to a very similar specification to the last one, but with a bit more compression and to try something a bit more radical with the head porting while still retaining standard size valves.
I don't have the benefit of high compression pistons this time, so getting the higher compression required is going to need a little more imagination on the machining of the pistons and block. To this end I have acquired a new set of 40 thou pistons as I have a block that is bored 20 thou over but which needs two liners replacing due to corrosion.
This block came from a mate who bought it to replace the RV8 in his Stag, but the pits in the bores were actually full of body filler!
The idea is to get a bit more swept volume which will help raising the compression. The block is currently away for a rebore and new liners. I had already replaced one liner that was hopelessly pitted but the pitting in the other was a bit too much to be taken out with the rebore. This block had already had 8 liners fitted so swapping a new one was simply a matter of grinding though one side with a carbide cutter then winding in a new one using an old brake disc as a flat surface and a large section threaded rod to do the pulling.
So far I have spent a lot of time over the last few weeks porting the heads using my home made flow bench.
When I say a lot of time, I am probably getting on for 100 hours so far. I am actually doing 3 heads, one is rather corroded but hopefully saveable, and the intention at the moment is to be able to use this for future reference just in case I ever do another pair of heads.
Unfortunately I cannot do a straight comparison with the heads of my project Stag as one of my original old flowbench hoovers went bang while using it as a hoover!
I have also done some porting work on my flowbench as there were a number of restrictions that needed removing. This tends to raise vacuum levels at high valve lift and so gives the impression of less effective porting of the inlet tract.
I shall keep updating this thread as work progresses, but I don't intend rushing it as I am not intending to fit the completed engine until next Winter.
Neil
For the first time in about 10 years I am not restoring a Triumph, and I needed something to do.
Since I finished my Stag project, it has left my Stag engine TR feeling a little sluggish, even if this is a false feeling with the TR weighing about a quarter of a ton less than the Stag.
I decided the solution would be to build it another engine, and recycle the old one through one of my other Triumphs.
I never expected to get the 246bhp I achieved with the Stag project, and I also never expected it to be quite happy on regular unleaded with a 10.5 : 1 compression ratio, especially since I am running a maximum advance of 31 degrees.
This gives the possibility of squeezing a bit more out of the Stag engine.
To this end I have been slowly accumulating bits over the last 12 months with the intention of starting when I ran out of other things to do, which has now happened.
The idea is to build this engine to a very similar specification to the last one, but with a bit more compression and to try something a bit more radical with the head porting while still retaining standard size valves.
I don't have the benefit of high compression pistons this time, so getting the higher compression required is going to need a little more imagination on the machining of the pistons and block. To this end I have acquired a new set of 40 thou pistons as I have a block that is bored 20 thou over but which needs two liners replacing due to corrosion.
This block came from a mate who bought it to replace the RV8 in his Stag, but the pits in the bores were actually full of body filler!
The idea is to get a bit more swept volume which will help raising the compression. The block is currently away for a rebore and new liners. I had already replaced one liner that was hopelessly pitted but the pitting in the other was a bit too much to be taken out with the rebore. This block had already had 8 liners fitted so swapping a new one was simply a matter of grinding though one side with a carbide cutter then winding in a new one using an old brake disc as a flat surface and a large section threaded rod to do the pulling.
So far I have spent a lot of time over the last few weeks porting the heads using my home made flow bench.
When I say a lot of time, I am probably getting on for 100 hours so far. I am actually doing 3 heads, one is rather corroded but hopefully saveable, and the intention at the moment is to be able to use this for future reference just in case I ever do another pair of heads.
Unfortunately I cannot do a straight comparison with the heads of my project Stag as one of my original old flowbench hoovers went bang while using it as a hoover!
I have also done some porting work on my flowbench as there were a number of restrictions that needed removing. This tends to raise vacuum levels at high valve lift and so gives the impression of less effective porting of the inlet tract.
I shall keep updating this thread as work progresses, but I don't intend rushing it as I am not intending to fit the completed engine until next Winter.
Neil
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