Start of another new project

[tony g]

I don't know about Triumph upgraded bolts but you can get ARP rod bolts for them.

Tony

[soe8m]

And for the head. These are going to be used for this engine.

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The head needs some grinding in the waterholes. These are too small and can be widened. This results in being able to drive in 30 degrees ouside temp through the Italien mountains towing a caravan with no cooling issues. Some castings have bigger holes and some even smaller. That is the difference in dolomites having no cooling issues and dolomites that do overheat all the time. Sprints do benefit also with this mod.

It is no use of polishing or smoothening. Just match them. The oil return hole has nothing to do with cooling issues but when i'm on to it i match this hole also.

The engine holes i already enlarged about 7 years ago when i started using that engine and it went to Italy many times but then in 1850 lpg injected form.

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[Henk]

Nice to see, Jeroen!
Did you skim the head at an angle, or straight this time? What kind of head gasket are you using? Payen seems to have a good reputation, but I can't seem to find them.

[tony g]

Jeroen, do you have a part number for the head studs/bolts please?

Tony

[soe8m]

206-4208

Jeroen

[tony g]

Thanks

Tony

[soe8m]

The head is now matched to the engine block. When matching it's important to enlarge the holes the total area and not just matching the "ends". In the picture below the left one is ok and the right one obviously not. It is not like inlet and outlet ports matching to prevent strange mixture turbulences between flanges/faces but to really enlarge the holes. There's no such thing as polishing waterholes so just enlarge and match is ok. The finish is not important.

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I did also enlarge the in and outlet ports. Not much but just to give them a square shape and not the odd cast shape. Do not widen the ports itself. These are close to waterway's and when opened too much they can crack during an overheating engine.

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Jeroen

[soe8m]

The ports you can just smoothen. You can feel where the bulges are, mostly just below the valve seats. Little grinding till you don't feel any strange shapes or angles anymore.


Before:

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After:

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Do not take too much effort in polishing and finishing as it won't add much to an 1850/tr7 type head. When you compare the area of the valve to the area of the ports the ports are quite large.

Jeroen

[soe8m]

Checking the oilpump.

These are the two sizes that are important. When the play between the rotors is too much you can bin them. The play between the top cover and rotors is adjustable by sanding the pump main housing or the rotors. I alway's use a 0,05mm play. This way the pump is the most effective. make sure not to oversand it and the o-ring becomes too thick for it's recess and causing to bend the cover. When fitting all check that all rotates free before fitting to the engine. When the play is too less the pump jams. You can check by fitting 4 long bolts and nuts through the holes and tighten. The two small screws keeping the halves together is not good enough for a good check.

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The housing you can match with the engineblock also. This pump i did not use when matching many years ago but it is close enough to use. I could grind some from the engine block but the edge seen is on the suction side and causes no flow blockage.

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This picture below shows the std hole matching of a dolomite engine and it's pump.

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Jeroen

[soe8m]

Checking the pistonrings.

I'm going to use std ae pistons including pistonrings. As you can see the gap is way too big. Alway's check the rings and the cilinderbore size. How shiny it may look after a rebore or hone who say's it's the correct size. These cilinders had the exact size so the rings were off size. '70s quality control i guess.

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The news rings i order locally by size and material. This is much cheaper and you have the ring you want. A chrome top and cast second. These ebay sets from for example Grant does work in a vintage stationary engine but not in a car.

The gap of the top ring is 0,3 and the second 0,4. Alway's choose a set so that the second ring has a slightly bigger gap. This way there's no pressure building up between the two upper rings.

The lower pic is the most ideal spacing of the piston rings when fitting into the cilinder.

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Jeroen

[tony g]

very informative Jeroen, thanks. I am surprised though at the ring gap placement. I wouldnt place a gap on the thrust side of the bore as in the sketch. is this correct?

Tony

[soe8m]

It is correct. This is the recommended spacing by mahle, JE and most other quality or OEM brands. Pistonrings do rotate during running but the spacing stay's about the same in their life.

I do not know why to start with the top ring gap on the thrust side but the only thing i can think of is to cool the ring ends. New rings do not have full contact with the cilinderbore and thus the heattransfer is less in the beginning. Ring ends are the hottest parts of the ring and have them at the thrust side they are the most "in" the pistonring groove during combustion to have the least exposure to heat and the most piston contact for cooling.

Jeroen

[soe8m]

Some random picturesof the waterpump. The rearseal does need about 8mm cut from the spring to have the original tension so it doesn't leak.

Jeroen

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[soe8m]

I did measure the volume of the combustion chambers.

All within 0,5cc. never did see that before. A sprint head can varie 4-5cc. Normally that isn't too bad but with high compressio ratio's it can happen that the one cilinder that has the least volume can detonate.

The piston had 3,5cc.

The compressio ratio cannot be determained exact yet because i do not know yet the hight of the piston above the deck but that will be around 0,5 mm

Volume combustion is 38,5cc
Volume piston is 3,5cc
Volume headgasket approx 5cc
Volume cilinder 499.5cc

A compessio ratio of 1:11,6

That is less that i hoped for but more isn't possible. All is max safe skimmed.

Jeroen

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[tinweevil]

Two questions:
Don't you think that headed note paper is showing off a tad?
When are you going to do a Stag engine to this spec?