Head off time

[Ian Vincent]

Bob,

I notice that you haven't gone for the TR4a chamfer shown on the Vizard drawing.  My understanding is that it was introduced by Triumph when they increased the bore from 83 to 86 to prevent the CR from being increased too much.  I copied it because I was using 87mm pistons and liners.

Rgds Ian

Edited April 11, 2020 by Ian Vincent

[BlueTR3A-5EKT]

1 hour ago, Lebro said:

1 done, 3 to go.  I left a slight curve on the profile (Visard profile was a stright line from base to surface) to save have ing to skim too much off.

Will measure capacity after lunch.

Bob.                                

Excellent progress Bob.

Do not forget to remove all sharp edges.

Cheers

Peter W

 

[Lebro]

volume of 1st one 64mL, so added 4. need to get back  to 60 by skimming to acheave around 9:1 with 87mm bores.

Whats needed is a program to calculate area from a template shape.

[iain]

Bob

apologies the gasket issue only occurs with Kastener mods, when you remove the shroud at the other side of the chamber.

 

Iain

[BlueTR3A-5EKT]

3 hours ago, Lebro said:

volume of 1st one 64mL, so added 4. need to get back  to 60 by skimming to acheave around 9:1 with 87mm bores.

Whats needed is a program to calculate area from a template shape.

 

 

Would this work?

Measure depth of chamber

Level the head

Fill with 60 - 61  cc of fluid.

Measure depth of fluid

Take fluid depth measurement from chamber depth and that is the amount to skim off.

Cheers

Peter W

 

[stillp]

Or:

measure depth of chamber

multiply by 60/64 (assuming chamber sides are vertical, which they aren't)

subtract from original depth

difference is the amount to be skimmed.

 

Now, the chamber sides aren't vertical, so the amount to be skimmed will be less that the estimate above, so skim a bit less, then measure the cc volume again and if wildly out, reskim.

Pete

[Motorsport Mickey]

2 hours ago, BlueTR3A-5EKT said:

 

 

Would this work?

Measure depth of chamber

Level the head

Fill with 60 - 61  cc of fluid.

Measure depth of fluid

Take fluid depth measurement from chamber depth and that is the amount to skim off.

Cheers

Peter W

 

+1 That's what I've done previously.

Mick Richards

[Lebro]

20 hours ago, Ian Vincent said:

Bob,

I notice that you haven't gone for the TR4a chamfer shown on the Vizard drawing.  My understanding is that it was introduced by Triumph when they increased the bore from 83 to 86 to prevent the CR from being increased too much.  I copied it because I was using 87mm pistons and liners.

Rgds Ian

Ian.

Yes If I had done that I would have to take even more off the surface to restor the CR. I think the mods done around the inlet valve will have more effect than taking the slope all the way across. I have read somewhere that the 4A "slope" did not not make much difference anyway.

   All done, using a Lidl air powered die grinder with tungston burrs & a couple of grinding wheels. 

Very pleased with it - plenty of grunt off 90 PSI.

I found a neat program online to do the area calculation.   Sketchandcalc.com   

I had already scanned the 1:1 template from the Vissard book, so just had to remove the lines I did not want to just leave the chamber outline,      

This is then imported into the program, & you then need to scale it by entering a know straight line measurement (78mm from one side to the other in this case)

you then draw a series of short straight lines, following the outline till you get back to where you started, the program then does the calculation, & presents the result as in the screen shot above. I entered the scale reference measurement in mm instead of cm so was 10:1 out, but easily corrected by dividing the result by 100.

which is 3590.04 mm2 or more usefully 35.9 cm2   So, the amount of surface to take off to remove 5mL (cc) is 5/35.9 = 0.139cm = 0.0548" (55 Thou)

Because the newly removed section is on quite a slope, the volume will actually reduce a bit less than 5mL, but won't be far off.

So, do we think 55 Thou is OK to remove ? Vissard states that up to 80 Thou gives no problems.

Bob.

Edited April 12, 2020 by Lebro

[Ian Vincent]

I have say I would be wary of removing that much in one go. I like the idea of adding your target volume of liquid and measuring the depth. I’d be inclined to do that first. 

Rgds Ian

[Lebro]

Will do.

[Lebro]

On 4/9/2020 at 10:38 PM, Ian Vincent said:

Bob,

I converted a standard 3/3a head to 4a spec using Vizard's book.  I also had hardened seats fitted and had the head skimmed 15 thou to deal with a slight bend.  When I used a burette to measure the combustion chamber volumes, they were all 63.5 cc which if I recall gave a CR of 9.5 with 87mm pistons.

Rgds Ian

 

Ian.

Those figures don't seem to tally with mine. you say you opened up the chambers to "Vissard spec", including grinding the 4A "slope" towards the exhaust side.

that would have increased the volume more than my efforts, yet you say only 15 Thou taken off to acheave 63.5cc.  I will do the "fill with 60mL" & check gap to the top next  & report back.

Bob.

[Motorsport Mickey]

1 hour ago, Ian Vincent said:

I have say I would be wary of removing that much in one go. I like the idea of adding your target volume of liquid and measuring the depth. I’d be inclined to do that first. 

Rgds Ian

If the head is virgin I've removed 170 thou before getting into "Oh bother" areas, so there's loads there.

Mick Richards 

[Lebro]

I am assuming the head is "virgin" I know it has not been off the car since 1971 when I bought it, & the engine is an FRE one so it does not go back to 1955,

the measured volume of 60mL works out well for the standard CR of 8.5:1 & 1991CC

I have just measured the depth of on of the chambers from next to the inlet valve (flat area) to the surface. is measures 0.624"  does that sound "virgin" ?

Using that measurement, & one of calculation methods mentioned above 0.624 / 65 * 5 =0.048"  (48 Thou)  to come off.

I have spent all morning trying various methods of measuring between the surface, & the level of liquid when only 60mL added to chamber.

Results were varied, the main problem being surface tension causing the liquid to jump up to meet the tip of the measuring probe (digital vernier caliper)

I tried water, water with a minute amount of detergent, & I tried white spirit. best result was water with detergent. 

 No Detergent       with detergent         final setup          poor photo of probe almost there.

1st 2 measurements I got were using water with D & without the two spacers,      38 Thou, & 31 Thou.

Now, I think there may have been water sitting in the spark plug for these (left over from yesterdays volume measurements,

which would make these lower than they should be.)

Next I tried white spirit, but the surface tension problem persisted, & the liquid was prone to wick under the horizontal bar I was using to bridge the chamber,

so no measurements taken.

Thirdly, I went back to water with a dab of detergent, & lifted the bar up with some accurately machined spacers. 53 Thou, & 53.5 Thou.

I then changed to a different chamber & repeated the last measurement, & got 67.5 Thou !

My conclusion is that the area calculating program had got it right (why wouldn't it?) at 55 Thou.

Oh, & by the way the head surface was absolutely level (checked with good sprit level)

Bob.

Edited April 12, 2020 by Lebro

[iain]

A virgin head has a face to face width/depth of 3.3125" (source Moss Catalogue),so you can easily check this before you get too carried away 

Iain

PS. To measure chamber volume I used a small piece of perspex, with a central hole to feed paraffin into via a syringe and needle. Perspex was sealed to head with a very light smear of Vaseline. 

Edited April 12, 2020 by iain

[Lebro]

I used glass& grease (see above)

Just measured head top to bottom  3.325"  

Bob

[Lebro]

On Tuesday I shall be ordering a set of standard (5/16") valves & guides, RB cheaper than M, have asked for prices from TRS.

are any of them better or worse than others ?

Bob.

[John L]

Bob

This may be of interest, perhaps you have already seen, its also part of the lots of documents loaded from the USA, just put on the 6 forum

https://drive.google.com/drive/folders/0B2H2NJt34OffMDVmOTZlZWItYTcyMy00ZDhkLTliOWEtOWU1OWRhNDZhYmRl

John

[Lebro]

Thanks John, these appeared a while ago on here, & I have the link stored on my PC.

Bob.

 

[Lebro]

Since I have a TR3A head, & tr 4A inlet manifold, the diameters are different, (1 5/8" head, & 1½" manifold), so since I cannot easily reduce the dia of the head ports, I am enlarging the ports in the manifold. I found that a large step drill was just the tool for starting this operation off.

    A recent Lidl purchase of a miniature die grinder (air powered) also came in useful    

Still a bit more work to do on this.

Bob.

P.S.   I know I will have remove all the swarf from the carbs !  should have bunged the tubes up before I started (hindsight is a wonderful thing)

Edited April 13, 2020 by Lebro

[Lebro]

  All done, now same size as "hole in the head" !

I note that 4A heads had the smaller size port at 1½" which explains why the two did not match.

Had just finished the final pass with a fine abrasive drum in the small die grinder, when my compressor tried to start up again, but just hummed instead, then tripped out.

Investigations showed nothing was siezed, so, off with the motor start cover, & low & behold a fried startup capacitor 

New one now on order from Ebay.

Since I have not heard anything against any of the suppliers of guides & valves I will probably order them from Rimmer Bros tomorrow.

Next job is de-coke the pistons, & clean up the block face. & measure the bores accurately (just out of interest as I wont by changing the liners on this occasion)

I may be tempted to drop the sump, & remove pistons to check the small ends, as I think that may be where my "tapping" noise is coming from.

Bob.

[Hamish]

Bob is there any merit in “tidying” up the other end of the inlet manifold, the carb side to smooth out or better define/sharpen up the 1:2 division on each intake. ?

[roger murray-evans]

On 4/12/2020 at 7:16 PM, Lebro said:

I used glass& grease (see above)

Just measured head top to bottom  3.325"  

Bob

Bob,

I have 2 spare heads (Hi port TR3).And for what it's worth

one has 3.333" and t'other 3.321".

Measured once, twice, three times etc.

 

Roger M-E

[Lebro]

2 hours ago, Hamish said:

Bob is there any merit in “tidying” up the other end of the inlet manifold, the carb side to smooth out or better define/sharpen up the 1:2 division on each intake. ?

I will be looking at that tomorrow, but I suspect that end is pretty good. I had not realised till today that the 4A head has reduced inlet port size compared to the earlier high port heads. Idealy I would have reduced the port sise in the head to match the manifold, but how !

Bob.

[Lebro]

2 hours ago, roger murray-evans said:

Bob,

I have 2 spare heads (Hi port TR3).And for what it's worth

one has 3.333" and t'other 3.321".

Measured once, twice, three times etc.

 

Roger M-E

Thanks Roger. the head comparison web page shown earlier in this thread quotes the nominal size of a "virgin" head as being 3.330"

it is unlikely that someone has taken just 5 thou off my head, so I am happy it has not been skimmed before. there must have been some tolerance in the making of them.

Bob.

[Motorsport Mickey]

14 minutes ago, Lebro said:

I will be looking at that tomorrow, but I suspect that end is pretty good. I had not realised till today that the 4A head has reduced inlet port size compared to the earlier high port heads. Idealy I would have reduced the port sise in the head to match the manifold, but how !

Bob.

Slip in handmade tapered collets which blend into the head over about 36mm or thereabouts. You may have to "tweak" the head 1 5/8 th bores to try and make sure they are round...ish but as I remember they were put in with a ball cutter so as long as left alone wouldn't be too bad. The outside diameter which pushes into the head is covered by inlet gasket and inlet manifold anyway so not critical, and where it blends into the head the gas is going like "Billy Whiz" and just wants to keep going. Inlet pulses don't appear to be affected.

Mick Richards

 

Edited April 13, 2020 by Motorsport Mickey