Head off time

[Lebro]

Ah I see, still too late now !

Bob.

[Ian Vincent]

9 hours ago, Lebro said:

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.

Hi Bob,

I think I remember you saying that your engine is a factory rebuild. Maybe the factory gave it a 5 thou clean up as a matter of course during that process. Just to make sure it’s flat. 

Rgds Ian

[Hamish]

This sounded similar to my car. The ex Tony Thompson car with which he undertook many of the period mods ( as you are doing bob)  in his 45 year ownership. He told me

”The cylinder head is TR4A (smaller inlet ports than the earlier head which paradoxically is considered better for mid-range with no loss of top end power). I modified the head according to the advice in a book by Kas Kastner who was the period TR guru in the USA. It has the inlet ports re-shaped and polished and matched to the inlet manifold”

The only unknown is what cam is in the car as it’s a VERY early revington version.

regular rolling road tests and carb set ups initially showed 108bhp at the flywheel then I changed the inlet trumpets with gauze to plain open ones and got 116bhp.

and 136ft/lb torque.

 

this is my inlet manifold 34mm and inlet ports  38mm 

should I match them to 38mm ?

keep up the good work and the reports 

H

Edited April 14, 2020 by Hamish

[Lebro]

I think I would do that yes. My head port size was 1 5/8" (41.275mm) so much more of a change, in hindsight I would have been better off inserting a ring into the head as Mick's suggestion above.  In your case the head port is 1½" dia to strt with, so already the right size. In the interests of a smooth air flow I would open up the manifold to suit.

I found the best tool for removing aluminium quickly was a small (¼") milling cutter used with a die grinder. The wider spaced flutes compared to a tungston burr did not clog up nearly as much. you will have to finish off with a burr, & finally small abrasive cylinder (or grindstone).

Ordered the bits for mine just now from Moss after all, & my local machine shop has siad they can do the job in a week or so from reciept, so I just have risk the journey over there.

Bob.

[Hamish]

Bob

perhaps you should try this manifold ?

believed to be a modified Derrington.

the outlet to the head is way too big to fit mine. I was going to make up some reducing spacers but really beyond me. So I’ve never used it.

but your head inlets sound the right size ?

it’s just missing the carb side bracket to take the throttle pivot. But a man of your talents could knock something up. 
 

it has a wonderfully defined split on each inlet. 

[Lebro]

Funny you should offer that Hamish.  When I bought the car in 1971 it was fitted with that exact same manifold. & thats how I ran it for decades.

On the big re-build in 2013 I wanted it to be as standard as possible (I have changed that thinking now !) so I found a standard manifold & sold off the old one.

I later found out that the old one was a Derringtons one, & was probably a lot better than the standard. Anyway I now have a 4A one, which now matches my head. So thanks for the offer, but no thanks !

  Photo circa 2011

Bob.

[Lebro]

For some reason I wasn't expecting this     

But having looked in the parts book, I see it is normal - Phew ! 

Can't budge the front two long ones, or the rear OS one (which was the one giving me all the TRouble lifting the head) so will leave them be.

Noticed that all the studs have a "saw cut" across the lower threads, is that normal ?  

One of the long studs looks a bit "waisted" where it exits the block, I guess it would be worth renewing that one ?

when re-inserting the long studs should one put some sealant around it as it enters the block to stop oil working up onto the block surface ?

Bob.

[Motorsport Mickey]

1 hour ago, Lebro said:

For some reason I wasn't expecting this     

But having looked in the parts book, I see it is normal - Phew ! 

Can't budge the front two long ones, or the rear OS one (which was the one giving me all the TRouble lifting the head) so will leave them be. I should try whilst you are this far, if you have to strip down again in the next decade or so they won't get better by being left

Noticed that all the studs have a "saw cut" across the lower threads, is that normal ?   Yes, the cut helps clean up the block threads as being fitted and prevents any fluid or oil inside the stud hole being hydrauliced or misleading you into thinking the studs are bottomed out, screw them in until there is no thread left...by hand, don't adversely tighten them up with mechanical means, if a nut picks up (it shouldn't you will check for "galling" of a rough thread surface right ?) it would try and screw the stud into the thread and likely cause a failure point in future use.

One of the long studs looks a bit "waisted" where it exits the block, I guess it would be worth renewing that one ?  That's unusual, normally the weak spot on studs are where the screw thread runs out into the dia, it forms a stress raiser.

If you determine to renew it gird your loins and use an impact driver with a blunt end on it and give the stud some Brrrrp Brrrrp with a nut on the end to prevent slipping off, to help break any corrosion and then use a double nut to TIGHTEN the stud a 1/4 turn if you can, again to break the corrosion. Then put a monkey wrench (Stilson) on it close to the block (cover the surface and don't mark it) and give it some severe aggro, constant pressure and the application of diesel and waiting a day or so normally does it. Normally I get past by on a running engine taking studs out as you are doing, but if the block is on the floor I'll turn onto it's side and doing all I've said above apply Mr Stlilsons product. These studs are very tough and I've never sheared one off, but there's always a first time.

when re-inserting the long studs should one put some sealant around it as it enters the block to stop oil working up onto the block surface ? NO...the studs should be dry on the bottom end of them, if you have a crack in the block inside you could try some Wellseal there after wrapping the thread in GP white tape and fitting carefully.

Bob.

Mick Richards

Edited April 15, 2020 by Motorsport Mickey

[Lebro]

Thanks for that Mick. the "waisted" long stud is already out, so I can easily replace that one. Having cleaned up the others which I could remove, 2 of the short ones have some pitting near the base, the 2 long ones at the head face level.

As for the "stuck" ones, The engine will be coming out if not next year then probably the year after for a bottom end check / rebuild & balancing, camshaft, & bearings change , chemical clean, & 87mm liners fitted etc, & the "stuck ones can come out then. I am reluctant to try too hard with the engine in the car in case one breaks inside the block. The back (short) one, if that breaks I could drill out etc. but would rather not have to at this time. I do have an SDS hammer drill, so I will give that idea a go tomorrow, they have all been soaked with diesel for a few days now anyway !

Anyway, block & pistons now cleaned up     Why do the pistons have holes in the middle !!   

Bob.

Edited April 16, 2020 by Lebro

[RAHTR4]

Hi Bob,

I see that your engine is fitted with BHB pistons, no idea why they have a depression at the centre, presumably to assist with the machining...?

However they were manufactured by Automotive Engineering Limited in Twickenham.

The advert below is from the Automobile Engineer dated September 1956.

Regards, Richard

 

[Lebro]

Just measured the bores in two directions using a Moor & Wright micrometer bore gauge , seems they are hardly worn at all !

[Motorsport Mickey]

22 hours ago, Lebro said:

 

Why do the pistons have holes in the middle !! 

To be honest I've never thought about it, probably because I can't remember seeing them before ! My guess would be the hole is used in the location of the piston (for a machine tailstock centre to centralise) in it's production process.

Also Bob might be an idea to measure the liners top and bottom checking for taper and of course checking for a thrust face wear ridge. 

Mick Richards

Edited April 16, 2020 by Motorsport Mickey

[Lebro]

The measurements were taken half way down the bores. academic really as intention is to go for 87mm eventualy.

Head studs still not budging, but again, that is a job for when engine is out of the car.

This exercise was to correct the lack of compression in No.3, & modify the head while it was off. Followers are back in, block face clean, all studs back in, ready for when the head comes back from machine shop.

Had a feel of the liner protrusion, they all are proud by a small ammount, all the way round,  they have given no trouble for the last 50 odd years, & I'm guessing the will take a lot of effort to shift them, so they can stay as is till engine out time.

Thanks for all help, will report back when head is back on (could be a while)

Bob.

[Lebro]

Well, valves & guides finally arrived, so set to turning a 20° taper on the port end of the inlet guides. following Visard's recommendations.

Looking at the inlet valves, they were already pretty close to the "modified" profile in the Visard book, so I left them alone.

Head, and everything else now on their way to the machinists to get the exhaust seats cut in, & the surface skimmed, should be done in a week or so.

Luckily a nearby friend had an Alpine block needing re-boring at the same time, so he has taken his block & my head to the machine shop "on his way to work"

thus saving me running the gauntlet of a 10 mile round trip, which I was a bit concerned about given the current restrictions.

Bob.

  

[Lebro]

  Head back from Machine shop.  Now removing sharp edges, final chamber volume balance, & a bit of work on the liners to smooth airflow below inlet valve.  Pencil lines on head are just inside the edge of gasket.

Bob.

[Hamish]

Great stuff Bob.

exciting to be getting to the rebuild stage.

H

[Lebro]

Quite lucky with the chamber size's - 3 were 58CC, 1 was 57, so only had to play with 1 to get them all the same. head now finished, tomorrow I will carefully relieve top of liners to match up with the head, then it's time to put it all back together.

Quick CR calculation comes up with 8.68:1   with current 83mm pistons, &     9.36:1  when I eventualy go to 87mm pistons.

Bob.

Edited May 4, 2020 by Lebro

[Lebro]

So I invented a way of marking the block where metal needed to be removed to line up with the area in the head around the inlet valve.

put a couple of layers of masking tape on the edge of the liners where the metal is to be removed, the put the head on top, giving it a little squeeze with the head studs, then remove, & look for marks on the masking tape.

Well, the first (anticipated) problem was that having skimmed 60 thou off the head it now hits the water pump before the block. so after using the masking tape method again, I found where it was hitting, & ground some meat off the water pump (I had already taken some off, but clearly not enough.)

Have got that sorted out the marking of the liners was sucesful.

    Then time to grind   I kept the filings out of the bore by wrapping a powerful magnet in tissue paper

& pressing into the bores  Which caught them all successfully.   While in grinding mode I noticed that three of the water channels in the block were not realy in the right place to match up with the holes in the head gasket, or the corresponding channels in the head. So I stretched those  holes to better match the gasket.

 Arrows show where.  Picture was taken after applying Wellseal    also on underside of head dangling from engine hoist

head now on & torqued up, rocker adjustment tomorrow.

Bob.

[iain]

Bob, it’s worth checking that the manifolds now don’t touch the block as the head has come down 060”. There are two bulges in the casting  that might need relieving. 

[BlueTR3A-5EKT]

48 minutes ago, iain said:

Bob, it’s worth checking that the manifolds now don’t touch the block as the head has come down 060”. There are two bulges in the casting  that might need relieving. 

Beat me to it.

Peter W

[Lebro]

Already checked that, had to trim the gaskets slightly, but exhaust manifold ( Phoenix 4 branch) is clear

Bob

[Lebro]

3 PM today I hit the road (well drove it round the block) All seems well, hard to say if any performance improvement, have to wait for lockdown to end for that test.

Compression tests show that things are better though.

Before:   Dry  151    168     88   173    & with oil in bores  189   199   99   203    difference  +38   +31   +11   +30   showing No. 1 has the leakyist rings

Now:      Dry   172    179  188   188     all done after a quick drive.

These are with 50 + year old liners & pistons (& rings) so not surprising they vary a bit.

Bob.

[BlueTR3A-5EKT]

It is a great feeling when it all works as intended.

Congratulations

Peter W

[Hamish]

Great stuff bob. That’s a big job well done. 
H

[Drewmotty]

Nice job Bob. Thanks for sharing the fun.