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Fast-road 1500?

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stage3 Avatar
stage3 Christian P
Saarbrücken, Saarland, Germany   DEU
Hi folks,

may I ask for your opinions and experiences about building a fast-road engine for my Spitfire… No racing, no auto-crossing, etc. but a bit more power for those Alpine passes… ;-)

I do have a used 1500 block sitting in my garage. It was built/tuned in 1999/2000 by Jigsaw racing in the UK and used in a road-going club racer for a short time. It needs at least taking the crank out for inspection and maybe a regrind, as I was told it did have a bearing failure at some point in the past. The bores and cylinders look fine to me (honing is present). Same goes for the cam lifters (cam is still in place). So my idea for the block is:
- Leave pistons in place
- Take out the crank, inspect it, maybe have it reground, install with new bearing shells
- Take out cam (Kent TH5, 280°) for inspection, re-install with it’s lifters if okay, re-time, etc.

Unfortunately I do not have the corresponding cylinder head to go with it, as that was nicked by someone. So I have to start with an standard TKC1155. There are several workshops who can do such work. Which mods should be done? And how do I find out how much to mill off for my planned CR of 9.5:1 (9.75:1)?

Aspiration will be via SU HS4s on a Mangoletsi inlet manifold for a start. Maybe twin DCOEs at a later point (need to re-build them first). Tubular exhaust and sports system are installed.

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Andy-Sherry Avatar
Andy-Sherry Gold Member Andy Martin
Portland, OR, USA   USA
My head was milled from 3.10" to 3.05" and with flat top pistons CR is about 9:1 i also have dual HS 4s and a 25/65 270 degree lift cam,Plenty fast,



Andy&Sherry
1974 Spit 1500 Carmine Red
1977 Spit 1500 Pink Panther Pink

Always learning something

clshore Carter Shore
Beverly Hills, FL, USA   USA
In reply to # 1512081 by stage3 Hi folks,

may I ask for your opinions and experiences about building a fast-road engine for my Spitfire… No racing, no auto-crossing, etc. but a bit more power for those Alpine passes… ;-)

I do have a used 1500 block sitting in my garage. It was built/tuned in 1999/2000 by Jigsaw racing in the UK and used in a road-going club racer for a short time. It needs at least taking the crank out for inspection and maybe a regrind, as I was told it did have a bearing failure at some point in the past. The bores and cylinders look fine to me (honing is present). Same goes for the cam lifters (cam is still in place). So my idea for the block is:
- Leave pistons in place
- Take out the crank, inspect it, maybe have it reground, install with new bearing shells
- Take out cam (Kent TH5, 280°) for inspection, re-install with it’s lifters if okay, re-time, etc.

Unfortunately I do not have the corresponding cylinder head to go with it, as that was nicked by someone. So I have to start with an standard TKC1155. There are several workshops who can do such work. Which mods should be done? And how do I find out how much to mill off for my planned CR of 9.5:1 (9.75:1)?

Aspiration will be via SU HS4s on a Mangoletsi inlet manifold for a start. Maybe twin DCOEs at a later point (need to re-build them first). Tubular exhaust and sports system are installed.

While the crank is out, check to see if was nitrided, and if not, have it done.
Also a good opportunity to have the balance checked.
Not saying that Jigsaw didn't do a good job, only that there is no proof it's the original crank (18 years !!).
With the crank out and the head already off, I would remove and inspect the rod/piston assemblies, ring condition, and check that weights are equal.
Re-installation is easy, requires only a piston ring compressor.
Remove the lifters, remove the cam, inspect the lifter faces and cam lobes.
Do keep track of exactly where and in what order and orientation each part is installed; label and/or bag parts, take pictures, take notes.
I've found it useful to have a logbook or journal.

You can spend some serious money on head modifications.
But for a street car, I would keep it simple; bad or misinformed work can degrade performance, rather than enhance it, ie 'less is more'.
There are very few folks who have the expertise and knowledge to do a proper job on a Spitfire head, the key is not what to remove, it's what to leave.
Get a good valve job if needed, clean up the rough surfaces in the tracts, follow the guidelines in the Competition Manual, and mill the head for desired compression.

Have fun!!



Edited 1 time(s). Last edit at 2018-02-08 01:53 PM by clshore.

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
My 1500 is pretty much what you have in mind, I now use it pretty much exclusively as a road car and I am very pleased with it.

My thoughts/experiance: Get the bottom/engine block end a good as you can, you can always play with the head seperatly.
I bought two heads and did my own porting etc. with help from the competition prep manual and the David Vizzard book.
I was afraid of goining too far, so would work on a head, switch and change to the other head and so on.

I ended up limiting the comp ratio to just over 9-1 which means I can run our mid grade gas or Farm/Marine gas without a problem. Premium is not always available in rural areas.

spitfire50 Avatar
spitfire50 Paul Mugford
Rochester, N.H., USA   USA
In reply to # 1512081 by stage3
And how do I find out how much to mill off for my planned CR of 9.5:1 (9.75:1)?


Christian,
There is only one way to find how much to mill from the head to achieve a particular compression ratio. You have to measure the volumes involved. Any metal removed from the combustion chamber to improve flow will lower the compression ratio, and increase the amount of metal that must be skimmed from the head to reach the same target ratio. Conversely new valves on new seats may project farther into the chamber and raise the compression. Less metal would have to be milled from these heads.
All the best,
Paul

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
In reply to # 1512242 by spitfire50
In reply to # 1512081 by stage3
And how do I find out how much to mill off for my planned CR of 9.5:1 (9.75:1)?


Christian,
There is only one way to find how much to mill from the head to achieve a particular compression ratio. You have to measure the volumes involved. Any metal removed from the combustion chamber to improve flow will lower the compression ratio, and increase the amount of metal that must be skimmed from the head to reach the same target ratio. Conversely new valves on new seats may project farther into the chamber and raise the compression. Less metal would have to be milled from these heads.
All the best,
Paul

This process is commonly called cc'ing. A sheet of plexiglass (perspex) is placed over the upturned combustion chamber. Light oil is measured though a hole to fill the combustion chamber. The resulting volume is thus measured. The volume over the piston in the engine block can be simply calulated (but consider if the piston is not exactly flat with the top of the block)

The relationship between these two volumes with give you your compression ratio.

DO NOT ASSUME that just taking x amount off your head will yeild a given comp ratio!

stage3 Avatar
stage3 Christian P
Saarbrücken, Saarland, Germany   DEU
Now the route is a bit clearer to me. I will start with the block, making sure it will be strong and reliable. Once that is finished I will start on the head, cc'ing it properly and thus finding out how much to mill off.

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grumpicus Steve Jackson
Leicester, Leicestershire, UK   GBR
Agreed that the correct method is to use a burette and measure each of the combustion chamber volumes, but measuring the head thickness will give a good indication of the expected CR, provided the chamber shape itself has not been modified. Paul Geithner's excellent website includes a good guide to nominal compression ratios of the different 1300/1500 heads:- http://auskellian.com/paul/links_files/performance_enhancements.htm (Just scroll down, it's near the bottom.)

From that, the stock TKC1155 head is shown as being 3.05" (77.5mm) thick. It can also be seen that by using a stock 515573 or 218141 head from a 1300 Herald/Dolomite/Toledo, the CR on a 1500 would be around 9.6:1. That head is 2.99" (76.0mm) thick, so machining 0.060" from the TKC1155 head would give the same nominal result. If you do use the head from the Herald, the inlet valve sizes would need to increased to at least the same size as the 1500 stock valves, but the 218141 head from either the Toledo or Dolomite already comes with larger inlet valves than the 1500, and the same exhaust valves.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
Quote:
If you do use the head from the Herald, the inlet valve sizes would need to increased to at least the same size as the 1500 stock valves, but the 218141 head from either the Toledo or Dolomite already comes with larger inlet valves than the 1500, and the same exhaust valves.
[/quote]

Interesting.
I have an early (North American spec) 1500 head, and I cannot see how the inlet valves can be any bigger than they are!
I will have to look up the spec.

One school of thought is that the valve size does not matter (much) as the valve is shielded by the Wall of the squish area.

Kastner suggests rounding over the squish wall in the area of the inlet valve. But this seems controversial.
I did not do it to the degree Kastner suggested. My thought was: For a road car the squish would be important to maintain turbulence at lower rpm.

On my head/s there was quite the restriction just below the inlet vale seat that created a rough cast pocket on the side of the large radius. This was easy to cut back, so as to make that area the same diameter as the valve seat, and eliminate the Hour-glass profile.

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grumpicus Steve Jackson
Leicester, Leicestershire, UK   GBR
In reply to # 1512371 by Tonyfixit Quote:
If you do use the head from the Herald, the inlet valve sizes would need to increased to at least the same size as the 1500 stock valves, but the 218141 head from either the Toledo or Dolomite already comes with larger inlet valves than the 1500, and the same exhaust valves.

Interesting.
I have an early (North American spec) 1500 head, and I cannot see how the inlet valves can be any bigger than they are!
I will have to look up the spec.

One school of thought is that the valve size does not matter (much) as the valve is shielded by the Wall of the squish area.

Kastner suggests rounding over the squish wall in the area of the inlet valve. But this seems controversial.
I did not do it to the degree Kastner suggested. My thought was: For a road car the squish would be important to maintain turbulence at lower rpm.

On my head/s there was quite the restriction just below the inlet vale seat that created a rough cast pocket on the side of the large radius. This was easy to cut back, so as to make that area the same diameter as the valve seat, and eliminate the Hour-glass profile.
[/quote]

Tony, the story goes something like this.....

The heads fitted to the Mk3 Spit and the Herald 13/60 came with inlet valves which had a head diameter of 1.306" and exhaust valves which had a head diameter of 1.170", and both used the 307871 casting. Towards the end of the 1960s, Triumph also produced the 1300 and 1500 FWD saloons/sedans, which used the same basic head casting. This casting, and the same size valves was also used on the Mk4 Spit 1300, for the 1971 and 1972 models. There was a relatively 'high performance' version of the 1500 saloon around 1972/1973 (which may have been a RWD model by then) badged as the '1500TC'. This had twin HS2 carbs, and the same 307871 head casting, but with larger inlet and exhaust valves. The inlet valves had a head diameter of 36.4mm (1.433" ), identified as Stanpart 145328, and the exhaust valves had a head diameter of 31.29mm ( 1.232" ). Obviously the head was modified to suit the larger valves, but it was based on the casting available at the time.

For 1973, the US got the 1500 engine, and the UK Mk 4 got the 18-58-58-18 camshaft, in place of the Mk3 cam used for the 1971 and 1972 UK models. Both the US Spit1500 and the UK 1300 got a revised cylinder head, using the same inlet valve (145328) as the 1500TC saloon, but with standard size 144965 exhaust valves. The story goes that the UK got the larger inlet valves to compensate for loss of the Mk3 cam. The head casting number was 312240 for these engines, and the head was also fitted to the Toledo saloon for those years.

In 1975, the head was again revised, using casting RKC0589, which reverted to a smaller inlet valve (UKC2460) with a head diameter of around 35mm.

So, if you've got a 1973 or 1974 model Spit 1500, you already have the largest inlet valves fitted by the factory to the Spitfire. It is possible to squeeze in a larger inlet valve (around 37.4mm head diameter, Triumphtune used to sell them), but valve shrouding makes this a dubious exercise. On the other hand, the larger exhaust valves as fitted to the 1500TC are still available should anyone want to try them, Stanpart 145015 is the reference.

I think that's pretty much all I know on this subject!



Edited 1 time(s). Last edit at 2018-02-09 01:49 PM by grumpicus.

SpitMan Avatar
SpitMan Silver Member Doug Walls
Brandywine, MD, USA   USA
1970 Triumph Spitfire MkIII "Lil' Red Fox"
1998 Chevrolet Corvette "Silver Fox"
2007 Chevrolet Silverado "Workhorse"
2013 Chevrolet Malibu "Pearl Baby"
Here is a link for Spitfire cylinder head specifications. Also, the pix from the website.


http://auskellian.com/paul/links_files/performance_enhancements.htm#heads

My engine has the 218139 stamped head from a Spitfire Mk IV and milled it .130" to get to 10:1. This is one of the big valve heads.

This seems to be pretty close to the maximum that can be milled from this particular head.

Although I skimmed the Block .020" which is fine for what I wanted to do with this engine, I do not recommend it for a daily driver.



Edited 1 time(s). Last edit at 2018-02-13 10:00 PM by SpitMan.


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