[TR] Advice on high compression head

Wed Apr 7 17:05:02 MDT 2021

Cliff:

I agree with Dave. A first step, however, would be to check the volume of the combustion chambers to see what your compression ratio actually is, using the formula CR = (swept volume + chamber volume)/chamber volume. This will give you an idea of whether you can reduce the CR to a more reasonable number by removing material, strategically, per Kas’s book, from the combustion chambers. While you’re doing this you can even match the intake manifold to the inlet ports and do a little cleaning  of the inlet tracts. I have done this work, albeit on an MG head, and it can be accomplished with simple tools - a small grinder preferably. Just double check your math at every step.

You can measure the chamber volume using a burette, using light oil as the liquid. In order to minimize the effects of the meniscus, you can drill a hole in a square of plexiglas (maybe 3/8” diameter), place the plexiglas over the combustion chamber, then fill the chamber from the burette, through the drilled hole in the plexiglas, noting the volume of liquid required to fill to the bottom of the hole. You can then compare the four chamber volumes to see how much you need to remove from each to get the desired CR.

It’s a fun and very satisfying process and you will have lemonade at the end, instead of lemons. 😊

Mike

Sent from my iPhone

On Apr 7, 2021, at 17:23, Dave Connitt <dconnitt at fuse.net> wrote:

 Hi Cliff,
A lot of racers have milled the heads of wet liner engines to increase compression. In Kas Kastner’s TR4/TR4A competition preparation manual, he goes into much detail about how to reshape the combustion chambers in the head to reduce/eliminate “hot spots”. This may be the cause of your pre-ignition. Yoy may want to get that book and read over his cylinder head chapter. Regarding the push rod length, the length reduction is directly related to how much material is removed from the head so just buying shortened pushrods won’t get you the best results. I think you should figure out how much material was removed from the “stock” head and shorten the pushrods accordingly.
I think you can certainly save the head but you will need to do some homework reading over Kas’s competition prep manual and find a good automotive machinist for the pushrods.
Dave Connitt

Sent from my iPhone

On Apr 7, 2021, at 5:41 PM, DAVID MASSEY <dave1massey at cs.com> wrote:

I went the band-aid route on my TR3 for the same reason.  But the right way is to get a machinist to shorten the pushrods.  BPNW sells short rods for the TR6/SC engine but at that time they didn't have any for the wet-sleeve engine.

Dave

-----Original Message-----
From: Cliff Hansen <cliff_hansen at outlook.com>
To: list Triumph <triumphs at autox.team.net>
Sent: Wed, Apr 7, 2021 4:23 pm
Subject: [TR] Advice on high compression head

The telenovela “What’s going on with this 4A cylinder head” has developed a new plot twist.

The head, after cleanup, measures 3.21” from bottom to the surface for the valve cover gasket. Stock is 3.330 (if I got the number correctly). Some PO cut 0.11 off, because only 0.010” was removed in this round of clean up. Now I can see an explanation for the persistent pinging I’ve dealt with over the last few years (head has been milled so compression is high, material near intake valves has been thinned, increasing likelihood of hot spots – I’m getting this from Kastner’s preparation book), which I had thought was due to leaking intakes, carb shafts, or operating at higher altitude.

As is, I can’t use this head because there is not enough slack in the valve train to give 0.010” clearance on several valves. I didn’t notice before, but now that I am looking, all the valve adjusters were nearly backed out all the way.

Looking for advice from the list: is there any reasonable way to use this head?
- I’d prefer to reduce compression but don’t see any reasonable way to accomplish that. I called GasketWorks and he gently discouraged me from getting a custom thick head gasket, saying instead I’d be better off finding a head which had not been milled so much.
 - Shimming the rocker pedestals to get valve clearance feels like a bandaid which certainly won’t address the pinging (assuming that the pinging is a result of the shortened head).

Would appreciate any advice on the way forward.

Cliff

Sent from Mail<https://urldefense.proofpoint.com/v2/url?u=https-3A__go.microsoft.com_fwlink_-3FLinkId-3D550986&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=HL4LAX-jeuoWNeqz1u1ryqDHfrhQ38xO3ECYGpjCniQ&m=xKy3rQJllI29_-VEx53KysB1cEL1hADtXt8rwc_5S8I&s=92G6frgOLMx_fGaqbVsFNihrxZzRNxNoZXlR9k9WTxE&e=> for Windows 10

** triumphs at autox.team.net<mailto:triumphs at autox.team.net> **

Donate: http://www.team.net/donate.html<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.team.net_donate.html&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=HL4LAX-jeuoWNeqz1u1ryqDHfrhQ38xO3ECYGpjCniQ&m=xKy3rQJllI29_-VEx53KysB1cEL1hADtXt8rwc_5S8I&s=xpyG3UWiFL2XqHWRBj1OMwcZ-I_keEM608ez-4aosE8&e=>
Archive: http://www.team.net/pipermail/triumphs <https://urldefense.proofpoint.com/v2/url?u=http-3A__www.team.net_pipermail_triumphs&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=HL4LAX-jeuoWNeqz1u1ryqDHfrhQ38xO3ECYGpjCniQ&m=xKy3rQJllI29_-VEx53KysB1cEL1hADtXt8rwc_5S8I&s=Qvd3IZU1OE_MJ3-7SyVKpNoUMlhJ6VFaO4OuORzXPl8&e=> http://www.team.net/archive<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.team.net_archive&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=HL4LAX-jeuoWNeqz1u1ryqDHfrhQ38xO3ECYGpjCniQ&m=xKy3rQJllI29_-VEx53KysB1cEL1hADtXt8rwc_5S8I&s=dGz-UuEP1Ta645u4AeQHFK82LR7Gits3mpPuZj7sqJc&e=>

Unsubscribe/Manage: http://autox.team.net/mailman/options/triumphs/dave1massey@cs.com<https://urldefense.proofpoint.com/v2/url?u=http-3A__autox.team.net_mailman_options_triumphs_dave1massey-40cs.com&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=HL4LAX-jeuoWNeqz1u1ryqDHfrhQ38xO3ECYGpjCniQ&m=xKy3rQJllI29_-VEx53KysB1cEL1hADtXt8rwc_5S8I&s=8Yo-lnwTpqjd-GAe_SbvnH1ImW3sAex6dLcHtGgPOaA&e=>
** triumphs at autox.team.net **

Donate: http://www.team.net/donate.html
Archive: http://www.team.net/pipermail/triumphs  http://www.team.net/archive

Unsubscribe/Manage: http://autox.team.net/mailman/options/triumphs/dconnitt@fuse.net
** triumphs at autox.team.net **

Donate: https://urldefense.proofpoint.com/v2/url?u=http-3A__www.team.net_donate.html&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=HL4LAX-jeuoWNeqz1u1ryqDHfrhQ38xO3ECYGpjCniQ&m=xKy3rQJllI29_-VEx53KysB1cEL1hADtXt8rwc_5S8I&s=xpyG3UWiFL2XqHWRBj1OMwcZ-I_keEM608ez-4aosE8&e=
Archive: https://urldefense.proofpoint.com/v2/url?u=http-3A__www.team.net_pipermail_triumphs&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=HL4LAX-jeuoWNeqz1u1ryqDHfrhQ38xO3ECYGpjCniQ&m=xKy3rQJllI29_-VEx53KysB1cEL1hADtXt8rwc_5S8I&s=Qvd3IZU1OE_MJ3-7SyVKpNoUMlhJ6VFaO4OuORzXPl8&e=  https://urldefense.proofpoint.com/v2/url?u=http-3A__www.team.net_archive&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=HL4LAX-jeuoWNeqz1u1ryqDHfrhQ38xO3ECYGpjCniQ&m=xKy3rQJllI29_-VEx53KysB1cEL1hADtXt8rwc_5S8I&s=dGz-UuEP1Ta645u4AeQHFK82LR7Gits3mpPuZj7sqJc&e=

Unsubscribe/Manage: https://urldefense.proofpoint.com/v2/url?u=http-3A__autox.team.net_mailman_options_triumphs_mmarr-40albiontechnical.com&d=DwICAg&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=HL4LAX-jeuoWNeqz1u1ryqDHfrhQ38xO3ECYGpjCniQ&m=xKy3rQJllI29_-VEx53KysB1cEL1hADtXt8rwc_5S8I&s=A6pZuPW-u2qZ9Ys37enF2Soq5SDdl4nRZk-uutyCpfQ&e=
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://autox.team.net/pipermail/triumphs/attachments/20210407/f288dfe2/attachment.htm>