The Triumph Dolomite Club - Discussion Forum

The Number One Club for owners of Triumph's range of small saloons from the 1960s and 1970s.
It is currently Sun Apr 21, 2019 10:59 pm

All times are UTC




Post new topic  Reply to topic  [ 13 posts ] 
Author Message
 Post subject: Sprint piston heights
PostPosted: Mon Apr 01, 2019 1:36 pm 
Offline
TDC Member

Joined: Tue Jan 10, 2012 12:39 am
Posts: 351
Just starting to rebuild a Sprint engine and have come across a surprise, the pistons are above the block face at TDC by about 0.025".

Image

The block needed a liner because one bore had some water damage after the engine was left on the garage floor so the machine shop had to skim the block face afterwards.
Question is, have they taken too much off and will I have to get them to take a bit off the top of the pistons as well?
The cam is supposed to be Newman PH3 but it has no markings at all.

I do have a "thicker" Payen gasket but will that be enough to avoid excessive compression ratio.

I posted this on the Official Triumph Dolomte FB page as well.

_________________
Russ Cooper
Dursley
UK


Top
   
PostPosted: Mon Apr 01, 2019 11:19 pm 
Offline
TDC Member

Joined: Tue Jan 10, 2012 12:39 am
Posts: 351
Discussed with the machine shop today and we decided to machine the top of the pistons to bring them dowm level with the block face. Two will need 0.025" and two need 0.027" taking off.

Image

_________________
Russ Cooper
Dursley
UK


Top
   
PostPosted: Tue Apr 02, 2019 8:25 am 
Offline
TDC Shropshire Area Organiser

Joined: Sun Aug 21, 2011 4:12 pm
Posts: 4957
Location: Highley, Shropshire
Will you not have to deepen the valve cut outs by a corresponding amount too? Especially as you (allegedly) have a hot cam!

Steve

_________________
2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, MOT prep. Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


Top
   
PostPosted: Tue Apr 02, 2019 9:22 am 
Offline
TDC West Mids Area Organiser
User avatar

Joined: Thu Sep 28, 2006 12:13 pm
Posts: 12161
Location: Over here...can't you see me?
Will not that bring the top land above the rings too close to the top? Having seen what can happen to lands from using lead free fuel and detonation, I'd not want to reduce the 'meat' there, particularly if using a hotter cam and altered timing.

Be careful that the machine shop aren't offering you a solution to their problem that compounds your problem later on...


Top
   
PostPosted: Tue Apr 02, 2019 12:20 pm 
Offline
TDC Member
User avatar

Joined: Sat Apr 12, 2014 10:02 pm
Posts: 2204
Location: Nr Kenilworth
I'd use a thicker head gasket, although with a std gasket if the piston was 0.8mm from the Head at TDC I'd leave it there for good squish and alter valve cutouts if needed to keep the valves clear of the pistons. Cam timing will be more important of course

Tony

_________________
Membership 2014047


Top
   
PostPosted: Tue Apr 02, 2019 1:37 pm 
Offline
TDC Member

Joined: Tue Jan 10, 2012 12:39 am
Posts: 351
Quote:
Will not that bring the top land above the rings too close to the top? Having seen what can happen to lands from using lead free fuel and detonation, I'd not want to reduce the 'meat' there, particularly if using a hotter cam and altered timing.

Be careful that the machine shop aren't offering you a solution to their problem that compounds your problem later on...
We only plan to take 0.025" off the pistons so I think the top land should still be OK.
I am hoping to keep the engine fairly civilised and nice to drive so trying to be a bit conservative and not too high a CR

_________________
Russ Cooper
Dursley
UK


Last edited by dursley92 on Tue Apr 02, 2019 1:40 pm, edited 1 time in total.

Top
   
PostPosted: Tue Apr 02, 2019 1:38 pm 
Offline
TDC Member

Joined: Tue Jan 10, 2012 12:39 am
Posts: 351
Quote:
Will you not have to deepen the valve cut outs by a corresponding amount too? Especially as you (allegedly) have a hot cam!

Steve
Yes I will get them to do that as part of the job.

ps Steve, its the engine that came out of the Red Sprint you had from Mark Maynard to break about 4/5 years ago.

_________________
Russ Cooper
Dursley
UK


Top
   
PostPosted: Tue Apr 02, 2019 2:12 pm 
Offline
TDC Shropshire Area Organiser

Joined: Sun Aug 21, 2011 4:12 pm
Posts: 4957
Location: Highley, Shropshire
Quote:


ps Steve, its the engine that came out of the Red Sprint you had from Mark Maynard to break about 4/5 years ago.
Glad to see it's getting built again, but dream on! I got that car from Mark in February 2012, more than 7 years ago! It's soul still lives on in my garage with the Dolomega project which is still under way, completion projected by June 2020!

Steve

_________________
2 door '73 Toledo with Vauxhall Carlton 2.0 8v engine OWF 797M (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine EGP 247T (The Dolomega)
'91 Cavalier 2ltr 8v auto
'95 Cavalier 2ltr 16v auto
Spectrum Auto Services, Servicing, Repairs, MOT prep. Apprentice served Triumph Specialist for 45 years and home of Maverick Triumph.PM for more info or quotes.


Top
   
PostPosted: Tue Apr 02, 2019 7:57 pm 
Offline
TDC West Mids Area Organiser
User avatar

Joined: Thu Sep 28, 2006 12:13 pm
Posts: 12161
Location: Over here...can't you see me?
Can you not source another block?


Top
   
PostPosted: Tue Apr 02, 2019 11:06 pm 
Offline
TDC Member

Joined: Tue Jan 10, 2012 12:39 am
Posts: 351
Quote:
Can you not source another block?
Yes I have another couple. One needs dipping to clean all the crud out of the waterways, one needs a plug getting out from the water pump position because it had an EWP and my old TR7 one that needs boring.

I just planned to use this one so I will see how it works out before going for Plan B, C or D!

_________________
Russ Cooper
Dursley
UK


Top
   
PostPosted: Thu Apr 04, 2019 8:51 am 
Offline
TDC Staffs Area Organiser
User avatar

Joined: Wed Oct 18, 2006 1:08 pm
Posts: 5576
Location: The Old Asylum
This is a similar solution to grinding valve stems to get the right valve clearances rather than sort the seats out i.e. a bit of a bodge. I'd source another block.

_________________
Mark

1961 Chevrolet Corvair Greenbrier Sportswagon
1980 Dolomite Sprint project using brand new shell
2009 Mazda MX5 2.0 Sport
2018 Infiniti Q30


Top
   
PostPosted: Thu Apr 04, 2019 10:38 am 
Offline
TDC West Mids Area Organiser
User avatar

Joined: Thu Sep 28, 2006 12:13 pm
Posts: 12161
Location: Over here...can't you see me?
Quote:
This is a similar solution to grinding valve stems to get the right valve clearances rather than sort the seats out i.e. a bit of a bodge. I'd source another block.
That's kind of my thoughts too, a block has been compromised, so why compromise a set of pistons too, in the hope it will work out OK? If it doesn't work out, you've scrapped a block and a set of pistons...


Top
   
PostPosted: Sun Apr 07, 2019 9:26 am 
Offline
TDC Member
User avatar

Joined: Sun Sep 08, 2013 2:35 pm
Posts: 744
On the issue of replacement blocks, has anybody replaced the TR7 dipstick insert with one from a Sprint (I don't know if the 1850 is like the Sprint or not).

As far I understand, apart from early Sprint blocks being a slightly different composition of the cast iron alloy, the blocks are otherwise the same.

Graham

_________________
The 16v Slant 4 engine is more fun than the 3.5 V8, because you mostly drive it on the upslope of the torque curve.

Factory 1977 TR7 Sprint FHC VVC 697S (Now all of, but still needs putting together)
B&Y 73 Dolomite Sprint UVB 274M (kids!)
1970 Maroon 13/60 Herald Convertable (wife's fun car).


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 13 posts ] 

All times are UTC


Who is online

Users browsing this forum: Bing [Bot] and 8 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited