3.0 with 2.5 crank question - Alfa Romeo Forum
You are currently unregistered, register for more features.    
 
Thread Tools
(Post Link) post #1 of 7 Old 04-12-15 Thread Starter
Status: Working Hard On 156 Veloce 3.0 Turbo Project
AO Silver Member
 
mirlock's Avatar
 
Join Date: Mar 2014
Location: United Kingdom
County: Northamptonshire
Posts: 1,309
3.0 with 2.5 crank question

Ive read as much as i can about the 2.8 conversion, But there seems to be some confusion on the way to go.

version 1. I want to know if i can put the 2.5 crank in the 3.0 engine using the 3.0 heads etc.

version 2. or do i have to use the 2.5 block and machine it for the 3.0 liners and pistons

i would like to do it version 1 way but people have been chatting about having to use the 2.5 heads etc.

If i cant do it version 1 way i will carry on as standard 3.0 and do the 2.8 conversion as a side project for rainy days

thanks

All spares parts for 156 and 147 being sold that i will not be using (cheap) nothing too small ask what you want , willing to post world wide Phone 07922123242 Ask for Neil and say Mark said to phone .

Download link for Alfa 156's http://www.filedropper.com/alfaelearn
mirlock is offline  
Sponsored Links
Advertisement
 
Status: Busy busy busy!
Club Member
Membro Premio
 
Pud237's Avatar
 
Club Member Number: 71
Join Date: Apr 2006
Location: United Kingdom
County: Cumbria
Posts: 44,752
From what I have read its only really version 1 which has any chance of being a budget conversion. Once you get into boring out blocks then things are super expensive.

You would need 3.0 heads if you were using 3.0 liners & pistons in a 3.0 block with a 2.5 crank. If you used 2.5 heads the dish wouldn't match the liners, I can't see how that would work. Obviously the new TDC would be lower than the top of the liner but so it wouldn't hit, but you'd still have that sharp angle of where the dish meets the flat of the head poking into the path of the piston.

Autolusso Penrith - UK's leading independent Alfa Romeo specialist with branches in Bedfordshire, Cumbria & Dorset

Wizard Exhaust systems available here

Tel: 01768 879 171
Pud237 is offline  
(Post Link) post #3 of 7 Old 04-12-15 Thread Starter
Status: Working Hard On 156 Veloce 3.0 Turbo Project
AO Silver Member
 
mirlock's Avatar
 
Join Date: Mar 2014
Location: United Kingdom
County: Northamptonshire
Posts: 1,309
Quote:
Originally Posted by Pud237 View Post
From what I have read its only really version 1 which has any chance of being a budget conversion. Once you get into boring out blocks then things are super expensive.

You would need 3.0 heads if you were using 3.0 liners & pistons in a 3.0 block with a 2.5 crank. If you used 2.5 heads the dish wouldn't match the liners, I can't see how that would work. Obviously the new TDC would be lower than the top of the liner but so it wouldn't hit, but you'd still have that sharp angle of where the dish meets the flat of the head poking into the path of the piston.
Thanks Pud , Ive read so many threads with so many ways of doing it but you have answered what i was hoping the best way.

as far as i have read the rods and the same in both engines, So just swap the crank over and i will have a 2.8 with lower compression 7:1 or something like that, Then i can have a higher boost.

Thanks dude
mirlock is offline  
Status: Busy busy busy!
Club Member
Membro Premio
 
Pud237's Avatar
 
Club Member Number: 71
Join Date: Apr 2006
Location: United Kingdom
County: Cumbria
Posts: 44,752
Yes.. But, possible issues with losing the 'squish' effect:

https://en.wikipedia.org/wiki/Squish_(piston_engine)

A better bet might be pistons that still come up to the same TDC height at the edges but are dished in the centre to lower compression. And then if you're going down the replacement piston route, you might as well stick with the 3.0 crank and just lower compression with pistons (and maybe rods) but leave the crank as-is.
Pud237 is offline  
(Post Link) post #5 of 7 Old 04-12-15 Thread Starter
Status: Working Hard On 156 Veloce 3.0 Turbo Project
AO Silver Member
 
mirlock's Avatar
 
Join Date: Mar 2014
Location: United Kingdom
County: Northamptonshire
Posts: 1,309
Quote:
Originally Posted by Pud237 View Post
Yes.. But, possible issues with losing the 'squish' effect:

https://en.wikipedia.org/wiki/Squish_(piston_engine)

A better bet might be pistons that still come up to the same TDC height at the edges but are dished in the centre to lower compression. And then if you're going down the replacement piston route, you might as well stick with the 3.0 crank and just lower compression with pistons (and maybe rods) but leave the crank as-is.
Yep i think your right Dan, I think i'll stick with the 3.0 and maybe do the 2.8 conversion as a complete rebuild project after im done with this car
mirlock is offline  
Status: Busy busy busy!
Club Member
Membro Premio
 
Pud237's Avatar
 
Club Member Number: 71
Join Date: Apr 2006
Location: United Kingdom
County: Cumbria
Posts: 44,752
Have you done anything to reduce compression on your current 3.0 engine which is turbo'd?
Pud237 is offline  
(Post Link) post #7 of 7 Old 04-12-15 Thread Starter
Status: Working Hard On 156 Veloce 3.0 Turbo Project
AO Silver Member
 
mirlock's Avatar
 
Join Date: Mar 2014
Location: United Kingdom
County: Northamptonshire
Posts: 1,309
Quote:
Originally Posted by Pud237 View Post
Have you done anything to reduce compression on your current 3.0 engine which is turbo'd?
Yeah i had some meat taken from the head dome 5cc from each cylinder which i think lowered it to 8:1
mirlock is offline  
Reply

Go Back   Alfa Romeo Forum > Supported Alfa Romeo Models > Technical & Vehicle Assistance > Engines (TS, JTS, JTD & V6)

Tags
crank , question

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome