Turbo Compression Question

JamesBaumann

Member

Nov 26, 2003

624

0

16

Vancouver Island

Aug 8, 2005

#1

• Aug 8, 2005

• #1

Ok guys, I have a quick question here. I have a cylinder head that I am currently using in my n/a 2.3. It is ported & polished, has the roller cam & roller followers, and it is shaved .050". Here is my question. If I wanted to build a turbo motor for this car, could I still use this cylinder head even though it is shaved a little? Or will the compression be too high. Lately I have been entertaining the idea of building a turbo motor and if I were to I sure would rather use this head than porting and polishing another one. Let me know how you feel about this guys. Thanks for any help you may be able to give me.

 

Red_LX

I’m not much help unless you’re looking for ****!

Founding Member

Nov 29, 1999

5,896

73

129

Morgantown, WV...where couches meet their doom

Aug 8, 2005

#2

• Aug 8, 2005

• #2

I would say it would probably be a bit too high for a turbo engine, since the head has been milled. The dished pistons in the turbo engine would drop the CR a little, but probably not enough (stock turbos had about a 8:1 CR, n/a's were 9:1). I don't know if you would be able to open up the combustion chamber to make up for the milling, or not.

 

JamesBaumann

Member

Nov 26, 2003

624

0

16

Vancouver Island

Aug 9, 2005

#3

• Aug 9, 2005

• #3

If the formula I am using is right, that much milling would add about .7:1 compression. (.007" = .1:1) So therefore I would be at around 8:7:1 compression, which is still lower than an average n/a engine. Anybody figure thats low enough or is that still a little high?

 

Dr_EluSivE

Founding Member

Apr 24, 2002

2,155

0

56

Central Illinois

Aug 9, 2005

#4

• Aug 9, 2005

• #4

i think you would also need to drop in some turbo valves.. I believe that the turbo motors had special valves that resist heat better then the N/A ones do.

Dr.

 

B

BELL

Founding Member

Feb 21, 2002

722

0

0

California

Aug 9, 2005

#5

• Aug 9, 2005

• #5

i'm gonna side with Dr. E on that i think the valves are different. ditch the n/a keep the cam for a turbo head...

 

Turbo_Raccoon

New Member

May 28, 2005

14

0

0

Del Rio TX

Aug 9, 2005

#6

• Aug 9, 2005

• #6

well yes the turbo motors had different valves but they had the same comprestion ration which was 9:1.

 

freakintiger

New Member

Apr 8, 2004

310

0

0

Virginia Beach, VA :TAX CAPITAL OF THE WORLD!

Aug 9, 2005

#7

• Aug 9, 2005

• #7

I thought only the early carbureted ones had the higher compression...

 

JamesBaumann

Member

Nov 26, 2003

624

0

16

Vancouver Island

Aug 10, 2005

#8

• Aug 10, 2005

• #8

I've never heard of turbo motors having different valves.

 

T

Touring23

Founding Member

Dec 29, 2001

294

0

0

Washington

Aug 10, 2005

#9

• Aug 10, 2005

• #9

*EDIT* What about a "head saver" shim:
http://www.partsamerica.com/product_images/AAP/FEL/8471SP_TOP.jpg
Fel-Pro 8471SP
It's a spacer specifically designed to add volume and thus reduce compression. Alas, I dunno by how much. Maybe someone can post in with that info...?

 

J

joebford

New Member

Aug 15, 2004

15

0

0

Aug 10, 2005

#10

• Aug 10, 2005

• #10

A .050 mill is going to get you close to 1 full point rise in compression ratio.

These engines don't like much over 8.5:1 until you get into detonation issues. They are marginal at the stock ratio of 8:1, especially the t-coupes. That is why they later engines have a fuel switch. If you raise boost pressures, you sure don't want an increase in compression ratio.

You can get a thicker head gasket, and I would go that route as opposed to shims. Too much combustion pressure under boost. Shims don't work well.

I would use the stock head.

The Merkur's are thought to have inconel exhaust valves. Haven't seen proof of that tho. Standard valves work fine. joe

 

JamesBaumann

Member

Nov 26, 2003

624

0

16

Vancouver Island

Aug 11, 2005

#11

• Aug 11, 2005

• #11

Thanks for the info Joe. I've got the old completely stock head that I took swapped off when I swapped this new one on, so perhaps I should just use that. We'll see, it'll be a whlie yet before I swap in a turbo motor, (if I even do) so I have some time to weigh my options.

 

bhuff30

Founding Member

Dec 11, 2001

6,037

35

129

Olathe KS

Aug 11, 2005

#12

• Aug 11, 2005

• #12

Touring23 said:

*EDIT* What about a "head saver" shim:
http://www.partsamerica.com/product_images/AAP/FEL/8471SP_TOP.jpg
Fel-Pro 8471SP
It's a spacer specifically designed to add volume and thus reduce compression. Alas, I dunno by how much. Maybe someone can post in with that info...?

Click to expand...

A thicker head gasket isn't a good solution. You loose all the quench area which of course increases the tendency for detonation. It is quite common to hear that someone had less detonation with the higher CR than a thick HG and lower CR.

 

T

Touring23

Founding Member

Dec 29, 2001

294

0

0

Washington

Aug 11, 2005

#13

• Aug 11, 2005

• #13

Good point

 

9

99blkcobravert

New Member

Apr 25, 2005

30

0

0

Vancouver, WA

Aug 13, 2005

#14

• Aug 13, 2005

• #14

I have an 88TC motor with a fresh build with all the tricks if you're interested.

 

JamesBaumann

Member

Nov 26, 2003

624

0

16

Vancouver Island

Aug 14, 2005

#15

• Aug 14, 2005

• #15

How much?

 

raceguy13

New Member

Jul 9, 2005

12

0

2

Albany, Oregon

Aug 14, 2005

#16

• Aug 14, 2005

• #16

just run methonal it wont detonate