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Old 03-03-2017, 06:56 AM   #1
IWantedAnAE86
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Default How to increase b21ft compression ratio?

Hi guys, thinking about picking up an '83 to '85 240 GLT turbo when a good one pops up. I love these cars so much, but the thing that bugs me is the crazy low compression ratio of 7.5:1. Is there any way to increase the compression ratio? Any pistons I can drop in from another Volvo? Thinner headgaskets? The reason being is that I want something that I don't have to floor to make power (worried about MPG) as this will be my DD.

I'm torn between getting an '88-'89 740 turbo or one of these. I really love the lines of the 240s so much, this is the only thing holding me back. Any help would be greatly appreciated.
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Old 03-03-2017, 08:48 AM   #2
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Swap in a B230F+T
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Old 03-03-2017, 09:03 AM   #3
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Originally Posted by IWantedAnAE86 View Post
Hi guys, thinking about picking up an '83 to '85 240 GLT turbo when a good one pops up. I love these cars so much, but the thing that bugs me is the crazy low compression ratio of 7.5:1. Is there any way to increase the compression ratio? Any pistons I can drop in from another Volvo? Thinner headgaskets? The reason being is that I want something that I don't have to floor to make power (worried about MPG) as this will be my DD.

I'm torn between getting an '88-'89 740 turbo or one of these. I really love the lines of the 240s so much, this is the only thing holding me back. Any help would be greatly appreciated.


Aside from milling the surface of the block, use a thinner head gasket.

Or, do nothing and just raise the boost. Low comp loves boost.
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Old 03-03-2017, 09:12 AM   #4
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Swap in a B230F+T
I would but I just don't have the tools to do so, heck I don't even have a garage!!
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Old 03-03-2017, 09:53 AM   #5
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Aside from milling the surface of the block, use a thinner head gasket.

Or, do nothing and just raise the boost. Low comp loves boost.
Any idea what the compression ratio would be with a 0.27" headgasket (the thinnest one) from RSI? Are there any other companies that make performance orientated head gaskets? Because $109.99 is pretty damn expensive for a head gasket lol. Boost isn't gonna help me when I'm trying to drive while MPG conscious
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Old 03-03-2017, 09:57 AM   #6
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I would but I just don't have the tools to do so, heck I don't even have a garage!!
You don't need a garage to swap an engine. Especially one that just bolts in.
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Old 03-03-2017, 09:57 AM   #7
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Any idea what the compression ratio would be with a 0.27" headgasket (the thinnest one) from RSI? Are there any other companies that make performance orientated head gaskets? Because $109.99 is pretty damn expensive for a head gasket lol. Boost isn't gonna help me when I'm trying to drive while MPG conscious
RSI went out of business too
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Old 03-03-2017, 10:07 AM   #8
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RSI went out of business too
Are you sure? Their website is still up and it looks like you can still purchase things.
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Old 03-03-2017, 10:14 AM   #9
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Originally Posted by IWantedAnAE86 View Post
The reason being is that I want something that I don't have to floor to make power (worried about MPG) as this will be my DD.

I'm torn between getting an '88-'89 740 turbo or one of these. I really love the lines of the 240s so much, this is the only thing holding me back. Any help would be greatly appreciated.
740 Turbos don't get stellar gas mileage either.

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Are you sure? Their website is still up and it looks like you can still purchase things.
They ceased operations a while back.

You seem to have conflicting goals here. That and the fact that you say you don't have tools or a garage (for dropping in pistons I assume) makes this whole conversation sort of silly.
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Old 03-03-2017, 10:33 AM   #10
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We be sure

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Are you sure? Their website is still up and it looks like you can still purchase things.
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Old 03-03-2017, 10:35 AM   #11
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740 Turbos don't get stellar gas mileage either.

You seem to have conflicting goals here. That and the fact that you say you don't have tools or a garage (for dropping in pistons I assume) makes this whole conversation sort of silly.
I'm aware of that don't worry lol, my goal is to make the car as efficient off boost as possible. As for dropping in pistons, you don't necessarily have to remove the entire block to do so, I live in a townhouse and our car port is sufficient to remove the cylinder head and oil pan. I don't however have space to store an entire engine.
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Old 03-03-2017, 10:36 AM   #12
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We be sure
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Old 03-03-2017, 10:45 AM   #13
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As for dropping in pistons, you don't necessarily have to remove the entire block to do so
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Old 03-03-2017, 10:46 AM   #14
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longer rods and shorter pistons with the right geometry will make that b21ft less of a turd.
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Old 03-03-2017, 10:53 AM   #15
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You can replace the original deep dish B21FT pistons with shallower dish B21A pistons, but you'll most likely need to buy a set new and have the block machined. Doing a B230FT engine swap, or just buying a 740T, are more practical.

The B21FTs will have a SCR of ~8.0:1, the B21As will get SCR up to ~9.5:1. http://forums.turbobricks.com/showthread.php?p=5421139
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Old 03-03-2017, 11:38 AM   #16
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No tools, no garage?

There is only one answer.


LS swap it!
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Old 03-03-2017, 11:44 AM   #17
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Originally Posted by IWantedAnAE86 View Post
Hi guys, thinking about picking up an '83 to '85 240 GLT turbo when a good one pops up. I love these cars so much, but the thing that bugs me is the crazy low compression ratio of 7.5:1. Is there any way to increase the compression ratio? Any pistons I can drop in from another Volvo? Thinner headgaskets? The reason being is that I want something that I don't have to floor to make power (worried about MPG) as this will be my DD.

I'm torn between getting an '88-'89 740 turbo or one of these. I really love the lines of the 240s so much, this is the only thing holding me back. Any help would be greatly appreciated.
#1 They're really not around much anymore,let alone a 'good' one.

#2 They're not TB ¢heap anymore when they do pop up.

#3 They'll get ~25mpg on the freeway with a stick.

#4 Gas is cheap now, stop complaining or get a Prius.
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Old 03-03-2017, 11:50 AM   #18
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No tools, no garage?

There is only one answer.


LS swap it!

gross
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Old 03-03-2017, 11:51 AM   #19
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#1 They're really not around much anymore,let alone a 'good' one.

#2 They're not TB ¢heap anymore when they do pop up.

#3 They'll get ~25mpg on the freeway with a stick.

#4 Gas is cheap now, stop complaining or get a Prius.
Gas isn't that cheap here in BC Canada, AND MAYBE I WILL!
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Old 03-03-2017, 11:57 AM   #20
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I think you should because what you're saying about old Volvos isn't adding up.

Or simply buy that AE86 you seem to lust after, and go bug the guys on the Toyota forums.

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Old 03-03-2017, 02:41 PM   #21
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I think you should because what you're saying about old Volvos isn't adding up.

Or simply buy that AE86 you seem to lust after, and go bug the guys on the Toyota forums.

I've been on the market for one for 4 years, only ones that pop are beat to hell by wannabe teen drifters who the try to resell the car after its become FUBAR for 5x what they bought it for.
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Old 03-03-2017, 02:42 PM   #22
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You can replace the original deep dish B21FT pistons with shallower dish B21A pistons, but you'll most likely need to buy a set new and have the block machined. Doing a B230FT engine swap, or just buying a 740T, are more practical.

The B21FTs will have a SCR of ~8.0:1, the B21As will get SCR up to ~9.5:1. http://forums.turbobricks.com/showthread.php?p=5421139
Wow, very helpful! Might just go this route, I wonder how the pistons will deal with boost tho.
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Old 03-03-2017, 02:56 PM   #23
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I've been on the market for one for 4 years, only ones that pop are beat to hell by wannabe teen drifters who the try to resell the car after its become FUBAR for 5x what they bought it for.
this is what happened to all the 240 GLTs, FYI
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Old 03-03-2017, 03:05 PM   #24
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Originally Posted by 740atl View Post
Aside from milling the surface of the block, use a thinner head gasket.

Or, do nothing and just raise the boost. Low comp loves boost.
Thinner headgasket meh realistically you have to leave something around 030, so going down from 044 to 030 ain't gonna do squat..Old B21 and B23 leave the piston down the bore a goodly amount--on paper around 027 below deck.. can't see the guy decking the block with no tools, no garage..

That leaves your answer...Keep the T cam cause that gets you the most static comp with its modest intake valve closing, and UP THE BEWST..
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Old 03-03-2017, 03:14 PM   #25
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Keep the t cam and throw on a 15g or a 16t on the cheap and have fun. I had a stock b21ft and a 16t with a t cam in my old Toyota and it was alot of fun
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