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Old 06-27-2017, 12:42 PM   #1
Ls1fst98
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Default Engine, trans swap questions.

Im new to volvos, but have built a few 4th gen ls1 fbody cars. Currently have 2 volvos at my disposal. The car i want to mod is a 1991 240 wagon. Auto Transmission takes forever shift when it gets warm from 2-3, snd the engine in it is spewing smoke and runs rough.

The donor car is a 1988 740 gle sedan that was involved in an accident to the front end that totalled it, but never touched engine. Car runs and drives like a dream.

Would it be better to rebuild the wagon, or swap over everything from the 740?

Future plan is a cheap turbo setup for a fun driver/beach wagon.

I have been lurking for a year or 2 and just now decided to take on this project.
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Old 06-27-2017, 12:44 PM   #2
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Swap 740 stuff into the 240.

In general 240's are better looking and the 740's had better drivetrains. It just writes itself....
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Old 06-27-2017, 12:50 PM   #3
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A few random things you'll need to do:
- change the head mounted distributor on the 740 to a block mounted distributor on the 240 - there is not enough room behind the engine on a 240. You will need an intermediate shaft that has the gears cut into it, most engines with head mounted distributors just have a round circle of metal - they skipped grinding teeth into it.

- Accessories and motor mounts - just pull all that off the 240 motor and put them onto the 740 motor's block. The 240 motor mounts on the crossmember are closer together. And some of the accessories were in different positions for whatever reason.

I think (but I'm not entirely sure) that you're in luck with the fuel injection system - both cars should have Bosch LH2.4. Just use the 240's engine harness and plug it into the 740 engine once it's in the car.
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Old 06-27-2017, 12:54 PM   #4
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I did read about the shafts and distributor issue, i am onnthe hunt for that stuff. I assume that means opening up the engine to do. If thats the case ill do head gasket, and maintenance items while in there. Appreciate all the quick responses. I assume the lh2.4 is fine for mild boost if running a good pump and maybe injectors and boost referenced fpr (at least what i can find searching) the limiting factor really is the compression ratio?
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Old 06-27-2017, 01:03 PM   #5
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You don't have to pull the head for the int shaft. Just pull the breather box and pull thr oil pump drive up and out, and take off the seal housing on the front of the engine, the int shaft comes out forward.

I think you are a bit limited in how much boost you can run on a higher compression N/A bottom end, but it will be perkier off boost. There are lots of threads here on '+t' methods of adding a turbo to a N/A motor.

I think you're generally better off just getting a Turbo LH2.4 computer - since the factory was nice enough to do all that engineering work for you. Instead of trying to get the NA computer to understand boost and messing with the fuel pressure.
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Old 06-27-2017, 01:17 PM   #6
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I gotvha, didnt realise it was that easy. Coming from a pushrod v8 world the ohc stuff can be intimidating to look at. The headgasket was in prep for boost, just to have it done, and didnt know if anyone made a thicker mls gasket to help offset some of that cr. I also run e85 in all my ls cars, so that is an easy option for this as well (update fuel lines, pump, injectors)
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Old 06-27-2017, 02:36 PM   #7
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I run E85 too, it's great stuff for boost.

The way the combustion chambers work on these old fashioned bathtub chamber heads means that spacing the head out with a thicker HG isn't necessarily a good approach. These heads are designed to have 'squish' or 'quench' - there are flat areas of the head that the piston *almost* touches at TDC. If that clearance is nice and tight, the piston really *snaps* the already burning air/fuel mixture out from that closing sliver of space and really swirls it into the central combustion chamber. If you increase that clearance (with HG thickness, or piston crown/block deck height) then the intensity of that *snap* rapidly diminishes. And less squish, less swirl, and more of a tendency to detonate, not less.

With E85 fuel you probably shouldn't worry too much about lowering the CR.

But that brings us to the next bit of not-so-great news for you - the 1988 motor is a 'skinny rod' motor. Volvo was trying to eek a mpg or two extra out of the motor, so they did a low friction (smaller bearings) and low inertia (lighter reciprocating mass) redesign. This resulted in skinny connecting rods. Which are fine in normal stock usage (N/A and 7 psi stock boost levels), but if you want to make a bunch more HP, theyr'e going to be the weak link. It doezsn't take much of a tuning error to detonate under boost and bend/break them. Like the saying goes 'ping, ping, boom'. Depending on your goals with the car, you might want to think about taking the bottom end apart and using either some later model 'thick' rods (Volvo sort of realized their mistake after a few years and went back to a burlier bottom end) or some H-beam aftermarket rods. Or just leave it alone if you aren't going to run too much boost and you're pretty confident in your tuning ability.
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Old 06-27-2017, 03:07 PM   #8
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I am getting both cars for free, but did want to be a "cheap" build. What is the realistic hp levels of the motor with a turbo ecu? Given a good pump and injectors with the na cr? Ive seen some h beam rods for about 200$ and its no biggy to swap them out, as im sure i have 95% of the tools from building small block v8s. My thought though is if im going that far into it, is there a better cam i can find on a budget, or get a head from a turbo car? Considered lile anjunkyard build if you will, but def want to keep reliability. (I know those dont always go hand in hand)

im still pouring over all the build threads here but alot seem to be missing pics, or the links are no good. If i can do the motor stuff (including turbo) for less than say 1500$ if possible thatd be great.

I do need suspension stuff on the wagon as its been sitting for about 2 years. So ill be replacing most with aftermarket parts. Thay will be my next line of research. Also the differentials in the wagon vs the 740 sedan, and are they amd open diff or a limited slip type unit. (Not sure id have traction issues)
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Old 06-27-2017, 03:15 PM   #9
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No need to swap a turbo head, it's the same thing other than the sodium filled exhaust valves in the turbo. Which is not required at all, I'm not sure you can really tell a difference between them in real world usage.

HP levels on the skinny rods are highly variable because if you can keep it from pinging you can make plenty of HP with them (300+), get the tuning a bit off and ping on them and you can break them at far lower HP levels.

8V motors can be made (economically) to put out 300 hp, if you're wanting more than that then the $/HP curve starts to tilt to other options.

Last edited by JohnMc; 06-27-2017 at 03:26 PM..
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Old 06-27-2017, 03:32 PM   #10
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Soo then looks like 300 will be the goal haha. Or just under. Maybe ill do rods while i have it out, freshen everything up for piece of mind. Cant be overly expensive. Hows the autos hold up under that power?
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Old 06-27-2017, 03:34 PM   #11
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shim the accumulators and use the turbo automatic.
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Old 06-27-2017, 07:06 PM   #12
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Having spent plenty of time working on pushrod V8s, to me anyway the Volvo redblocks are a dream to work on. Everything is laid out so logically, it all comes apart and goes back together so painlessly. Then again, I had more experience and more tools by the time I got a Volvo but I still get flashbacks when I think of working on my friend's old truck.
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Old 06-27-2017, 07:45 PM   #13
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Originally Posted by James10952001 View Post
Having spent plenty of time working on pushrod V8s, to me anyway the Volvo redblocks are a dream to work on. Everything is laid out so logically, it all comes apart and goes back together so painlessly. Then again, I had more experience and more tools by the time I got a Volvo but I still get flashbacks when I think of working on my friend's old truck.
Haha i guess its all comfort zones? Im sure once i dive in, ill be lile wth was i so worried about. Now im wlndering if its just better off building the wagon motor but using the 740 trans since its in good shape...ill need to oull everything out and look over both. Thanks again for the help everyone
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Old 06-27-2017, 08:24 PM   #14
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Both motors and transmissions are quite affordable. Certainly nothing wrong with doing a full rebuild but you may want to check around in case there's a better starting point to be had.

Also: have you adjusted the kickdown cable for the 240 transmission? If it's set wrong or stuck/rusty it'll cause strange behavior.
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