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  #1  
Old 08-30-2014, 12:57 PM
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Question 350 engine swap on 91 350 SDL

Finally giving up and putting a 300 engine in the 91 350 SDL I'm restoring. I would like to get a little more power from the 300 engine. I will turn the ALDA screw out some. Would it help to put the #17 head on with angled injectors? Can the timing be changed a little without causing anything nasty to happen? Any other suggestions would be appreciated. I adjusted the turbo up on my 90 350 to 15 psi years ago without any problems and am planning to do the same here. Would it help to put the 350 turbo on? I've got all kinds of spare parts to play with, just need some input from you fellas that have changed these out before. Thanks
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Old 08-30-2014, 01:30 PM
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FWIW "superturbodiesel" is a forum site all about performance tuning MB diesels.
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Old 08-31-2014, 10:57 AM
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I don't have the money or inclination to into complicated or expensive modifications. According to MB specs the 300 engine has 28 less ft-lbs torque than the 350 and a little more HP. I expect that when MB found out they had problems (which they wouldn't admit being good Germans) with the 350 engine they detuned it to keep it running. Just need a little more power, not a fire breathing dragon-my wife's Acura RSX serves that purpose if I get nostalgic about my youth.
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Old 08-31-2014, 11:18 PM
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I would use the the 3.5 head, turbo and injection pump on the 3.0 block. ALDA removal helped my 300SDL.
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  #5  
Old 09-01-2014, 11:06 AM
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I did this swap a few months back, and I elected to keep the 3.0 pump and turbo on the motor when I installed it. I used the head from the 3.5 because it was a newer #20 or 21 head.

The main reason for my decision was that the 3.0 has a redline that's about 1,000rpm higher than the 3.5, so I wanted to use the 3.0's injection pump. I think the 3.0 would be a real dog if you lost the top 1,000rpm.

I also kept the 3.0 transmission because the shift points were correct for the 3.0 engine. I've read comments from people who have kept the 3.5 transmission and they say that it works, but feels just a bit off, apparently. I find this rather surprising; I'd think it would be a direct swap, but I'm just repeating what I had read.

The 3.5 that I removed ran pretty well but it was going through a TON of oil. I've driven a number of 3.0 cars and two 3.5's. The increased low end torque is very noticeable off the line in the 3.5, but once the car is moving I really don't see many differences.

While I was doing the swap, I deleted the EGR and did a number of other maintenance items. It's a nice car to drive and I'd do it again- it really wasn't that hard. The car is sitting in the driveway right now awaiting a new crank seal- I replaced pretty much every seal but forgot this one. Sure enough, it started spraying oil last week. Oh well.
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Old 09-03-2014, 06:50 AM
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Quote:
Originally Posted by upshift View Post
I did this swap a few months back, and I elected to keep the 3.0 pump and turbo on the motor when I installed it. I used the head from the 3.5 because it was a newer #20 or 21 head.

The main reason for my decision was that the 3.0 has a redline that's about 1,000rpm higher than the 3.5, so I wanted to use the 3.0's injection pump. I think the 3.0 would be a real dog if you lost the top 1,000rpm.

I also kept the 3.0 transmission because the shift points were correct for the 3.0 engine. I've read comments from people who have kept the 3.5 transmission and they say that it works, but feels just a bit off, apparently. I find this rather surprising; I'd think it would be a direct swap, but I'm just repeating what I had read.

The 3.5 that I removed ran pretty well but it was going through a TON of oil. I've driven a number of 3.0 cars and two 3.5's. The increased low end torque is very noticeable off the line in the 3.5, but once the car is moving I really don't see many differences.

While I was doing the swap, I deleted the EGR and did a number of other maintenance items. It's a nice car to drive and I'd do it again- it really wasn't that hard. The car is sitting in the driveway right now awaiting a new crank seal- I replaced pretty much every seal but forgot this one. Sure enough, it started spraying oil last week. Oh well.
Thanks for the advice. I can adjust the governor up on the 350 pump so I will probably use it. Probably will switch heads but may wait and see how it runs first. Not sure what you gain by using the head with angled injectors.
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Old 09-03-2014, 06:53 AM
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A cheap mod would be propane injection for extra power when needed.
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Old 09-03-2014, 08:39 AM
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Quote:
Originally Posted by loneranger View Post
Not sure what you gain by using the head with angled injectors.
I would guess any power difference is negligible. The reason why I switched heads was for reliability. And the 3.0 I put in the car had been sitting on a pallet for 10 or more years so I wanted to refresh all the gaskets- it was the perfect time to switch the head and put a new chain on.
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Old 09-03-2014, 09:07 AM
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I'm not sure why you need any more power than it has now. Turning the ALDA screw isn't going to do much at all.

A 603 under any circumstance running correctly has plenty of power. Shouldn't be an issue.
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