1970 Olds 350 from a Cutlass S - ClassicOldsmobile.com


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Old September 13th, 2018, 12:14 PM   #1  
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1970 Olds 350 from a Cutlass S

Found one for sale locally that I'm interested in as a candidate for a rebuild and swap-in. Looking to replace the 307 in my '89 RWD Caddy. I'm trying to learn as much as I can about this engine, I have to imagine it's THIS VERSION as I'm sure it's the most common? I'm sure this is the um-teenth post about 307-->350 swaps on here, but is this a good candidate for someone who's never attempted a swap before? I'd love it if this swap would give my Caddy a significant power boost.
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Old September 13th, 2018, 12:36 PM   #2  
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The 1970 350 came in a low compression (9.0:1) 2bbl and a high compression (10.25:1) 4bbl configuration. Since you said you will be rebuilding the engine, it doesn't really matter which one it is, other than if you want a 4bbl and the one for sale is a 2bbl, then you would need to locate an intake manifold and a carburetor.

In regards to the rebuild, be aware that the common cast aluminum replacement pistons end up with a lot lower compression than they advertise due to too-short compression height. Do some homework and ask questions about the rebuild here to ensure your engine ends up the way you want it and you're not disappointed with the end results.
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Old September 14th, 2018, 05:54 AM   #3  
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As said, figure out which version it is. While it is a power upgrade, it has basically the same lame cam as you 307, just a flat tappet version. A cam with more duration on the high compression version is a good idea. The 9 to 1 version would work with your stock CCC set up, are you keeping it? Change all the gaskets, except the head gaskets, unless you want lower compression. Also replace the timing set as well. Also get cast iron manifolds or headers, those tubular exhaust manifold's are a major choke point.
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Old September 14th, 2018, 06:43 AM   #4  
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As said, figure out which version it is. While it is a power upgrade, it has basically the same lame cam as you 307, just a flat tappet version. A cam with more duration on the high compression version is a good idea. The 9 to 1 version would work with your stock CCC set up, are you keeping it? Change all the gaskets, except the head gaskets, unless you want lower compression. Also replace the timing set as well. Also get cast iron manifolds or headers, those tubular exhaust manifold's are a major choke point.
I just recently learned the difference between SAE gross and SAE net power measurements so it seems the two 350 engine candidates I found are going to be only a small 20 point boost (worst case scenario) from what my 307's output is. However I think it's still worth it as the 350s I hear have more potential than any 307.

I'm interested in keeping the CCC setup mainly because it ensures things like my electronic climate, cruise control, lock-up TCC, and other features will still work. People tell me that the CCC setup will mostly give me smoother performance across a broad spectrum of conditions. I can't say I know how true all of that is, but it sounds nice and would result in less swapping. Hahaha.

I'm really just looking for my 4,200lb Cadillac to have better get-up-and-go performance and not necessarily turn it into a tire squealing monster. I think I'd be pretty happy with some kind of performance in the 200hp/315lb-ft range for such a heavy car. What do you guys think?

By the way, one engine and trans couple I found has a casting number on the block of 395558 2 and there's a number 6 on the head. The seller thinks it's from a '71 Cutlass. The intake also looks like it's made for a 4-barrel carb. Does that mean that the engine is a 68-70?

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Old September 14th, 2018, 10:36 AM   #5  
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The #6 heads are from 1970. I would add Felpro head gaskets if it is a 4 barrel engine to lower the compression along with a custom cam or suitable grind for the ccc. Of course maybe a bore scope or pulling a head is a good idea. I would also do a compression test and oil pressure check as well, if possible.
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Old September 14th, 2018, 12:04 PM   #6  
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395558 2 blocks were used from 1968 to 1976. There's mis-information out there on the net that they are 68-70 blocks.
The 6 heads were used on all 1970 350 engines.
The way to tell for certain the year of the engine is to look at the VIN pad on the block. The second number is the year of manufacture.

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Old September 15th, 2018, 08:27 AM   #7  
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Here are some photos from the ad. Judging by the taped-up area on top of the intake it looks like it's the 4bbl version? Either way the engine looks like a clean survivor that just hasn't been run in 10 years.





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Old September 15th, 2018, 08:04 PM   #8  
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Looks like a good candidate. It should be closer to 9.6 to 1 with the usual 68 to 70 head cc, 6cc dish pistons .025" below deck and the factory .017" thick head gaskets. Use .040" Felpro head gaskets will put you around 9 to 1. You could get the generic 204/214 cam, which has either a 112 or 114 LSA. It worked like **** with 9.6 to 1 for me. You need a minimum 112 LSA to work with the CCC and probably more duration but around 215 duration max. You also can't have too much cylinder pressure, the factory swirl port timing curve is very aggressive, the stock tiny 350 cam won't work in my opinion. You will need manifolds, any 74 and up catalytic converter manifolds will bolt to your current exhaust. The early manifolds will also work but have a different flange and angle than later manifolds on the passenger side.

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Old September 16th, 2018, 07:37 AM   #9  
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This cam might fit the bill and would be as big as I would go with CCC. http://www.supercarsunlimited.com/35...aft-d1100.aspx A 2000+ stall in the 2004R will help launch and still lock up, a trans cooler should added anyways for extra slippage off the line and hauling your heavy car. Here is more info on the above cam. https://classicoldsmobile.com/forums...nual+trans+cam

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Old September 19th, 2018, 10:53 AM   #10  
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Looks like a good candidate. It should be closer to 9.6 to 1 with the usual 68 to 70 head cc, 6cc dish pistons .025" below deck and the factory .017" thick head gaskets. Use .040" Felpro head gaskets will put you around 9 to 1. You could get the generic 204/214 cam, which has either a 112 or 114 LSA. It worked like **** with 9.6 to 1 for me. You need a minimum 112 LSA to work with the CCC and probably more duration but around 215 duration max. You also can't have too much cylinder pressure, the factory swirl port timing curve is very aggressive, the stock tiny 350 cam won't work in my opinion. You will need manifolds, any 74 and up catalytic converter manifolds will bolt to your current exhaust. The early manifolds will also work but have a different flange and angle than later manifolds on the passenger side.
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This cam might fit the bill and would be as big as I would go with CCC. http://www.supercarsunlimited.com/35...aft-d1100.aspx A 2000+ stall in the 2004R will help launch and still lock up, a trans cooler should added anyways for extra slippage off the line and hauling your heavy car. Here is more info on the above cam. https://classicoldsmobile.com/forums...nual+trans+cam
Thanks, that's really helpful advice. I've never rebuilt or swapped an engine before, but I'm confident that I'm more than capable of doing it. This info will be great to reference if and when I get into it. The seller is away on vacation and won't be back until October, so this gives me some time to plan things out. He's offering $400 with the engine and trans together. I don't intend to use the trans but the seller doesn't want to separate the two. I suppose I could sell that THM-350 and make some of my money back.

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Old September 19th, 2018, 07:09 PM   #11  
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Keep the TH350 as back up, it will bolt right in place of your 2004R in a pinch.
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Old September 20th, 2018, 08:20 AM   #12  
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So, how well will the CCC system attach or hookup to the new 350 engine? Will the E4MC carb connect to the 350's intake? What about all the hookups for vacuum and emissions systems? Do these 350s use EGR? If not can I bypass that system without upsetting the CCC? Id hate to be looking at a blaring Check Engine light after the swap.
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Old September 20th, 2018, 09:20 AM   #13  
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Your best bet is eliminating the CCC. The carb will bolt on but either a Performer, A4 or 70's EGR manifold will be needed. The biggest issue is the super aggressive timing curve the CCC has programmed in, a 9.6 to 1 motor won't like it.
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Old September 21st, 2018, 06:50 AM   #14  
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Your best bet is eliminating the CCC. The carb will bolt on but either a Performer, A4 or 70's EGR manifold will be needed. The biggest issue is the super aggressive timing curve the CCC has programmed in, a 9.6 to 1 motor won't like it.
What sort of issues will I run into with the less than favorable timing curve? Is there any way to adjust that?
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Old September 21st, 2018, 08:03 AM   #15  
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Are you sure that engine was stored inside? The spark plug has rusted so much, the hex is gone from it. To me this says it has been outside. Be sure to inspect the block for freeze cracking. Also don't plan on using the exhaust manifolds from the 307. They will fit and bolt up but will be very restrictive.

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Old September 22nd, 2018, 07:15 AM   #16  
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Are you sure that engine was stored inside? The spark plug has rusted so much, the hex is gone from it. To me this says it has been outside. Be sure to inspect the block for freeze cracking. Also don't plan on using the exhaust manifolds from the 307. They will fit and bolt up but will be very restrictive.
I don't know for sure, it never really came up in conversation. I just assumed since it's been inactive for 10 years that it's been indoors. I thought it would a lot worse if it spent a decade out in the elements in coastal NY.
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Old September 22nd, 2018, 07:26 AM   #17  
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Old September 22nd, 2018, 08:31 AM   #18  
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Thanks, but I'm very far away from that one's location.
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Old September 22nd, 2018, 10:32 AM   #19  
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What sort of issues will I run into with the less than favorable timing curve? Is there any way to adjust that?
Get the factory service manual and the special tool to adjust the part throttle mixture. An ultra lean mixture with aggressive timing will ping. Your car should have a knock sensor, make sure it torqued to whatever the torque spec is. Without it, the speed sensor needs grounded for the cruise to work and the torque converter controlled either by toggle switch or by a lock up controller.
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