Hello, noobe here. I inherited my dad's 88 Cutlass Supreme Classic, with the 307, and 200r4 trans. I have a 1975 Olds 350 I want to swap in. I understand most everything is plug and play, (I plan on keeping the computer), but I have a few questions about the swap. First, will the stock 307 (with egr tubes) exhaust manifolds fit the earlier 350 (no egr tubes), and if I go for headers, would there be any difference in the fit on these? I understand I would have to drill and tap, or drill and weld in a bung for the o2 sensor in the 350 manifolds, or possibly do the same for headers. I already have installed a set of "true" duals, using the stock 307 manifolds. Also, any suggestions as to what brand of headers to put on it? I'm not planning on slaying any 5.slows, just want a little more power than the 307. Basically, a daily driver with a little more oomph. I'm trying to keep this fairly cheap and easy. Thanks for any input.
88 Cutlass 307/350 swap
- Thread starter cburd88cutlass
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What are you refering to when you say 'EGR tubes'?
Anyway, some have claimed that some of the later 307's came with the earlier style bigger exhaust manifolds ( which look alot like the manifolds on earler Olds small blocks ) but most came with the smaller stupid looking ones. If you have the stupid ones, then just get a set of exhaust manifolds from an earlier 307 and you'll be good. They will fit perfect on your 350.
Anyway, some have claimed that some of the later 307's came with the earlier style bigger exhaust manifolds ( which look alot like the manifolds on earler Olds small blocks ) but most came with the smaller stupid looking ones. If you have the stupid ones, then just get a set of exhaust manifolds from an earlier 307 and you'll be good. They will fit perfect on your 350.
For a cheap header, get the Hedman headers, supposed to fit well. I would also consider a new timing chain and gaskets, except head gaskets. I also added the Performer cam in my 76 350, advanced 2 degrees. It gave a nice boost over the tiny stock cam.
cburd88cutlass said:
To answer your first question,
Yes the 350 can run on the computer as is. You can use the stock 350 intake or use a A4 aluminum intake from any 307 before 1985. How good is the '75 350 you have? Is it high miles? If it was a good running engine, I'd just put a new timing chain on it and some valve cover gaskets and go cruising. The 350 is a leap over the power of the 307 in stock form. If you stick to your cheap and easy then keep it stock as possible.
Second question,
Double V just said it, There are no tubes on the Old exhaust manifolds or Olds headers. Also as mentioned, Just get early 307 '78-'85 manifolds and you'll be good. The 350 manifolds are a tad wide but, will also work. (just put the O2 sensor in the down tube)
As far as AIR pump hook up you won't be using the upper air tubes any more. Block them off and just use the one tube that empties into the CAT. That will keep you looking legal. If you have duals then you need another CAT and split the AIR tube to it. You will call it a factory mod if asked. And make sure you paint that 350 black. I did this with a 455 on the computer in a '84 98 Regency and it passed all sniff and visual test. (Tester didn't know the difference between Olds motors. Most don't look twice if it sounds stock. Cam lopes make them look harder at the motor.)
JMO
T
Keeping the 350 all stock and on the computer may or may not gain you anything over the 307:
'77-'80 350 170hp @ 3800rpm, 275lb-ft @ 2000rpm
'77-'79 403 185hp @ 3600rpm, 320lb-ft @ 2200rpm
'83-'85 307 VIN 9 180hp @ 4000rpm, 245lb-ft @ 3200rpm
'86-'87 307 VIN 9 170hp @ 4000rpm, 250lb-ft @ 2600rpm
Took this from a thread over on ROP. Thought it was kind of interesting.
But the 350 wins hands down once you start throwing the aftermarket go fast parts at it.
'77-'80 350 170hp @ 3800rpm, 275lb-ft @ 2000rpm
'77-'79 403 185hp @ 3600rpm, 320lb-ft @ 2200rpm
'83-'85 307 VIN 9 180hp @ 4000rpm, 245lb-ft @ 3200rpm
'86-'87 307 VIN 9 170hp @ 4000rpm, 250lb-ft @ 2600rpm
Took this from a thread over on ROP. Thought it was kind of interesting.
But the 350 wins hands down once you start throwing the aftermarket go fast parts at it.
FE3X CLONE said:
Do you really believe that? His pos swirlport 307 is rated at whopping 140 hp. Regardless of the published hp ratings though, I would think even a bone stock 75 350 with a good tune would run circles around a roller 307. They wouldn't be big circles, but circles nonetheless.
DoubleV said:
X2 on that. Plus, the official numbers from the 70s were fudged beyond reason to keep the law makers happy.
The torque numbers were more accurate.T
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