MyFathersOldsmobile

Hi everyone, I know this has been hashed over a zillion times before but I have a two questions that I can't seem to find an answer to. I have a 1987 cutlass with the Y block 307. Stainless headers, 7A heads, and A5 intake. Today I got a 1973 olds 350 complete from carb to oil pan with th350 still attached. These are the questions I have:


1) Will the 1973 exhaust manifolds physically fit or will there be clearance issues. Since I'm trying to go for a stock look, I know I'll have to replace the RH one to get an o2 sensor port. But, will I have to replace the left?


2) Will a 4V intake from a 1973-74 350 have all the ports I need or would I be better off looking for an A4 intake. (I'm a freak for the Oldsmobile lettering on the intake)


I'm in no rush to get this done. The 307 is still running well with no oil leaks. But, more power would be nice.


Thanks!

svnt442

Those later heads have different intake and exhaust ports and you will want to use the earlier manifolds on the 350. You might be able to have the older exhaust manifold tapped for the O2 sensor. Not 100% sure about this as I have never had the need.
The early intake should have all of the holes you'll need for vacuum and water, but it will be cast iron, not aluminum.

joe_padavano

Randy is correct. The welded tubular manifolds on your 307 are not "headers", they are possibly the worst-flowing exhaust manifolds ever used on an Olds motor. Since the 7A heads on the roller cam motors have peanut ports, the port mismatch alone will kill any additional performance from the 350. Get a set of iron manifolds from a 1981-84 307.

The A4 intake has an additional port in the coolant crossover for the coolant temp sensor for the CCC system, in addition to the port for the HOT light sensor. Some earlier intakes also have these additional ports, but why mess with iron when the A4 is cheap and plentiful?

MyFathersOldsmobile

Thanks for the replies! Sorry about the Terminology. Meant to say "manifolds" and not "headers". I know that my engine is a slug for the most part and that all the main parts (ie intake, exhaust manifolds, heads) are pretty much worthless from a performance standpoint. The CI intake was a "that would be cool!" thought. But, if it doesn't have the ports I need, then it's no longer a consideration.


Now I do have another question. Are the dimensions as the SS Tubular manifolds the same as the CI? Would like to know if this would be a "plug and play" swap for the exhaust or if modifications will be needed. I do plan on doing the exhaust down the road, but would prefer to wait until the engine is in and running.

joe_padavano

The exhaust outlets are in the same place on the cast iron and tubular 307 manifolds, so the exhaust pipes should bolt up with no issues. The earlier manifolds may have a different angle or bolt pattern on the outlets, which is why I suggested the early 307 manifolds.

MyFathersOldsmobile

One question, will the 307 5A heads bolt up? If I'm going to the bone yard for the intake, wondering if it's worth while to grab the heads as well.

joe_padavano

Will the 5A heads bolt up to what? The 87 307 or the 73 350?

The short answer is yes to both. The longer answer is that the 350 used 7/16" head bolts vs. the 1/2" head bolts on the later motors. They will still bolt up, but be sure to verify dowel pins and head bolt washer fitment.

The bigger question is, why would you want to do this? The 350 heads have 1.88/1.57 valves. The 5A heads have 1.75/1.50 valves. You'd be better off getting earlier 350 heads and installing the 2.00/1.625 W-31 valves.

MyFathersOldsmobile

I was looking at combustion chamber size. I have the number 8 heads on the 350. Larger combustion chamber but didn't look at the difference in valve size. So, for now it's probably better to keep the number 8 heads?

CRUZN 66

If you are not going to change the exhaust at the same time, be sure you use a right hand exhaust manifold that has the three bolt mounting flange to match your front exhaust pipe.... Like Joe said, the 307 manifold would be your best choice since the 73 350 manifold most likely has a two bolt flange..

olds 307 and 403

Since you are planning on running the computer, as said early cast 307 manifold with the O2 sensor would be needed. I would seriously consider dual exhaust with the 350 swap, as long as no emissions testing is done in your area. Also consider a quality timing set, factory nylon gears end up in the oil pump pick up. And maybe add a cam like the Lunati High Efficiency .461/.461 207/207 112 LSA. I put 5A heads on a 76 350, same block as yours, it did OK in my 4x4 but shift points were just over 4000 rpm. If your motor still has the stock shim heads gaskets, you will only gain .5 compression with early 350 heads unmilled but they flow better on the exhaust side untouched. If you did put on early heads, a valve job and slight mill would be a very good idea.

MyFathersOldsmobile

That was my next question. I plan on getting earlier heads down the road but not right now. I was undecided about the exhaust but now I'm thinking a 2 1/2" dual exhaust.

As far as emissions go, anything later than '96 is exempt here. Wisconsin. However, I do have a question about the AIR system. I know it can be taken off and the mil will only come one during start up and then should go off. But, I've also read about later models, such as mine, where the computer is looking for solenoids and such. Any thoughts on that?

joe_padavano

Yeah.

The CCC system is far from a "later model". It uses a primordial OBD I computer that has extremely limited capability. The computer and software date to the late 1970s and is less capable than an Atari 2600.

The ECU only commands the A.I.R. system in open loop. There is no feedback or monitoring of the solenoids. Remove the A.I.R. system and there will be absolutely no impact on the MIL or the ECU. Be careful, however, that if you retain the cat, the A.I.R. does blow fresh air into the cat once the system goes closed loop. This helps cool the cat and prevent matrix meltdown. This is only an issue if the car runs rich, however. If the carb is running properly, there will not be a problem.

olds 307 and 403

As said, ditch the air setup. 2.5" will be fine, don't go any smaller than 2.25". I would throw in the Lunati cam I suggested or the generic 204/214 cam as either will work with the computer. I ran the 204/214 cam in my stock 76 short block and ran mid 15's with ignition issues.The reason I am suggesting the cam because it is a pain to do in car and the stock cam is super weak. Swapping to early heads will almost do nothing with the stock cam. I would do all the gaskets including a rubber rear main seal except the head gaskets. Adding any aftermarket head gaskets will lower your 7.9 to 1 compression even lower.