Andrew1980

Hello everyone! After much research, I recently purchased a 403 engine sourced from a 1977 Toronado that I plan on installing in my 1985 Toronado.


The 85 Toronado is my daily driver; thus, I'm not trying to turn it into a race car, I just want more power than the 140 HP that the stock 307 (5A) delivers.


My plan is to retain the CCC and the ECM controlled distributor. I will also reuse the exhaust manifolds from the 307.


Thus far in my research I have learned that I need to replace the DD secondary metering rods with AU rods and modify the secondary air valve cam. (What exactly has to be done to the secondary air valve cam?)


I'll also need to drill and tap an additional port in the intake for the CCC temp sensor.




Thus, my to-do list is as follows:


1. Swap CCC Carb from 307 to 403 with modifications.


2. Swap ECM distributor from 307 to 403.


3. Drill intake coolant passage in 403 intake for ECM temp sensor.


4. Swap exhaust manifolds.


5. Swap oil pan from 307 to 403.


(Hypothetically speaking) the EGR, A.I.R. and cat are not applicable currently and will not be after the swap either. No current codes or check engine light with the ECM system.

Is anything else necessary to successfully accomplish this engine swap? Any insight from anyone else who has done a CCC / ECM swap to a 350 or 403 would be very helpful.


Thanks,


Andrew

olds 307 and 403

You need to run the EGR, the air injection can and should be eliminated. You can either remove the cat, replace with a piece of pipe or plug the air line going to cat. Use the secondary rods from the 403 carb. Does your 307 have tubular or cast iron manifolds? The factory exhaust sucks, tubular swirl port manifolds make it worse. The good part about the 7.8 to 1 403 is it should tolerate the 60 degrees of part throttle timing your ECM puts out. Make sure your vacuum lines are all replaced and routed properly. I would also drill out the caps over the idle mixture screws if it hasn't already been done. I would service the transaxle and add a big trans cooler as well.

joe_padavano

The problem with keeping the CCC system is that you can't alter the advance curve unless you burn a new PROM. This can be a problem with eliminating the EGR. The stock timing curve assumes the EGR is active at part throttle and light loads. The diluted intake mixture is slower burning, so the stock PROM advances the timing under those conditions. Without the intake charge dilution, the timing may be too advanced and cause pinging at part throttle. This is not uncommon on 307s where the EGR is removed.

Frankly, EGR is only active at part throttle cruise. It has zero impact on wide open throttle performance, assuming the valve is operating correctly.

droptopron

It goes w/out saying but check the oil pick up too

Andrew1980

Thank you for the information! From my research, the oil pump itself if the same, but I will verify the pickup.


It's amazing how many parts are interchangeable between the 307 and the 403. Even the camshafts were the same until the 7A changeover in 85.


The existing engine has the cast iron manifolds. The car is a November of 84 build. It has the 5a motor, but I don't know whether the current engine is original to the car.


Speaking of camshafts, would it be worthwhile to install a mild performance cam such as a 205/215? Or would that be asking for trouble with the CCC carb and distributor?

jcdynamic88

why not use the 403 carb and distrtibutor ? seems like a better match

Andrew1980

It would certainly be a better match, but the 325-4L's TCC lockup solenoid is controlled by the ECM. Without the CCC carb and distributor, the car will default to limp mode which disables the TCC lockup. The ECM also controls the A/C compressor clutch WOT cutout, while not necessary, the cutout is a nice feature. Cruise control is also ECM dependent, but it will operate in limp mode.


If for some reason I could not get the CCC carb and distributor to work with the 403 plan B would be to install an aftermarket TCC lockup switch / wiring, but I would prefer to avoid that if possible.

olds 307 and 403

Those manifolds will be fine. Hopefully your Tornado 307 starter is better than the regular wimpy 307 starter. The 204/214 cam is OK. I think the 207/207 .461"/.461" on a 112 LSA, key for the computer, Lunati High Efficiency series cam would be even better.

Andrew1980

I cant speak to the RWD 307 starter, but the FWD 307 starter is pretty sizable. I think it's about as heavy as my Buick Riviera's 455 starter.

joe_padavano

The RWD 307 starter is tiny and does not generate a lot of torque.

ALso, be aware that the TH325L4 trans requires a flexplate that is smaller in diameter than any other 1964-1990 Olds flexplate, so be sure to use the flexplate from the 307.

Andrew1980

I now have the 403 on a stand in my garage. Over the upcoming weeks I'm going to clean it up, repaint it, replace the timing chain, water pump, fuel pump and the gaskets. I'm not in any rush, but if all goes as planned i'll do the swap in July or August.

Thank you to everyone for your input and your advice!

425HP409

I agree...

olds 307 and 403

I agree with the above. The good part is with 7.8 to 1 compression, it should tolerate the 50+ degrees the of the early non swirl port 307.

Oldcoyote

I swapped a 403 for a 307 and tried to retain the CCC. It did not work. I was using a 206/206 cam. I switched to a non CCC carb and distributor.

You can probably get the CCC to work if, as I've said before, you make it your purpose in life.

I used a non lockup converter but many have used lockup with various switches. I eliminated AC cutout, not at all necessary. 307 starter was inadequate and I replaced with a 455. I do not recall that the cruise control was controlled by the primitive computer.

Andrew1980

Sorry it has been a while since my last update! Over the past month or so I have been in the process of the 403 swap. To make a long story short, I swapped out the 307 for the 403. In doing so, I had to change the flywheel, oil pan & pickup screen, and oil filter adapter.


The install / removal wasn't too difficult. (I'm a 20+ year hobby mechanic with a few engine pulls under my belt, but I've never wrenched professionally)


Initially, I dropped in the 403 as-is with new gaskets, water pump and a fuel pump. This proved to be a mistake...read on...


Upon firing up the 403 I was happy to discover that the complete CCC from the 307 system played nice with the 403. However, once the car warmed up, I realized there was a BIG mechanical problem with the 403 in the form of a ROD KNOCK!


I was able to get the 403 up to operating temp and was happy to say that it did not throw any check engine lights. So I didn't consider the 403 CCC swap to be a total failure.


In the couple trips I made around the neighborhood, I realized that the stock 403 didn't have much guts. In fact, I really didn't feel much difference from my 307...at least not enough to make this whole swap worthwhile.


A few days after the initial install, I pulled the 403 to get it rebuilt and reinstalled the 307 to drive in the interim.


Since I wasn't impressed with the performance of the stock 403, I decided to step up to an Edelbrock "RV" cam 204/214 114LSA. Based upon my research, this cam would provide good torque, a smooth idle and play nice with the CCC system. So I purchased the cam, and dropped the cam and engine off at the rebuilder.


Fast forward to this week. On Monday night I pulled the 307 and reinstalled the rebuilt 403. I finished the install on Tuesday night and did some break in driving / fine tuning. In short, I was downright impressed with the low end torque and overall performance compared to the stock 307 or even to pre-rebuild 403. The idle was a little choppy, but I think that may have something to do with an exhaust leak at the manifold to y-pipe connection.


I did not get any check engine lights with the new engine / cam combo. Vacuum was good and all vacuum operated accessories (power brakes, HVAC and cruise control all worked without issues). I even ran it with the air on for a bit to make sure the temp stayed in the normal range, which it did. I'm sure the brand new radiator, heavy duty clutch and 7 blade fan all helped.


However, when doing some fine tuning idle adjustments, the 403 appears to have suffered a complete head gasket failure (or worse) at 57-58 miles! From what I can tell, the coolant passage has been compromised with the oil drain-back passage. In short, the entire coolant system depressurized into the crankcase! Thankfully, the problem occurred in my driveway and I caught it immediately. I took a video with my phone of a coolant system pressure test to document the fact that it is dumping coolant into the crankcase. The leak is so obvious, you can hear the hissing from the oil fill tube at 2 PSI in the cooling system..ugh.


So far, my engine rebuilder is standing behind their warranty, but we will see. I've already pulled the 403 and have it ready for the engine rebuilder to pick up.


Ironically, despite the fact that my biggest concern was getting the CCC system to work with the 403, as it turns out that has been the only aspect of this project that hasn't gone wrong thus far!


Hopefully the next 403 install is the last time I have to put an engine in this car for a good long while!


On an aside, I confirmed that if you use an engine lift plate and remove the hood latch and harmonic balancer pulley and engine mount cradle, you can pull the engine with the hood on the car! This saves a bunch of time and makes the engine swap a one-man job! This comes in really handy especially when you do the job 3 or 4 times LOL.

olds403

olds 307 and 403

I had many over heating issues and I never blew the Corteco head gaskets. I plan on running Felpro head gaskets on my next build. With 8 to 1 compression and iron heads, stock head gaskets should work.