Hey guys I have an 86 Cadillac Brougham with the Olds 307,I’ve been in a relationship for about 20 years now very dependable over this time however I wanted a little more power so I’m having an olds 350 long block built.I know my accessories and brackets off the olds 307 will work on it,except Oil pan/exhaust manifold,and intake,not sure about the water pump but all accessories from the 307 is new..any knowledge will be appreciated..

 

All the accessories will transfer directly to the 350.

 

Everything other than the intake manifold and tubular exhaust manifolds are a direct swap. Are you planning on running the factory carb and CCC distributor? Seriously consider new dual exhaust. The Thornton JR 350 manifolds allow dual exhaust without capping the extra pipe and have slightly larger outlets and flow, if you have trouble finding used manifolds locally. Good luck.

 

Yep I plan on using the factory carb and distributor..

 

Thanks for the info..

 

What cam and compression ratio are you planning on?

 

The cam they offered/I went with is part # Mel-Mto-1..melling;compression 10.25:1 ..

 

I already have dual exhaust flowmasters with hi flow cats on each pipe and no mufflers,but what issue could I have with factory single exhaust

 

That compression ratio is high and that cam. You want to say around those duration numbers, 220 duration is about the limit with a 112 LSA or wider. The later swirl port CCC timing curve is very aggressive, like 60 degrees part throttle. I would shoot for about below 1 to 1 below that, 9 to 9.25 to 1 compression. Either the DSS 12 cc or Mahle 10cc dish forged pistons will give that with early 350 heads. Also get the secondary air door to open more with a richer secondary hanger and rods on the CCC Qjet. Most dump the air injection system as well. Good luck.

 

He said compression will be 8.4:1 //

 

What year Olds 350 is being built? Problem is the only readily available cast pistons are the 24cc dish model. It will require quite a bit of block decking and milling to even get 8.4 to 1 with early heads. Yeah, 8.4 to 1 will work just find with that cam and the CCC. Make sure modify the secondary opening on the Qjet to open more and check the secondary hanger and rods as well.

 

( ok thanks much needed)
// they say it’s 70-76 rated at about 180hp stock close to 200 with the stage 1 //

 

[QUOTE=olds 307 and 403;1408997]Everything other than the intake manifold and tubular exhaust manifolds are a direct swap. Are you planning on running the factory carb and CCC distributor? Seriously consider new dual exhaust. The Thornton JR 350 manifolds allow dual exhaust without capping the extra pipe and have slightly larger outlets and flow, if you have trouble finding used manifolds locally. Good luck.[/QUOTE. ///// So you saying the Oil Pan,water pump,fuel pump,starter,flywheel will Work?

 

The only fundamental difference between the 350 and 307 is the bore. Everything else is the same and interchanges (yes, I'm aware that the roller cam 307s use 0.921 lifters instead of 0.842).

 

////olds 307,403 said exhaust and intake manifold won’t interchange..

 

The 1985-1990 307 motors have heads with tiny ports. The manifolds from those motors have matching small ports. The manifolds will bolt up, but the port mismatch will cause a flow disruption and lost power.

 

As Joe said, keeping both swirl port intake and exhaust manifolds make a mild 350 swap pretty worthless. Any of the iron SBO intakes or a 80 to 84 Olds 307 A4 aluminum intake will also work. Many people use the A4 due it being aluminum, it is also EGR. They are very rare up here in Canada. I had to get mine off Ebay from the US. Other than the H/O and 442, I have never seen one on a car here, all had the #17 iron intake, which will also work. Our Cutlass line except the two above and the 88 Cutlass Classic were Buick 3.8 V6 or sbc powered🤨.

 

////so what all accessories will I need that the roller 307 don’t have?

 

The intake and exhaust manifolds are the major differences. You also have the air injection pump and lines which attach to your cylinder heads. Many have removed the air pump when swapping a 350 or 403 in place of the 307. Just block the line where it goes into the exhaust.

 

Thanks 403.

 

You guys have been a big help as far as guidance on this exchange, Joe and 403 know your stuff it has been accurate so far..I thank you guys..

 

What do you know about the PMD # 3A heads,they sent this stock remanufactured engine to me 77-80 vin r 3B Block..?are they that bad as common threads suggest?

 

Yeah, you got the worst of the Olds 350 but if built right will still out perform the 307 and last just fine. Hopefully the heads were checked for cracks. Did they add the Melling cam to it? I would make sure the compression ratio is actually 8.4 to 1. It could be more like 7 to 1 with 24cc cast dish pistons at .040" below deck.

 

$$$$. ok thanks bro I’ll have compression checked

 

Hey the olds 350 engine is in with the 307 behind it and I road tested the 86 caddy..engine dies while driving but restarts easily, any idea what’s going on?

 

Any check engine lights? Are all the factory wiring and vacuum hoses properly hooked up? Where does it stall? At idle or cruising down the road?

 

Check engine light is on but I went with a non cpu distributor and carb so it wouldn’t run or respond like the 307,it idles smooth and fires up great it has an electric choke but it stalls at cruise.

 

I suppose my mechanic connected all wiring and vacuum to factory,everything look and seem clean as the connections with OE

 

What carb, a Qjet? New or used? Talking about the carb and distributor both. What is the timing set at? I find most stalling happens at idle. Is it when you put your foot on the gas or let off? Does it sputter first or just die? Simple things like fuel filter and fuel pump condition and checking to make sure there is a full 12 volts at the HEI. Then maybe vacuum leaks. Let us know.

 

It’s a new q jet the engine quits when I take my foot off the gas or applying just enough for cruising..it sputters only when accelerating.

 

It could be a weak fuel pump. I had a defective pump out of box starve a 307 like this.

 

I will check