Hi guys im very new and GREEN to these American power units , I recently purchased an Olds 350 engine which has a manufacture date of 1977-80 so not good for a start apparently but anyway it is a low compression engine and has 3A heads with tubes running into the exhaust ports which have been cleated over ,can I remove them as buying parts in the UK is proving difficult , I would like to increase the power what is the best way to go ,any advise will be greatly appreciated

 

Your 3A heads have about 75cc chambers. If you can get your hands on a set of 1967-1972 small block Olds heads (no. 4, 5, 6, 7, or 7A), the chambers will be around 64-ish cc, so you'll get a compression bump. You'll want to have the W-31 sized valves (2.000/1.625) installed in those heads also. Get a good cam, intake, and exhaust, and you'll be good to go.

 

Many thanks Joe , finding stuff here in the UK is proving hard so may take some time

 

Good advice. Don't forget, you will also need to open up the head both holes to17/32".

 

Well after an extensive search of the UK there appears to be no heads available , shipping in from the USA is not an option as the cost is mega expensive so im stuck with these 3A heads ,they are in good condition so I will have to work with these . Flat top pistons will bring the cr up to around 9.15 - 1 so out come the tubes and get grinding , question ,can I block the port opening back into the inlet manifold ,also what else can I do ,at present I have a Holley 4 barrel carb on an Offenhauser manifold , Flowtech exhaust manifold ,reground crankshaft so the bottom end has been rebuilt ,over to you clever boys for suggestions

 

9-ish to 1 is not bad for today's gas with iron heads. If possible, install the 2.000/1.625 valves as used by the factory on the W-31 motors. Be sure that whoever works on the heads understands how important it is to set the installed valve stem height as directed in the factory Chassis Service Manual. The Olds valvetrain is not adjustable unless you install aftermarket rockers.

The Offy manifold is not the best technology. Depending on your intended use, I'd suggest an Edelbrock Performer RPM. I'm also not a Holley fan. If you can't get a Qjet, I'd suggest an Edelbrock/Carter carb. 650 CFM for a mild motor, 750 for a more radical motor. Contact CutlassEFI on this site for cam suggestions.

While most folks simply screw brass pipe plugs into the A.I.R. ports in the head, those are actually inverted flare fittings, like the ones on brake lines. The threads are straight, not tapered (though the brass plugs are soft enough to deform). Dorman Products sells the correct steel inverted flare plugs. If you plan to do any porting in the exhaust side, some of the Olds specialty vendors sell special plugs that not only seal the threaded port but actually fill the hole all the way into the exhaust port, allowing you to grind away the A.I.R. bumps and smooth the ports without that hole being a flow disruption.

If by blocking the port to the intake manifold, you are talking about the exhaust crossover, keep in mind that the crossover provides carb heat for fuel atomization in a cold motor. For a street-driven car you'll be hard-pressed to feel any performance difference - though you WILL feel the rough cold idle. For a performance build, folks do fill those ports with aluminum (melting down old pistons is a good source) but then you need to do some porting work. You can also simply use blockoff plates at the intake gasket, but then you don't get the flow benefit from filling the port in the head. Your call on whether you build needs this or not.

 

What year of car will your engine be going in ? I have a smog engine in my 76 currently, although I have #8 heads. I found headers and duals along with a 3:42 rear gear and shift kit in the trans helped take my boat off the line a little better. I also added an 2711 edelbrock performer intake along with a 600 cfm 1406 with a 1" 4 hole spacer for a small torque gain over an open spacer.
Hope this helps
Eric

 

As long they are crack free, 3A heads had known issues, build them. The exhaust port is terrible on those heads. Bigger valves as said, open up the bowls, tear drop the guide areas and work on the exhaust roof and remove the air bumps. The Probe 3CC .030" oversize or CP 1.5CC dish pistons that work with a block hone only are much lighter than stock or Speedpro's and have a modern, thin ring pack. Less weight with windowed block isn't a bad idea or get something like the Halo or PRW girdle.

 

Addendum to this: If you DO go with an aluminum intake manifold, this will be less of a problem, as the aluminum heats the carb a lot faster than the cast iron manifold does. The Edelbrock Performer RPM suggested by Joe is aluminum.

 

Many thanks you guys

 

Hi guys Joe mentioned the item that allow to do this ,can anyone give me the name of a company that sell these please , I have copied part of Joe's suggestion




Olds specialty vendors sell special plugs that not only seal the threaded port but actually fill the hole all the way into the exhaust port, allowing you to grind away the A.I.R. bumps and smooth the ports without that hole being a flow disruption.

 

Was not thinking ,I can make these plugs , I have a Lathe ,I can do them in Steel, Brass or Aluminium any preference ??

 

Hi Guys I have removed the tubes from the exhaust ports and am making the plugs to fill the holes left so I can grind away the bumps from the top of the port ,there is a lump on the bottom of the port as well , do I remove this as well ???

 

The bumps at the top of the port do not kill flow as much as everybody says it does, it just looks that way to the untrained eye. I have never seen a set of 3As to my naked eyes before, so I don't know what the bottom bump looks like. You got a pic?