Olds 403 Buildup

[foxtrot]

I guess that is the story of my life that I could have done it better. 🙂

BUT, in this case I didn't want to spend lots of money and couldn't find any older heads to install. I did use stock dish pistons and could not find heads with the smaller chamber. This combo will have an 8.0:1 ratio. I think that the updated intake, cam, port-job, and high flow exhaust will be a BIG improvement over the 307 that was in the car.

I'm not going to be bringing this car to the quarter mile so I just want some power when I STOMP on it from time to time.

Results should be good....

 

[olds307 and 403]

Recurve the distributor, add an adjustable vacuum advance, run 22 initial timing and put good flowing exhaust on it. I like that you kept Olds, instead of the usual sbc route.

 

[foxtrot]

I’m a creature of habit – a long time ago when I did a g-body engine swap it was an olds to olds engine swap.

The sbo is a decent engine with nice torque and the car was originally designed for this engine.

 

[foxtrot]

The gear ratio in the rear is 3:73 this is a good combo with the 2004r transmission. Also have a 2000 -- 2400 stall converter. I'm still thinking that this will be a mid 14 sec car but I will never know since it's not going to the track...

 

[olds307 and 403]

You have the right gearing first off, too much if anything, what size tires? I get away with 2.56 gears because of my 25.5" tires, go bigger. If your convertor stalls at 2400, it is more than enough. My 2000-2600 stall maybe 2000 on a good day. If your engine isn't up to your liking, adding a set of early #5,6,7,7A 68-72 350 heads will put around 9-9.3 to 1 range with Corteco gaskets and flow decent too.

 

[foxtrot]

Just finished cleaning up loys of "spy-bots" that were slowing down my computer. What an arduous task…

I actually not sure of the tire size, I'll have to take a look. The rims are the '86 Grand National style and they have 235 tires... The gears do make a huge difference and this can is not a daily driver...

Thanks for the advice on the heads -- I'll have to finish up with the current project first. 🙂

 

[TBRtat2]

The biggist weak point i know of is the cooling system, thats where i hear about problems. IMO never bore a 403 more then 40 over, or you will drasticly increase ur chance of over heating.

Mine is running flat top pistons, giving around 10-1 compession, which lets me run any type of gas with no detination. And I have a slightly more agressive "truck" cam then you which is giving me much more tourqe and a bit more hp. (which is perfect for my tall rear gear)

Deffinitly get a dual exhaust with headers, the 403 needs a lot of room to breath, my motor was first in a buick with with the stock exhaust, which it ran good but when it went into my cutlass with headers and duals, it completely change the way it runs, and woke it up.

My 403 now has around 20,000 miles on the rebuild and it runs as good as ever

As for the heads, i kept the stock heads, but the heads and the block where each milled 0.010 (0.020 combined)(BUT doing that much required some creative milling for the intake to seat properly :lol: )
From what we looked at, the 350 heads had to small of chambers for the 403, the pistons are wider then the combustion chambers. Which may increase compression, but it limits the spread of the burn on the pistons.

 

[olds307 and 403]

I have had MANY cooling problems. Killed a very fresh looking bottom end, copper bearings in a short time. I am sure now after adding two different radiators(now a 2 1/4" dual core aluminum), Flowcooler hi flow aluminum water pump, a 160 high flow thermostat, new 16# rad cap and Plymouth breeze dual fans(was a 7 blade clutch fan). Without the fans cutting in, it gets to 210 in -30 temps. The underdrive pulleys have got to go period, before spring.

 

[TBRtat2]

1 option when having a cooling issue, is to run an engine oil cooler.

 

[foxtrot]

I've never run an oil cooler -- how do you plumb that in? Does the oil boss(oil filter manifold) need to be removed? Any part numbers for the kits that were used on your olds motor?

Also, I'm wondering if an aluminum radiator would be a big improvement?

Thanks.