Just curious what would be the average cost to have a 403 rebuilt . My motor is all original 90 k on it number matching to the car runs great just no HP . I would like it to still appear stock on the outside no headers or big intake keep the 4A heads for shows reasons but would love to end up with 400 HP . If this would be possible what do you think the average cost would be to have it done by a rebuilder ? Thanks for your help

 

Until the engine is apart and inspected you will have a wide range of estimation.
Have you done any tests, compression and leak down? Does it smoke and use oil?

 

Hey Patrick . I have had the valve covers off just to change what could have been original gaskets very clean inside from that point . I would think the crank and rods and cylinders would be in good shape . If some one could give me an idea of cost with all machine work labor new pistons and cam to get me around the 400 Hp that would be helpful

 

Talk to Mark aka CutlassEFI.

 

It comes down to what you want to do. I have a 355 olds engine carb to oil pan i have about 4k into it. But i used alot of used / swap meet / and hand me downs and freebies.

Its about 370 hp is running 12.40's on pump gas.

My bottom end machining alone on that build which im still running cost me about 800 then parts including cam and all parts for the short block ran me about 750 ish and add the 500 for the original short block w/forged slugs i got at a swap meet . then add 1500 for the top end. heads where done by rocket racing and the intake used was 120 . and the rest was in odds and ends.

* One of the new parts i bought ( cam ) actually ate up the bearings in the original build back in 2012 but i didnt catch the problem until 2014 i then replace the cam , bearings and a few other odds and ends which would add a 500 dollar repair build to that build * but thats an incedental imo but im putting that out there.

 

i would pull the matching numbers running engine put it on a stand and drop in this 403

https://classicoldsmobile.com/forums...-403-sale.html

problem solved

 

thats actually a hell of a deal at 4500.

 

Thanks all for your reply to this that.s what i was looking for . I think i will give Mark a call to fine tune the build and talk to him about the motor that;s for sale .

 

4A heads making 400HP = a lot of work. Jim at J&S might be able to make it happen, but you'll be spending >$1k just on the heads. Those heads are really very bad. Terrible, even.

A bare bones basic refresh can be done for <$1k, but you're just talking about keeping the engine running at that point.
The cost for a build depends on the condition of all the parts, plus how far you want to go on modifications. It's easy to spend $10k on a motor. Agreed that the 403 that's been posted is a screaming deal.

The 403 has a couple of weak points that need to be addressed:
1) 4A heads are junk. Many hours of grinding to make them decent, or just replace with earlier small block or Edelbrock or big block heads.

2) The stock T/A intake for the shaker hood, with the sunken carb mount, is a real bottleneck. Just something to be aware of if you've got it.

3) The stock cam was a joke. Changing cams means making sure the whole combination works well together and fixing any valvetrain issues (e.g., switch to adjustable rockers)

4) The block is comparatively weak, but 400HP isn't a huge demand. Putting in a 330 forged crank and/or a halo girdle with studs are somewhat cheap insurance that doesn't affect drivability (compared to filling the block). But at 400HP, especially a driver that won't see that much flogging, may not even need those upgrades. I'd strongly recommend that you do NOT bore the block more than 0.030" oversize.

5) The pistons have massive dishes, and aftermarket shelf selection for the 403 isn't great. So picking a cam+head+piston combo that gives the right compression ratio and good performance can take a little research.

Other than that is just the normal Olds rebuild headaches.

 

Either the KB Hyper or Arias and Diamond forged small dish pistons will be needed. As said, the 4A exhaust side is terrible, needs a 1.625" valve and many hours fixing the exhaust port with a grinder. Intake needs less work than some heads but the exhaust side makes up for it.

 

It has an rpm intake. Nice motor though will be a challenge in a trans am. Will need to strap shaker to hood find a drop base air cleaner. Thought about this motor myself.

 

Just curious, where are you located?

 

I am on the west side of the state in Michigan Grand Rapids

 

Thanks for taking the time typing that up appreciate it good stuff .