Olds 403 buildup

[CamaroAdam73]

Alright so i picked up a 403 last year in feb with a 79' Trans Am. Trans Am ended up being a gift for my little brother, he's in high shcool now taking auto tech and his senior project will be his T/A. I kept the 403 however.

It's a 4A block, when i bought the car they told me the bottom end was new(er) shortblock from somewhere because the old 403 puked its guts. I still havn't popped the old heads off but i think i'm going to do that today and measure the bore, i've heard it's common for these engines to be bored .020 over when being rebuilt.

I picked up a set of #5 heads from 44whoo, C.I 397742, 64cc, 1.995/1.624 int/exh.

I've got an edelbrock performer intake, 3711 not the RPM performer. I'll be running the original 850CFm Qjet, modified to run with whatever cam i decide to go with.

Got a new Dizzy, stock right now. I'll be regutting/recurve it with some of the D.U.I products that look and perform pretty nice from what i can tell.

I've got a set of Hooker Headers 3107HKR - Hooker Super Competition Headers that i'm going to have to modify to make them fit a gbody with a 403, because they're for an Fbody with a 403. I would just go with another set, but these where almost 500$. At my shop i've got access to pipe benders, and a welder that owes me a few favors.

So i'd say i've got a pretty good start here, still along ways to go though. I want to fit the heads with bigger valves, any suggestions? Keep in mind i'd like to keep this engines peak power under 6000. I'll be installing a crank girdle to help the bottom end.

I'm reading around on the net for other 403 build ups, anybody got any good info?

 

[foxtrot]

That sounds like a great start. Just don't cheap out on the machine work. Also, some simple cleanup polishing on the heads would be good. Some decking to bring the ratio up to 9.5 : 1, would also be good. A good cam would be the Ultradyne 231/239 @ 50. These upgrades along with some good gearing should easily get a Gbody into the 13's! Good luck with the build.

 

[CamaroAdam73]

Thanks for the tips foxtrot. The dragstrips the farthest thing from my mind, I like lower gearing and higher top speeds. However my initial setup will be the opposite, the exact opposite hah. I've got a brand spanking new (rebuilt) TH350 with some shift improvements, and the original 3.73 rear gears. Down the road the options are either rebuilding a 700R4 and sticking with the 3.73's, or converting to a manual to use my M22, and dropping the rear down to 3.42s? or something around there, maybe even lower.

Performance is the goal here, but so is streetability because i want to have my cake and eat it too. By that i mean i want to drive this car everday because i love driving it.


I plan on having some work done to the heads, i'm thinking about 2.02 valves on the intake side. My machinest gave me some pretty fair prices so minor bowl work, and some porting are on the table with these heads. Plus the heads are pretty clean already and they've had some level of porting + ready to fit onto a 403 as is. 44whoo really gave me a good deal and made this build possible.

I want this engine to last, so the next big chunk is going to be oil control and some bottom end improvements that i've read to be necessary. Oil pan/pump/ pickup w/o gasket $400 + tax SP-754 high volume with pickup OP-805 7 Quart Oil Pan

SG-490 Halo Support Girdle 400$ + tax

I havn't pulled the old waterpump off for inspection but if all is well i'm probably just going to stick with stock, i'm already dishing out almost 1000$ into the bottom end so i can't justify another 140$ if the stock water pumps got no problems.


Havn't put much thought into head gaskets yet, i'd like to go with the best here though, i've learned the hardway not to ever go cheap on head gaskets.

 

[DoubleV]

I plan on having some work done to the heads, i'm thinking about 2.02 valves on the intake side.

2.02 valves are a Chubby valve size. According to the valve sizes you posted, your heads have already been upped to the next bigger valve size so you're already there. You may want to measure them to make sure. Also, you need to cc the heads because 64 cc chambers are NOT what they really measure out to be stock, though many claim that's what they are because of erroneous info posted on the net about them. If they are untouched heads, they are probably around 68-70 cc's.

havn't put much thought into head gaskets yet, i'd like to go with the best here though, i've learned the hardway not to ever go cheap on head gaskets.

Cometic .028 gaskets seem to be a very popular choice in Olds builds.

 

[CamaroAdam73]

I've already measured the valves to check sizes. Yeah i've got mixed info on the net claiming from between 64cc to 70cc, most of the sources said 64cc so thats what i assumed they where. A few really good sources claimed they where 70CC

 

[DoubleV]

I've already measured the valves to check sizes. Yeah i've got mixed info on the net claiming from between 64cc to 70cc, most of the sources said 64cc so thats what i assumed they where. A few really good sources claimed they where 70CC

The ones who claim 64 are just people who are passing along the false info from the Olds FAQ site. People who actually measure untouched older 350 heads get about 68-69 on the average and that's real world info unlike much of the BS from Olds FAQ. Just make sure you cc them and measure everything so you know for sure what your final CR will be.

 

[CamaroAdam73]

Deff will. How much of the info from olds FAQ is BS? i've been using that website for information, i'd hate to find out it's mostly BS

 

[DoubleV]

Well lets put it this way, how much BS and misinformation is spewed on a typical car ( or any other ) forum? Alot, right? Well all the sh*t in Olds FAQ was compiled from internet forums. Doesn't matter if the info was never proven or validated. If it looked good, it was thrown into the FAQ. Alot of the stuff on FAQ is OPINION too, not fact.

People have been contacting the owner of Olds FAQ for years begging him to change, delete, and correct lots of the BS, but it always falls on deaf ears. Now anyone trying to get into Olds who comes across that site and tries to learn something just gets a bunch inaccurate info instead.

So I can't honestly say 'x' amount of info is BS, but alot of it is so don't EVER do anything like mod your car or buy new parts based off of anything you've read there.

 

[86-blk442]

I agree with DoubleV, Olds FAQ is far from the best place for information. If you want some decent Olds tips check out ROP, or High Performance Olds which is Bill Trovato's site. He also has a book that is good if you are looking for information and tips on building these engines. I bought it and learned quite a few things. His info comes from his years of experience building everything from street to 1000+ hp engines. He is a very accomplished Olds engine builder. I had him do the work on my #5 heads installing the larger valves, machining, and doing bowl work, and I he's currently building my 383 chubby motor for my 1972 C10.

These heads are definitely not 64cc from the factory. Mine were milled .038" to bring the chamber volume down. As far as head gaskets go, Cometics are definitely a good choice if you plan to beat on the motor or have really high compression. When I was at BTR talking with Bill, I brought them up and his opinion was they are not needed for lower compression engines. He gave me a set of Mr Gasket Ultra Seals for my engine ( I am somewhere around 10:1) and they are working just fine not a single problem with me beating on my 350 and making repeated trips to 5000 rpm.

These are just opinions, and information that was passed to me through my process of building my 350. I don't claim to be an expert, but it never hurts the maybe learn from what others have done.

 

[FE3X CLONE]

Specs on the 403 in my '81 below:

403 bored .030" over
Stock crank
Stock rods
Stock cast replacement pistons
ARP bolts throughout

Rollmaster double roller timing chain (junk, don't use one of these. Go with a Cloyes double roller)
Ultradyne camshaft 221/227 @.050, .485"/.485" lift, 112 LS
Stock 7a heads with stock valves. Just a 3 angle valve job performed. Came in at 67-68 cc's. No porting.
Edelbrock Performer RPM intake
750cfm Speed Demon vacuum secondary carb
Stock HEI distributor
Cheap 1-3/4" Dynomax headers

TH-2004R trans with 3000 stall converter
7.5" rear with Auburn limited slip, 3.73 gears and aftermarket axles

Best times have been 13.1@102mph or so on drag radials. This was straight out of the box. I've never actually tuned the thing other than installing smaller jets in the carb. If I'd ever get around to tinkering with it more this would be a high 12 second car.