I have a 403 that I bought to go in my 79 trans am. This is not a drag car or a daily driver, I just want something that is dependable and fun that also has a little extra power. It has a Comp Cam 42-229-4 (i think it is 218/218 @.05lift) and a set of headers that will go on too. I plan to add the edelbrock performer aluminum intake (Idle-5500 RPM Range), large aluminum radiator, performance water pump, and high flow thermostat. Any ideas of anything else that could be added/upgraded that wouldnt break the bank but would allow for a little more power?

 

Early 330 or 350 heads, mill and add some W31 valves. You currently have less than 8 to 1 compression. The Performer has smaller runners than your current #16 iron intake.

 

Set a budget and a goal and work from there.
Switch to the Performer RPM if you can. Hood clearance may be an issue. It's a much better intake all-around than the performer.
As said, there's a few main points that hold back the 403:
compression is low. Can switch to earlier small block heads or switch to flat top pistons (which requires bore/hone)
4A heads are pretty terrible. Can be fixed with lots of porting, but easier to switch to earlier heads or Edelbrock heads.
Cam should be picked based on what you do with the compression and the rest of the drivetrain. 218/218 is still real mild and will work with the stock compression. The Olds does like more exhaust duration than intake, so feel free to pick a split pattern cam.

Headers will add some power, but the heads are holding you back. The intake won't make that much of a difference. Unfortunately the first step for the 403 - addressing the heads and compression - is a big step.

 

The real problem here is that people want to put SBO heads on an engine that moves as much air as an E-block 400 BBO. You wouldn't put 350 heads on one of those. The E-brock SBO heads were designed for 403 T/As. Alternately, get a set of C heads, mill to get the CR you want, and have at it. Of course the problem in a T/A is fitting the correct manifold under the shaker scoop. That Performer has smaller ports than your original intake and other than the weight reduction won't help performance. The Performer RPM has the meat to port match to the BBO heads but is too tall for a stock shaker scoop (I don't know if you can mod the scoop and air cleaner. I suspect that an OL4B will work, but I don't have any first-hand experience.

 

As mentioned use the 7111 intake. You can search drop bases online that’ll help make that work with the shaker hood.
Per Joes statement, here’s a 9.8:1 403 with the new Edelbrock “big block” heads. It made 471/519.

 

from what i've read the Performer RPM is too tall to work with shaker scoop even with the drop bases (the kit i looked at specifically said wont work on 79 403).
A general outline of what I have in mind is to give the 403 just a little extra help here and there for fun performance without breaking the bank. This is my first build and im learning, but these are my thoughts as of now. I wont go with RPM intake because i dont want to have to mess with making the shaker scoop fit. I have read that increasing compression is the best thing you can do for the 403, can someone tell me if these would fit as well as increase compression? https://www.jegs.com/i/ATK-Engines/059/2C09/10002/-1
if I can find heads for about $600 and increase compression then i believe i would be happy.
Current parts list: 350 cast heads, headers, high volume fuel pump, large aluminum radiator, hi-flow water pump and 180 thermostat.
also thinking of changing gears from 2.73 to 3.42, would this make a noticeable difference?

 

No, those are chevy heads, totally different.

 

 

That and the headers alone will do plenty.

 

do you know if I could use the same gear carrier in the swap?

 

Yes, it should use the same carrier. I gained 1/2 a second in the 1/8 mile swapping from 2.56 to 3.42. It felt much stronger from a stop on the street.

 

XR262HR 42-413-11 roller kit needed
https://www.compcams.com/xtreme-energy-210-216-hydraulic-roller-cam-for-oldsmobile-260-455-cpg.html
work your 403 heads , good intake size already, some smart porting and shave, less dish piston
maybe an A4 intake with some work.
Do a proper setup on the Quad , nothing wild and keep the hot air choke working.
​​​​​Keep the 2.73 gear posi and put a built 200-4R behind it with lockup and 2200 stall.
Set of pipes on ex side milled heads to meet the divider, big quiet mufflers.

 

I have a pair of #6 heads that were worked for a 403 with a little bit of porting. Head bolt holes already opened up for the 403 head bolt size. Comp adjustable rockers and springs.
I need to sell these heads since I am not doing a small block in the foreseeable future...

 

What are the thoughts on having the 4a heads slightly shaved and going with standard bore flat top pistons (if i can find them)?
this should increase compression, is there a guess as too what my compression would be after having this done and if there would be a problem in doing so? i dont want to put myself in a position that compression ratio is too high and i have to use a higher octane. Should I just choose one or the other?
Thanks

 

A few things to consider, best way to 9.25-9.4cr, deck, dish, chamber and gasket. It'll need good pump gas, you'll do the ign curve with the jetting for the compression.
In the FAQs section you'll find a chart that'll give you an idea of cr with the chamber volume and cc of piston, but still need to consider deck height and gasket. The heads will wake right up with some porting without going too much on volume and with valve cut. It'll take some work but guides and seals and springs all gone through for reliability with the cam choice. The roller is good, more investment but will payoff in the long run with reliability with good head work. Some good information in books/papers written on doing correct things with Olds heads for just what you're trying to do.
A good strong flat torque curve and early too with plenty of HP, build smart.

 

The 4A heads have a terrible exhaust side and are 83+cc. My set measured at 86cc. You are honestly better grabbing a set of Procomp heads which measure the same CC out of the box and flow much better than the 4A. Finding a set of standard bore flat top may be difficult and your bore might need more to properly clean up. See what he rfpowerdude asking for the #6 heads above. See what CC they are. You need about 64cc for 9 to 1. Figure . 042" thick Felpro head gaskets and pistons .025" in the hole. Another important part for acceleration is a higher stall converter. I just had a 9+1 to 1 Olds 403 with 204/214 cam and 2.78 gears. I had a 2350 flash stall, rated at 2200 to 2500 stall. It would do 1/4 block burnouts. I swapped in a stock 1600 stall TH350 trans, did work on the 2004R. Would barely break the one tire. I wouldn't do any less than the converter above with your cam choice.

 

I am having trouble finding choices of standard bore pistons. I found these but these with the Piston Head Volume (cc):+18.50cc ...... would this lower my compression?
https://www.summitracing.com/parts/u...ake/oldsmobile

 

Keith Black
https://cnc-motorsports.com/keith-black-pistons-kb405-024-fits-oldsmobile-403-dish-6cc-bore-4-375.html

 

I cant find keith black for standard bore

 

​​​​​​ Maybe measure the bores and see , I wouldn't know about just wanting to swap same sized pistons in tired out of round holes. Those look .024" up size, maybe on the cheap you'll get there with a hone only but you'll have to take a close look at the bores, ridges scuffs etc. You either build a motor or you don't.

 

I am going to hone, but i dont get the deal about me not wanting to have it bored and just going back with same size pistons? Budget is a factor, im new to this and ive read about the thin walls of the 403. I dont want to take any chances with boring and end up back to square one with no budget lol.

 

best deal for a low budget is to use 350 heads along with a thinner head gasket. Reuse the stock pistons if they are ok plus a good ring set. No machining involved to do any of that except a quick deglazing of the cylinders

that mild cam with those additions will wake it right up. Keep the factory intake , add some headers and free flowing mufflers

3 series gears will also help bunch…that can be decided after it’s up and running

 

The 4A heads are there to build , the 2" intake which the other heads prob don't have, then you're into the whole thing again and more putting in bigger valves on someones old heads. I'd take the extra time , get the better pistons , use your heads with some porting and build it with that small roller as mentioned , but that's just me. Once you're in the motor you 'll prob find other things that need attention.
Good luck with it

 

Yep, you’re right, they are not 2.00” intake. They are 2.07” intake and 1.68” exhaust. They have already been worked to some degree.

I’ll supply pics if the original poster is remotely interested. Otherwise, they stay bagged up until someone REALLY wants them.

 

Now things make more sense, I put my glasses on and I'll go back and fix something.

Those are interesting heads, probably more than his target needs.

The 4A could use little more ex valve but..it depends on what the interpretation of fun is.
Highway gears, OD , loads of torque for miles of open road cruising at low rpm with decent mpg can also be fun.

 

I'm going to stick with the heads I have and go with new pistons. Appreciate the offer tho!

 

It's not the valves - it's the ports that hurt the 4A. Remember we're talking "4A" (upper case A), not "4a" (lower case a). The lower case letter heads were the 60's and early 70's and were, across the board, much better than the upper case letter heads. 4A's can be made to work but need a lot more porting time than other Olds heads. Jim from J&S got a good baseline with them but admitted it took a while. He had some good pictures and notes on his website but I don't know if it's still up. He shut down several years ago now.
If you have plenty of free time and the tools to port cast, then it's no big deal. If you're paying someone to refresh OE heads then it's often cheaper to get new heads. Jim offered a porting package for the 4A but with the labor hours involved, well, I don't think he sold many of them.

There are several routes to go to wake up a 403. Just depends on how much you want to spend and how far you want to go.

Boring 0.024" is no big deal. It's going over 0.045" or so that gets interesting. Any other olds block can bore to 0.060" without even thinking about it, but the 403 often has overheating problems over 0.030" or so. My 403 has the KB pistons and runs perfectly well, although I do have a big radiator and a big fan.

 

which new pistons did you decide on?