Author Topic: 403 build  (Read 995 times)

pjwrench

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403 build
« on: February 12, 2018, 09:54:49 AM »
Good Morning: I am going to rebuild my 79 403 - I would like a concrete answer on intake manifolds and cylinder heads, I know there is a large bank of opinions here but I would like to use the small chamber heads and intake offered by Edelbrock but everything I read here points to using 350 heads and doing a bunch of machine works etc. There must be a product I can use right out of the box that will boost the performance of the car while keeping sane and drive able.
I'm thinking between 350 and 400HP while keeping the current torque curve is more than enough for a cruise car.I would like to know what cylinder head , intake, cam and chain combo works best and who it can be purchased from.

Thanks

70RAIV455

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Re: 403 build
« Reply #1 on: February 12, 2018, 10:04:13 AM »
The Real Bernard Mondello. He is on Facebook. Joe Mondello's son.

Aus78Formula

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Re: 403 build
« Reply #2 on: February 12, 2018, 12:03:31 PM »
Free flowing true- dual exhaust and a more exciting rear gear will wake it up. But there is no secret hp adder that exists.
Otherwise it's increasing the lowly compression by either headswap or different pistons, and a cam to match. For less dramas with shaker stick to stock or Edelbrock Performer intakes only (not RPM), which already creates another restriction on the engine. You may choose just a cam swap and exhaust/gear but aim closer to 250hp.
« Last Edit: February 12, 2018, 12:11:55 PM by Aus78Formula »

pjwrench

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Re: 403 build
« Reply #3 on: February 12, 2018, 06:40:39 PM »
wow okay cool I already have 2.5" true dual exhaust on the car, I sincerly was looking to put small chamber heads on it and the performer intake with a matching cam if it will boost the car and not further restrict it. The conflict comes in where I've read that the Edelbrock heads aren't really designed for the 403 but are more suited for the 455 big block? So I'm looking for some confirmation on the value of a head swap as well - I'm not shy and know how to do the job I just want to know it will be worth it at the end of the day.

Thanks guys

Aus78Formula

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Re: 403 build
« Reply #4 on: February 12, 2018, 09:45:03 PM »
Forget the Edelbrock heads, they are not needed and require many further mods to even fit, and there goes your shaker, fuel pump, tank, and of course they won't do much for the compression if simply slapped on. There's other headss out there now, but still probably forget them also, not necessary and lead to long dramas ahead to make work.

Re: 403 build
« Reply #4 on: February 12, 2018, 09:45:03 PM »

70RAIV455

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Re: 403 build
« Reply #5 on: February 13, 2018, 06:10:43 PM »
The 403 Olds 4A heads make the engine run.
The Exhaust to intake Ratio is terrible. Never make big Hp. Maybe 300-325.
Flow charts are online.
J&S Machine in Illinois was modifing Edelbrock heads for 403 use.
Good feedback.
7 sbo 350 heads most popular swap.

Big Block 425-400-455 Heads can be used if you drill out the head bolt holes to 1/2".
1965 "A" 425 heads the Best of all stock.
Along with the 1970 W30 442 455 heads.
« Last Edit: February 13, 2018, 06:12:30 PM by 70RAIV455 »

olds403

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Re: 403 build
« Reply #6 on: February 13, 2018, 10:03:37 PM »
There are a couple of ways to do this and all depends on what you want to achieve and your budget.  We doing two 403's now. Each one is slightly different from each other. 

You can run either BB heads....just drill them to 1/2 bolts.  BB heads and port matched RPM intake is probably the best all round set up for cost reasons.  BB heads can be iron. Any of them will be OK if you port them.  Everyone likes "C". The shaker is out of the question as will sit up very high and shaker will be in hood.  This works if you find a piston and get it custom made or run the Airas pistons.  In my mind this is a good option for a motor that is being rebuilt.  Its been done.  No reason for Alum heads. Plenty of olds BB heads in iron exist. 

KB Pistions with the Stock 4A heads will work.  That is a decent combo for those looking for minimal work and have a good amount of power over stock. I've not done it myself, but have a set of those pistons.  Changes are we will never build this combo.

What we are doing is using small block #6 heads on both 403's.  One motor is a zero decked TRW forged old stock pistons stock crank.  The other has a 330 stroked crank with with Racetec custom pistons. 





pjwrench

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Re: 403 build
« Reply #7 on: February 20, 2018, 12:59:02 PM »
Okay thanks guys I think for now I'll look into a cam and an intake - I don't want to loose the shaker I just want a little more power. Also a stage 1 street shift kit is in order. I have no intentions of racing this car at the strip, its just a cruiser - I'd like it to be a little more lively is all.

Thanks for the feedback.

Aus78Formula

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Re: 403 build
« Reply #8 on: February 20, 2018, 07:13:56 PM »
381hp/481tq here with 4A heads, KB pistons, Standard Performer intake and Thornton exhaust manifolds. More would have been nice but had to keep within some restrictive guidelines or create more headaches. Probably decent for a cruiser, double the stock hp, headers and RPM intake would add a bit more but then cam might not be quite as ideal as another may be. Build it how you plan to use it.
« Last Edit: February 20, 2018, 07:21:57 PM by Aus78Formula »

mikebooms

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Re: 403 build
« Reply #9 on: February 20, 2018, 09:12:22 PM »
Aus, what camshaft are you running in that set up? What rear end ratio?

Aus78Formula

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Re: 403 build
« Reply #10 on: February 20, 2018, 10:58:53 PM »
Custom Erson grind based on my unusual setup of non-performance features!
Rear end is 3.42 in readiness for an overdrive box. Car hasn't been on the road yet.

mikebooms

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Re: 403 build
« Reply #11 on: February 21, 2018, 08:22:54 AM »
My build is similar.  Have a 3.42 going in as well. Waiting on machine shops reply for necessary overbore cleanup, then kb's get ordered. More than likely it seems thorntons over shortys. Performer and carb/ignition work.

via3d

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Re: 403 build
« Reply #12 on: May 08, 2018, 06:35:18 PM »
Aus78,  what order did you build up or was it all at once.

Is a different cam necessary (yes I am noob). In other words at what point is cam necessary?
If I go this entailed, pistons, cam etc I will find a shop.

I was thinking 3.23 posi rear as it came stock on some as an option on some 79's.  I want a street crusiser only.
Several chose 3.42, cu ft ious, for drag track?
~ J

via3d

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Re: 403 build
« Reply #13 on: May 08, 2018, 07:04:36 PM »
Also I find it curious, go BB or SBO heads?
What else is necessary to be done if anything if a person goes BB heads? Does BB heads really have higher compression?

Is it possible to just bolt up some certain heads....and avoid the myriad of other suggestions of internal work? especially if engine is low mileage ?  What gains would just heads be?

If an engine has 30 to 35k on it, at this point I assume its not entirely necessary to bore.... which 403's  are thin anyways.  I know pistons add performance, but I am just trying to understand and balance hp/tq gains with minimalist approach.

I am in process in finding a rebuild shop to get tear down and hot tank the block, new seals, etc. (I am in Georgia and will consider up to 2.5hr drive)
 What is a minimalist approach per nominal nominal gain itemized?

  I thought the crank was good in the late 70's 403....  I thought a cam was only necessary if new pistons and excessive high compression....  :shock:  noob I am....

I will go true dual exhaust... 2-1/4 though, not 2.5 like most seem to.... my thought is the headers ( shorty or iron Thornton) are 2-1/4 and back flow pressure is important. Big isnt always performance...
Dual 2.25 = 410 CFM = 370 HP
Dual 2.5.  = 510 CFM = 480 HP
(Approx.)
So as you see.... depends on the hp gains expected... I am just or more interested in torque... hence rear gear upgrade.

I will do an intake if gain and keep shaker.

I am eager to learn here.....
« Last Edit: May 08, 2018, 09:42:36 PM by via3d »
~ J

Aus78Formula

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Re: 403 build
« Reply #14 on: May 09, 2018, 01:10:44 AM »
I did mine all at once with a new block. I didn't even bother upgrading the previous engine, wasted money when you know you can only go so far with bolt-ons.

Big block heads are only slightly smaller chambers to increase compression on the late 70's sbo heads, you aren't using BBO heads for compression but flow and larger ports that match larger intakes. Ignore these if you want to use a shaker in your TA.

A larger exhaust isn't too critical for flow if it is still using a restriction up front like stock manifolds, it won't really see the benefit.

Any change in the engine also affects what cam is most suitable, but doesn't mean you have to change either. It depends on what your engine mods are as to which cams will work and see the potential or not.

Re: 403 build
« Reply #14 on: May 09, 2018, 01:10:44 AM »

via3d

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Re: 403 build
« Reply #15 on: May 09, 2018, 08:15:59 AM »
Here is my minmum agenda for a 403 build on my Firebird #1:

A. Teardown and get shortblock magnafluxed and hot tanked
B. Buildup fresh seals, etc.
C. Shorty or Iron Thornton exhaust manifolds
D. Dual 2.25 exhaust (unless I do mods while opened that expect > 350hp)
E. Upgrade rear gear (was considering 3.23 gear)
F. Rebuild quadrajet.  (new seals, soda blast, Chem soak, etc.   to freshen up).

So at this point I am just letting the Firebird breathe and feel more  lively with a lower gear that seems more appropriate for her.
----------------

When I have it opened up is where I am contemplating, Is this possible:
- 350 heads
- new intake
- keep stock crank/cam/pistons/valves

      1. A shop is saying to bore and get new pistons while opened up.
         With mileage so low is it necessary to change pistons?
         Cost and gain?
 (This car/engine has 33k original. Other car I may own soon under 50k)
      2.  I was considering Bolt on heads for compression. But does this cause everything else to change too?
      3.  Should I consider cam? Will it be near absolute necessary if I get 350 heads?   What is cost and gain ?
      4. I thought the stock crank and pistons were decent in 403's for a mild mod street cruiser?
      5. I was considering new intake, if it would help performance with more cfm,  as long as I can keep shaker.
      6. Keeping the quadrajet but rebuilding (new seals, soda blast, Chem soak, etc.   to freshen up)


~ J

Re: 403 build
« Reply #15 on: May 09, 2018, 08:15:59 AM »
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