77olds

I have a 403 olds at my local machine shop I have a set of 30 over “stock” dish pistons. Going to bore balance it. I have a set of #5 heads going on it with edelbrock performer intake I’ll be using stock exhaust manifold but using dual exhaust. Engine going in 1977 cutlass turbo 400 and 2:73 gears. Going for stock appearances. My question is do need oil restriction and what cam? I have adjustable rocker arms. Head gasket thickness? Any other info would be helpful machine shop normally build Sbc.
Thanks.

Fun71

Be very careful as the factory pistons gave around 8:1 compression and aftermarket cast replacement pistons are shorter than the factory pistons, so you could end up with 7:1 compression ratio. That would be great for running the crappiest gasoline you can find, but awful for any sort of performance.

cutlassefi

True but he said he has #5 heads to put on it.

Op, what comp ratio are you looking to get?

Gerald Nickels

With that 403 you need to bore the head bolts holes out for the 1/2" head bolts.

77olds

Looking to get around 9:5:1 or little higher.

cutlassefi

63cc Head with .027 head gasket should get you around 9.5:1.
Hope this helps.

77olds

I’ve been reading about oil restriction didn’t know exactly what I needed to do and what cams are good won’t be going over 5500 rpm.

MrEarl

before figuring out what cam, are you sure you aren't going to swap the 2.73 rear end out for something like a 3.23 or 3.42 in the future. A 3.42 and a mild cam would complete the package.

77olds

Your prolly right I’ve kicked around the idea of putting 3.73 and 2004r in the near future.

olds 307 and 403

You will need a fairly aggressive cam with 9.5 to 1 especially on anything less than 93 octane. You will probably need to deck the block a bunch and mill the heads to hit 9.5 to 1. Around 9 to 1 might make a better cruiser. I would just use the cheap Felpro .040" head gaskets, Cometic head gaskets are 4x as much money. I would look at the Jegs $100 2000 to 2300 stall, stock 1700 rpm stall will be doggy especially with a bigger cam.

cutlassefi

Actually Christian he won’t need that much cam necessarily in order to run on 93.
I’ve done a bunch of 10.0:1 iron headed stuff that run fine on 91.
HOWEVER I don’t push it when it comes to total advance and they’re all jetted correctly. That’s the biggest factor in my experience

oddball

Back to the OP: Don't bother with the cam restrictors. That's snake oil. Joe Mondello was a great dude, but he got that part totally wrong. Bill Trovato's book is a better up-to-date reference for building Olds engines.
As said, compression should be fine with the 5 heads.

Sticking with flat tappet or going roller?

I ran the voodoo 60803 in my 403 which was built a step or two more aggressive than yours. Ran great, but I had a cam lobe failure. So the 60801 would be an option for you. Lunati's catalog is more useful than their website - find it under the 'about us' section. Those are the old part numbers, I can't be bothered to memorize the new ones.
Anyway, if I was you, I'd aim for 0.050 durations in the 210-225 range, sticking around 0.5" lift.

77olds

Thanks for the advice. I will be going over this with my machinist. Also a guy I know has a stage 3 Quadrajet brand new 800 cfm part number 36003 for sale never used for 200 would that carb be to big?

cutlassefi

Its not too big but don’t assume it’s jetted right, buy a wideband to be sure.
For the cam I’d do an Erson Hi Flow AH. It’s 220/220@.050 with right about .500 lift on both. Should work well in your combo.

olds 307 and 403

Good to know 10 to 1 is possible with iron heads on 91. I would assume very little vacuum advance? I plan on getting a wide band when I am done as well.

oddball

I would be cautious. Very precise timing control will be required.
I had a whole serious of headaches with Accel, OE, and Pertronix distributors with a wide collection of springs and weights. Finally went for the "nuke from space" approach and switched to MSD 6al2 programmable.

olds 307 and 403

Going for 9.6 to 1 and have a Mallory 6AL box and distributor. I can add in any timing curve I want.

starfire65

Currently building a 403 for a friend. Current specs/measurements to give you a baseline of compression. Block bored .030 for a bore of 4.381.
Head gasket (Felpro blue) 4.385 dia X .040 thick = 9.9 cc
Piston sits .045 deep in bore 4.381 x .045 deep = 11.12 cc
Cast replacement pistons with dish (radius at bottom of dish) as measured 3.21 x .150 deep = 18.57 cc (factoring in radius)
# 7 Cylinder heads (have not yet CC'd them yet) so we will take the factory spec of 70 cc
this will calculate out to around 8.63 compression ratio.
Will be running a Eljin Cam E-977-P with a 214-224 .050 duration & .472 - .496 lift 289-300 advertised duration which will give 70 deg. overlap, a little lump but not too much.
Edelbrock #7311 stock type Aluminum Intake.
Going in an 83 Hurst with all accessories.
Corrected version

cutlassefi

Your math is wrong. Gasket bore will be approx 4.400, so that’s comes to just over 100cc, not 6.
Piston is the hole is 4.381, not 3.381. That’s a bit over 11cc, not 6.6.
And Edelbrock doesn’t make a 7311 Intake. Do you mean mean 7111 or 3711? In a G body with a 403 use the 7111.
I’m going to go out on a limb here and say maybe numbers aren’t your forte?😎 Sorry but the real math says compression will be about 8.5, not 9.0.
If you haven’t purchased that cam yet then don’t, it’ll be a pig with your combination.
Sorry to be so blunt but hope this helps.

starfire65

So there is a few typos Stuff happens when you type in the wrong #'s you get wrong #'s. It was late last night when I wrote the #'s down ! Head gaskets as measured are 4.385 I'm sure the mfg calls out 4.400
Sorry but the guy wants the 3711 intake so it looks stock as possible it may have the EGR valve mounted there there but it will be non functioning. And yes the manifold will be painted black and Edelbrock ground off. Going for the stock look enough to fool the non Olds experts. Cam selection is not final as of yet. Also have access to a NOS Olds cam 562302 may use it.

olds 307 and 403

Felpro head gaskets? I need to measure mine, my 403 is going to a 4.390" bore. Is that the 4 speed 350 manual trans cam? I believe it specs out at 216/217 with .472" lift.

starfire65

Yes those are the blue Felpro head gaskets. As far as the cam specs for the 562302 is as follows(listed as a 1977 marine cam for a 350/403) it was measured on a Cam Pro Plus cam Inspection machine.
Int. lift .475 Exh. lift .472 Int. duration at .050 = 215.78 and the Exh. duration is .050 = 218.86 or factory listing spec of 286/287 with 61 deg. overlap. The 350 4 speed cam maybe very slightly different as in ground 2 deg advanced or retarded. That is the case with the 70-442 4 speed cam # 406768 verses the 71-72 442 W-30 stick camshaft 409759 both are identical specs except the 71-72 442 cam is ground in a 2 deg. retarded position.

OLDSter Ralph

Sounds close to the '70 442 Auto cam. I think it was 285/287 degrees. I think the '70 442 SMT was 292/296 degrees or close to that. Either one would be the minimum I would use.

olds 307 and 403

I would think that cam will work better than the 214/224 cam. Yeah, Felpro claims a 4.395" bore on their 403 head gaskets.

rktpwrdc10

The only oil mod I would consider is oil restricted pushrods and then run a roller valve train setup. Or focus on improving oil drain back to the pan. Boat guys run external oil drain tubes from the back of the heads to the pan or trapped into the pain rail on the block on 455's. That is basically the only things that make any sense at all to me for oil mods.