So I have a stock 403 in my 69 Cutlass convertible. Car and car related have very much been on the back burner for years. Kids are getting a little older and I have the itch to wrench and improve again. I have a collection of various parts from my single days and I'm looking for advice regarding what combination works best for what I have, I can't justify spending a lot at this time.

Current combo is stock 403, OEM quadrajet, TH400, pegleg 2 series rear end. Dual exhaust, but stock manifolds for now, I'm open to getting headers. Exhaust might only be 2", need to check.

Parts available from my single days 'stash'.
Performer RPM and regular Performer
New pertronix flamethrower HEI
7a and maybe #5 heads. One of those two sets came off a mildly cammed car and were redone shortly before I obtained them probably 15 years ago. Newer performance type springs, I will measure the valves to see if they are bigger than stock.
Quadrajet from my 69 455 that was done by the Carb shop years ago.

Camshafts
JM 20-22 300/310 224/234 .496/.520 112 lc
Erson TQ20 292/292 214/214 .478/.478 111 lc 4 advance
includes full kit with lifters, springs, retainers, and valve locks.

I have a friend with a machine shop that will allow/help me to drill the head bolt holes bigger.
If the engine hasn't been opened before, is the stock head gasket a steel shim? Will I lose compression with Cometic .027" gaskets? I know I will pick some up with the older heads. Am I better off getting the heads milled a bit and using cheaper/thicker Felpro?

The car will be mostly street driven, with maybe an occasional trip to the track just to see what it can do. I have several 200-4r's sitting on the shelf, but I figure those are for the future when I get a posi and a higher numerical rear gear.

Any advice on cam/heads/gasket combo would be appreciated. 403 guys and engine builders...Dan? Mark? others? Your thoughts?

Thanks in advance.
Charlie

 

BBO heads with pistons to match so you get the desired CR. You wouldn't put SBO heads on a 400 big block, and the 403 flows just as much air. Performer RPM port-matched to the heads.

 

Joe,
I agree BB heads are the ideal solution. If I had some sitting on the shelf, or stumbled onto some cheaply enough, I would go iron. If I decided to splurge, I would get aluminum ones prepped by Bernard Mondello or J&S. I would still need to mill them to bump compression, as I wasn't planning on getting pistons.

Right now I'm trying to figure out the best combination with what's on my shelf or perhaps obtainable via selling those items, but not looking to spend new $$.
This isn't happening immediately, so if the right BB heads come along you never know...

P.S. If I had greater budget and aspirations, I would start with another 403, not in the car, and contact Mark for the stroker crank, pistons, ring pack, and maybe make a milder version of what Dan built..

 

If you’re budget is such that you’re just trying to use what you have then use the small block head, although I agree with Joe, they’re essentially too small for a 403 but.....
Use the Rpm intake with at least an 800cfm carb if some sort, you need the volume.

 

I used a custom Erson very similar to the TQ20, it worked well a 2300 stall 2004R and 2.78 gears in a 9 to 1 350. With a stock stall TH350 it sucked. You need a couple of upgrades and a better converter plus a shorter driveshaft and different yoke to run a 2004R. I would get an affordable higher stall converter for your TH400, Jegs brand is cheap and well rated. The 2000 to 2300 stall would work OK. The #5 heads due to spring depth will probably work best with the Erson cam, lifters and springs. Regular cheap Felpro head gaskets will give close to 9 to 1, a big improvement from high 7 to 1 compression with better exhaust side flow with early heads. The 69 455 carb will be closer to the right tune for a warm 403 but the 403 carb with a custom tune has an extra 50 cfm on the primary side but is calibrated super lean especially on the idle circuit. Use the Performer RPM intake.

 

Thanks for the input guys. What about the cometic gaskets? Is there enough of a bump to make it worth it the $$?
I'll definitely keep my eyes open for bb heads, maybe sell off some other items to help finance.

 

The only problem with BBO heads is you need new small dish pistons. For what you are doing, early 350 heads with Felpro head gaskets is the way to go, IF the motor is healthy. You gain .25 to 1 with the thinner Cometic gaskets. Get a clean up mill, the bowls opened along with 2"/1.625" W31 valves, if you want more performance than slapping on bone stock early 350 heads. You will only gain performance as long as the valves are sealing properly on the replacement heads. My stock 4A 403 heads measured 86cc, your 350 heads should measure 68 to 70cc untouched, your piston will be .020" down in the hole at TDC. My rebuilt set of #6 heads measured 65cc with the larger intake valve. Do a compression test and throw an oil gauge on the motor. If the bottom end is healthy 350 heads, either decent shape original or modified 350 heads is the cheapest way to go. A total overhaul, BBO heads make more sense. Remember the 350 runners are smaller which should help low end velocity with your 2 something gearing.

 

Ok so I obtained some C casting heads. I know they will need the same head bolt hole mods as the 7a. The performer rpm needs to be ported. I've heard of fuel pump interference problems? What exactly is the problem and how have people solved it?

 

The fuel pump issue is ONLY with aftermarket aluminum heads, NOT factory heads. The E-brock heads extend out further from the front of the block than do the OEM heads.

 

Thanks Joe. To you or anyone else that knows cams, if I use the c casting, still go tq-20, or does the other cam make more sense?

 

What is your final comp ratio going to be?

 

Hi Mark,
I really appreciate you chiming in. I guess I would like to target the highest that is safe to run on premium unleaded and makes sense with either of those cams. I can't find the. 028 corteco gasket from BTRs book, so it looks like either. 040 felpro or step up to cometic. 027 MLS if needed.

I haven't ccd the heads yet, they are complete but not assessed, and the engine in the car still isn't apart to measure how far in the hole the pistons are.

 

What do you recommend?

 

If you aren't milling the heads, you will be right around 8 to 1. Yeah, that Erson cam should work well with that on a 403.