Redbud40

72 stock CS vert. AC Dual exhaust Flow master I think 3.23 lim slip. Auto Q jet 4 350 Engine rebuilt to stock about 20 years ago. points ign. I drive it on nice days but not allot of miles per year. Love cruising , but have always thought it lacked get up and go. Semi Retired and finally a big garage where I could actually work on it a little more. I might also add most of my ability is pull something and have someone else do the real work or buy a new part. Most of the build threads I understand about half what people are talking about.
So a few questions, comments
1. Are headers a reasonable solution to more power vs the what seems to be PITA installment procedure.
2. Any engine mods that I might consider that would increase performance without a major engine disassembly.
3. Do a significant engine rebuild along with headers all at once to coordinate everything. ( that would definitely be sourced out)
4. Drive as is.. Enjoy the performance it does have and call it good.
Thanks for any suggestions , ideas or a good Olds shop in DFW that might “ encourage” me in the right direction.
Mike.

joe_padavano

Full length headers are worth 20-30 HP over manifolds. The real benefit is in conjunction with any other mods, since the engine parts need to be matched as a system. Shorty headers and aftermarket manifolds are a waste of money in my opinion. If you want the HP increase, you'll put up with the drawbacks. If the hassle is a problem, keep it stock.

69CSHC

So much to touch on I'm going to try and answer in a different fashion. Going with a blue hue to make for an easy back and forth pattern.

Ok got that out of my system, my next post will tackle the questions my old fashioned way.

Fun71

Stock rebuild means low compression, maybe even lower than factory depending upon the pistons used. Factory was 8.5:1 and aftermarket pistons could be as low as 7.5:1 so not really anything you can do to increase performance over what you currently have without replacing the pistons.

bccan

I wouldn’t hesitate to install headers, plumb them into existing exhaust or even better into a new 2 1/2” exhaust, maybe w/ xover or X pipe. If you had no plans to modify your engine 1 5/8” tubes would be good, if not sure or likely to modify in future go 1 3/4” tubes.

BUT to get the most out of your combo you may want to get your carb checked & recalibrated if appropriate by someone who knows Qjets.

Either way an ignition recurve and a bit more initial timing would help some with responsiveness.

After that you gotta go internal and the plan starts with more compression. (refer to Kenneth’s post above)

69CSHC

The 3 best automatic powertrains for 1972 Oldsmobile Cutlass Supreme Convertible are.

1) 200 HP 350 = 16.6 seconds elapsed time in the 1/4 mile.
2) 250 HP 455 = 15.7 seconds elapsed time in the 1/4 mile.
3) 270 HP 455 = 15.5 seconds elapsed time in the 1/4 mile.

All are factory dual exhaust, all are 2.73 rear gear base optioned (automobile catalog).

Depending on your daily driver all may feel inadequate in the acceleration department. 14s or what 14s feels like on the street is probably the answer.

Gaining 50 or 70 HP without a rebuild/cam swap/etc is just about impossible. As is modding, assume a clean 20 HP gain via long tube headers. So we are talking 220 HP, now you need better gearing 3.42 is the only option with no overdrive on a cruiser... Better torque converter (2000 RPM stall), shift kit. Nice tune to blend all into a healthy mover.

My car shows 217 HP by best MPH and 203 by best ET. My drivetrain is poor for acceleration same as yours base optioned. My engine is supposed to be 250 HP net so its leaving about 30 HP on table. Your car is likely leaving the same equivalent. Most regular everyday cars leave plenty on the table. If you make the best of your engines power it will be a significant difference.

But your ride is no lightweight and everything just right shows a 15.3 @ 89 MPH (4000 LBS test weight) perfect setup showing 220 HP on both ends. These are of course calculations so its just to give you an idea but its probably not that far off.

Road & Track 1986 saw a 350 CID 220 HP IROC Z run 15.3 @ 90.5 MPH at 3720 LBS test weight. This is a factory performance car obviously and very well setup to take advantage of its power.

https://www.thirdgen.org/rt_october1..._camaro_irocz/


I'm leaning big block, built small block, or built big block.

oldcutlass

Ahhhh, me ol stompin grounds. I recommend you get involved with the N Texas Olds Club, great group of guys and gals. Once this covid thing is over, a bunch of old car people gather at the Dairy Queen on Thurs. nights spring through fall, Piston Slingers Car Club.
Piston-Slingers Car Club | Facebook

Richard Holeman, H&H Automotive is a good shop for mechanical repairs to your car. (817) 326-2354

Granbury Muffler for exhaust work, he is an artist. (817) 573-9111

oldsmoboogie

There are many ways to approach this. The first thing we need to know is what is your budget? Next would be how much more power do you want? I can say that the first engine i put in my 72 was a mildly built 455. It had 9.5:1 compression, mild cam, rebuilt mildly ported heads, a quadrajet, headers, and 2 1/2” duel exhaust. The car was very easy to drive, had plenty of pep, and low maintenance. All of the accessories from the 350 will bolt on the 455. Keep in mind that shop labor in my area is 75-90$ an hour and can easily double the price of a build. You should consider buying a core engine, either a 455 or 350 and have it built up by a competent machine shop. Then when you have the engine and parts available you can do the swap yourself. Torque is your friend for a fun, peppy street cruiser.

Redbud40

Thanks for all the ideas. It kind of reminds me of trying to increase the wake on a ski boat so the kids ( and me ) could wake board behind I kept adding this and that, poles , fat sacs , ballast etc it was never quite right and I sold it and bought a wake board boat. Maybe I should look for a four speed hard top 455 that someone has been sitting on. Have a functional car while building the other one. Anybody have one : -). Eric what a coincidence I almost called Granbury Muffler yesterday just to see what they might offer. Think I will on Monday.

olds 307 and 403

And as a bunch of dyno tests have shown for other brand motors, shorty headers gain over log style manifolds, usually at least 10 HP and TQ. They fit better, allow a full size starter but need either custom or manifold down pipes in the case of the Thornton shorties. I want Cutlassefi to do the Sanderson and or the latest Thornton shorties. Joe claims they do nothing, I say there will be a gain. SB cast iron manifolds are awful. I am willing to pony up for a set of Sanderson and get 2.5" and 3" down pipes made or get Thornton Shorties and Ram Air Restorations down pipes for Cutlassefi to dyno test. My only issue with the newest Thornton header is them using the BBO set and flattening one pipe to fit them on the SB. They could have moved that one pipe and made them that much better.

Mr Nick

The Hedman shorties seem to have slightly longer primary tubes than the Sanderson's, but whether or not it makes any difference is anybody's guess till we have data.

I think a nice pair of mid-length headers for SB and BB Olds applictions would sell well, but considering how small the Olds market is to begin with I'm not sure any manufacturer would put the effort into producing them.



Hedman 1 3/4" primary, 2 1/2" collector:


Sanderson 1 5/8" primary, 3" collector:

69CSHC

Bingo !

455,455,455...

Great analogy, I figure your car runs great as is and that still doesn't do much for you, as far as performance goes. Small mods will leave you wanting in my opinion. I owned an original 1971 Eldorado ran like a champ. When you tapped the gas pedal it was impressive when you stomped the gas pedal it was breathtaking. And she was just a cruiser. A lot of fun driving with big block torque.

You have to load up on a 350 both with mods and driving techniques to feel even remotely like a big block.

olds 307 and 403

Yeah, the Hedman are almost a mid length header. Problem Is, they pointed the collector straight down. I know one member had ground clearance issues because of it. If I am going to have ground clearance issues, I may as well scrape full length headers. The thick 3/8 flange that only requires RTV on the Sanderson is better than the thinner Hedman flange as well. The Sanderson are the best designed to actually fit without drama of any Olds header but at what cost is the question.

coppercutlass

I would personally do full length headers . As far as your lack of power . It might just need a really good tune. I built a no nothing mild 350 low compression engine for a friend . Full trim street car with a 3.42 gear I might add and he can light the tires up easily running low 15's his first time ever at the track. This was a 350 with Pistons that sat .045 in the cylinders just making under 8.4 to 1 compression. I salvaged his hurt engine. And a jasper rebuilt engine to make something work lol. Nothing about that build was ideal but it works.

olds 307 and 403

Unfortunately to greatly improve the performance of a 72 Olds 350, you need different pistons. Stock it will be around 8 to 1 compression with a small cam. Headers and dual exhaust will help but only so much. My 88 Cutlass would probably be in the low 15's. Stock 73 8 to 1 Olds 350 with a custom tuned Qjet, recurved HEI, Sanderson shorties with 2.5" X pipe exhaust, 1900 stall 2004R trans and 3.42 gears. Your factory 1600 stall converter does not help, consider a 2000 stall. Everyone says 455 but be very careful building or buying one. People rev them like a small block. Nearly all the used ones in my area are knocking and they are still $500+. There have been too many failed 455 builds on these forums, hardly any failed 350 builds but also less built. The heavy parts and big mains aren't very forgiving, especially as RPM climbs. I think it boils down to improper machine work, too tight of clearances or both. Good luck.

coppercutlass

To add to what was just posted. I spin my current 355 to 7k rpm on stock rods and crank. Just arp bolts on the rods. The lighter prove Pistons help. With the speed pro flat tops 6500 was the norm with my old engine. You spin a 455 to 6k during a burnout by accident and it's a kiss of death.

OldSoldier

You might want to look into a supercharger for that stock 72 350, if it runs well otherwise. The low compression plus some boost could make good power on available gas and keep from having to rebuild the motor. Of course, if your engine is hurt in any way or your pistons and rings aren't up to snuff... https://torqstorm.com/product/kits_single_olds_350-455/

dc2x4drvr

Yah, hookup with NTOC, a lot of Olds guys that can help with engine performance suggestions.