ClassicOldsmobile.com - Small Blocks

Exhaust manifold gaskets on a 403?

MrEarl — Sat, 30 May 2026 01:46:10 GMT

79 Buick Estate Wagon, 180,000 mile, 403 engine. Noticing an increased exhaust noise in engine bay, can't tell exactly where it's coming from. Hopefully just at the manifold tailpipe connections. Will be taking to a shop but would like to know a bit more than I do such as are there gaskets (donut type or other) at the manifold tailpipe connections?

Ultra basic home bottom end rebuild advice

illumined — Wed, 27 May 2026 01:52:47 GMT

My 403 has had oil burning issues for a while, probably stuck rings from sitting for so long before being put back into service. Some people had some great advice for engine flush options to unstick them but before I could try it out one of the main crank bearings went bad. I got this confirmed today by a professional mechanic. Now I have no choice but to do some kind of rebuild. The ideal option, as the heads were already rebuilt last year and are perfectly fine, would be to take the block to a local machine shop and have them do things the right way. Unfortunately in reality that's not realistic, all the local engine builders are swamped with 6 month to 1+ year backlogs. Given that the car is meant to be a driver, having it off the road that long is not acceptable unless it absolutely can't be avoided. That forces me to try and do it myself and learn something new. According to the manual, there is actually a procedure for pulling the crank and pistons without having to take anything off the top end. Since the top end works perfectly this is very appealing. It does raise a few questions:

1.) What is the best brand for bearings (both rod and crank) and rings? I know part quality is at an all time low which makes finding that one company that still cares about their customers all the more important
2.) There seems to be a lot of ring varieties, for a stock 403 what would be best for durability so I don't have to do this again for a really, really long time while putting gazillions of miles on it?
3.) What is the break in procedure for this amount of engine work?
4.) Does anyone have suggestions for what assembly lubricant works best?

Thank you.

78 Olds 350 Timing chain

regency98us — Tue, 26 May 2026 02:40:30 GMT

Ity has been awhile since I have posted anything. I still have the 1978 Royale and has 93k miles. About two years ago I started it in the storage facility and it died quickly. It wouldnt start and the starter had the freewheeing sound. I knew what it was. It jumped time. I finally got around to working on it a few months ago. I have it apart, and the new chain installed with both cap and #1 cyl at tdc. I havent replaced the front cover yet since I wanted to get a mobile oil change company to come out with an extractor and stick the tube through the front cover first and suck out the oil and any debris. Then remove the pan bolt to drain the rest. So far its gone well and have been careful. It is hard to find anyone around Charlottesville to help. I called an oil place and he made excuses twice. It is like no one wants to work anymore.

in place

403 Used Engine Price

1970CutlassSupreme455 — Mon, 25 May 2026 23:45:21 GMT

If I were to sell this engine, how much should I ask for? It was running when it was removed from the car.

Are there casting numbers on the block that would be good information to put in the listing? I could not find any just casually looking.

Cooling System Mods

kuseetha — Sun, 24 May 2026 12:08:59 GMT

Hi friends,

This is a swap and the topmost part of the coolant circuit sits (unfortunately) above the radiator cap.

Coolant escaping the thermostat (in orange) would sit higher than the radiator. Note the inlet manifold sits below, thankfully. (in yellow)

How the hose connects to the radiator (ignore the kink, I've just re-fitted the hose to take a picture)

I don't have the heater matrix connected (thanks global warming)
Previously I have connected a coolant crossover pipe, so that hot coolant at the back of the heads would not stagnate there.

Coolant crossover pipe

Continued on next post --->

Painting engine in car- 1972 350

OLdGreenPaint — Sun, 17 May 2026 21:35:28 GMT

Old fella here, so not a lot of desire to pull the engine and do a rebuild of a 72 Cutlass 350 with 70,000 miles on the clock. I have been working car Sheetmetal and have both quarter panels installed, right door and fender reworked and in epoxy primer. Left fender also currently off the car, patch panel welded in and fender in epoxy primer. Day after day I walked by the old faded black metal under the hood and decided to remove it and paint it. In process, found a radiator leaking that is currently being re-cored. So the engine is a whole bunch easier to get to with bumper and left fender off the car, and radiator and fan shroud also off the car. With fender off car, I can step between the frame rail and wheel and work the engine standing up, rather than stooped over. Had back surgery 8 months ago and don�t care to revisit that. So�.I decided to paint what I can get to on the top parts of the engine. Already had some parts painted with single stage catalyzed black urethane. They look nice and should wear well. Now in process of removing AC brackets, Alternator brackets, currently stalled on the Power steering pump bracket. I think it wise to pull water pump and change timing gears and chain. Maybe also the intake manifold, as it looks like maybe it was leaking oil too? I think the valve covers are an easy target to remove and replace gaskets. So I should do it while relatively easier.

Any comments on what else to do will also be appreciated. Any comments on valve cover gaskets, timing chain set, that type of thing much appreciated. Last time I was this deep into an engine was in 1972 when I put a solid lifter camshaft into a SS396 Camaro.

Already have some of the parts painted with urethane single stage

Bracket removal in process

Pulling the carb will open up the intake manifold a bunch.

I checked some videos on how to remove the oil fill tube, but I think I can work around it with it in place

I will blast all accessory brackets and paint black, off the car

I checked AC pressure and there is no refrigerant left in system, so I will remove AC to where I can get to right valve cover for removal

I am not sure if the oil seep behind the steering pump is an intake manifold gasket failure or not? But if it is, now is the time to remove intake and fix it, as much as I hate the thought of doing it.

Currently stuck at the steering pump pulley. I will likely leave the pump in place and paint it in place to avoid draining down the pump oil. I may be overthinking this.

Stock bore 350 pistons?

DocN — Fri, 15 May 2026 18:04:19 GMT

Dug out my '72 350 block and gave it a preliminary scrubbing. Interestingly enough, careful bore measurement shows virtually no wear- I plan to run it by the local automotive shop to confirm, but near as I can measure, just below the ring land might be 4.0575". An inch below that is 4.057" even.

Again, I want to confirm with better measuring equipment than I have, but I might be able to give it a quick hone to break the glaze, and drop in some stock-bore pistons. I could use the ones that came out- stock deep-dish cast, in good shape- since I'm not going for max power, but as I understand it, that with a thick gasket would likely only barely give me 8:1. Am I right on that?

I've found a number of stock-bore pistons available, but I'm wondering if anyone can recommend a specific good, budget set. Again, not shooting for max output, 250 to 300HP would be fine. (Still twice what I have now. :) )

Stock 7a heads, and presumably a thick modern gasket, though decking either head or block or both is by no means out of the question.

Thanks.
Doc.

Backfire under load?

71supreme — Thu, 14 May 2026 20:50:23 GMT

Hey all, I'm working on getting my 71 cutlass supreme road ready after about 30 years. The 206,000 mile 350 starts right up and idles smoothly just under 900 RPM with 20 inches of steady vacuum. The trouble starts around 1600RPM when the vacuum needle starts to flutter a bit, not wildly, and I get a persistent exhaust backfire. Not rapid, just a slow pop, pop, pop. I haven't done a proper tune up on it in probably close to 20 years, but I haven't done anything other than start it and run it on occasion either. I will start there with new plugs points, rotor and cap, but thought I would toss the question out to see what thoughts you all may have beyond the basic tune up. Thanks for any thoughts orinsight you may have.

Where to start 350 rebuild

jroq — Wed, 13 May 2026 13:56:31 GMT

Hello all, I need some guidance on rebuilding a olds 350. It was my dad's and im trying to revive it. I believe its a 1973 or 1974 based on the block casting numbers 395558 and the no.8 cylinder heads. Its been sitting for a long while and I still need to take it apart and see if its ok, id like to get an idea of what id need to rebuild it to give it more get up and go.

So what's a good set of pistons, rods(if needed), and cam (im thinking roller cam) I know the heads arent the greatest and in the future I would like to replace with something way better.

Thank you in advance

New engine build - timing issues

ej69 — Thu, 07 May 2026 18:13:59 GMT

Had 350 olds rebuilt, broke in fine. HEI distributor (summit racing new). Set engine to TDC and then adjusted timing mark to 12 degrees before. Dropped in distributor. Started fine and appears to run fine in driveway but when check timing with light it shows around 4 degrees After. Rechecked distributor and looks right (brought to tdc and advanced to 12 degrees and rotor points to #1 on cap). Used 2 timing lights same. Advance hooked up to timed vacuum port on car (check w and without vacuum hose plugged). Stock replacement balancer but original timing tab.
Any ideas what I�m doing wrong.
im going to recheck tonight and probably pull distributor and reinstall
thanks

Progression Ignition

goatwgn — Wed, 06 May 2026 22:19:10 GMT

I am basically an unfrozen caveman mechanic. I don't usually like, or trust things that are too complicated. However, I am intrigued by the idea of the Progression Ignition HEi. I think it would be something that would work well on my '74 Cutlass 350 with an HEI unit installed, as this engine loves extra timing, at the lower end of the RPM range, but not too much total. I drive this car on long trips, including mountain driving. I think this would be better than my present system of fiddling with weights springs and vacuum advance limiters. I am a bit concerned with reliability of a system like this, but I can stick a spare HEI in the trunk if I am traveling. I am looking for real world experience with this.

Garbage newer fuel pumps.

goatwgn — Tue, 05 May 2026 19:03:12 GMT

This is the second one of these replacement fuel pumps I have had come apart internally with less than 10000 miles on each, on my '74 Cutlass 350. Have any of you had a similar experience?? I have driven this car since 1989, put 400000 miles over the 135000 it had when I bought it from a family member, and prior to 2020, only put 4 fuel pumps on it. The symptoms are, dying randomly, and all the time under full throttle, or load.

Olds 403 cuts out and shutters under load/rpm

Lunched — Sun, 03 May 2026 15:10:51 GMT

79 403, been trying to solve this for over a year. Engine is stock with general maintenence.

Car starts great, idles and runs good cold. Good power and revs out fine when cold. Once driving for 30 or so minutes the problems begin. Whats shown in the linked video is how it begins to act. It will downshift and pull through 1st, then getting through second it stumbles, loses power, and falls. if i let off the throttle the engine returns to an idle like nothing happened.
after say 10 more minutes it gets worse, driving off from a light, or trying to pass someone does the same stumble thing, no matter gear or moderate/heavy engine load.

Ive checked over fuel, hei, timing, choke, wires/plugs... Seen this before? Any help? Its been driving me nuts trying to tinker with it, only to drive around for 30ish minutes untill its hot and does the same thing... such a waste of time and fuel. Thanks all.

https://youtu.be/2YoRVdefd6w?si=gK6UpGxQF20HBPbc

84 Olds 307 exhaust manifold interchange

Coco 84 — Fri, 01 May 2026 23:53:51 GMT

Hello, I am looking to replace my factory exhaust manifolds with smog air pump lines to a none emissions exhaust manifold. The lines are rusty and keeping leaking exhaust and its getting old with the ticking it makes. Looking for a permanent solution to the issue.. Will any Olds 350, 403 manifolds from the 1970s fit the 1984 307 without changing the factory exhaust? I am guessing the manifolds are the same,(correct me if I'm wrong), but will the factory exhaust pipes bolt up to it? Cant find any info about it. Thank you in advance for any info on this.