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1978 Olds Custom Cruiser, blown head. All i know is what you guys have taught me and what ive learned myself through trual and error, so I hope you all can accompany me on this major project ive gotten myself into. Ive never had to dig this deep before, and this surpasses what i know but with the help of you guys i am comfortable to take it down.
I guess we should start with whether or not i should rebuild this engine or install another. Assuming that rebuilding is a viable option can you help me get together a list of what ill need so i can have everything here and planned accordingly?
Im a fan of MAW, but obviously do not have bottomless pockets. This is a simple cruiser, and thats all i intend it to be, so no over-the-top parts are necessary but quality and longevity are a must.
Im 22 and want to show kids of my generation what real cars are made of, so lets get it!
The 403 SBO in your Custom Cruiser is a great engine to rebuild. First of all, how do you know that the head gasket is blown? Did you do a compression test?
I believe its a 350, its blue and the sticker says so. I had the valve cover off and upon cranking i can hear a discharge of air coming from the 5th cylinder and milky watery oil coming from that rod. I think that means collapsed lifter and blown head..
Those heads are known to crack, make sure to get them pressure tested. Are you losing coolant? A cracked head or blown head gasket will empty a radiator in a hurry in my experience.
A small amount of coolant has been lost yes, but i havent ran the engine for fear of further damage. I will check for cracks.
Should I go ahead and start yanking off the top to see how bad it is?
I was unaware these 350s were prone to cracking and assumed blown head. Is there a way to tell without taking the intake off? If the engine is worth saving ill do everything i have to do to make it right, but i dont want to beat a dead horse..
I would do a cylinder leak down test. It will confirm that you have a blown head gasket and it will let you know the condition of the rings. You should be able to rent these at the local auto parts store.
My guess would be that you'll find either 2 cylinders blew a shared section of head gasket, or 1 cylinder blew the head gasket into the water jacket. The other cylinders should have minimal leakage into the crankcase and no leakage past the intake/exhaust valves.
Hi I would like to add my 2 cents. If you do happen to have a cracked cylinder head on your motor. I would suggest getting some 1980-84 307 5A casting heads as replacements. The reason I say this is they are easier to find in salvage yards. They do have smaller intake valves 1.75 vs 1.875 for 350 heads. But any machine shop can install the 350 size intake valves in the 5A heads. They have smaller combustion chambers 67cc vs the 75cc of the 3A heads. Which will help maintain your compression ratio with the felpro blue head gaskets. And honestly I would just pull motor and regasket the whole thing and install a new timing set and either replace the cam and lifters or at a minimum tear apart clean and reassemble your current lifters. I say this from experience I battled valve train and lifter problems with my olds 350 in my truck. Your car is a 78 wagon and a nice cruiser. So I wouldn't get distracted with the temptation of trying to build a race motor for it. Follow what I said and your 350 will be a nice solid reliable driver. I learned my lesson about doing minimal repairs and half assed fixes on old motors. Gasket sealing and having accurate valve timing and properly working lifters is critical to engine reliability and performance. It sucks to realize that's what needs to be done but that's the only way to do it right. If you only have a bad head gasket then pull both heads and replace both head gaskets. Also check your harmonic balancer to see if the outer ring has slipped from old age if it has you will need to replace it because you will never get the timing right. I recommend the powerbond 1147n harmonic balancer it's a very well made replacement.
Beautifully put sir, i will digest all of that information and follow accordingly. Still trying to get some daylight to do the leakdown test and see whats really going on!
I have used 5A heads with the 204/214 cam on a 76 350. They worked nicely in a truck application, think idle to 4200 rpm. With Felpro head gaskets, you will be around 8.5 to 1 with 5A heads. Remove the air tube extension in the exhaust port and plug. The 5A heads will definitely be improved with 1.87/1.56 valves from early 350 heads and a bowl hog cutter at the machine shop.
Here i am so far, i had this all apart last week but was just able to upload pictures.
What/how should i inspect while im in here? All the pushrods look straight although im sure a few were clogged. Im also sure that metal was of a better quality back then, so if it isnt broken, should i fix it with newer possibly lower quality materials?
Seriously ive never been this deep in a motor, so any tips or advice you have to offer i shall heed. Also im going to order a csm for it to get the torque specs and all that good stuff here tonight. Thanks in advance!
Were the head gaskets blown? I think one size smaller cam might be good Mark if the stock gears and converter are used. My 214/214 cam loved the 2300 stall even with 2.78 gears. That was 9 to 1 compression, you will be at 8 to 1 with 3A heads. With the 1700 stall it works Ok, more lively with 6 degrees added over the 36 base/mechanical with 11 vacuum.
If you can afford it replace the pushrods. I think the stock pushrods are made of sae 1140 steel. I upgraded to an adjustable valve train with roller rockers. The kit I got came with chinese procomp hardened push rods and they are way higher quality than any stock peice. Honestly if this is the farthest you have been inside a motor before I wouldn't change the camshaft and lifters. I would recommend taking out and disassembling each lifter cleaning all of the peices and then reassembling it. You have to keep each lifter matched to the cam lobe that it came off of. they are mated for life and you will destroy the cam and lifters if you mix them up. I'm off work tomorrow and can provide detailed pictures and instructions for doing this i assume you have never disassembled a lifter before. I dont mind walking you through the steps this is worth doing because. It prevents you from having to spend money on a new cam and lifters and having to perform a camshaft break in. But disassembling and cleaning the lifters corrects any sticky lifter issues the engine might have had and allow the valve train to function correctly.
The stock cam sucks, super mild but the stock non adjustable valve train I like. Simple and works as long as the rocker arms aren't worn out, check for big shiny spots where they contact the pushrods. Even if he doesn't change the cam, the timing stock timing chain and gears with it's nylon cam gear could be ready to fail. Good luck and maybe get the heads pressure tested especially if the head gaskets weren't blown.
Water (coolant) somehow got into one of the pistons and was running hot when it happened, looks steam cleaned to me.I apologize if this has been discussed to death previously... I'll now leave you A body guys and return to the first generation section where I belong. Tedd
Largest valves in a 5A head before you start seeing a water jacket are 1.875/1.624. Consider with replacement head gaskets, you’re losing ~.025” of deck from the thicket replacement head gasket. I suggest using a set of #3 or #4 heads with some big valves or the 5A head will be a decent, cheap alternative. Reach out to Mk performance on Facebook for thin head gaskets (.011”) but they’re like $140...
I would only do 1.875 intake with 1.522 exahust it's not like the exhaust ports are going to out flow a 1.522 valve with a bowl cut. So no need to cut the heads for the max exhaust valve size.
So, i might need to sit down and take a bit of this information in.
What heads should be on my engine? When i was moving things around i noticed a giant 5A on one side. My head gaskets didnt appear blown to me, so would that mean one of the heads must be cracked?
As far as all of the measurements go for what i assume are the intake and exhaust valves, what are my options that dont require machining anything? Forgive my ignorance, i just dont know how to figure out what heads/valves/lifters/cam/gasket combinations are possible and which would require what alterations.
What are the big numbers in front of the oil fill tube? You should have a big 3A on the factory 350 heads. The 5A heads don't usually crack, post pics of the head gaskets.
3A are the correct head castings for a 1977 to 1980 olds 350. They are a crack prone casting so inspect them thoroughly for any obvious cracks usually in or around the exhaust port area if I'm not mistaken. If there are cracks in the heads just get the 307 5A castings they are easier to find. Then just have the machine shop install the larger intake valves for a 1977 to 1980 olds 350.
Thank you! All of the numbers and measurments were getting alittle confusing. Hoefully my csm gets here today as id like to make alittke sense of it all
Some of the valves on the back side of the engine were stark white while others were pitch black towards the front
I am betting when the machine shop pressure tests the heads, one will fail. When one of my Magnum heads failed on the 5.9 in my Dakota it big time pressurized the cooling system and overheated quickly. I bought a pair of the Ram EQ heads. As said 330, early 350 or 307 heads are options for a stock 350.
The advantage of going the 5A head route is they are a direct bolt on for a 77-80 model year 350. And the valve kits for a 77-80 350 are cheaper than the earlier 350s also. And I bet he could find some locally in a salvage yard. There are differences between the 68-76 350s valves and the 77-80 year valves when it comes to the length and the degree on the valve face 45 vs 30 I believe. Oh a side note if he finds some 5A heads that are in usable shape I wouldn't even bother changing the intake valve size. They made 180hp on a low compression 307 so they will flow good enough as is for a low performance 350.
Last edited by rktpwrdc10; October 10th, 2019 at 06:37 PM.
I agree on something like a wagon where low end torque is king, stock 5A heads will work Ok. I used them on a stock 76 350, the same pistons as the 78 with a 204/214 cam, shorty headers and 2.25" dual exhaust on my 94 Z71. It moved pretty well.
Went to a place called stark wrecking company that has a collection of cars all the back back to the 20s and 30s and found one lonely set of of 3a heads and one set of 7a heads.... i was able to track down the "5" heads which if im not mistaken are in fact from a 350 from 68 or 69.
Yes, the number 5 are good heads. Which 7a heads? The swirl port 307 heads or the 72 350 heads? If the latter, also a good choice and have induction hardened exhaust seats if you plan on slapping them on without machine work. Olds doesn't seem to have the issue sbc heads have with valve recession from unleaded fuel, hardened or not.
So your saying the 5 heads will be a good choice that wont require machining or exchanging valves around? And im also assuming the 5 heads dont have hardend valves but you say that doesnt matter much?
The 5 heads are far away and it'll cost a pretty penny to get them to me, but if theyre a good upgrade then by all means ill send it
Also, will the felpro gaskets for these heads and engine work and match up for the "5" heads?
Last edited by Goodoldsreliable; October 15th, 2019 at 03:01 PM.
You will at least need to drill out the head bolt holes to 17/32 to accommodate the 1/2" bolts. Those Fel-Pro gaskets are also .042" thick vs the .017" thick on the stock ones. milling the head .025" can fix this so there's no loss of compression. Shouldn't have an issue with intake alignment until .040" removed. Where are you located? There's an even better option with the #3 heads for $130 in Michigan but the guy won't ship.
You will at least need to drill out the head bolt holes to 17/32 to accommodate the 1/2" bolts. Those Fel-Pro gaskets are also .042" thick vs the .017" thick on the stock ones. milling the head .025" can fix this so there's no loss of compression. Shouldn't have an issue with intake alignment until .040" removed. Where are you located? There's an even better option with the #3 heads for $130 in Michigan but the guy won't ship.
Im located in southwestern ohio north of Cincinnati.
Didn't the "5" heads have a smaller compression chamber than the original 3A heads therefore the thickness of the gasket minus the smaller combustion chamber equals out the same?
Also, your saying the head bolt holes need to be drilled as well, im assuming this would be done by a machine shop. Are the angles the same? I read something about some being 39° angles rather than 45°.
I thought the 5 heads (no "A", being from 68 or 69) would be a good match? Are there any options besides 3A that are a direct bolt on? I just was to upgrade while im at it but dont really have to funds do go have something machined. I have no idea how much and of that would cost.
I was just told the "5" heads were highly desirable and a good fit
Yes the number 5 heads are a good heads. They are not however a direct bolt on for your application. The 1977-90 oldsmobile engines use a larger 1/2 inch head bolt diameter. Vs the 1964-76 oldsmobile engines. You can easily have a machine shop drill them out to work though. I can't remember clearly but I remember reading somewhere that the head locating dowels can be different also so you might want to check for that also.
So i found a set of #5 heads that include Crane high performance Dual Valve Springs and retainers. Should i get them as well with the deal or is there a better option?
by going with the #5 heads which have 64cc combistion chamber rather than the 75cc combustion chamber will i need to do any milling or adaptions other than incrwasing the head bolt hole size to fit the half inch bolts?
No I think you will be ok. But i would check your valve train geometry and pushrod length if your going to be using the factory rocker arms and pivots. The factory olds valve train is none adjustable. So going with new thicker head gaskets could make it to where you would need slightly longer or shorter push rods to get proper lifter preload. More than likely you will be fine but you need to measure it and verify. I decided to cough up the coin and invested in adjustable roller rockers for my olds. Simply for the convenience factor I so could set each valve individually.
Unless the heads have been milled, which they may have been with new springs, most early heads like the #5 heads actually measure 68 to 70cc unmilled. Either way, you will be around 8.5 to 1 even with thicker .040" gaskets with the factory pistons .015" to .020" below deck. If they had a clean up mill closer to 9 to 1. If they are a good price get them for sure.
September 24th, 2019, 12:55 PM
