First things first, I’m just a hobby gearhead that set a wildly unrealistic goal of building an entire car in 6 months (already over a month in), and the engine is just one piece of that puzzle. This is my first time working on Oldsmobile engines and im already starting to become fond of them.

i currently have in my possession:

1) 1977 Olds 350 from the project car in question. It looks greasy and high mile but it ran like a clock when i pulled it. Maintained steady temp, oil pressure on the factory gauge showed between 10-35psi at temp, and it had impressively snappy throttle response. It didn’t seem to be an oil burner, maybe just the slightest haze. It is however a windowed main, 3A head, dog dish piston smogger deluxe and the timing set is one of the most stretched ive seen. I only ran it in my garage/driveway since the car was not driveable.

2) 1972 Olds 350 complete parts engine for which i have to give the block back to its original owner (numbers matching block to his car & slightly spun bearings). It has some really good parts on it that i got for a great price. 7A heads, comp 210/216 hydraulic roller cam & 1.6 pro mags, performer rpm intake, nice valve covers and hooker competition headers. When the engine was built the pushrods were measured wrong and the intake gasket failed immediately resulting in P-T-V contact and cylinder 8 hydrolocking on coolant. but despite all that happening the top end seems good. I also have a melling oil pump with standard and high pressure springs to choose from.

my plan is to swap the top end of the 72 onto the 77. Question is, what considerations do i need to make to make a good street engine that can see a lot of miles. It won’t be raced. just want it to sound healthy, be fun to drive and have enough power to not feel pathetic.., something like 300hp with good usable torque. I plan on using a performer intake instead of the performer rpm for use case reasons and hood clearance.

Questions:

1)i know compression is an issue. How far can i mill 7A heads to get the most out of my setup? Is there a specific head gasket that would work best?

2) I’ve never done a DIY bottom end rebuild, but this might be the time i take the leap. Does a re-ring and bearings make sense or am i better off leaving well enough alone and just running it? What kind of things should i check to help decide?

3) strength wise, am i going to have any issues with the 77 bottom end for what I'm doing?

... or anything else i might be overlooking. Thank you!

 

Welcome to C.O.

 

The oil pressure is a bit on the lower side, it will need new bearings at minimum. A compression test is another good tool. You can mill the heads a good amount but the intake will also need cut to fit. Even a cleanup mill would require the thin intake gaskets. Welcome.

 

A compression test, better yet a leak down test would be a great starting point to know the ring condition. A complete bearing inspection on a 45 year old motor that is being upped in HP is absolutely necessary.

Good luck!!!
​​​

 

The 1977 block has windowed main webs. The 1972 is solid.

 

 

Those pistons and some early head should give you useable compression if you mill the heads. I build a budget 350 with a low compression bottom end and 7A heads maybe at best we had 8.2 to 1 compression I used a 260h comp cam , built a th350 for the guy with a 2200 stall converter 3.42 gear full weight street trim car ran 14.8's which was impressive imo. You'd be amazed at how well the olds rev. My current 355 which is a budget build for a " race " engine I wind up to 7k rpm on stock rods and crank , car runs 11.50's but it's more strip / street car lol. The comp 260h is my go to choice . I ran 13's with a near stock 350 9 to 1 compression performer intake , stock valve train , headers , 600 cfm carb th400 2200 stall and 3.73 gears in my 72 cutlass. The pistons from 73 and up where 14cc with bigger chambers in the heads. So the later pistons would be the better choice.

 

You will be close to 8.5 to 1 with stock 7A heads on a stock 77 block with .042" compressed Felpro head gaskets. The regular. 040" Mahle 3533 is slightly thinner. CC those 7A combustion chambers, which may have been cut at some point and be closer to the factory 64cc blueprint spec. Usually uncut, they are larger. See where you are at to start and plan from there.

 

Good to know, i thought the oil pressure was questionable but it seemed like a lot of people on here were saying that Olds don't run as high as SBC's (which im more accustomed to). So milling the heads will mess with the geometry that much? Would .030 off require the intake to be redrilled?

thank you!

I plan on doing that, I probably should have went ahead and did that before I made this post. Thank you!

I know, unfortunately I can't use the 72 block. I got it from friend and its numbers matching to his car so he wants it back. I might be able to rob the crank out of it though, I think i read the earlier cranks were stronger. Not sure if it would be worth while since the bearings were starting to spin on it.

Thanks for the info! I thought the pistons from 72 up were 23cc dish, is that not correct? I actually found your youtube channel last week and watched every video you had on 350 builds - so thanks for putting those out there. Very impressive how strong your car runs. Do you think RPM will be an issue on this windowed block? If I was building this for me I would probably source another block to start from and do something closer to your setup, but this is a side project I'm putting together for my parents. The reality is it'll probably get driven very lightly except for when i borrow it. I wont be pushing it anywhere near 7k, but maybe something in the 5500 ballpark.

8.5 would be great, I had calculated about 8.25 compression if i put everything together stock but maybe I don't have the right info. I do plan on CC'ing the heads before I do anything with them.


Thanks everyone for the information. I will do a leakdown test and CC these heads and go from there.

 

Why not put 1968-70 high compression pistons in it, a cam and lifters and be done with it ? You don't need to mill anything, or get different push rods. With the thicker head gaskets available, you'll lose compression ratio anyway. How far in the hole are the pistons now ?

 

Where are thise pistons available? Mahle males a 10cc hone to fit in a 4.065" bore that will give 9.5 to 1, give or take with those 7A heads.

 

The 1971-1972 engines have huge 24cc dishes.
The 73-later engines had 14 cc dishes.
The 68-70 2bbl engines had 12(?)cc pistons.
the 68-70 4bbl engines had 6 cc pistons.

 

If it's a cruiser I would just get the compression around 9 to 1 with a nice cam like the 260h ( my favorite) it will have plenty of pep and make power to about 5k rpm.

 

I thought of that, but it looks like pistons are pretty pricey. Maybe I don't need them if my 77 has 14cc pistons. I bore scoped the cylinders and it looked like they were the same in both engines but sounds like i was wrong about that.

Ok thank you.

Ok thanks. I plan on using the hydraulic roller that came in my parts engine. 210/216 so similar size.

 

I started digging in to this a bit today and while it is blatantly obvious to me that the pushrods are too long as i had mentioned before. That being said, I have no experience with Oldsmobiles and my wisdom for other engines is such that the rocker should be perpendicular around mid throw. On this engine, the rockers are starting perpendicular at the base circle. The pushrods measure 8.250" and I read on another post that pushrods with hydraulic lifters should be somewhere in the 7 range, problem is when I do that, the rocker doesn't have enough adjustment to even reach the pushrod. It seems the mounting stud is way too tall, and the guideplates are contributing to that problem. Any thoughts on this situation and how it would be resolved? I'll put some pictures in the next reply.

 

Max lift as built

As built base circle


7.650 length, large gap on both sides.

 

So you’re using roller rip rockers with a roller cam? Good luck with that.

 

I didn't spec this out, bought the engine this way for parts and am diagnosing their mistakes. It had obvious issues and should have never been ran in the first place because the valves hit the pistons. I would not have assumed there was a problem with combining roller rockers and roller lifters, but sounds like there is in this case? The engine I plan on transferring parts to is still completely stock, so i have those rockers as well.

 

The SBO will have at minimum an 8.250 pushrod. My current set up with ford rocker arms is 8.650 with a solid flat tappet cam. Obviously with roller lifters the length will be different due to height this is where the checker will be your friend and understanding proper geometry. Contrary to popular belief a sweep isn't bad and your contact pattern on the valve stem does not have to be dead center.

 

Mark, for the clueless people in the peanut gallery (me) can you explain why this is not advisable? I know a few things, and am always willing to learn one or two more.

 

I should have mentioned that. The pushrods in the engine as it was ran with pistons hitting valves, were 8.250s.

 

You state the valves are hitting the pistons. What valve lift is the cam. It would have to be really high for pistons and valves to touch.

 

.505 / .505 at least if it whats the owner says it was which is:

comp k42-413-9
Xtreme Energy Retro-Fit XR262HR Hydraulic Roller Camshaft Small Kit
Lift: .505''/.505''
Duration: 262°/268°
Lobe Separation Angle: 110°
RPM Range: 1000-5000

 

There is no way with that lift the valves are hitting the pistons. Not even close

 

I've got a bone stock 425 with a .520 lift cam and it doesn't even come close to touching a piston.

 

Its possible it isn’t. I don’t hear/feel anything when i roll it over but the previous owner said there were not witness marks on the pistons when he installed the heads and cam.

I don’t know what the truth is. Thought about putting playdough in there or something because my borescope doesn’t get me a good look at it.

 

Your pictures show valve contact. There has to be a big timing issue or you have a way bigger cam than you suggest.

 

Pushrod length with the roller lifters is going to be different then an hydralic flat tappet cam. You need to get the length checked out

 

So at the timing set possibly? This looked correct to me but maybe not.

 

Looks correct but at that setting your 180 degrees out.

 

wow, surprising it ran then. Thank you!

 

Roll the engine 180 degrees then set the distributor in as normal

 

this engine is hurt it wont be running anytime soon. I was just trying to understand what the issues were before using the heads and cam in another engine. Sounds like you solved the mystery though, i appreciate it. I need to find the documentation on this timing set.

 

Those timing marks are correct, as shown in the Olds factory service manual. I would actually degree it, could be many degrees off, due to a possible inaccurate timing set or improper cam grinding. Also are those rocker studs the conversion studs with a 5/16" base? Not a good idea with the increased spring pressure of a roller cam. Maybe the orginal timing chain failed badly and the pistons kissed the valves at that point?

 

i think he wouldve known if a timing set let go, but i do wonder id comp’s defintion of correct is different than factory? I couldnt find documentation for this specific timing set, suppose i’ll have to contact comp.

interesting question on the studs i havent pulled one off yet but ill check.

 

this chain set is not lined up correctly. It’s supposed to line up dot to dot, not cam gear dot to crank keyway… the way it is set in this picture is your problem. Look for the dot on the crank gear closer to the teeth. this dot the cam gear should be lined up to.

 

Agreed. That is set way off. The 0 near the tooth is the one to line up to the cam 0.

 

Good catch. That is an aftermarket timing kit with three different keyways to allow you to degree the cam. The marks on the keyway side of the gear correspond to the same marks on the teeth side of the gear. You can see the round and square marks in this photo. There will be a third set not seen here. If the round mark is used for the keyway, the round mark on the teeth is aligned with the cam gear. If the square mark is used on the keyway, use the square on the teeth, etc. The instructions that came with the timing set will tell you which marks are supposed to be straight up, which are advanced, and which are retarded. It appears that the square mark is -4 deg per the stamping on the crank gear. The third set will likely be marked +4.

 

Seems to be alot of confusion with this, I have always thought is needs to be 12 and 12 with #1TDC, dot to dot would make #6 TDC?

 

Totally different issue. The problem here is not reading the instructions that came with the timing set.

And by the way, there is zero confusion here. Once again, if the marks are aligned at 12 - 12, turn the crank one full turn and they will also be aligned at 12 - 6. The piston is at TDC both times. The issue is compression vs exhaust, and that only matters once the distributor is installed.