I have a 20 yr old build that never ran. I finally got to running it and couldn't get it to idle properly a few weeks ago. Tried everything but gave up and figured I pull the intake and timing cover to check everything out. Seems some water got into one of the hydraulic lifters as one seemed quite rust where the pushrod sits. All others look good though. I'm guess from sitting/condensation. The cam looks good.

I'm not too happy with the measured compression at 150psi (at cold but WOT) so I'm thinking since its in pieces, possibly look into replacing pistons with higher compression ones. Also, remove the heads to make sure there aren't any issues and get a machine shop to put in some hardened valve seats.

Based on the specs below, would replacing the pistons to a flat top be worth it (and do I need to get the whole crank assembly rebalanced?). Is the cam too aggressive or not enough? I'm looking for a fun drivable ride that could possibly do 12-13 seconds at the track if that is possible. Would stock rods still be ok?

1969 Olds 442
455 Block with .060 overbore
Sealed Power Pistons with -18cc dish. Measured compression averages around 150psi.
Camshaft: Lobe separation at 110. Ex closes at 11 ATDC, opens 51 BBDC. Intake opens 7 BTDC, closes 47 ABDC. Intake/Exhaust lift is .565 in. Duration at .050 tappet lift is 234 deg in, 242 ex.
Rocker ratio is 1.6 (roller rockers with hydraulic roller lifters)
Ported 'C' Heads with 2.072 inch intake, 1.625 exhaust valves
Carb is a Holley Street Avenger - 770 CFM.
MSD distributor with MSD 6AL box (new but 20 years old)
TH400 with shift kit (rebuilt)
3.42 Rearend with positrac

 

Couple of thoughts:
1) Overall, sounds like ingredients for a great build.
2) That's a lot of cam. With that much cam you'll probably want more compression. Although cylinder pressure does not vary predictably with compression ratio, it's certainly an indicator.
3) If the build is ~20 years old, would the valve seats not already be hardened? Do you know that they're not? Regardless, unless you're towing uphill on the freeway or running hard and frequently at the track, I don't know that it's necessary. Same goes for rod upgrade and crank balancing.
4) Actually, a lot of this will be dependent on two things: your intended use for the car and how much you want to spend. You say you want a 12-13 second car, but do you actually plan to run it at the track? Also, there's a lot of daylight between those two numbers -- it's no big trick to coax 13 second times from a 455, but getting to low 12s requires a little more effort.

Just trying to help you streamline and clarify your thinking.

 

I did the build 20 years ago but never got the engine started due to life and avoiding doing body work. When I did it, I didn't get the valve seats redone with hardened ones due to money issues.
I probably wont go to the track but second guessing what I have since if I do anything more with the engine, I want to get it done now. I want a fun ride that can really tear it up but not idle like it's going to die. I plan on using 93 octane.
While money is always an issue, I don't mind spending it where I can get better results, even if that means a different cam.

I'm thinking that cylinder pressure is just low because it was measured cold? I'd assume it would go up when things warm up/expand.

 

If you’re planning to remove the heads, then I’d consider cc’ing and then maybe cutting them and use a thinner head gasket before I swapped pistons.
Then you can check pieces for possible leaks etc as you reassemble it.

 

Thanks, feel like that's a good direction. I'll be cc'ing the heads later this week and depending on that, I'll maybe send it to a shop to get milled a little maybe if needed.

 

I would not be concerned with the 150 psi ,especially if checked cold as long as it was even. That cam is possibly a little big for a street car. We're you planning on running power brakes? Would likely need a vacuum reserve can.
I would also not be concerned about hardened valve seats. That engine should be easily capable of low 12 second passes.
I would vote for replacing bad lifter, reassemble, and let it rip.

 

My first Old's build was very close to yours and I had the same issue. It was still a good street motor, but you are leaving HP on the table with the low compression. Between the pistons being down in the bore and the .040 head gasket, you never get the advertised static CR in my opinion.
The next time, I zero decked the block as part of the build.

Marks advice to cc and shave the heads is what I would do in your situation.
Enjoy getting your car back on the road.

 

I did an unprofessional cc measure at home with a syringe, and the heads are roughly 80-85 cc's as you would've guessed.
I ordered a Cometic .027 head gasket, and will mill the heads down a bit, not sure how much. Compression calcs give me a 9.33:1 without milling (i need to verify deck clearance but set it at .03 for now)
I want to stay with pump gas so I'm guessing I should stay below 10.5:1. If I get 1 cc per .005 of milling, that means mill down to 75cc to get 10.04:1 and 10.5:1 to mill to 70cc. So depending on what the stock cc's actually are, milling down .05-.07 in. Too much?

My one concern is piston to valve clearance, or am I safe with those dished pistons and the .565 in valve lift?

 

I think I mentioned in your other post that you weren’t anywhere near what you thought regarding comp ratio.
Have them cc them exactly first, then you’ll know how much to take off.
You’ll have a mile and a half valve to piston clearance.

 

I'll work on getting proper measurements on deck height, etc before any milling happens.

 

Good. And while you’re at it, make sure the previous shop put the right valve springs in it for the roller you have.

 

I did it all way back but given recommendation from fcrperformance.com. no info on the springs from them tho. I got most of the upper drivetrain from them. Doubt they have records from 20 yrs ago!

 

Check em anyway.

 

Although I'm looking into the milling route, if you'd select different pistons, are there any you all would recommend for my setup that would keep it okay with 93 octane?
I've had a slow leak from either the real oil seal on the pan, or the rear main seal. If its the main seal, I may as well put in pistons while apart that I'll be more happy with. Though, still just trying to explore my options.

I totally missed the compression height on the sealed power pistons, Thanks @cutlassefi

 

Check the head cc first, then we can talk about pistons.

 

I cc'd the heads, and got between 81 and 82 cc's.

 

Ok, what’s your target comp ratio?

 

I'm thinking maybe 10.5 to 11? Is that reasonable on 93 octane or too much for my setup? I've been reading that a piston with a D shape or valve reliefs may be better at high compression with lower octane (where they wouldnt need above 93). True?

I'd like a great powerful cruiser but not too ridiculous, and have it be reliable.

 

Well, you're not alone there. At a guess, that's what 95% of CO members want!

Absent a sophisticated engine management system, I don't think straight 93 octane ethanol-laced fuel can support an engine with an 11:1 compression ratio. You'd want to use some additives.

 

i get it, what do you think is manageable?

Based on everything I read, 10.5 seems to be the limit with pump gas/iron heads on 93. So if I sat around 10.25, that should give me room to avoid issues. I see DSS Racing has 12cc flat tops that would put me right between 10.2 and 10.4.

I've also run some numbers and if im right, dynamic compression is at 8:1 if I have a 10.5;1 static

 

I wouldn't muddy the water by introducing dynamic compression into the mix. For benchmark and comparison purposes, static will do fine.

 

Gasoline is rated differently now than in the 1960's. Head gaskets are thicker than old steel gaskets. Unless you have decked the block to get pistons .002" below the head gasket surface, you won't get 11 to 1. In the old NHRA Stock, Oldsmobile specs days, a .030" overbore would get you 11.14 to 1 compression ratio.

 

Not sure what your budget is for this build? I have 455 with 10.5 probably closer to 11.0 compression forged diamond pistons Comp cam 280H 280*/280* duration 480"/480" .040 overbore. I was running 1969 C factory heads with hardened valve seats 2.072" intake / 1,680' exhaust. Running 93 octane had a ping on acceleration had to add octane boost to resolve it. Ran across a good deal on some 6051 Edelbrock aluminum heads 77cc installed them with Cometic 0.28 mls head gaskets. Ping went away did not need octane boost anymore unless I wanted to add it. You can get away with a little more compression using aluminum heads just a thought.

 

Where did you read that?

 

I can't find it, just some rumblings I came across on other forums. Didn't know if I should believe it. If i recall, it had something to do with more quench that allowed for it, which I don't really understand why that would help.

 

Thanks for the info, makes me feel more comfortable running between 10.25 and 10.5. If I have to use an octane booster, it's ok, just would rather not. And Im not ready to let go of the original heads yet 😂

 

You can make an engine ping and knock with just 8.5:1 as well if the tune is off.
Buy a wide band O2 and tune it right. That’ll lessen your chances of detonation etc.

 

Are you using stock connecting rods?

 

Yes stock rods that have been reworked.

 

“Reworked” stock rods is like putting lipstick on a pig. Useless, waste of time and money.