How do u measure it and, how does it relate to Compression ratio? What is the purpose/benefit of getting your block "decked"?

 

Go to KB pistons and use their calculator. Most factory Olds have between .015" and .030" depth below the deck. Aftermarket cast replacements are much worse, .040" or more. Most basic replacement head gaskets are .038-.041" for thickness. 0 deck adds compression and should actually help detination.

 

Use a depth gauge, set piston at TDC, measure from the head gasket sealing surface to the top (not the dish) of the piston.
Do this at all four "corners" of the engine (#1, 2, 7, and 8).


The depth of the piston in the hole at TDC represents part of the combustion chamber - dead space that will never be compressed.


1. To reduce inconsistencies in the original manufacturing, ie: slightly crooked machining that will create slightly different combustion chamber sizes in different cylinders
2. To reduce overall combustion chamber size, in order to use pistons with a different compression height, or to increase compression in general.

- Eric

 

Just so we're clear, "deck height" is actually the dimension from the crankshaft centerline to the deck surface of the block, as shown in this illustration:



The dimension that all the posts above are calling "deck height" is really the deck clearance, as illustrated here:

 

Ok, so the reason I asked about deck height is bc bill travato's book explains that even the thickness of your head gasket affects CR. It also recommends cometic head gaskets. As I'm sure you all know those things are NOT cheap ! So, for the sake of getting my future mods or build right the first time I need to know, what size (compressed)thickness gasket I should get .027 or .040?

 

Whichever size works with the specifications you intend for your new build.

- Eric

 

And you don't HAVE to use Cometics. There are other quality gaskets out there for your average street build.

 

Your Cr depends on more than deck height, take a look at this
https://www.rbracing-rsr.com/compstaticcalc.html

 

That's a good summary, but even that isn't entirely complete. Calculating CR requires you to measure the ENTIRE combustion volume. As noted, this includes the cylinder head, the compressed head gasket volume, the piston deck clearance, any dome or dish on the piston, and for complete accuracy, the trapped volume alongside the piston above the top compression ring. This latter is small and most people ignore it, but it is part of the combustion volume.

Now, take this number and divide it into the sum of this number and the swept volume of the cylinder to get the CR.

In math terms, where CV = Combustion Volume as described above, and swept volume = (bore x bore x stroke x pi)/4, which is simply the volume of a cylinder, you get:

CR = (CV + swept volume)/CV

 

Ok

 

Don't forget to figure your squish/squash area, that is the distance between the top of the piston and the bottom of the head, you should try and get in between .040 and .045. I see a lot of people putting engines together and pay no attention to this, a small squish/squash area gives good mixing in the cylinder and helps prevent pinging. Oldsmobile heads have a very small squish/squash area because of there design and it's good to use what little they have to your advantage.

 

Will do. Still strongly considering ebrock aluminum heads for my 72 cutlass 350 tho. I guess I should've called this thread , "best head gasket for non racing applications" bc that's what I really need to know. I guess I cant go wrong with fel-pro or Mr. gasket but still there are Soo many types of head gaskets out there it's hard for a laymen to pick the right one. My car is a daily driver not a racer, but I've learned going cheap usually means doing a job twice and I've had enough of that :/

 

This is a bit contradictory. If your not building a race car ( or a hot street car ) and just use your car as a daily driver, why would you want Edelbrock heads? They would be a poor choice for your application. Unless I'm confusing you with someone else, didn't the experienced people here already talk you out of Ebrock's by explaining their disadvantages?

 

Unless you change your pistons to flat top, Edelbrock heads would need a ton of milling to reach 9 to 1 and you need more like 10 to 1 compression. They can work but you need a much larger cam, headers, 2500+stall converter and 3.42 and up gears. Get your current heads reworked with W31 valves and bowl work. You need to find out what pistons are in your engine, the stock pistons are huge 24cc dish. Speed Pro has 6cc dish forged replacement pistons, Probe has 3cc forged replacement pistons. I too considered Procomp or Edelbrock heads to use on my 350 and then on my 403 block. Even reducing the chamber 10cc to 67cc would only give me 9 to 1 with better 14cc dish pistons. Get yourself a **** box to drive around. I hated my Olds much more when it was a daily driver, had to always be running. Now it can sit for months and no big deal

 

Thx for the input. I'm still searching for a trustworthy shop to rebuild my bottom end. I am not sure what duration cam to use but was thinking somewhere in the high 280's low 290's. Flat top forged pistons seem to be the way to go from all the homework I've done. Car came with headers (2 1/2-2 3/4" not exactly sure which). Still doing research on gears but will keep your suggestion in mind when the time comes. Been looking at stall converters but didn't think I'd need to go to 2500+. For the ebrock heads I was planning on having bowl work and porting done and figured that should pretty much cover it. Also, having read travato's book I've decided to go with Harland sharp rocker arms (1.7).

 

A HOT street car (that I can drive daily) is exactly what I'm after. I'm well aware that I need to focus on the bottom end first but as per the recommendations of said experienced members, I'm planning my build on paper first. That being said, I'm still looking at the big picture, or at least trying to, and searching for a combo of parts that best compliment each other. So, ebrock seems to be the best option for reliable performance parts for olds and that's why I keep coming back to them. I've already got one of their carbs (1406 ) and plan on going with intake (7111) and heads as well.

 

Any of u guys used cp pistons before? Are there forged crankshafts for olds 350 out there? If not , what brand offers a solid replacement ?

 

Ok, you need to get your priorities in line.
You don't need a forged crank, and the Procomps would be a better choice.
Plus Harland sharp is a quality rocker but not absolutely necessary in a 400hp street build.

Jmo

 

Duely noted

 

What is your budget for this build?

 

Roughly $5k

 

CP pistons are high quality. As said, the stock 350 N crank is plenty strong. The only forged crank out there, other than custom is the 64-67 330 crank.

 

Just curious do have the rest of the car done? Because a $5K engine is going to murder everything else in the car.

 

I'm not sure what u mean but the 5k budget is for improvements on an existing engine (already runs).

 

The car could use a little paint but right now I'm all about function over form, Everything else is solid.

 

That does not make sense to me. A smaller quench area would make getting it right LESS important, not more. The quench area on a stock Olds head with dished pistons is tiny, virtually insignificant. Sure, if starting from scratch and you can get it .040, do it, but IMO it is not as important on Olds engines as it is in other makes.

 

Quench is important on any engine. I clearly stated Oldsmobiles don't have much quench but I still wouldn't ignore this step. An .080 quench isn't going to do anything for you.

 

All I was asking was to see if you have rebuilt the rest of the car to stand up to this $5000 monster you want to drop under the hood.

 

Just got off the phone with BTR !!! Bill helped make sense of my current situation and recommended that I replace my 6AL with the 6AL(2). We also discussed getting a 468 short block started for about $3500. now that I've got a starting point my stupid question should be few and far between. Thx to all who have humored my ignorance and tried to help.
-Luke

 

Bill's not going to ship that motor to Hawaii, is he?

- Eric

 

Lol, Eric we have not gotten to that point yet , but I'll keep u posted if you'd like. Tbh I dredd the shipping fees whether it's to FLA or HI. More good news: I finally caught up with Walt's performance here in Waipahu !! As it turns out walt has 40+ yrs of experience racing olds and is the exact opposite of the other local mechanics bc he doesn't want you to spend more $$ than necessary. He seems most interested in saving me money and achieving max performance which is extremely rare these days( and even more rare here in HI!!!). So in the coming weeks/months I should finally see what this 350 is truly capable of !

 

NOW you're talking!

Pay attention, listen, and ask questions - this is the best way to really learn.

And if anything seems too odd or confusing, ask us here and we should be able to help.

- Eric

 

[QUOTE=Oldskool84;653957] More good news: I finally caught up with Walt's performance here in Waipahu !!


Dam, Cheers to that guy in Waipahu !!!! Waipahu achoo .

 

That's the plan Eric , that's the plan. Hell if all goes according to plan , I might just stick around his shop on the weekends and try to absorb as much knowledge as possible. I'm sure he might appreciate an extra pair of hands considering that it's just him and one other guy turning wrenches. I'm probably getting way ahead of myself but this seems like a good a start as any.
On a different note: do any of you guys have experience with UTI? I've been thinking about using my GI BILL to attend but want to hear from a few former students &/or employers of said students about the quality of training and level knowledgeability. Nothing worse than wasting time AND hard earned $$& on useless training.

 

One of my nephews went to UTI in Phoenix while I was living there. He was SHARP! He was hired by Mercedes Benz right out of school. He made some pretty good bank until he was injured. He lived in the SF Bay area so pay was higher anyway, but he had a great job. If you go to any of the trade schools it is important to be at the top of the class and distinguish yourself so you get drafted by the better paying companies. All of the modern vehicles are very computer reliant so good software skills are a bonus.

 

Thx bro

 

Have you considered CNC programming and machining ? Their are so many jobs and its very hard to find decent guys with good experience. Aerospace, mining and nat-gas , tool and die etc , all need CNC guys. I'm having a hard time finding guys with 5+ yrs experience since the down turn of the economy.


Just a suggestion !!!

 

That's the problem with CNC, nobody wants to hire a guy with no experience and train him.

 

I'm all ears man, tell me how To get started. I would be starting from square one. my MOS is 25U (jack of all trades communications guy but mostly used for programming and troubleshooting radios) and has nothing to do with anything mechanical. It's only within the past 6-8 mo that I discovered that I have a passion for tinkering on old muscle cars. If you are willing to point me in The right direction , feel free to PM me some basic info.
Thx -luke