Interesting compression ratio and deck height stuff.

So I was poking around the garage the other day and I noticed an engine that I had built the short block a long time ago and then oiled and stored it. I built the engine for turbos so I was not worried around the compression ratio being over 9:1. I was not worried about quench as it was planned to have iron heads with no real quench area. I took it apart the other day and did some measuring.

So here is what it was:

1. 1977 Buick 350 with 50,000 miles. It was in great condition, needed very little.
2. It was bored 30 over
3. The block deck was squared off perpendicular to the mains, but no extra taken off. They said it was actually almost bang on square.
4. ARP main studs
5. Align honed

Custom Diamond Forged pistons with 15 CC dish, 1.875 compression height. Herche forged rods, crank cut 10 thou on the mains and rods. Internal balance job.

With this combo the pistons sat 59 Thou in the hole and the block deck measured out to 10.246" vs the supposed Buick 350 blueprint deck height of 10.187"! This gave roughly 9:1 compression with a 40 thou gasket and a 58 CC head.

I took the block and pistons to a machine shop and had 20 thou taken off the pistons. This put them at 11 CC of dish volume. The piston rings are super far down the piston for a boosted application and Diamond had advised me this was not an issue at all. I then knocked 70 thou off the block putting it at 10.176" deck height which is 10 thou less than they are supposed to be! The engine was re-balanced, it didn't take much weight removed from the crank. The pistons now sit 9 thou in the hole.

The new combo works out to about 10.2:1 using 40 thou gaskets and 58 cc heads.

Swapping to my ported irons that are converted to a closed chamber design yields about 12:1 using a 20 thou gasket with a 29 thou quench zone.

Just some info about just how tall some of these later Buick 350s deck heights are!

 

Are those the irons that you bought that the guy passed away before he had a chance to run 'em?

 

Yes that’s the ones. We flow tested them and are now revising the porting. I still need to CC them but they will give at least 12:1 compression with this short block. Combined with that huge roller cam it will be a mean NA engine that we can also test the alum heads on at about 11:1.

 

The lesson here is to measure twice and cut once really..

No offense to the OP or his machinist but this all should have been measured and known before the machine work started the first time. Stabbing "10:1" pistons in and calling it good rarely results in a 10:1 compression.

 

It it’s pretty much normal for a 1.805 piston to sit .090 below deck, add any change due to rod rebuild, piston variation, crank cut . Steve mentioned he yanked similar pistons out of an engine at similar specs.

 

Never saw any 350 with 10.187 deck stock. they've all been tall.

 

Was talking about finding pistons at .100 below deck

 

I wasn’t looking for 10:1 when I built it. I wanted 8.5-9.3:1 compression for turbos. Then I shelved it and built a better engine:

Once the block deck was squared off we mocked it up with TRW forged 8:1 pistons with 24cc dish and had 7:1 compression. I wanted more compression so got in on an order of 10:1 custom diamond pistons. And with the tall deck height it put me exactly where I wanted the compression. I also upgraded to the $1200 Herche forged rods at the same time.

Things all changed once we developed the block girdle so I shelved that engine. I never measure the deck heights till last week. I didn’t care about the deck height when I built it originally, I just cared about the compression ratio.

But now that this engine was wasting away I found a way to make it a 12:1 NA monster.

this is the new turbo engine. 9.3:1 compression with the alum heads.

https://smg.photobucket.com/user/seanbuick76/media/1 NEW ENGINE/IMG_0229_zpsuiny85jt.jpg.html?sort=4&o=42

 

Some more interesting stuff, depending.
Got my 3.0 pistons/rods back from the machine shop. Plopped one in, sans rings, feeler gauges to take up the slack in the bore. At TDC it came out to .0945 in the hole. Pistons have an 1.805 compression height, bone stock '71 block. No machine work. With a .042 gasket that pat kelly calculator says it will be 9.69:1. Essentially where I wanted it. I put 56.5 for the head CC as some sources say 58, others 55. I split it down the middle. Also I use 3.9 for the head gasket bore as that's what my .042 gasket measured out to be.

 

I would take .010 off block. And go with the 58 cc head. That will be about 9.75. With the pistons sitting so far down hole, you got alittle detonation resistance.

 

Doesn't matter to me much. Just need somethin that runs. Popped in a couple more pistons, deck is nearly bang on in terms of being square. I was hoping for mid 9s anyway. Only gas within reasonable distance is 91 cornwater. I gotta go to the next zipcode for non corn flavored gas. If this was the engine that was getting the AL heads I'd do more with it. I'm A-Ok with 9.69:1.

 

yes 55-58 cc is normal. I agree, fir a low budget setup the 3.0 pistons are an easy way to get 9.5-10.5:1 with iron heads. No quench zone anyway. A fellow ran mid 12s NA with those pistons, just saying.

my machine shop Bill for removing 70 thou from the block was $280 Canadian or about $190 US. The deck was already squared off so it was an easy procedure. My other good engine I just ordered the pistons to give zero deck to save on machine costs.

It’s been said before on here that often time it’s better to invest $ in custom pistons vs extra machine work. But that being said the high end parts deserve way more attention to detail and $ anyway.

 

I wanna know how you forgot you had this built short block?
Just how many motors or how big is your shop??
Oh yes it's screaming for the TA AL heads.

 

I cant imagine putting all that money in a build then doing nothing with it

 

Well I didn't fully forget about it, but I had no use for it until last week LOL. I am blessed to have both a house in the city and one in the country that I rent out but still have a shop there for my use. The house in the city has a 1200 square foot garage with 12 foot ceilings, 4 post lift, welders etc. The country shop is a 40x60 pole barn. I lost track of how many Buick 350s I have, well over a dozen. 3 built up with forged internals. I also do a lot of 4x4 GM truck LS stuff so there are a pile of 5.3 and 6.0 engines kicking around. I also collect Th-350, 2004R, and 4L80E trans. All 3 of my Buicks either are or will be Buick 350 powered including my 2006 Buick Rainier which is going from an LS to the 350.

It was my spare, backup engine, once I built the better short block I just put the spare aside. All my 350s use the same rods and lots of other parts to help with interchangeability. For example they are all 30 over, stock stroke, stock rod length.

 

Like Phil Rizzuto used to say. ""Holy Cow""
and those slicks are huge!!
I thought I luck out as my home in the city of Boston have a big driveway. Could tuck in 9 car's but that is good for a city..
Can't wait to see

 

That’s awesome, I can only fit 5 cars in the driveway. I do have some good depth I can fit my car hauler trailer, but for $25 a month I can store it 1/2 mile away all secure. The lift is nice I can double stack cars and save space.

 

DO IT SEAN DO IT!!!
Rip that LS engine out and put the Buick in it!
SWEEEEEEEET

 

That's the biggest problem in my city. On top of paying a price of a small mortgage for space with a garage or even without, they are brutally hard to find.
I keep my 2 non running cars down the Cape at my sister house but outside. They know the local Police enough and have a good community standing to not be bothered without them being insured.
Now when I mean 9 cars in the city's driveway it would be tight and would have to play shuffle to move them.
It is also a SNOB town and when I was younger and really really active car wise the snobs complained about me making the neighborhood look like a junkyard, because I had all kinds of parts tucked behind outside in the back of the house.. Yes I did destroy the driveway some with jack and jackstand marks and the oil and all the stuff that comes with working on cars which my father wanted to kill me
I even used some air tools at times as I had a compressor, today I probably wouldn't even be able to take one lug nut off before the complaints came.
House was built in 1907 and have been there since 1963. I don't know if it was built with a garage or more a likely barn as there isn't one now. To build some type of garage even a small one, i'm thinking unless it had one when it was built in the days, the city's "historical" department might not let one be built.
All the paper records were lost in a fire in the 1940's so don't know??
Sean so sorry I got this off track buddie.. It's kinda not fair to be a car guy sometimes

Put those AL heads on!!!!!!!

 

All good! Chat away anytime! I did a nice epoxy floor coating so oil just wipes right up. Yes I hear ya, I struggled in the 2 car garage at the last house. It was just my luck that during an engine swap I had forced my wife to park outside for a few days and a hail storm came and damaged her vehicle...

It belonged to my neighbour, he is a professional fabricator, welder and specializes in turbo LS stuff... He has a 1500 HP Chevelle and he just finished a 580 cubic inch twin turbo chevelle that makes 2450 HP.

We just happened to build a house beside him!! The Rainier is fully loaded, leather sunroof etc. It has a 5.3 Alum engine, and he had just did a new $3000 trans and it failed a year later. So he got fed up with it and sold it to me for $800 minus the engine as he wanted to use it. Im swapping in a Buick 350 and 4L80E. It will start out NA but hopefully get a turbo after.