350 build

Alright guys, I recently bought a 72 skylark and the motor knocks so I'm in the process of pulling it for a rebuild. I am looking for advice if I am going in the right direction with my plans to build it. Here's my plan. I'm going to bore to .030 over and do a high compression rebuild kit off of ebay. I know I know but I have read decent things on the kit. I will attach a link at the bottom of this post. So bore .030 over and I'm pretty sure I'll need the machine the crank so I will get oversized bearing for that. then deck the heads .020. Also planning on an aluminum intake and headers. The car is a factory 4 barrel car. So to summerize, bore .030 over, hi compression pistons, deck heads .020, aluminum intake and headers. All this is assuming the block is good and I'll have the heads checked too. Am I heading in the right direction?

Here is the rebuild kit I'm looking at... http://m.ebay.com/itm/Buick-350-Performance-Engine-Rebuild-Kit-HI-COMP-Piston-/200311825826

 

Have the bore checked before getting pistons. Make sure cylinders clean up at .030. Deck block not heads. Getting the piston up to top of deck does more for efficient burn of fuel then mill heads. What cam do you expect to run? Do you have other plans like gears,convertor?exhaust?

 

Get the double roller timing chain and don't get the hi volume oil pump kit. Drill out oil pump passage to 1/2 inch or 9/16 if shop can center it well enough. Get the 5/8 melling pickup screen. Get the oil pump booster plate and set oil pump gear clearance to specs. Use the white oil pump spring for 60 psi relief pressure.

 

It's got Saul exhaust with I'm guessing flowmasters I'd like to keep the exhaust for cost reasons. As far as stall what is recommended? Gears I'm keeping stock I'm not sure the ratio I haven't even checked. And cam I would like that nice lope to it but at the same time be good for driving. My goal with the car is to have a nice driver and if I get on it it will get up and go. I'll never take it to the strip or anything. Just a nice little hotrod driver.

 

Cam specs determine what stall would be best but with stock gears you really are limited for cam choice. The TA 212 ,or Crower level 2 cam would be the better choices with stock gears . a 2000 stall would be good there. Keep your tires short. Neither cam takes advantage of the approximate compression ratio you will have with .030 and .020 of block or heads will bring you about 9.75 . the 284-88 cam would be better in that range but needs 3000 stall and at least 3.23 gears. You could just do cleanup and square block deck for about 9.5 and run the Crower level 3 can with a stock height rear tire and 2200 convertor. It should make a lot of torque at lower rpm so expect a lot of traction loss off the line. Personally I would skip the aluminum intake go with the Crower level 3 cam and look on eBay for some used gm 3.08 or 3.23 gears.

 

Thank you for all of the advice! So to make sure I'm understanding right. If I do the crower level 3 cam with a 2200 stall just rebuild the motor if able to .030 over with stock type pistons not the high compression and then deck the block .020? And then look for used gears? Are there any good rebuild kits out there that you recomend? Sorry for all the questions. This is my first build by myself. I've helped with several while I was in school though so I know the basics. I just want to make sure I'm not doing things over.

 

cutting the block is the LAST thing I would do if I have to. heads are cheap compared to a corrected finished block.
you really need to figure out what you want to do. you have to live with the end result. unless you have big checkbook.
just my.02

 

Figure out what I want to do as far as how I'm going to use the car? I have already explained my goal. If you mean figure out what i want to do as far as building the motoelr thats what im here trying to figure out.Also Alec 296 recommend to shave the block deck .020 instead of the heads. I am just trying to figure out my best route to go as far as building it for cruising on the weekends but if I get on it I want it to go a little and not be a dog. I have no intentions of racing this thing or taking it to the strip.

 

I hope that engine kit isn't a true representation of the Buick kit, cause that looks like Chevy stuffuzzled:

 

I would do a lot more research and learn more before you dive in head first. The only way to get the compression ratio right is to build the shortblock first. Measure piston depth and surface volume. Measure compression chamber volume. Add in the gasket thickness. And then decide what needs to be machined to meet your compression goals. I would certainly machine the heads at that time before anything else like gsjohnny1 says.

Or you can just screw a bunch of stuff together and hope for the best.In that case stick with a mild cam like the 212 or crower level 2. Headers seem like a huge PITA for a mild build.

In ANY EVENT, a lumpity lumpity cam will not be your friend without ALL of the other aspects of the build and the car being in sync with it. IE static comp ratio, convertor, and gears. Then you kind of get away from just a riding around car.

My .02

 

You need to do the math to determine the compression ratio. Find out what the compression DISTANCE on those pistons are. That will help determine how much you need to cut off the block. Could be as much as .070 or .080".
Get it to 9.5 and put in a Crower level 3 with an iron intake and you'll love it. If you want it to lope and run like crap stick a thumper cam in it. But you'll have your ass handed to you by about anything.

 

So to me it sounds like your average at home mechanic can't build these engines? Surely theyes can be mildly built with a decent set of basic tools. I'm not looking to break speed records here.

 

And I hope im not coming off as close minded or anything like that since that's far from the truth. It just seems that someone out there has figured out a good combo for what I'm trying to achieve.

 

The challenge is building a 350 Buick engine for mid level performance with the parts that are available.
Many of us have spent much time looking and there a lot of pages devoted to this in the Small Block Tech section so I'll summarize.

The object is to have an engine that will run on pump gas without detonation and not be a nightmare to tune as in ignition timing and air fuel ratio.

Mid performance cams like the TA 212 and the Crower level 3 cams mentioned earlier are great choices but they require a Static Compression Ratio of no more that 9.5:1 to allow for some margin when selecting gas at the pump.
Being tied to premium gas only is not a good thing.
This is related to the point the intake valve closes and actual compression begins that is responsible for raising cylinder temperature or the Dynamic Compression Ratio.
For Buick 350 and 455 with iron heads a DCR of 7.5:1 works well. Any more and the engine is prone to detonation and any less you give up engine torque.

Next conversation above was about squish distance or quench which is also responsible for detonation resistance.
Ideally you would like to have .040" between the top of the piston and the cylinder head at TDC but the Buick 350 has an open chamber design making that impossible without using a domed piston top.
So you settle on second best by having the piston at the top of the block at TDC. (Zero Deck)

Now here is the challenge. In order to have the piston at zero deck AND have a 9.5:1 Static Compression Ratio ,The piston needs to have a 18-20 cc dish.
The available pistons have either a 10-13 cc dish or 25-30 cc dish as in the turbo V6 pistons.
Unless a person wants to spend the extra money for a custom piston there needs to be a compromise.

In your case it will be piston to deck clearance which is not a big deal since the head is open chamber.

The piston in the kit you are looking at uses the cast 340P piston that Falcon carries.
It has a around a 10 cc dish with a compression height (pin location) of 1.835".
If you add up 1/2 the engine stroke + the rod length + the CH, 1.925" + 6.388" + 1.835" = 10.148.
The block deck height is 10.188". Subtract 10.188-10.148 = .040" for piston to deck clearance.

Combustion chamber volume = 58cc
piston volume 10 cc
Head gasket .040" thick
Gasket bore 3.9"
Cylinder Bore 3.830"
Deck clearance .040"
Stroke 3.85"
Rod length 6.388"
Intake valve closing point for the Crower level 3 cam = 66* ABDC

Plug those numbers into the calculator.
Static compression ratio = 9.7
Dynamic = 7.7
A little high but doable.

https://www.uempistons.com/index.ph...e=comp&zenid=810e3f9fc6070e5573012081988816a8

So you start to look at places you can improve the results.
One example would be increasing the chamber volume by grinding out the locating boss used in production next to the spark plug hole.
If you can gain 2 cc for a 60 cc chamber volume you get 9.5 SCR and 7.5 DCR.

This is what the planning stage looks like.
Of course as Larry said, everything must be measured as the build progresses and make adjustments as you find discrepancies.

Paul

 

Paul, thank you a lot for all that. That's a lot to take in! But I think I'm starting to understand! Looks like I'll be renting a lot of the specialty tools from the local parts store to do all the measurements. So as mentioned above I should build my shortblock first then measure to find out how much to shave the block to get it to zero deck? Those numbers you plugged in were assuming .030 over on the bore correct? So I will need to find out what the exact numbers I have to plug into the calculator, then adjust from there

 

Deck height varies so it should be measured. 10.188 is blueprint. Doesn't mean the gm machinist measured it exact. Chances are its .020-.030 taller than spec. My 70,and 71 blocks the piston measured .058 in hole at tdc. I have heard others get a similar spec with original pistons. I have heard rebuilt engine being .090 or more down hole at tdc. Head chambers can vary also. But I suggest sticking with combos that others have had good luck. Pull heads and measure piston depth at tdc on both sides( use front two pistons since you may have spun bearings at 7 or 8). . use a straight edge and feeler gauges if you don't have depth gauge. Should still be good enough for estimate. If you are about .058 then my estimates for my engine should match yours. I have 340p piston. Its about 10 cc like mentioned. It should match current piston height when installed but smaller dish. Fel pro gaskets are about .043 after crush.

 

I realize that details can get buried in a large post.

The piston to deck height is where you need to compromise to keep the compression ratio near 9.5:1
The piston needs to stay .040" in the hole at TDC to have near a 9.5:1 SCR and it is not a big deal as far as squish distance since the head has an open chamber.

Yes .030" is an assumption as a starting place.
The block will need to be cleaned and magnafluxed for cracks first.
Then your machinist will determine either by measuring or taking an initial boring cut to determine what oversize piston is needed.

The same for the crank. Clean and magnaflux, then turn the main and rod journals so you know what undersize bearings are needed.

The heads should be done first so you know what the chamber volume is.

I just noticed alec296 posted.
He is giving you "hands on" details. Good stuff

Paul

 

Thanks guys a lot! It's all coming together now! I don't know why, but I read dished pistons a dozen times but in my head I was seeing domed pistons and that was throwing me for a loop. Now that I have that glitch out of the way things make 100% more sense haha! I think i have a good starting point as to what to do now. I'm sure I'll have more questions as I go. But now it's time to start tearing into this thing and get some of my measurements!

 

here is a pic of some pistons. one has a deep dish- low compression. one has a very shallow dish- hi compression.
the shiny one is a silvolite hyperutectic. has valve recessions and about 11 cc for "dish"with them. there are also rated at 1.855 comp height. I added this if you are going to zero deck they would need .020 less milled off block and then you have extra clearance for valves since the other pistons will not. compression ratio will be higher on them also.