Flattop pistons and valve reliefs

Good to hear I'm somewhere in the right direction :)

I'm not intending on going past 5500 except for the occasional WOT take off (god I love flooring it from a standstill :devil:).
 
MYBAD79 said:
I checked their KB 4 valve relief pistons and they're also listed as +7cc. The distance from wrist pin centerline to the top is listed as 1.561 (4 valve relief). Therefore half stroke (1.740") plus rod length (5.700") plus 1.561" is 9.001". It is a flat top piston with 7cc valve relief volume, the description is wrong, it should be -7cc.

Hyper piston and 11:1CR would be a bad choice :cry:
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Well, I have 11:1cr with Alum heads, Hyper pistons and the 30 30 cam. No problem with 91 octane.:beer:

Got a real close look at the spring this week-end. Nice, very nice.:drink:
 
Wow I did not think that hyper pistons would work with 11:1 cr and 91 octane gas... I thought that with that combo you're dumping two bottles booster in the tank everytime you fill up :sweat:

Hyper pistons are sensitive to detonation, it would worry me and I'd listen for the slightest pinging noise... it would drive me nutz....

Anyways, at 9.5:1 cr the engine should run fine. The cam and the primaries are not a perfect match but it should still work out pretty nice.

With a .028" gasket (MrGasket) you're at 9.85:1CR with -7cc pistons. That should work very good.
 
Great! I like to plan ahead to avoid as much surprises as possible.

Too bad corteco hasn't responded yet, but since I'm pressed for time due to an exam anyway I'll give them another few days (before calling them or something).
 
I used corteco because they were recommended to me by the person who helped me assemble the new parts. The kit included every gasket needed and they did seem good quality to me (I am a n00b however, what do I know ;)).

In the meantime they have replied (I'm so impatient :D) and using this compressed gasket thickness my calculator comes to 8.67:1 compression. Stepping up to -7 cc pistons would bring me to 9.2:1 and flat would take me to a theoretical 9.91:1 compression.

Below is Corteco's full reply:

The set 32222-1CS is for the Chevrolet V-8 application often referred to as
the 'small block V-8". The gasket, part number 20312, is extremely robust
for street use and performance applications. We have seen its successful
use in typical street engines making 300 hp and performance engines up to
700 hp. It has a special steel shim between the center cylinders to prevent
crush out and burn out common on competitor products. The gasket is white
in color and uses our patented coating process that provides excellent
sealing, motion accommodation, and clean release on disassembly. I believe
this is the best gasket available for this Chevrolet V-8 application.

The gasket will accommodate a 4.1inch bore size. Fit depends on your
cylinder chamfer, not just the bore size; always check fit. The
manufactured thickness is nominally 0.056 inches and the compressed
thickness will be about 0.052inches. Always use clean lightly lubricated
bolts with a drop of oil under the head. Follow the torque spec. Use
sealer on the appropriate bolts on this application as a few of the bolts go
into the block coolant jacket.

This gasket will seal any surface finish from very smooth (20 micro inches
roughness average, Ra) to rough at more than 100 micro inches Ra.
The range of 50-70 micro inch Ra surface finish, which looks very smooth, is ideal. We never recommend a rough surface finish for any gasket. Some machine shops are only capable of achieving a rough surface finish, and our coating system accommodates reasonably rough finishes to help our customers.

Regards,

[name removed]
Director of Technology, Sealing Products
ROL Manufacturing
Click to expand...
 
With .052" compressed thickness head gaskets and the piston .025" down in the hole you have really bad quench (.077"). With the Victor Reitz or MrGasket head gasket it'll be a lot better (.051"-.053").

Do these corteco gaskets need to be retorqued ? The MrGasket gaskets that I use don't require re-torquing.
 
MYBAD79 said:
With .052" compressed thickness head gaskets and the piston .025" down in the hole you have really bad quench (.077"). With the Victor Reitz or MrGasket head gasket it'll be a lot better (.051"-.053").

Do these corteco gaskets need to be retorqued ? The MrGasket gaskets that I use don't require re-torquing.
Click to expand...

I think not, but will check. Should I install new gaskets, I'll install new pistons as well. This is purely a matter of being efficient: I don't have my own garage. So if I have to rent a place to be able (be allowed to) to take off the heads, I might as well do it right (should have done that in the first place, I know, I know :blush:) while everything is off.
 
How many miles on that motor? For new pistons you want to have the bores bored and honed to get a fresh bore (not tapered) and for a proper cross hatch finish to break in the new rings.

Don't have someone clown around with a drill and a 3 stone hone, it's not a 2 stroke bike you're working with here. For a proper sealing cylinder you'll need a lot more than that. You need a sunnen or similar powerhone and the tools to check the bore diameter so you have the proper piston clearance. Buy the pistons first and then match the bores to the pistons. might as well want to either replace the rods or install some arp bolts and check the big end for out of stretch (they're always out of round over the side this so the bearing shells don't crush inward and screw up the bearing clearance), these stock (X) rods like to stretch and give bearing clearance problems. Might as well do it right and get some powder machined rods. They are cheap and plenty strong. Some fresh main bearings, a good journal polish and if you can spring for it some bob weight/spin balancing on the crank won't hurt either, otherwise just weight match and trim to match the sets of rods & pistons you'll be using.

IF you do not want to have the block bored & honed oversize and know (or want to believe) you have little or no bore taper you can get a fresh finish on the bore with a bottle brush hone. It's vastly superior to a glaze breaker hone and much easier to use.

Of course you'll need new gaskets, you can't reuse the old.
 
About 27.500 miles on the motor. It was installed in '95 or '97 (have to check invoice previous owner) at 72-something K-miles and just recently I past the 99999 marker.


According to the invoice supposedly a performer cam was installed, but during disassembly a GM camshaft came out :suspicious:

So, if I want to do things properly (and I do), then I have to:

- buy new pistons, .030 over (Speed Pro ZH100CP30 ?),
- buy new connecting rods (GM Performance 12495071 ?),
- buy new rings (type/brand?),
- buy new bearings (type/brand?),
- buy new connecting rod bolts (type/ARP?),
- machine shop bore and hone,
- journal polish,
- bob weight/spin balancing on the crank or weight match and
- trim to match the sets of rods & pistons.

Correct?

I wonder if those costs weigh up to for example installing smaller combustion chamber heads (say 60cc) and a thinner head gasket plus perhaps decking the block? What about milling the heads combined with decking and thinner gaskets?

Perhaps even buying a new shortblock (383...?) could be more cost-effective?

Any thoughts on this? I'd like to consider every option and then choose a route to follow.
 
Considering that you could sell your short block (I believe in Europe they're more valuable than here) a 383 short block might be the best way to go, however shipping to Europe isn't cheap....a "average" 383 short block with name brand parts is about $1500 assembled, the cheap ones start at $1000.

Thoughts ? Find out how much the machine work for your block will cost you and then go from there.

You could also just disassemble and measure the bores, if they're in good shape bottle brush them and slap a set of new pistons/rings in there and go (with balancing and new bearings of course).
 
Well, For all those machining operations you can count on at least 1500 euros to have it done properly, not including shaving the deck down (which is a good idea, you'll end up with a nice straight deck and you can cut it down to be able to use a decent thickness gasket without having too much quench height)

Rings, bearings..most will do. Some hastings moly faced rings, some clevite 77 bearings, it'll do just fine. If you buy connecting rods and arp bolts you might as well get some rods that already come with them. Many shops sell aftermarket rods with arp bolts for a good price, certainly less than having your stockers resized.

What are you exactly aiming for? If you are aiming for oh say 350 horse <5K rpm mostly, decent cruiser I wouldn't go through the trouble of balancing the crank. Just get some new psitons and decent rods or if the old ones check out use those (but DO check the big end for stretch) and then go from there. Bottle brush hone the bores and weight match the rods & pistons as good as you can. It'll run just fine.

IF you decide to go with different rods and pistons, might as well get some floaters and do away with the press fit.
 
300 to 350 horse would do just fine indeed, otherwise I'd have to beef up other parts of my corvette way sooner than I'm planning to (next up: new rad., elec. fan, spreaderbar, fiber spring, koni shocks, even foose/boyd wheels perhaps).

So, in short the plan would be:
- new pistons, rings and bearings,
- check rod ends for strech / new rods and bolts if streched,
- Bottle brush hone bores,
- Weight match rods & pistons,
- Deck the block.

Is the weight matching a machine job or something I should do during part selection?
 
What you need to do first is get yourself some bore dials to measure the cylinders for taper and the rod big ends. If you don't have one, there's another trick. You can assume the rods are stretched, they all are. Most of them even come with 0.0005" oversized bearing shells from the factory. That's half of the commercially available first oversize. If you have that problem, and you want to reuse everything you can buy a set of 10 and std and mix up the shells. Use the thicker shell on the cap (bottom) and the other on the top.

For the cyls however, get a fresh ring and put it in the bore, use a flat top piston to push it down square. Measure the gap on several sections down the bore. The difference will give you an idea on bore taper.

A bottle brush hone will run you 100$ from mcmaster, however they don't ship internationally anymore.

The weight matching can easily done with a lab scale. Just put all your rods and pistons on there (for accuracy also rings, pins and retainers) and sort them all according to size. Then match them all up to get them as equal (paired rods & pistons) as possible. Then you can trim the balance pads on the rods and/or pistons to fine tune.

You can also buy a balancing fixture for your rods, that still leaves the pistons to be done.

The key to getting it right is meticulous working practices and cleanliness.

Do you have an SBC building book? It will be a worthwhile addition to your book collection. It will guide you through everything, tolerances, bearing crush, ring gap clocking and so on...and so on. It's just too much to lay it all out here.
 
Thanks Marck :thumbs:

It probably will be some time before I actually get to measuring the bores, have to address current issues first and ofcourse there will be something with a newborn in august ;)

Twin_Turbo said:
Do you have an SBC building book? It will be a worthwhile addition to your book collection. It will guide you through everything, tolerances, bearing crush, ring gap clocking and so on...and so on. It's just too much to lay it all out here.
Click to expand...

Yep: Rebuilding The Small Block Chevy (Larry Atherton & Larry Schreib), which comes with a handy DVD, a buyers guide (Micheal Lamm), a Haynes, a Chiltons, an AIM and another SBC assembly DVD which I can't find right now.

However, theory and practice -even with DVD's- differ a lot in my opinion. I learned a great deal from the first upgrade, just by watching and listening to someone who has done a build many times before. I think half of what he told me during assembly wasn't in a book.

But: if you know a few more good books or DVD's, please let me know.
 
A DVD huh? I think I have that book but no DVD.

There's a step by step book on building SBCs too, I think it's blue.
 
The upper right one I have and it does have a DVD included. Perhaps TT has an earlier print? I also have the ChevyHighperformance book 'How to build a chevy small-block for the street', but that's more a collection of their articles.

I'll get myself an amazon account right away :idea:
 
You're correct, the newer version includes a DVD

The "big inch small blocks" book is great, you might want to consider a inexpensive cast stroker assembly: includes crank,rods,pistons, rings, maybe bearings for under $900 (600 Euro) :1st:
 
Yes, I talked things through with my mechanic and he said the same thing. However his price for a stroker shortblock was around € 1700,- ex. Where would I find a block for $900,-?
 
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