high compression setup

[gectek]

the valve reliefs will be far enough into the piston that you should not have to worry about ring land issues. I have seen quite a few stock bottom end LS guys run larger hits of nitrous (150+) and high HP on a set of pistons that were flycut with .110 eyebrows cut into them on their stock hyper-e pistons, so a small fillet on ours doesnt seem like much of an issue

[IsaacHayes]

Hey Ben if you are reading this, what was the IVC on the guy with the malibu that had 12.5:1 compression? Just for reference/comparison...

[Superdave]

my piston to exhaust valve clearance with the plungers in my home built solid lifters all the way up is -.023.. so assuming .060" of preload i have about .040 of clearance.


There was a ton of clearance on the intake valve.. the exhaust valve cut the tootsie rolls in half.

[gectek]

badunk a DUNK lol

[geldartb]

haha nooo the tootsie roll died.

i should throw the heads and stuff on the other block to see what kind of tootsie roll death i can create.

Dave did you have any issues this time with valve to piston contact. i remember your pics from before.

[IsaacHayes]

Yup he just pulled the heads and found that he had some contact even with .060 stock head gaskets.

[BillS]

Just noticed this thread.

Running too little clearance between piston and head makes me very nervous.

I tried .030" deck height on one engine (not a V6-60) and when I tore it down to do something else on the head found a nice little imprint of the combustion chamber in the carbon on the tops of the pistons and wee little marks where the valve heads had touched reliefs I'd cut at the top of the cylinder walls, but not enough to bend - about as close as you can push it and live.

Amazing how everything seems to stretch at high RPM.....

[Classick Century Custom]

Ok so I am just gonna throw this out there, I am looking to go N/A with a High Compression motor setup, keeping in mind I want it to be somewhat streetable with a nice lopey cam that rumbles yet won't reduce driveablity.

I have looked on WOT and want the Race Heads, Race Cam and Competition Upper and Lower Manifolds, will the Iron Head pistons they talk about give me the last answer to what it is I am looking to get out of my 3100 motor?????


Please respond with any help advice or direction on what I need or should do to achieve this High Compression. My Goal is 250+ Horsepower....

[3400-95-Modified]

Any input running 12+ CR on my cam and setup?

I'm not sure of all those numbers you guys got from ben, or if I can even get those... I know I have the old 1280/1331 combo grind... it is supposed to be a boost cam so thats why I ask if that much CR is too much for n/a and then if with that much CR will my 100 shot likely kill it on the first pass.

I can bring her to ~11.9:1 with a .080 thick MLS gasket instead of the .060... I'm also using the stock bore size for the 3500 MLS which is 3.72"

[geldartb]

well im thinking about using the .051 thickness head gaskets. not much thinner than the stock ones so i should be good with that right?

this will net me a 11.94.1 CR. if i use the .036 headgasket thickness to bring the quench into the green i get a 12.54:1 CR. would it be advisable running a headgasket that thin with my cam. i know dave had piston contact with stock headgaskets but his cam is a little rowdier than mine.

all of this would be done using the 3500 MLS headgaskets with the 3.72 bore.

already have the 3.4 ironhead pistons so im good to go on that area.

[Classick Century Custom]

Barring the same question here since I am attempting the same setup, what cam would you guys think is the best for my 3100 motor with a high compression motor. I went on WOT reminding that its gonna be streetable I'm looking for the most rumble before vacume becomes an issue.

Forgive me for the questions I am just not as savy when it comes to these motors as most of you are which I was I joined to learn.

[pocket-rocket]

Well, if you are worried about vacuum for accessories you could always get one of those vacuum pumps for diesel vehicles that run their brake booster Although if you want some good power, you should upgrade to at least a 3400 to start with. Even with our small V6's the old saying still holds true- "There is no replacement for displacement"... Well, until you go to boost

[IsaacHayes]

Jon, with Iron head pistons the quench suffers with .060 headgaskets, you need to drop the heads to have ideal quench. Raising them more will only make it worse. Quench can help fight pre-detonation. I would not run .080...

My cam could be bigger to run 11.51:1 but it does run on 93. I will find out if it will run on 91......... I will try colder spark plugs if I have issues and hope for the best...

I don't know your cam specs to well, but for 12:1 I'd want a big cam...

CCC: Play with the compression calc, and look up dynamic compression calcs. The later is only a guess at what it will come out with, but you can compare others setups. I forget what the iron head 3.1 pistons work out to be in a 3100. But it's different than using gen3 heads and 3.4 iron heads in a 3400...

[3400-95-Modified]

I missed the whole piston deck clearance setting so that's why I had different numbers when I was doing the CR calculator.

Stock thickness 3500 MLS headgaskets I would be 11.6:1

To get good quench I would end up at 12.5:1

my cam specs are in my sig you dope, At least what I know of it... the rest you would have to ask Ben to see if he has any info on the old 1280 intake and 1331 exhaust lobe's
Cam 216/240 .050 dur .517/.568 lift 112LSA

Its starting to sound like I really can't get a usable CR with stock parts so if I want to mess with this I really need to pick a CR and get a set of Diamond pistons made... Thats gonna be a year or so off then... I guess I'll stick with the .060 thick gasket with my stock bottom end and just make sure to port the shit out of the top end this year. I still feel like my setup was off on the 270hp that I was quoted... so I gotta reach that before doing more to it.


HEY I actually started working on the car yesterday too!!! Drained the oil, the antifreeze disconnected and removed the battery, the alternator the front header, the fan, the coils... and all that fun stuff... Now I'm gonna drop the frame rails, and get the trans out then pull the engine... That way I can reach the bolts to remove the rear header

[Joseph Upson]

You guys are working in an area that many shy away from due to the limitations of old technology in head design and the outdated books reinforcing those rules still in print being spread around.

Lindy Tools makes a far better valve relief cutter than the tool available from one of the cam companies which I understand takes quite a while to do its job. The tool is designed for use through the valve guide with the piston installed for accuracy of location. That should take care of any potential valve interference issues resulting from headgasket and cam lift changes.

An important trend for everyone to take into considereation is that by default the introduction of ethanol into fuel automatically provides some increased antidetonation properties as well as a drop in fuel energy so in a way our engines need the higher compression to recover what was lost from the pure gasoline blend.

Remember all of the current GM 60 deg engines being manufactured are at least 9.8:1 compression on 87 octane, the 3.6L 10.2:1. I see no reason why you can't run a full 12:1 with modern aluminum heads and pump gas possibly with less than 93 octane.

If you keep coolant temps close to 200 deg or less I don't believe you'll have any problem at all.

The increase in efficiency with the higher compression provided you don't go overboard with cam duration may provide equal to or better fuel economy on higher grade fuel than the stock motor currently gets on low grade. I'm talking about the dollar per mile average here.

I like what you're doing as you can tell by the length of this post.