Compression Ratio Question?

So anyone know if and how i can make it safe to run 12 to 1 compression pistons?  If not i have a set of 11to1s i can run.  I'm pretty sure running richer is not an option due to the fact that i'll be running the stock pcm, and do not want to turn up the fuel pressure.  If im correct its @ 60 psi.  injectors start locking up at 80 psi or so.   Any thoughts?
 
 
Why run 12to1.....1)cause i can........well maybe.  2) cause power is never a bad thing /carefully planned that is         
 

You can run 12-1 with no problems at all, just fill the tank with 116 octane race gas. If you find that too expensive use the 11-1's and run 100 octane unleaded which isn't that hard to find and only cost's about $5.00 a gallon, now that 93 is about $3.00 that may be low. By the way, if you go with the 12-1 figure on dumping the cat.
PS: As far as being canted valves I thought you had the heads off?.
PPS: I'm not sure the heads are even as good as the V8 Vortecs I've never had a set off. Just because the engine says Vortech doesn't mean the heads are in fact true Vortecs. 
Going by your knowledgable questions, and your evident need for speed, may I suggest you sell your Blazer?. It's either that or put in a V8, because these this are dogs, I know, I've had 3, all of then at the drag strip. And if any of you have gotten yours into the 9's in the 1/8th or 14's in the 1/4 for under a grand (plus) please tell me how. And please unless you've actually taken it down the strip don't bother replying.

Why can't anyone that hasn't had their blazer to a strip reply?  As if you have to have had your truck to a strip to know anything about engines or what makes them tick...

As far as the combustion chamber and intake/exhaust runner designs, the 4.3L heads on the SCFI motors use the same runner/chamber design as the v8 heads.  In fact, the v6 heads are essentially the v8 heads minus one cylinder.  And I do not think that the older CPI heads were all that much different either.

Pretty much everything on the 4.3 is the V8 minus 1 cylinder, lol

I was givven a donor engine, with a Head casting # : 10238181  1992 thru 1995 and a Engine Block # : 10105867  1987 thru 1992.  I forgot the company i got this info from.  I was just wondering whats these heads are considered.  I don't know the difference between canted, wedge, and so on.  I have software that helps you deside how you want to build your engine (which i know software isn't completely accurate so i don't want to here it) Also i did end up sending my pcm out to get reprogrammed, so i asked if it was safe to rum my pistons that are 12.5 to 1 on 93 octane......his reply was yes he has done it many times without a problem.  I warned him the pcm was for a blazer.  Bryan Herter from "PCMforless.com" is who is programming it.  Owe trust Vortec heads are noticable they have a intresting shape leading up to the valve guide and valve.  You can see the shape would easily help create a vortec, and increase the velocity of air flowing through them.  No im not planning on drag racing my truck, but i do plan on dynoing it when its done.  I simply don't want to go through the effort of putting a v8 in there, and have already purchased the parts when i found that its not that bad to squease the v8 in there.  We'll leave that up to Kyle.  Thanks guys.

Oh if you guys wanna talk about drag racing trucks check out the vid of the Blue silverado its a 10 second truck!!  I'm sure some of you already know Parish's truck. 
http://www.1320video.com/videos.php its the 5th video from the top.
 
p.s. this is NOT a street racing vid....he is at the track!
 

Your heads aren't possibly Vortec's they were released on trucks in 1996 (V8's). You have plain ordinary combustion chambers and a plain ordinary cylinder head. As far as running 12 point anythings on the street you have to have an engine designed for that compression and no octane, or your going to go into detonations anytime you get in it. When THAT ahppens don't have a knock sensor still on your engine.
 
To eliminate detonation, which is the biggest destroyer of engines you have to have cool EVERYTHING, and you'll see that when GM started raising compression to near 10 to one they did it on engines with aluminum heads, USUALLY you can run 1/2 to 3/4 point MORE compression with aluminum heads over iron heads. Cool air is a MUST with higher compression, it helps prevent/delay detonation, the cooler the better.
 
Camshaft design also affects how high a compression ratio you can run. Anyone who's racing in the "pump gas" class knows what it takes to run high compression and 93 octane gas. Read about it when Hot Rod or Car Craft runs article on pump gas drags, and what they do to the engines.
 
A 4.3 can't run 12-1, can't run 11-1, and is pushing it at 10-1. I say can't because it can't, the special cam and aluminum heads aren't available to begin with.
 
In YOUR case, with YOUR engine, may I seriously suggest nitrous?. That's the only way your going to afford over 250 real horsepower.

No offense but you realy don't know what you are talking about on this one!!  They made Vortecs in at least 1992 which i had a guy look them up for me.  Also i am using the set of the 97 engine anyways, because after disassembly of the others I found that the older set there was 1 damaged.   Also i'll let you know when i melt the pistons down.  BTW did you know that Chevy made a 302 cubic inch engine just for the sake of starting another argument.  I am very aware Ford did too.  I mean chevy did.  Even

quote:

ORIGINAL: 2000BlazerSS

Your heads aren't possibly Vortec's they were released on trucks in 1996 (V8's). You have plain ordinary combustion chambers and a plain ordinary cylinder head. As far as running 12 point anythings on the street you have to have an engine designed for that compression and no octane, or your going to go into detonations anytime you get in it. When THAT ahppens don't have a knock sensor still on your engine.

To eliminate detonation, which is the biggest destroyer of engines you have to have cool EVERYTHING, and you'll see that when GM started raising compression to near 10 to one they did it on engines with aluminum heads, USUALLY you can run 1/2 to 3/4 point MORE compression with aluminum heads over iron heads. Cool air is a MUST with higher compression, it helps prevent/delay detonation, the cooler the better.

Camshaft design also affects how high a compression ratio you can run. Anyone who's racing in the "pump gas" class knows what it takes to run high compression and 93 octane gas. Read about it when Hot Rod or Car Craft runs article on pump gas drags, and what they do to the engines.

A 4.3 can't run 12-1, can't run 11-1, and is pushing it at 10-1. I say can't because it can't, the special cam and aluminum heads aren't available to begin with.

In YOUR case, with YOUR engine, may I seriously suggest nitrous?. That's the only way your going to afford over 250 real horsepower.

Oh might i add heres the guy i emailed His Name is mark from: http://www.marineandstreetmotorsport.com/links.php
 
 
Hi Bill the block you have was used from 1987 through to 1992 it it can be used with roller factory cam in most blocks depends if the lifter bores are machined at the top...the heads the heads are the first of the vortec that were produced from 1992 to 1995...the heads are vortec heads yet the block is pre vortec...i have used this combo many times...if we use the latter vortec engines we remove the balance shaft & balance the engine...the balance shaft is a heavey bit of metal that I think if machining is done properly can be left out...the combo you have is a good start...both engines are capible of the same performance ...regards Mark

The casting marks on the donor engine are....
Head casting # : 10238181
Engine Block # : 10105867
Thanks Again Bill

Chevy made a 302?. Are you SURE?.
 
The Vortec head that everyone is talking about was first used in 1996. The Vortec name on the V6 was first used when the 90 was changed from TBI to PFI.
 
The balance shaft has nothing to do with the BALANCE of the engine, it's to stop vibrations caused by the inherant imbalance of a 90 degree V6. When they went to that they also changed to a roller lifter camshaft. To use roller lifters in an engine that didn't have them originally the lifter valley has to have drilled and tapped bosses for the "spider" that holds the roller lifters in place and the tops of the lifter bores have to be machined flat.
 
How do I know this?. I worked at the Chevy engine plant that first built the 90 degree V6 in 1978 thru the time they put in the balance shafts and roller lifters. I worked in the case department and saw MILLIONS OF THE GOD DAMN THINGS!. (half the engines they built for 13 years, I left the 90 job in 1992 or 3). 

quote:

ORIGINAL: 2000BlazerSS

Your heads aren't possibly Vortec's they were released on trucks in 1996 (V8's). You have plain ordinary combustion chambers and a plain ordinary cylinder head. As far as running 12 point anythings on the street you have to have an engine designed for that compression and no octane, or your going to go into detonations anytime you get in it. When THAT ahppens don't have a knock sensor still on your engine.

To eliminate detonation, which is the biggest destroyer of engines you have to have cool EVERYTHING, and you'll see that when GM started raising compression to near 10 to one they did it on engines with aluminum heads, USUALLY you can run 1/2 to 3/4 point MORE compression with aluminum heads over iron heads. Cool air is a MUST with higher compression, it helps prevent/delay detonation, the cooler the better.

Camshaft design also affects how high a compression ratio you can run. Anyone who's racing in the "pump gas" class knows what it takes to run high compression and 93 octane gas. Read about it when Hot Rod or Car Craft runs article on pump gas drags, and what they do to the engines.

A 4.3 can't run 12-1, can't run 11-1, and is pushing it at 10-1. I say can't because it can't, the special cam and aluminum heads aren't available to begin with.

In YOUR case, with YOUR engine, may I seriously suggest nitrous?. That's the only way your going to afford over 250 real horsepower.

Not to be a dick. But in this article I pulled from another post see link
http://www.hotrod.com/techarticles/engine/113_0208_chevy_43l_262ci_v6_engine_build/

They made over 250 HP. But they were not using a 12:1 compression they ended up using 9.08:1

Jackal: You may want to look into to what they did. If you do let me know how it turned out and roughly how much you spent. Is yours FI? If it is I defenately am interested. I need more power out of my blazer for towing and running the larger tires. besides trying to do a front and rear gear change to 3.73 or 4.10's

I don't know everything about motors Yet! But will be getting my head filled with the knowledge there is here shortly.

   I don't  know you tell me :)
 
 

quote:

ORIGINAL: 2000BlazerSS

Chevy made a 302?. Are you SURE?.  

That link doesn't work give me the month and year of the issue I have them all.

Thanks Bro...
 
I deffunatly will, i am running 12:1 cr.  You may not want to do that for towing.  I also do not know everyting about engines.  If knowledge was a beach i would the amount of a grain of sand!  I am hear to learn, thats why i am trying to build power below my cams capabilities.  I have ran 12.5:1 one on many Street cars so it depends on what your looking for.   An engine simply needs to breath, wheather its a cam, headers, heads, back cut valves, and so on.  Your looking for ways to increase Volumetric efficiancy, which is a fancy way of saying what percent of air fuel mixture you can squaze through a 4.3l. 

Heres the cam i am going to run.
LUNATI Solid Lifter Camshaft for the Chevrolet V6 262 Engine. Part #  43507 Grind # M-239-249 Serial # T6KT Lobe Sep 106. Ex Closes @ 14.5 ATDC Ex Opens @ 54.5 BBDC  In Opens @ 17.5 BTDC In Closes @ 41.5 ABDC. Duration @ .050 is 239/249 Advertised is 278/288. .517/.542 Lift, with a 1.5 Rocker and valve adjustment is .018/.020.   it should be pretty sweet!

I'm not sure. I just tried the link and it worked for me.

Here is the orginal post it was brought up in.

http://www.blazerforum.com/m_63537/tm.htm

There is 2 links in that one from hotrod. I couldn't figure out what issue it was in.

ceanern: I posted that I got it to work but Swartz deleted my post because I refered to "jerkle". The link showed an engine that seems to be EXACTLY what he needs. I hope he he does.

I didn't delete your post...  

After ceanern posted it worked I posted I went to the site using his link. The story was about a 262 that was built by Hot Rod. The engine is TOTALLY a street/race engine, but go there using the link and see. I figured when it didn't show up you deleted it because I refered to Jackle as Jerkle. There was more to what I said than just that but the article is on an engine that wouldn't pass a smog test, and they speak of having a super hard problem coming up with a decent set of heads. If the 96 and/or later 4.3's had true Vortec heads they would have used those, they didn't they spend big money trying to get a stock head to work. Like I say, unless I look at a96 and later 4.3 head and compare it to the V8 vortec on my bench I'll wait.
 
PS: Around 86/87 I built a "performance" 90 degree V6 for display at the engine plant. I built it using a set of aluminum heads and intake donated by Chevy in Michigan. The intake looked like an old "Smokey Ram", neat as hell. But not available for years. Chevy made a bunch of stuff like this back in the 80's.

     I will be running my 97 vortec heads, which are steal.  I am running the older bottum end, before the balance shaft.  I am certain you know your stuff, things are probaly getting lost in my deciffering of what your trying to say.  I do not have to pass any smog tests here.  Also stop living in the 70's and 80's cause that was 37, and 27 yrs ago.   To be honest i don't even know how to rebuild a carburator, but to me that would be asking me how to tune a steam engine, i have no use for knowing that. 

Jackle: I understand that kids today don't know, let's say, as much as us older folks. But then most of us older folks don't know SQUAT about fuel injection and have to learn everything new. Not fun.
 
Go to the link ceanern provided, just click it on, then read it. There's 2 pages and you have to print one and then the other, do that. Then read what they say about the cylinder heads they used, and all the choices they had to chose from.
Ask yourself a question, why didn't they start with a 1996 or later Vortec head if that's what they used on a later 4.3?. I know it's a GREAT head, I've been reading tests on it for YEARS. Why did they use a pre-Vortec head to modify?.
But I digress, if your going to do all those modifications  you should at least learn about how the pro's build an engine like that. Don't just go by what your "experts" say, but go to the site, read about it yourself. And the heads that they used, and the choices they had to choose from.
 
I'm 90% sure that when I look at the combustion chambers of a late model 4.3 they won't look like my V8's.

Here's an excellent (but dated) rundown on the 262cid v6:

Rebuilding The Chevy 262, Doug Anderson, Automotive Rebuilder, March 1998

Thanks, that answers a whole BUNCH of questions, especially and particularly the heads, that head chamber used in 1996 is the same heart shape as the V8 Vortec. It means that the 1996 and later head is a pretty damn good head as is. The valves are 1.94 and 1.50 plenty for a 350V8. They add 40hp to most V8's just bolting them on. This is a big thing to me. But I question why the people building the "hot rod" engine in HRM used an earlier head and modified that instead of the better Vortec head. They didn't I would've but that's what makes the world go round.
 
I'll hit print anad print it out when I get done with some ZL-1 sheets I copied, I was asked to "prove" the 3rd Corvette ZL-1, but I feel it's another bogus one.
 
Thanks for passing this along, you can't have too much information. Like I said, I was there from day one on the 90 degree V6, I never paid much attention because I never thought I'd ever have a need to build or play with one. Unless I stumble across a LOW mileage engine complete I never will, too much trouble for not enough reward.
 
PS: I would suggest you guys take the time to print out what Swartz provided, it's a terrific reference piece and handy to have. Thanks again 

On thing about that HRM article is that it seems like it was written in the '95 time frame where the newer vortec heads may not have been really known about.  They make some mention of them as the true vortec heads were the only ones that came with the vertical intake bolt alignment.

Also worth noting is that I have heard it mentioned in quite a few places that the newer vortec heads do not have the material around the runners for a major port job.  They really don't need much but a good smoothing cleanup, however, they also may not have the material to punch out the intake and exhaust like what was done in the HRM article either.

From what you say you could very possibly be right, either this was before the Vortecs came out or just as they did. I have the issue but would have to go thru a whole lot just to find it. I'm certain that if the Vortecs had been available, and they knew how good they really were, that's the head they would have used, the ports and chambers are most probably the same as the V8 head.
The true Vortecs wouldn't need major port work to be suitable for all but an engine with major modifications, they used mildly reworked ones on engines making over 400hp. What you say should be noted in any case. Also, the late intake and exhaust valves had "back cuts", that is a second angle which is considered prefered and adds to the flow at all RPM's. When they started I don't know, but trust me they did. You wouldn't be able to tell unless you took them out.
 
Also, and IMPORTANT is the "net lash" rocker studs and when they were used. They can be replaced with screw in studs and then you can use regular rocker arms with guides and adjust the lash as needed, if you change the cam or rockers I'd suggest putting them in (read the article).
 
But read this, print it out and keep it in a folder, it's chocked full of interesting and needed information if your going to pull one of these apart. I never realized what a pain in the ass it would be, all the nickle and dime changes they made.
 
Side note: They mention a "whine" when the balance shaft was first put in the engine. You CANNOT believe what a "situation" this created!. When the first engines hit the Baltimore plant they started sending almost every one back!. Trust me, Baltimore SCREAMED to the Corporation that Tonawanda was building JUNK!. **** hit the fan BIG time!. As it turned out, as this article states, the first gears were cut at an angle that caused a gear whine. This was at first blamed on our workers, but all WE did was put the parts THEY gave us in the way THEY told us too!. Turns out the engineers had the supplier cut the gears at a bad angle, wasn't the worker, wasn't the supplier, was the engineers. After thousands of engines were sent back and torn down for "excessive noise".
 
Anyway, print this article out, it's worth having a copy. Thanks again Swartz.