Compression Ratio Question?
#1
02-15-2007, 11:31 PM
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
Why run 12to1.....1)cause i can........well maybe. 2) cause power is never a bad thing /carefully planned that is
#2
02-23-2007, 06:30 PM
RE: Compression Ratio Question?
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 evenas good as the V8 Vortecs I've neverhad 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.
PS: As far as being canted valves I thought you had the heads off?.
PPS: I'm not sure the heads are evenas good as the V8 Vortecs I've neverhad 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.
#3
02-23-2007, 06:53 PM
RE: Compression Ratio Question?
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.
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.
#5
02-23-2007, 10:41 PM
RE: Compression Ratio Question?
I was givven a donor engine, with a Head casting # : 10238181 1992 thru 1995 and aEngine 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 himthe 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.
#6
02-23-2007, 10:45 PM
RE: Compression Ratio Question?
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.phpits the 5th video from the top.
p.s. this is NOT a street racing vid....he is at the track!
http://www.1320video.com/videos.phpits the 5th video from the top.
p.s. this is NOT a street racing vid....he is at the track!
#7
02-24-2007, 02:11 AM
RE: Compression Ratio Question?
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.
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.
#8
02-25-2007, 01:15 AM
RE: Compression Ratio Question?
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
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.
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.
#9
02-25-2007, 01:19 AM
RE: Compression Ratio Question?
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
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
#10
02-25-2007, 01:47 AM
RE: Compression Ratio Question?
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).
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).