396ci LT4, YSI and 15lb of boost dyno result :(
03-16-2010, 09:19 PM
#16
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Join Date: Nov 2002
Posts: 27
I e-mailed Lloyd Elliott www.Elliottsportworks.com asking for advice and this is his replay:
"Big thing that sticks out to me is the cam (248/254 is TOO MUCH duration). Something in the 223/234 duration range would be MUCH better at trapping cylinder pressure (and making more power) and having less overlap. Overlap allows exhaust to go up intake port and contaminate the mixture (before TDC) and also allows boost to right out the tail pipe (after TDC).
With all that boost and the size of the SC, you do not need the intake open that long to fill the cylinders well.
I would also make sure the springs have about 165-170 lbs of seat pressure for that much boost and aggressive lobes. I would use a lobe with a slower ramp speed and make sure it remains stable under high boost.
I would rather see around 9.25 compression and if we have less than 8.0 compression, that could be killing us.
Do the math for chamber size, -37 cc pistons, head gasket thickness and piston deck ht to see what the compression really is. "
Big thing that sticks out to me is the cam (248/254 is TOO MUCH duration). Something in the 223/234 duration range would be MUCH better at trapping cylinder pressure (and making more power) and having less overlap. Overlap allows exhaust to go up intake port and contaminate the mixture (before TDC) and also allows boost to right out the tail pipe (after TDC).
With all that boost and the size of the SC, you do not need the intake open that long to fill the cylinders well.
I would also make sure the springs have about 165-170 lbs of seat pressure for that much boost and aggressive lobes. I would use a lobe with a slower ramp speed and make sure it remains stable under high boost.
I would rather see around 9.25 compression and if we have less than 8.0 compression, that could be killing us.
Do the math for chamber size, -37 cc pistons, head gasket thickness and piston deck ht to see what the compression really is. "
"boost is just the pressure in the intake but that doesn't tell you how much fresh air is in the cylinder during combustion or how much exhaust pulse is mixed in contaminating the mixture. It just shows pressure and that is it.
Smaller duration cams will work MUCH better for you at the compression level you are talking about and a wide LSA to cut down even more overlap will make it even better.
Have you checked the cylinder pressure on that set up? it is probably about 100-110 lbs of cranking pressure and will NEVER make any power. You want it to be in the 140-150 psi range to actually work well with that amount of boost.
Might be lots of things to cause the low #'s but a cam swap would be my first step. I prefer my Bullet/Ultradyne asymmetrical lobes and can get you 223/234 .565/.592 115 LSA billet cam for $320 for a standard base or $340 for a small base cam. These asymmetrical lobes open the valves almost like a solid roller and fill the cylinders MUCH better than similar duration lobes from other companies. They make power like a lobe that is 5-6 degrees larger than there @ .050 duration #'s. The closing ramp speed on the lobe is a lot slower and allows the valve trane to be stable at high RPM like the Comp Magnum lobes while packing more in/out of the cylinders. These lobes are the reason I chose Bullet/Ultradyne to make my cams for me.
If you chose to use Comp, get a 224/236 .560/.608 (3119/3122 lobes) on a 115 LSA plus 7 (108 ICL) and see how it does. This will need 155 lbs or more seat pressure and 350+ open pressure to remain stable at high RPM. Comp only makes lobes every 6 degrees of duration so you have to go a lil different on the specs than what I would like but it will still be TONS better than what you have.
A cam swap would be my first swap and then go from there. Other than tearing the engine down and shoving more compression in there, this is the easiest (and cheapest) thing to change."
"The cam specs will be the same up to 9.25-9.5 compression.
If we actually have 8.00 or less compression, the thing may run even better with a 211/223 .565/.565 114 LSA cam just to keep as much cylinder pressure as we can but it will run out of steam up top trying to feed all those cubes. kind of a give./take thing and I would prefer not to "band-aid up" the cam specs for the compression and then require a different cam later when you get the right compression. Once you get 9.0-9.25 compression, the cam will be perfect.
Definitely get a 1.6 rocker."
"Big thing that sticks out to me is the cam (248/254 is TOO MUCH duration). Something in the 223/234 duration range would be MUCH better at trapping cylinder pressure (and making more power) and having less overlap. Overlap allows exhaust to go up intake port and contaminate the mixture (before TDC) and also allows boost to right out the tail pipe (after TDC).
With all that boost and the size of the SC, you do not need the intake open that long to fill the cylinders well.
I would also make sure the springs have about 165-170 lbs of seat pressure for that much boost and aggressive lobes. I would use a lobe with a slower ramp speed and make sure it remains stable under high boost.
I would rather see around 9.25 compression and if we have less than 8.0 compression, that could be killing us.
Do the math for chamber size, -37 cc pistons, head gasket thickness and piston deck ht to see what the compression really is. "
Big thing that sticks out to me is the cam (248/254 is TOO MUCH duration). Something in the 223/234 duration range would be MUCH better at trapping cylinder pressure (and making more power) and having less overlap. Overlap allows exhaust to go up intake port and contaminate the mixture (before TDC) and also allows boost to right out the tail pipe (after TDC).
With all that boost and the size of the SC, you do not need the intake open that long to fill the cylinders well.
I would also make sure the springs have about 165-170 lbs of seat pressure for that much boost and aggressive lobes. I would use a lobe with a slower ramp speed and make sure it remains stable under high boost.
I would rather see around 9.25 compression and if we have less than 8.0 compression, that could be killing us.
Do the math for chamber size, -37 cc pistons, head gasket thickness and piston deck ht to see what the compression really is. "
"boost is just the pressure in the intake but that doesn't tell you how much fresh air is in the cylinder during combustion or how much exhaust pulse is mixed in contaminating the mixture. It just shows pressure and that is it.
Smaller duration cams will work MUCH better for you at the compression level you are talking about and a wide LSA to cut down even more overlap will make it even better.
Have you checked the cylinder pressure on that set up? it is probably about 100-110 lbs of cranking pressure and will NEVER make any power. You want it to be in the 140-150 psi range to actually work well with that amount of boost.
Might be lots of things to cause the low #'s but a cam swap would be my first step. I prefer my Bullet/Ultradyne asymmetrical lobes and can get you 223/234 .565/.592 115 LSA billet cam for $320 for a standard base or $340 for a small base cam. These asymmetrical lobes open the valves almost like a solid roller and fill the cylinders MUCH better than similar duration lobes from other companies. They make power like a lobe that is 5-6 degrees larger than there @ .050 duration #'s. The closing ramp speed on the lobe is a lot slower and allows the valve trane to be stable at high RPM like the Comp Magnum lobes while packing more in/out of the cylinders. These lobes are the reason I chose Bullet/Ultradyne to make my cams for me.
If you chose to use Comp, get a 224/236 .560/.608 (3119/3122 lobes) on a 115 LSA plus 7 (108 ICL) and see how it does. This will need 155 lbs or more seat pressure and 350+ open pressure to remain stable at high RPM. Comp only makes lobes every 6 degrees of duration so you have to go a lil different on the specs than what I would like but it will still be TONS better than what you have.
A cam swap would be my first swap and then go from there. Other than tearing the engine down and shoving more compression in there, this is the easiest (and cheapest) thing to change."
"The cam specs will be the same up to 9.25-9.5 compression.
If we actually have 8.00 or less compression, the thing may run even better with a 211/223 .565/.565 114 LSA cam just to keep as much cylinder pressure as we can but it will run out of steam up top trying to feed all those cubes. kind of a give./take thing and I would prefer not to "band-aid up" the cam specs for the compression and then require a different cam later when you get the right compression. Once you get 9.0-9.25 compression, the cam will be perfect.
Definitely get a 1.6 rocker."
03-17-2010, 08:54 AM
#17
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Join Date: Feb 2004
Location: Moore OK
Posts: 2,182
All very good information and in more detail than the rest of us usually explain.
I do agree with Loyd. But I like to always add - cam it the way you want it to drive. If you are happy with the monster cam try putting more boost through it first. If you are more worried about power then look at the cam swap.
I am going bigger - nowhere near your size 230/236 - because I was not happy with my baby cam. I want to make more power higher up.
I do agree with Loyd. But I like to always add - cam it the way you want it to drive. If you are happy with the monster cam try putting more boost through it first. If you are more worried about power then look at the cam swap.
I am going bigger - nowhere near your size 230/236 - because I was not happy with my baby cam. I want to make more power higher up.
03-18-2010, 10:39 PM
#18
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Join Date: May 2004
Location: A-town, TX
Posts: 666
how thick of a head gasket your runnin? maybe you can gain some cr with a thinner one? what cc are the heads? mill them some maybe? id up the boost and up the compression! id go 8.5 min possibly even 9.0 if you stay just pump gas, more if you go race gas!
03-19-2010, 05:41 AM
#19
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Join Date: Nov 2002
Posts: 27
I,ve got some e-mail replies:
www.golenengineservice.com
"Is this an LT1?If so the compression is way too low, we normally run 9.5:1 compression and the total timing is way to high we normally run it at 26degrees with 15 psi of boost. But 671 RWHP is pretty big power.Yes the cam is way too big to say the least, you would never want to use a cam with that big of a duration. I did not look up the grind # until now so I would install a much smaller cam like a 224/230 or so."
www.guerragroup.com
"The cam looks like it has too much overlap for a blower motor. The timing seems too high for a boost application (even with race fuel). I would have expected to see a duration closer to the low to mid 230s on intake and high 240s or low 250s on exhaust with an LSA around 115"
Patrick Guerra
www.golenengineservice.com
"Is this an LT1?If so the compression is way too low, we normally run 9.5:1 compression and the total timing is way to high we normally run it at 26degrees with 15 psi of boost. But 671 RWHP is pretty big power.Yes the cam is way too big to say the least, you would never want to use a cam with that big of a duration. I did not look up the grind # until now so I would install a much smaller cam like a 224/230 or so."
www.guerragroup.com
"The cam looks like it has too much overlap for a blower motor. The timing seems too high for a boost application (even with race fuel). I would have expected to see a duration closer to the low to mid 230s on intake and high 240s or low 250s on exhaust with an LSA around 115"
Patrick Guerra
03-20-2010, 08:12 AM
#21
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Join Date: Oct 2004
Location: Florida
Posts: 1,228
Yup, youve got this engine setup for massive amounts of boost (like 30psi). Then, without the CR being taken into acount, it looks like an NA setup. You need to ditch that cam. You'll likely see more boost and have better results. As far as the CR goes, you could cut the heads or get another set and sell yours. It all depends how deep you want to go back in. Cam can be done in a weekend and back on the road, although you're halfway there to remove the heads. If it were me I would swap cams and spin the ysi to near max rpm. If that dont satisfy you, spray a 150 shot on it to bring the cylinder pressure up. I think you'll find plenty of power with this route, and its quicker, easier, and cheaper.
03-22-2010, 08:01 AM
#22
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Thread Starter
Join Date: Nov 2002
Posts: 27
Did few check and here is what I found so far:
1- sprark plug for cyl# 6 was lose..not even hand tight.
2- Cylindrs pressure was 135 psi.
3- I think that my y-pipe is restrictive,the vrtex inserts I've put in there to reduce the noise was a bad idea.they where welded inplace and the came off just after two puls on the dyno. So, they are coming out and the y pipe is going to be altered.
4- the cooler is definitaly going to be changed.But before that I am going to do a dyno run with the new y-pipe and i will check the pressure before and after the cooler.I have this cooler fitted because- I alredy have it, bought it years ago for different setup- I want to see how much is it realy capable of cooling discharge air.and it did realy well- temp drop from 44 deg C to 24 deg - that with ice in the tank.soon we will fine out how restrictive it is. Vortech aftercooler pdf file says it for vehicle making approximately 580hp!
1- sprark plug for cyl# 6 was lose..not even hand tight.
2- Cylindrs pressure was 135 psi.
3- I think that my y-pipe is restrictive,the vrtex inserts I've put in there to reduce the noise was a bad idea.they where welded inplace and the came off just after two puls on the dyno. So, they are coming out and the y pipe is going to be altered.
4- the cooler is definitaly going to be changed.But before that I am going to do a dyno run with the new y-pipe and i will check the pressure before and after the cooler.I have this cooler fitted because- I alredy have it, bought it years ago for different setup- I want to see how much is it realy capable of cooling discharge air.and it did realy well- temp drop from 44 deg C to 24 deg - that with ice in the tank.soon we will fine out how restrictive it is. Vortech aftercooler pdf file says it for vehicle making approximately 580hp!
Last edited by kazdevil; 03-22-2010 at 08:05 AM.
07-28-2010, 01:49 AM
#23
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Thread Starter
Join Date: Nov 2002
Posts: 27
last dyno run with a new intercooler.
It gained about 1 psi.its rated 700cfm which is not enough but I thought I give it a try since I already have it.bought it long time ago of ebay.
http://www.youtube.com/watch#!v=5WS3...eature=channel
http://www.youtube.com/watch#!v=5WS3...eature=channel
Last edited by kazdevil; 07-28-2010 at 01:53 AM.
. Just fitted the engine in the car tonight. Should be running tomorrow.
