How much nitrous can an LT1 flow?
And whether or not your engine is built for that big of a shot because unless you've gapped your rings for a big shot the ring ends will butt together and you'll break the ringlands on your pistons.
I have a built motor with Hellfire top rings gapped for nitrous and my engine builder told me "no more than a 200 shot, and 150 would be better". So I'm going to follow his advise to keep my new engine safe.
I have a built motor with Hellfire top rings gapped for nitrous and my engine builder told me "no more than a 200 shot, and 150 would be better". So I'm going to follow his advise to keep my new engine safe.
Not really my engine is not strictly a nitrous drag engine, it's a daily driver with very occassional nitrous use. So if I were building a drag race only car I would have gapped the rings for heavy nitrous use, say 300 -400 shot and it wouldn't matter that the engine would have so much blowby under non nitrous use that it would be a turd anytime the spray wasn't on. My engine builder is just fine as he built the engine based on what my intended use of the car was and occassional nitrous use.
Now I see from you sig that you have a 147k stock shortblock are you going to try a 250 -400 shot on that, if so please post carnage pics and I hope you have another block to start your new engine build with, good luck.
Now I see from you sig that you have a 147k stock shortblock are you going to try a 250 -400 shot on that, if so please post carnage pics and I hope you have another block to start your new engine build with, good luck.
Anyway, assuming stock: I think I've pretty much gotten as much as you can get out of a stock LT1 both on and off the jug, 309 STD rwhp thru A4 / 12.3 sec @ 108 NA and 425 STD / 11.33 @ 117 on the 150 shot in a 3900 lb car, so I feel qualified to answer your question.
Short answer: 150 shot
I've not sprayed more than the 150 shot on the dyno, but in two seasons of drag racing with 175 pills, I never surpassed the 60' times, ET's, nor mph of what I previously did with the 150. That tells me the combination of the stock exhaust ports, and more likely the short exhaust event of the stock cam, just doesn't allow the spent mixture to evacuate sufficiently with more than 150 hp added. I posted NA results above also to show that the engine was truly optimized NA before adding the spray. If you have an engine that dynos much lower than that NA, then you may possibly get results from a bigger shot, but I've yet to see that on anybody else's car either; in fact, if an exhaust restriction is holding you back, then it surely will not respond to more than a 150 shot. BUT.....here's another variable: the Fbody cam's earlier exhaust opening than my B-body cam in theory should allow for better exhaust evacuation, so you might see results from a 175 shot that I didn't see. But I'm betting 175 is your limit of seeing any further results. No way is a 200 shot going to be beneficial in a stock LT1.
Now for the other scenario: you list a Hotcam in your sig. The significantly longer exhaust event of that cam would make more power with a 200 shot; HOWEVER, IF you have the car tuned well NA, with good breathing intake and exhaust, then you're going to surpass the cylinder pressure and top ring temp of what the stock short block will tolerate when you add more than 150 hp to an optimized NA hp number,...let's say about 340 rwhp NA. So again, the answer to your original question comes back to........150 shot.
Backup data point: a guy who has been racing heads/cam stock shortblock motors for years has had his motors survive very well on a 150 shot, but has yet to make more than two race weekends in a row when spraying 175 or more....end result has been either broken piston tops or pounded out/spun rod bearings.
Edit: After posting, I saw your sig, that you're at 6000 feet. Adjust my recommendation upward by 25 hp shot for sure, and by 50 hp on a warm day when you're not making as much NA hp. Hopefully, you're hitting the full shot right at the line and have the suspension/tires to hold it......and your 60' times will see the benefit of the bigger shot.
Last edited by bowtienut; Jan 24, 2010 at 06:52 AM.
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From: colorado springs Elevation: 6035 ft
Good info there for sure. Kind of what I was thinking on the extra 50 shot at my altitude. Sounds like better heads will be needed as well as forged pistons For anything over a 200 shot in my application. And just an
FYI I lose 70 rwhp at my altitude. So on motor I really only make 250rwhp up here in the clouds
FYI I lose 70 rwhp at my altitude. So on motor I really only make 250rwhp up here in the clouds
You say "stock LT1", but your sig says otherwise. ??
Anyway, assuming stock: I think I've pretty much gotten as much as you can get out of a stock LT1 both on and off the jug, 309 STD rwhp thru A4 / 12.3 sec @ 108 NA and 425 STD / 11.33 @ 117 on the 150 shot in a 3900 lb car, so I feel qualified to answer your question.
Short answer: 150 shot
I've not sprayed more than the 150 shot on the dyno, but in two seasons of drag racing with 175 pills, I never surpassed the 60' times, ET's, nor mph of what I previously did with the 150. That tells me the combination of the stock exhaust ports, and more likely the short exhaust event of the stock cam, just doesn't allow the spent mixture to evacuate sufficiently with more than 150 hp added. I posted NA results above also to show that the engine was truly optimized NA before adding the spray. If you have an engine that dynos much lower than that NA, then you may possibly get results from a bigger shot, but I've yet to see that on anybody else's car either; in fact, if an exhaust restriction is holding you back, then it surely will not respond to more than a 150 shot. BUT.....here's another variable: the Fbody cam's earlier exhaust opening than my B-body cam in theory should allow for better exhaust evacuation, so you might see results from a 175 shot that I didn't see. But I'm betting 175 is your limit of seeing any further results. No way is a 200 shot going to be beneficial in a stock LT1.
Now for the other scenario: you list a Hotcam in your sig. The significantly longer exhaust event of that cam would make more power with a 200 shot; HOWEVER, IF you have the car tuned well NA, with good breathing intake and exhaust, then you're going to surpass the cylinder pressure and top ring temp of what the stock short block will tolerate when you add more than 150 hp to an optimized NA hp number,...let's say about 340 rwhp NA. So again, the answer to your original question comes back to........150 shot.
Backup data point: a guy who has been racing heads/cam stock shortblock motors for years has had his motors survive very well on a 150 shot, but has yet to make more than two race weekends in a row when spraying 175 or more....end result has been either broken piston tops or pounded out/spun rod bearings.
Edit: After posting, I saw your sig, that you're at 6000 feet. Adjust my recommendation upward by 25 hp shot for sure, and by 50 hp on a warm day when you're not making as much NA hp. Hopefully, you're hitting the full shot right at the line and have the suspension/tires to hold it......and your 60' times will see the benefit of the bigger shot.
Anyway, assuming stock: I think I've pretty much gotten as much as you can get out of a stock LT1 both on and off the jug, 309 STD rwhp thru A4 / 12.3 sec @ 108 NA and 425 STD / 11.33 @ 117 on the 150 shot in a 3900 lb car, so I feel qualified to answer your question.
Short answer: 150 shot
I've not sprayed more than the 150 shot on the dyno, but in two seasons of drag racing with 175 pills, I never surpassed the 60' times, ET's, nor mph of what I previously did with the 150. That tells me the combination of the stock exhaust ports, and more likely the short exhaust event of the stock cam, just doesn't allow the spent mixture to evacuate sufficiently with more than 150 hp added. I posted NA results above also to show that the engine was truly optimized NA before adding the spray. If you have an engine that dynos much lower than that NA, then you may possibly get results from a bigger shot, but I've yet to see that on anybody else's car either; in fact, if an exhaust restriction is holding you back, then it surely will not respond to more than a 150 shot. BUT.....here's another variable: the Fbody cam's earlier exhaust opening than my B-body cam in theory should allow for better exhaust evacuation, so you might see results from a 175 shot that I didn't see. But I'm betting 175 is your limit of seeing any further results. No way is a 200 shot going to be beneficial in a stock LT1.
Now for the other scenario: you list a Hotcam in your sig. The significantly longer exhaust event of that cam would make more power with a 200 shot; HOWEVER, IF you have the car tuned well NA, with good breathing intake and exhaust, then you're going to surpass the cylinder pressure and top ring temp of what the stock short block will tolerate when you add more than 150 hp to an optimized NA hp number,...let's say about 340 rwhp NA. So again, the answer to your original question comes back to........150 shot.
Backup data point: a guy who has been racing heads/cam stock shortblock motors for years has had his motors survive very well on a 150 shot, but has yet to make more than two race weekends in a row when spraying 175 or more....end result has been either broken piston tops or pounded out/spun rod bearings.
Edit: After posting, I saw your sig, that you're at 6000 feet. Adjust my recommendation upward by 25 hp shot for sure, and by 50 hp on a warm day when you're not making as much NA hp. Hopefully, you're hitting the full shot right at the line and have the suspension/tires to hold it......and your 60' times will see the benefit of the bigger shot.
You say "stock LT1", but your sig says otherwise. ??
Anyway, assuming stock: I think I've pretty much gotten as much as you can get out of a stock LT1 both on and off the jug, 309 STD rwhp thru A4 / 12.3 sec @ 108 NA and 425 STD / 11.33 @ 117 on the 150 shot in a 3900 lb car, so I feel qualified to answer your question.
Short answer: 150 shot
I've not sprayed more than the 150 shot on the dyno, but in two seasons of drag racing with 175 pills, I never surpassed the 60' times, ET's, nor mph of what I previously did with the 150. That tells me the combination of the stock exhaust ports, and more likely the short exhaust event of the stock cam, just doesn't allow the spent mixture to evacuate sufficiently with more than 150 hp added. I posted NA results above also to show that the engine was truly optimized NA before adding the spray. If you have an engine that dynos much lower than that NA, then you may possibly get results from a bigger shot, but I've yet to see that on anybody else's car either; in fact, if an exhaust restriction is holding you back, then it surely will not respond to more than a 150 shot. BUT.....here's another variable: the Fbody cam's earlier exhaust opening than my B-body cam in theory should allow for better exhaust evacuation, so you might see results from a 175 shot that I didn't see. But I'm betting 175 is your limit of seeing any further results. No way is a 200 shot going to be beneficial in a stock LT1.
Now for the other scenario: you list a Hotcam in your sig. The significantly longer exhaust event of that cam would make more power with a 200 shot; HOWEVER, IF you have the car tuned well NA, with good breathing intake and exhaust, then you're going to surpass the cylinder pressure and top ring temp of what the stock short block will tolerate when you add more than 150 hp to an optimized NA hp number,...let's say about 340 rwhp NA. So again, the answer to your original question comes back to........150 shot.
Backup data point: a guy who has been racing heads/cam stock shortblock motors for years has had his motors survive very well on a 150 shot, but has yet to make more than two race weekends in a row when spraying 175 or more....end result has been either broken piston tops or pounded out/spun rod bearings.
Edit: After posting, I saw your sig, that you're at 6000 feet. Adjust my recommendation upward by 25 hp shot for sure, and by 50 hp on a warm day when you're not making as much NA hp. Hopefully, you're hitting the full shot right at the line and have the suspension/tires to hold it......and your 60' times will see the benefit of the bigger shot.
Anyway, assuming stock: I think I've pretty much gotten as much as you can get out of a stock LT1 both on and off the jug, 309 STD rwhp thru A4 / 12.3 sec @ 108 NA and 425 STD / 11.33 @ 117 on the 150 shot in a 3900 lb car, so I feel qualified to answer your question.
Short answer: 150 shot
I've not sprayed more than the 150 shot on the dyno, but in two seasons of drag racing with 175 pills, I never surpassed the 60' times, ET's, nor mph of what I previously did with the 150. That tells me the combination of the stock exhaust ports, and more likely the short exhaust event of the stock cam, just doesn't allow the spent mixture to evacuate sufficiently with more than 150 hp added. I posted NA results above also to show that the engine was truly optimized NA before adding the spray. If you have an engine that dynos much lower than that NA, then you may possibly get results from a bigger shot, but I've yet to see that on anybody else's car either; in fact, if an exhaust restriction is holding you back, then it surely will not respond to more than a 150 shot. BUT.....here's another variable: the Fbody cam's earlier exhaust opening than my B-body cam in theory should allow for better exhaust evacuation, so you might see results from a 175 shot that I didn't see. But I'm betting 175 is your limit of seeing any further results. No way is a 200 shot going to be beneficial in a stock LT1.
Now for the other scenario: you list a Hotcam in your sig. The significantly longer exhaust event of that cam would make more power with a 200 shot; HOWEVER, IF you have the car tuned well NA, with good breathing intake and exhaust, then you're going to surpass the cylinder pressure and top ring temp of what the stock short block will tolerate when you add more than 150 hp to an optimized NA hp number,...let's say about 340 rwhp NA. So again, the answer to your original question comes back to........150 shot.
Backup data point: a guy who has been racing heads/cam stock shortblock motors for years has had his motors survive very well on a 150 shot, but has yet to make more than two race weekends in a row when spraying 175 or more....end result has been either broken piston tops or pounded out/spun rod bearings.
Edit: After posting, I saw your sig, that you're at 6000 feet. Adjust my recommendation upward by 25 hp shot for sure, and by 50 hp on a warm day when you're not making as much NA hp. Hopefully, you're hitting the full shot right at the line and have the suspension/tires to hold it......and your 60' times will see the benefit of the bigger shot.
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From: colorado springs Elevation: 6035 ft
So a 250 through a DP wouldnt back up?
I don't understand your term "Back up"...... If you spray a 250-300 shot with those hyperutectic pistons there won't be enough time to "back up"... it'll just BLOW UP....
I've run a 175 shot on a stock motor and it was fine..... Putting a 250 on it would most likely create enough cylinder pressure to overlap your rings and jack some stuff up bad unless your tune was DEAD NUTS on from the beginning.... problem is is that rarely are tuneups that "on" from the beginning.. it would require alot of testing to get it there.... and any mistake would blow the motor up with those cast pistons...
this is all assuming you could even ignite the mixture. Alot of ppl that think they can just put whatever jets in and make it work aren't really understanding how it works.... even aftermarket coils would have trouble keeping up the spark under cylinder pressures created by that much spray. On the 350 shot I run it requires an HVC2 coil, a pro billet distributor, and plug gaps in the .025 area, a crank trigger and the best wires you can get. I think Tony shepherd starting having ignition issues with his coil around teh 275 shot area....
I've run a 175 shot on a stock motor and it was fine..... Putting a 250 on it would most likely create enough cylinder pressure to overlap your rings and jack some stuff up bad unless your tune was DEAD NUTS on from the beginning.... problem is is that rarely are tuneups that "on" from the beginning.. it would require alot of testing to get it there.... and any mistake would blow the motor up with those cast pistons...
this is all assuming you could even ignite the mixture. Alot of ppl that think they can just put whatever jets in and make it work aren't really understanding how it works.... even aftermarket coils would have trouble keeping up the spark under cylinder pressures created by that much spray. On the 350 shot I run it requires an HVC2 coil, a pro billet distributor, and plug gaps in the .025 area, a crank trigger and the best wires you can get. I think Tony shepherd starting having ignition issues with his coil around teh 275 shot area....
So many people here are not getting it. The concern is not the intake port flow.....not by a long shot!!!!! It's all liquid going in there folks. The exhaust is the flow limiter, the "backup" if you wish, when it's all been combusted and is now all gasses.
I see OutlawZ understands the picture. And 96lt1m6 makes a good point about distribution of the fuel through the intake; if it weren't for that problem, and a 200 shot with its fuel actually got divided evenly among the 8 cylinders, then we might not see all the carnage that is typical when going over the 150-175 range.
Don't give me that "wrong" crap; you obviously haven't been there
Don't forget, the OP said stock LT1. To me that means stock pistons and stock ring gaps.
I see OutlawZ understands the picture. And 96lt1m6 makes a good point about distribution of the fuel through the intake; if it weren't for that problem, and a 200 shot with its fuel actually got divided evenly among the 8 cylinders, then we might not see all the carnage that is typical when going over the 150-175 range.
Don't give me that "wrong" crap; you obviously haven't been there
Don't forget, the OP said stock LT1. To me that means stock pistons and stock ring gaps.
Im very curious as well.. I want to put a lil spray on my car but not sure what my limits are.. I assume just throw a 100 shot on it and call it a day. But if a 125 isnt a difference, Ill go with that..
I wanna hear from expereince here...
Kris
I wanna hear from expereince here...
Kris
I think what he is trying to say in the term "Back up" Is like an incidence we had years ago on a carbed small block inhaling a healthy dose of the gas. on the dyno at wot I saw nitrous coming back out of the carb, telling me either it was too much for the set up, ignition ect. Maybe this is what he is saying by back up??
I think thats what hes getting at.^^^ Ive seen guys add an extra 100hp and didnt make any difference on the track. There becomes a point to where the engine just wont except anymore. At What point that is Im not sure.
What I was saying above, and trying to explain why, is that point on a STOCK LT1 is in the 150-175 hp range, depending on if it's the b-body or f-body cam, and depending on how well the engine is tuned and breathing on its own before the nitrous is added. Now, if you're starting with a non-optimized 250 rwhp "stock" LT1 rather than my 305 rwhp "stock" LT1, then sure, you'll see results beyond the 150-175 shot, simply because the engine wasn't pulling good air to start with, and thus the "liquid" atmosphere is more beneficial to it. Kinda like getting more response with an oxygen tube on a 90-yr old on their death bed than you do with the same tube on an athlete.
Fwiw I have seen stock lt1's with stand alone fuel systems run up to a 275 shot. Although the gains are minimal after a 225. So I would say 150-175 max thru the stock fuel system(obviously the pump will need upgraded), 200-225 with a standalone... The rule of thumb is not to spray more than 50% of the engines power na. So if you have 400hp(crank), then 200-225 is about max.