Thoughts on my LT1 Shortcomings
Launching!
Joined: Oct 2011
Posts: 253
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From: CenTex
http://www.ws6project.com/user_stor/...r-injectors-1/ Here's a injector recommendation table
As 96Caprice said:
"Cars are actually quickest when run near max injector duty cycle, the 85% rule is wrong. IF he needed injectors 30lbs would be MORE than enough."
Ask the LT1 Stock Eliminator guys. I know of none (A good friend has one of the fastest on the planet) NHRA Stock Eliminator LT1 cars runing bigger than 30 lbs, and making way more than any "cam only" car, or "cam & head" cars around here. Or 95% of the built engines for that matter.
Higher fuel pressure atomizes the fuel better, making more power than larger injectors. I have proved this multiple times on my dyno. Stock 24lb Injectors at 60 psi are 28 lbs. Lots of 400 rwhp LS1s running around with stock 28 lb injectors. I'm at 600 hp with 36lb. plenty of injector.
"Cars are actually quickest when run near max injector duty cycle, the 85% rule is wrong. IF he needed injectors 30lbs would be MORE than enough."
Ask the LT1 Stock Eliminator guys. I know of none (A good friend has one of the fastest on the planet) NHRA Stock Eliminator LT1 cars runing bigger than 30 lbs, and making way more than any "cam only" car, or "cam & head" cars around here. Or 95% of the built engines for that matter.
Higher fuel pressure atomizes the fuel better, making more power than larger injectors. I have proved this multiple times on my dyno. Stock 24lb Injectors at 60 psi are 28 lbs. Lots of 400 rwhp LS1s running around with stock 28 lb injectors. I'm at 600 hp with 36lb. plenty of injector.
The charts you are referencing are SALES TOOLS not legitimate information charts.
People think running an injector at 100%DC will hurt it but in the course of a say 12 second 1/4 mile run the injector would only hit peak at the top of each gear, spending maybe a second or so at a time near 100%. If that were damaging then how on earth can they survive flow testing?
Plus there is a nice cooling flow of fuel going through.
Maybe YEARS ago when injector technology was newer running injectors at 100% damaged them but it is not the case with LT1 and newer stuff.
The charts you are referencing are SALES TOOLS not legitimate information charts.
People think running an injector at 100%DC will hurt it but in the course of a say 12 second 1/4 mile run the injector would only hit peak at the top of each gear, spending maybe a second or so at a time near 100%. If that were damaging then how on earth can they survive flow testing?
Plus there is a nice cooling flow of fuel going through.
Maybe YEARS ago when injector technology was newer running injectors at 100% damaged them but it is not the case with LT1 and newer stuff.
People think running an injector at 100%DC will hurt it but in the course of a say 12 second 1/4 mile run the injector would only hit peak at the top of each gear, spending maybe a second or so at a time near 100%. If that were damaging then how on earth can they survive flow testing?
Plus there is a nice cooling flow of fuel going through.
Maybe YEARS ago when injector technology was newer running injectors at 100% damaged them but it is not the case with LT1 and newer stuff.
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Thread Starter
Staging Lane
Joined: Dec 2013
Posts: 59
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I have not calculated it, I'm going off of what Boyettes told me after they did machine work on the block and heads. I believe he calculated it using the deck height, bore, stroke, HG thickness and head volume and said it was right around 12:1. The engine on a compression test does right about 195psi. I cant remember how much the pistons weigh, I did weight them though but just to make sure they all weighed the same. I got the car dyno'd with open headers and 1ft extensions on the header tubes to get better O2 readings. Ive got a custom welded Y on the car now with a bullet muffler.
195 psi is not much if you held the throttle wide open like you are supposed to, unless you have a very BIG cam, or somebody installed it in a retarded position for some reason.
Those 12" header extensions aren't likely doing your hp numbers any good. They will only help your O2 readings at idle, part throttle and lower RPM. WOT above 2500 or so, they won't help.
Open headers makes your power numbers look even worse. Hope you find your problem. Sure can be frustrating.
Those 12" header extensions aren't likely doing your hp numbers any good. They will only help your O2 readings at idle, part throttle and lower RPM. WOT above 2500 or so, they won't help.
Open headers makes your power numbers look even worse. Hope you find your problem. Sure can be frustrating.
Cam affects cranking compression but for comparison a stock LT1 will often crank more than that, I have checked compression on a 185K mile stock Caprice engine which is 10:1 and come up with 185-190, believe f-body motors usually crank 200-210. The aftermarket cam would tend to lower that number but you would expect the point and a half of static compression to make it back up, my two heads/cam setups cranked 230 and 245 both custom grinds with fairly different specs than the 306.
The pistons probably weighed 600grams or so, that sound ballpark? Stock is about 530 if memory serves.
Stock crank is great money spent on a forged 3.48 stroke crank is a pretty poor choice unless the crank has some other advantage like lighter weight and a stocker would have saved even more money by being easier to balance.
If the 320rwhp was near accurate any decent catback isn't going to cost you much power, the wide LSA of that cam wont make it terribly exhaust sensitive.
Get the tranny fixed and take it to the track, if it runs say 106mph you will know the dyno test was in the ballpark and it it runs say 113 you will have an indication the tranny was slipping hurting the dyno number a lot.
ET can vary dramatically with the launch but MPH while it will vary a little is far more consistent with a good or bad launch.
The pistons probably weighed 600grams or so, that sound ballpark? Stock is about 530 if memory serves.
Stock crank is great money spent on a forged 3.48 stroke crank is a pretty poor choice unless the crank has some other advantage like lighter weight and a stocker would have saved even more money by being easier to balance.
If the 320rwhp was near accurate any decent catback isn't going to cost you much power, the wide LSA of that cam wont make it terribly exhaust sensitive.
Get the tranny fixed and take it to the track, if it runs say 106mph you will know the dyno test was in the ballpark and it it runs say 113 you will have an indication the tranny was slipping hurting the dyno number a lot.
ET can vary dramatically with the launch but MPH while it will vary a little is far more consistent with a good or bad launch.
Thread Starter
Staging Lane
Joined: Dec 2013
Posts: 59
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Working on getting a custom kit put together by Dana and hopefully rebuild it sometime next week. Ill get back with track results after I get some tires that are worth a damn. As for the compression, I dont know. Im just going off what my machine shop told me. Between the 2 of those guys they have over 80 years experience so I trust their work. I'm eventually planning on spraying it into the 11's with the help of a N20 Outlet LT1 plate kit. Any of you GM Lt1 engineers have anything I need to be aware of/precautions?
Thing is if you had done good heads and cam on a decent condition stock shortblock it would run 11s NA in a reasonably setup street car.
Doing things "inexpensively" often costs a whole lot more in the end. A well done 355 or rather 357 with the .040 bore should need a rollbar in good weather NA in a street car.
Far as the nitrous how much do you plan to spray? Just enough to get into the 11s or are you thinking 200hp worth? The more you spray the harder it is to keep balanced when spraying this intake from the front, more than a few LT1s have fragged #1 or #2 when sprayed hard from the front because the fuel can't make the downward turn to those cylinders as well as the nitrous can and BOOM. A LOT of guys have hit LT1s with 150 or so for a long time successfully if tuned well.
I would look at a Mallory 685 box for spark based rev limit, on demand timing retard, and window switch functions.
Doing things "inexpensively" often costs a whole lot more in the end. A well done 355 or rather 357 with the .040 bore should need a rollbar in good weather NA in a street car.
Far as the nitrous how much do you plan to spray? Just enough to get into the 11s or are you thinking 200hp worth? The more you spray the harder it is to keep balanced when spraying this intake from the front, more than a few LT1s have fragged #1 or #2 when sprayed hard from the front because the fuel can't make the downward turn to those cylinders as well as the nitrous can and BOOM. A LOT of guys have hit LT1s with 150 or so for a long time successfully if tuned well.
I would look at a Mallory 685 box for spark based rev limit, on demand timing retard, and window switch functions.
Thread Starter
Staging Lane
Joined: Dec 2013
Posts: 59
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150 would be about the maximum I would spray... no sense in spraying the extra 50. Not like the extra 50 is gonna take me from high 10s into the 9s. I would undoubtably be utilizing a window switch to keeping from blowing the tires off and from damaging in the event of a broken rear or similar. Does that Mallory box have built in ondemand timing retard?
Thread Starter
Staging Lane
Joined: Dec 2013
Posts: 59
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With a correctly setup suspension, (e.g., Adj. LCA's w/ Relocation brackets, Adjustable Tq Arm, Anti-roll, Good shocks & springs on all 4 corners and a good set of tires) assuming everything was set up the way it should be for optimal performance what do you think a motor like mine (mediocre, yeah thanks I really appreciate it..) spraying 150 could go in the 1/4? Yeah I know there are a ton of different variables to take into account, altitude (im 400 above sea), weight and ect. the list could go on for days. Perhaps you know the know the best time of a friend with a stock bottom end, lightly worked heads, decent size cam and a 150 shot? Just trying to get an idea. I'm well aware anything 11.49 or faster needs a roll bar. You wouldn't happen to know out of the suspension pieces I mentioned above, which ones are a must and which ones are a so/so in importance on a car at my power level. I know tires are obviously a must. Sorry for getting so side tracked on a thread, I just feel like its more efficient than opening another thread in drag racing suspension sub-forum just for a specific horsepower range.
TECH Regular
Joined: Sep 2003
Posts: 442
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From: Raleigh, NC
Assuming you'd spray it to around 500rwhp, my guess is bottom 11s to high 10s depending on how well it hooks.
None of the tracks tech around here for TnT sessions so you don't really have to worry about a roll bar. I've seen people running 11s and 10s with no helmet on many times.
None of the tracks tech around here for TnT sessions so you don't really have to worry about a roll bar. I've seen people running 11s and 10s with no helmet on many times.
MIR will kick you out if you go under 11.5 without a roll bar, but don't care if you stay high 13s with no helmet. A properly built heads/cam 350-357 with some weight reduction can see high 10s, vtec was down to what, high 8s or low 9s on a 200 shot on a stock bottom end?
I agree with quik95, take it to the track to see how botched it is. It's really easy to screw up these heads, I bought mine super cheap which are home ported, and though the runners and valves are huge, they may be only worth the springs (which is what I paid). Size doesn't matter, it's the motion of the ocean, at least that's what my wife tells me, even though it takes a long time to get to England in a row boat.
I agree with quik95, take it to the track to see how botched it is. It's really easy to screw up these heads, I bought mine super cheap which are home ported, and though the runners and valves are huge, they may be only worth the springs (which is what I paid). Size doesn't matter, it's the motion of the ocean, at least that's what my wife tells me, even though it takes a long time to get to England in a row boat.
Thread Starter
Staging Lane
Joined: Dec 2013
Posts: 59
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Only problem is tracks around here don't open up until March. Its running pretty rich, blowing plenty of black smoke. Once I get the trans worked out ill probably take it back to the tuner, there was only so much he could do at the time because there was no exhaust on it.
