Stock motor vs iat vs #boost

I plan on boosting the caprice very soon (stock motor). I measured the nose of the car and will easily be able to fit the 33" X 12" X 4" intercooler from vsracing. Along with some meth/h20 my iats should be reasonably cool. Even close to ambient as long as I’m not loading the car up or doing highway runs. Now here is the real question......

If the iats are kept as low as possible, and the tune is conservative, and the pcv system is done well, plenty of fuel etc what causes the hypereutectic pistons to take a poo? Any little detonation? Is it the heat from the increased backpressure in the exhaust?

How do i keep the ring lands intact?

I want to make boosting the stock motor as safe as possible. Hopeing i can get her to live at 5 lbs around town and 8-9 lbs when racing.

Any other sugestions?

I have read on a stock lt1 4psi is max to play it safe but i have seen other say 6 to 7 psi but the more boost the more short lived the lt1 becomes.

good luck

I was running 9Psi just fine until one cold night I got a 11Psi spike. Bye bye ring lands on three pistons ;)

Many have ran 6-7Psi for years. Some have ran as high as 12Psi for a long time. There is no telling how they drove them though.

Back when I was running 9Psi on my Stock engine we had no tuning tools. I was running nothing more then a MAF Translator and a FMU:D

When I was running 14Psi I just added 36Lph injectors.

My how things have changed!

I could see alot more then I was running then today very safely. A nice safe tune with lots of extra fuel under boost.

So for a good "tune up" I would imagine ngk tr6's or autolite 103's gapped at 0.035". Would an even colder plug help prevent detonation more?

What sort of a/f ratio am I looking at to be "safe" 11.1:1-11.7:1 ?
What sort of timing should I start at when under boost? What should the timing peak at (basically what sounds like too much timing at x rpm)? Should I back off 8-10 degrees across the board in the boosted section then add degree by degree till I start getting knock retard? Or should i pull 8-10 degrees for 1-6 psi then 10-18 degress for 6-12 psi? Do the timing curves "ramp" the same way? I was thinking timing should peak a little after peak tq then be pulled 1 degree for every 500rpm

I’m trying to understand what the order of operations on tuning the setup is. Offset stock tables for 2 bar -> remove 10 degrees of timing in boost -> set boost level -> dial in a/f ratio -> bump timing slowly till the slightest amount of knock retard is apparent? Then back off 2 degrees?

This is gonna be a lot of fun!!! :D :D

the only way i would everf run more than 7psi on a stock motor is with race gas. And i mean c16 or 110 octane. The hyper POS pistons do not tolerate anything so when you said consertative tune i hope you mean just that.
The h20/meth and fmic are going to be whats saving you. But that isnt going to do much without very good tuning. Which i think will be what determines the life of your stock shortblock.
If you have any money that could be put towards heads you would make your situation a thousand times better. A set of out of the box tfs's would put your stock motor around 9.3.1-9.5.1 i think? But whatever it is its going to be much better than the stock 10.4.1. good luck your going down a risky road

I would prefer not to pull the heads. If im pulling the heads off the whole motor is going to be done from the bottom up.

I guess you could say.... what is a conservative tune?

Are those plugs mentioned above appropriate or should i go colder? is 11.1:1-11.7:1 where i want to be? What kind of numbers am i looking at for timing(to be safe).

Well you asked, so I will give you my take on your situation;

You follow many others that want to "boost" a stock motor. The absolute safest way to do it is to run race gas with a big intercooler and not much boost. 4-6#'s would be the max I would ever run on a stock motor. Bare minimum, you'll need methanol if you can't run race gas on every tank. Even then, you'll also need the other supporting mods such as ignition, fuel upgrades like injectors, fuel pump, dyno tune, ect. ect., this is all to say nothing about the actual head unit (blower) you decide to run. All and all I never understood the logic, because as it sits to make it "as safe as possible boosting a stock bottom end", you're gonna be out probably around $7,000 and for what? 4-6#'s of boost ain't gonna give you much extra power. Not the kind thats gonna throw you back in your seat like never before. And even then, over time, you will put more wear on the engine than if you were to stay N/A, and its only a matter of time before even 6#'s takes something out on the stock non-forged internals.

It's much more cost effective to just stay N/A and go with a killer heads/cam/intake combo. It will cost you a fraction of the price going boosted would, and you'd probably end up with the same if not more power.

If you wanted more power, and don't mind risking the stock motor, and don't want the cost of being boosted, you could always buy a nitrous kit. This would at least be cheeper, and will do the same damage boost would to the stock internals with high CR.

If you are dead set on going boosted, why not just do it right? The only way you know you will be 100% safe is if you take the stock motor out, and build it for boost with a lower CR, and forged internals. You'll still need all the supporting mods you'd need before, but now by having the engine that can withstand safely 18+#'s of boost you can have a reliable monster.

It's by no means cheep to do. You can save some money by buying the cheeper parts like "Summit" or "Eagle", or you can get the bulletproof stuff like "Lunati" and "Oliver" like I did. Even if you went with the cheeper parts, all said and done with all the supporting mods, engine work, tune, you're gonna be in the $17,000+ range. This is all to say nothing that the added power will require a stronger tranny or clutch, better driveshaft, rear end, and if you want to be able to use the power, suspension.

It's not cheep to be boosted and have it done right, thats why you don't see every other modded LT1 with a blower on them. Thats why many people such as yourself try to go the "cheep route" by boosting the stock motor. IMO, its just not a good idea, as you will be out thousands, and it will no longer be reliable unless you run next to no boost, and then with what little extra power it will actually give you for the money invested, whats the point?

If you don't care about the engine, and just want cheep un-reliable power, then run more than 6#'s. You might be lucky like some and make it 25,000 miles before a rebuild is in your future, or you might not make it to 2500 miles before something goes "BOOM". But then you will have a fast car for cheep (just not for long).

The car is already setup 60# mototron injectors, aeromotive fuel system, built tranny, built rear.

I understand were i am going, Ive always wanted a turbo. I will eventually build the motor.

I UNDERSTAND ALL THE RISKS!!! Everyone just seems deadset on trying to talk me out of it. The piping is already done. all i need to know is

WHAT a/f ratio, what plugs, and what kind of timing am i looking at

None of what we do here is cheap. Even with the very best parts and tunes there are failures ;)

Hell I made 602RWHP and 780Tq with only seven cylinders. . .

Well you asked, so I will give you my take on your situation;

You follow many others that want to "boost" a stock motor. The absolute safest way to do it is to run race gas with a big intercooler and not much boost. 4-6#'s would be the max I would ever run on a stock motor. Bare minimum, you'll need methanol if you can't run race gas on every tank. Even then, you'll also need the other supporting mods such as ignition, fuel upgrades like injectors, fuel pump, dyno tune, ect. ect., this is all to say nothing about the actual head unit (blower) you decide to run. All and all I never understood the logic, because as it sits to make it "as safe as possible boosting a stock bottom end", you're gonna be out probably around $7,000 and for what? 4-6#'s of boost ain't gonna give you much extra power. Not the kind thats gonna throw you back in your seat like never before. And even then, over time, you will put more wear on the engine than if you were to stay N/A, and its only a matter of time before even 6#'s takes something out on the stock non-forged internals.

It's much more cost effective to just stay N/A and go with a killer heads/cam/intake combo. It will cost you a fraction of the price going boosted would, and you'd probably end up with the same if not more power.

If you wanted more power, and don't mind risking the stock motor, and don't want the cost of being boosted, you could always buy a nitrous kit. This would at least be cheeper, and will do the same damage boost would to the stock internals with high CR.

If you are dead set on going boosted, why not just do it right? The only way you know you will be 100% safe is if you take the stock motor out, and build it for boost with a lower CR, and forged internals. You'll still need all the supporting mods you'd need before, but now by having the engine that can withstand safely 18+#'s of boost you can have a reliable monster.

It's by no means cheep to do. You can save some money by buying the cheeper parts like "Summit" or "Eagle", or you can get the bulletproof stuff like "Lunati" and "Oliver" like I did. Even if you went with the cheeper parts, all said and done with all the supporting mods, engine work, tune, you're gonna be in the $17,000+ range. This is all to say nothing that the added power will require a stronger tranny or clutch, better driveshaft, rear end, and if you want to be able to use the power, suspension.

It's not cheep to be boosted and have it done right, thats why you don't see every other modded LT1 with a blower on them. Thats why many people such as yourself try to go the "cheep route" by boosting the stock motor. IMO, its just not a good idea, as you will be out thousands, and it will no longer be reliable unless you run next to no boost, and then with what little extra power it will actually give you for the money invested, whats the point?

If you don't care about the engine, and just want cheep un-reliable power, then run more than 6#'s. You might be lucky like some and make it 25,000 miles before a rebuild is in your future, or you might not make it to 2500 miles before something goes "BOOM". But then you will have a fast car for cheep (just not for long).

The car is already setup 60# mototron injectors, aeromotive fuel system, built tranny, built rear.

I understand were i am going, Ive always wanted a turbo. I will eventually build the motor.

I UNDERSTAND ALL THE RISKS!!! Everyone just seems deadset on trying to talk me out of it. The piping is already done. all i need to know is

WHAT a/f ratio, what plugs, and what kind of timing am i looking at

Well if you didn't want that info, you probably should not have named your thread "Stock motor vs iat vs #boost". If you would have named it "what a/f ratio, plugs and timing to run" then you may have gotten more specifically what you were looking for.

We are not trying to talk anyone out of being boosted. We are mearly making sure that people who think about going boosted with the stock engine know all the risks (because there are plenty). That way when they do go boosted on the stock motor, and fry a piston before their next oil change at least they knew what they were getting into.

I blew up my stock motor after about 8 months with a powerdyne 4.5 psi kit. I had all the supporting mods and a dyno tune. Finally a head gasket went and the coolant slowly filled my oil pan. With the new motor and same boost set up I'm pulling around 110 degree Fahrenheit IATs on a 75 degree day at WOT.

NGK TR55s would be a good plug for that heat range. They come gapped to .35 which is a good start for a boosted motor. Timing and A/F I would have done on the dyno, because I wouldn't trust myself doing that. Hope this helps.

-Pete-

i would try to find a baseline tune arond here or on www.forcedinductions.com or maybe even at ls1tech.com. The plugs should be okay and gapped a .035 to start. As for the a/f, same deal ask around or find someone who has already done it. 11.5.1 i would think would be a good starting point. They will be able to speak from experience, which i cannot.
Mainly and above all you need to get the car on a dyno. You need to know whats exactly going on to make sure its going to last 20 min being boosted. Otherwise you could end up like many who only made it a thousand miles before their rebuild. I think after everybody being all over you about you initial boost levels you ll bring them down to start. Than once you have it tuned properly and have an extra shortbock you can push it to 8, 10psi. good luck

Anyone have any suggestions for how much timeing i should pull? And were i should pull it?

Anyone have any suggestions for how much timeing i should pull? And were i should pull it?
It's not about how much you pull, but how much timing you're running. I'm going to start at 16 with my built motor to get my AFR right. Probably only go up a couple degrees from there, I want to keep mine really safe on the streets.

cause4panic:
My boost is quite mild. I'm planning to limit my advance at high rpm & map to the mid or low 20s. I think people are reluctant to give specific answers because the serious players have lots of dyno time and money invested in getting it right. ISTR reading some suggestions of pulling at least 2 degrees of advance for every pound of boost above an NA motor at the upper end.

I will give you one part. Make SURE you adjust the Minimum advance tables. You can fill the other tables with what ever you want if the Min table is not adjusted you will get what ever is in them. Cost me a head gasket to find those tables.
http://i7.photobucket.com/albums/y294/picsaplenty/OUCH/07Sept04025.jpg

I would say that most people who have tried to boost a stock engine have failed, including myself. I ran the d1sc with twin highflows at 8 psi, ran for a few months real hard, then the rings got tired and lost compression in a coupple of cylinders. My advise is do it right and buid the damn motor...because you will be doing it soon if you arent carefull.

OneFlyn95z28:

Thanks for the tip.

Anyone have any suggestions for how much timeing i should pull? And were i should pull it?

cause4panic:
My boost is quite mild. I'm planning to limit my advance at high rpm & map to the mid or low 20s. I think people are reluctant to give specific answers because the serious players have lots of dyno time and money invested in getting it right. ISTR reading some suggestions of pulling at least 2 degrees of advance for every pound of boost above an NA motor at the upper end.

People aren't reluctant to give specific answers on timing, people don't want to throw out a specific number because it is such a huge variable. Timing is something that needs to be adjusted as you are doing your tuning. What I am running for timing, is probably not even close to what you will be needing to run timing wise. It needs to be done with the tuning to where the car is specifically. Only then you can advance or retard the timing to make your adjustments to the ideal setting. Any good tuner will do this for you.

Unless you have lots of experience with tuning FI LT1's, I would strongly reccomend leaving the tuning to the experts like Bryan Herter at PCM's for less. Then you can leave all the timing and fine adjustments you'll need to make up to the pro, and you'll know its a good tune.

Really good replies guys, much appreciated. one flyn z thanks for the advice on the min tables. call 911 thanks for the advice aswell.

so im gonna try to get my a/f r's in the low 11's and retard the timing to all hell. Im just worried that pulling the timing down to 16 deg or so will raise my egts up very high.

How can i tell what the engine "wants" besides experimenting? or looking at other peoples tunes.

So i believe end of this week (pay week) i will be ordering the mpt70 and that big ace intercooler. Sill need to get a new spring for the wastegate since its a 9 lb spring currently. Can anyone reccomend a good meth/h20 kit? Im gonna need to drench the pistons in water/meth to keep these things alive.

BTW i dont know how you guys drive your cars but i can tell you that i drive like a fricking grandmother unless the pedel is to the floor(maybe a handfull of times a weekend). There are weeks were i dont even floor the car!!!! Being in queens with anything that makes noise or even looks like it goes fast gets WAAAAYY to much attention from the cops.

again guys thanks for the help. Once i start getting parts in i will be doing a build up thread.

Like I said before, unless you have lots of experience tuning FI LT1's, I would leave the tuning up to someone who knows what they are doing there, as it is fairly difficult to get a sound tune on a FI LT1, given the fact the MAF usually maxes out after a while, and we only have 1 bar MAP sensors.

If you get a FAST XFI setup with maybe a wideband 02 sensor, and have lots of good experience using it, a good tune can be performed yourself, but I can't stress enough that you should spend the $ and get a good tuner to tune the car.

BTW, I am running a Snow Performance meth injection kit with great success. Most people go with either Alky Control's kit or Snow Performance (both are great). There are other kits available like Devils own, and AIS.

Thanks for the suggestion on the meth/h20 thing. That’s another question in my mind. Do I want to run straight meth or a 50/50 water meth mix? I’m pretty sure straight meth would make more power, but in my mind a 50/50 mix would produce more of a cooling effect (save the pistons) by introducing an inert fluid like water. Slowing the flame propagation also effectively reduces the overall timing.

I have a wideband and tuner cat, I don’t want to sound or act stubborn but the thing I enjoy most about modifying anything is the satisfaction of doing it yourself. Likewise i am fairly familiar with the software and capable of logging the wideband via a/c input and plotting a/f vs rpm in excel etc etc.... If I was doing this for the final outcome I would just buy a vette and call it a day although I do appreciate you warning me about the importance of a good tune. The car will be tuned in speed density with a two bar map sensor and all changes will be done in very small increments. We all have to get our start somewhere and if this costs me a stock motor thats gonna get rebuilt anyway so be it.

But i REALLY REALLY appreciate all the help, if anyone has any suggestions i am all ears.

Thanks for the suggestion on the meth/h20 thing. That’s another question in my mind. Do I want to run straight meth or a 50/50 water meth mix? I’m pretty sure straight meth would make more power, but in my mind a 50/50 mix would produce more of a cooling effect (save the pistons) by introducing an inert fluid like water. Slowing the flame propagation also effectively reduces the overall timing.

I have a wideband and tuner cat, I don’t want to sound or act stubborn but the thing I enjoy most about modifying anything is the satisfaction of doing it yourself. Likewise i am fairly familiar with the software and capable of logging the wideband via a/c input and plotting a/f vs rpm in excel etc etc.... If I was doing this for the final outcome I would just buy a vette and call it a day although I do appreciate you warning me about the importance of a good tune. The car will be tuned in speed density with a two bar map sensor and all changes will be done in very small increments. We all have to get our start somewhere and if this costs me a stock motor thats gonna get rebuilt anyway so be it.

But i REALLY REALLY appreciate all the help, if anyone has any suggestions i am all ears.


Water/methanol mix vs straight methanol is really up to you. People will argue which is better mix wise, but both have been used successfully, and honestly niether will yeild you more noticable power over the other. I am running a 50/50 water meth mix, but know several others running straight meth with good results as well. The deciding factor for me was that having a water/meth mix was cheeper than running all meth, and running 100% methanol is much harder on your system and will corrode more (and possibly take out the pump earlier).

As for the tuning, at least you understand what the risks are. You can have a fully bullet proof built motor setup to withstand tons of boost and power, but if the tune is not done properly, it can go "BOOM" just as soon as a stock motor with mild boost with a bad tune. Tuning is everything. Hopefully you get to learn a bit before you be in need of a new engine.

Ok so just as a recap to this point

autolite 103's gapped at 0.035"
keep the boost low
2 bar sd tune
50/50 meth/h20
big intercooler
low 11:1 a/f ratio


But im still unsure on the precautions on timing. Should the engine never see more then 16deg advance? Should the timing peak at peak tq then start retarding towards redline?

please enligten me guys or send me a tune to look at
cause4panic@gmail.com

thank you all

Ok so just as a recap to this point

autolite 103's gapped at 0.035"
keep the boost low
2 bar sd tune
50/50 meth/h20
big intercooler
low 11:1 a/f ratio


But im still unsure on the precautions on timing. Should the engine never see more then 16deg advance? Should the timing peak at peak tq then start retarding towards redline?

please enligten me guys or send me a tune to look at
cause4panic@gmail.com

thank you all

I would reccomend sticking with a MAF personally, but others have successfully done the SD tune. Most FI guys go a little leaner like 11:5 on the wideband. As for timing, I keep telling you we can't give you good figures as it differs from car to car and setup to setup. My timing won't be what your timing is as we don't have the same setup. If you want more guesses on it, I reccomend shooting the question up in the tuing section of the board.

well thanks to all who helped. build thread soon to come.