5.7 to 383 tuning question
03-17-2015, 08:16 AM
#1
5.7 to 383 tuning question Looking for some tuning guidance.
I have a 5.7 LT1 with a vortech s trim V1 supercharger, ported heads, blower cam, 42# injectors, etc that was custom tuned and ran great. Block is cracked and I just came across a fresh built 383 long block that I can get for about the same price as building a new 5.7 short block.
If I were to move all the parts from the 350 over to the 383 including the cam, using tunercats is there just a cylinder volume change to be made or will all parameters be thrown off by the change in displacement? Or no change needed at all?
Thanks for any help, I had posted this in the PCM tuning section but so far no response. I am not ready to move to the LS platform yet, I still have a bunch of LTs on the shelf and they have worked fine for me.
I have a 5.7 LT1 with a vortech s trim V1 supercharger, ported heads, blower cam, 42# injectors, etc that was custom tuned and ran great. Block is cracked and I just came across a fresh built 383 long block that I can get for about the same price as building a new 5.7 short block.
If I were to move all the parts from the 350 over to the 383 including the cam, using tunercats is there just a cylinder volume change to be made or will all parameters be thrown off by the change in displacement? Or no change needed at all?
Thanks for any help, I had posted this in the PCM tuning section but so far no response. I am not ready to move to the LS platform yet, I still have a bunch of LTs on the shelf and they have worked fine for me.
03-17-2015, 10:13 AM
#4
Both blocks are .030 over, so 4.030 bore. Pistons in both engines are similar, but different MFG, both are 31cc dish (JE in the cracked 350, Mahle in the 383) with 58cc chambers, 1074 felpro head gaskets, so assuming around 9:1 compression.
Last edited by drptop70ss; 03-17-2015 at 10:19 AM.
03-17-2015, 04:59 PM
#7
TECH Addict
It WILL be different between the two. The 383 WILL have a higher static CR. the piston is traveling further down the bore and further up. So it's drawing in more air and squeezing it more. Do the math and make sure is still safe for your blower.
I know if all I changed was the stroke on my 355 to a 383 my SCR will go from 11.8 to over 13.
A complete retune should be in order. Start with volume constants the adjust VE and spark. The 383 will have different VE curve than the 355 with the same cam and heads.
I know if all I changed was the stroke on my 355 to a 383 my SCR will go from 11.8 to over 13.
A complete retune should be in order. Start with volume constants the adjust VE and spark. The 383 will have different VE curve than the 355 with the same cam and heads.
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03-17-2015, 06:00 PM
#9
My mistake picked the wrong line on the JE page, the 5.7 pistons are actually 24cc dish, but still the same 9:1 as the 383 with the -31cc.
The piston choice is already made for me, so 9:1 is what I have to work with, I think that should be fine. No racing with this one, just street duty in a 1951 ford pickup. Not sure how much boost the vortech will put out, it has the purple pulley but I dont remember the diameter offhand. Supposedly this engine put out 542HP to the wheels while in the 95 camaro I pulled the engine from.
So if I do nothing but change from a 5.7 to a 383 using all the other 5.7 parts I should do the cylinder volume change and then will need to get re-tuned.
Will the engine run well enough to drive with just the cylinder displacement change? I have tunercats but will have to learn to do the tuning, I would rather learn to do it myself.
The piston choice is already made for me, so 9:1 is what I have to work with, I think that should be fine. No racing with this one, just street duty in a 1951 ford pickup. Not sure how much boost the vortech will put out, it has the purple pulley but I dont remember the diameter offhand. Supposedly this engine put out 542HP to the wheels while in the 95 camaro I pulled the engine from.
So if I do nothing but change from a 5.7 to a 383 using all the other 5.7 parts I should do the cylinder volume change and then will need to get re-tuned.
Will the engine run well enough to drive with just the cylinder displacement change? I have tunercats but will have to learn to do the tuning, I would rather learn to do it myself.
Last edited by drptop70ss; 03-18-2015 at 02:40 PM.
03-18-2015, 03:26 AM
#10
TECH Addict
Yes. The curve will move down. It'll act like the 355 at higher rpms. So you'll have to increase the VE tables to match (move them up at lower rpms). It's not a straight across move. Do your volume change then data log and tune your VE tables according to the LT blms in your data logs. Not much to learn. If you have a MAF tune it'll run fine with the occasional hiccup here and there until you fix your VE tables.
You will need a wide band o2 to tune your PE tables.
You will need a wide band o2 to tune your PE tables.
03-18-2015, 09:35 AM
#11
LT1 PCMs, unless put into Speed Density mode, pretty much ignore the VE tables. Scaling them up is a good idea, in case you have a MAF failure. Changing the Cylinder Volume pretty much only effects start up. The LS PCMs, and Vortec truck PCMs do use VE tables in normal MAF mode.
03-18-2015, 02:38 PM
#12
Yes. The curve will move down. It'll act like the 355 at higher rpms. So you'll have to increase the VE tables to match (move them up at lower rpms). It's not a straight across move. Do your volume change then data log and tune your VE tables according to the LT blms in your data logs. Not much to learn. If you have a MAF tune it'll run fine with the occasional hiccup here and there until you fix your VE tables.
You will need a wide band o2 to tune your PE tables.
You will need a wide band o2 to tune your PE tables.
LT1 PCMs, unless put into Speed Density mode, pretty much ignore the VE tables. Scaling them up is a good idea, in case you have a MAF failure. Changing the Cylinder Volume pretty much only effects start up. The LS PCMs, and Vortec truck PCMs do use VE tables in normal MAF mode.
I am new to tuning other than changing fan temps, speedo settings, VATS, etc, I have only done the basics, so any help is appreciated.
FYI also had another variable thrown in, when tearing down the 5.7 to salvage the lower end parts I found the cam to be badly pitted on a lot of the lobes so I cannot use it in the 383. None of the lobes looked flat, but the pitting is disappointing since the engine only had 20K miles on it. Cam is a comp custom grind with 215/220 @.050 and 114 lobe separation. Pretty close to the LT1 266HR-14 which is a pretty mild cam. Anyone think I could step up to the LT1 276HR-14 with the blower and not be blowing the boost out the exhaust? Numbers are 220/230@.050 and 114 lobe separation.
Last edited by drptop70ss; 03-18-2015 at 03:44 PM.
03-18-2015, 03:57 PM
#13
TECH Addict
LT1 PCMs, unless put into Speed Density mode, pretty much ignore the VE tables. Scaling them up is a good idea, in case you have a MAF failure. Changing the Cylinder Volume pretty much only effects start up. The LS PCMs, and Vortec truck PCMs do use VE tables in normal MAF mode.
Last edited by hrcslam; 03-18-2015 at 04:47 PM.
03-18-2015, 04:13 PM
#14
TECH Addict
OK trying to understand..so since the 1995 LT1 PCM does not look at the VE tables unless it goes into speed density mode, where would changes need to be made to the tune while running with the MAF? Will data logging with the stock O2 sensors not give enough data to know what to change? I believe I have the data logger that I got with tunercats but I have not used it yet.
I am new to tuning other than changing fan temps, speedo settings, VATS, etc, I have only done the basics, so any help is appreciated.
FYI also had another variable thrown in, when tearing down the 5.7 to salvage the lower end parts I found the cam to be badly pitted on a lot of the lobes so I cannot use it in the 383. None of the lobes looked flat, but the pitting is disappointing since the engine only had 20K miles on it. Cam is a comp custom grind with 215/220 @.050 and 114 lobe separation. Pretty close to the LT1 266HR-14 which is a pretty mild cam. Anyone think I could step up to the LT1 276HR-14 with the blower and not be blowing the boost out the exhaust? Numbers are 220/230@.050 and 114 lobe separation.
I am new to tuning other than changing fan temps, speedo settings, VATS, etc, I have only done the basics, so any help is appreciated.
FYI also had another variable thrown in, when tearing down the 5.7 to salvage the lower end parts I found the cam to be badly pitted on a lot of the lobes so I cannot use it in the 383. None of the lobes looked flat, but the pitting is disappointing since the engine only had 20K miles on it. Cam is a comp custom grind with 215/220 @.050 and 114 lobe separation. Pretty close to the LT1 266HR-14 which is a pretty mild cam. Anyone think I could step up to the LT1 276HR-14 with the blower and not be blowing the boost out the exhaust? Numbers are 220/230@.050 and 114 lobe separation.
You will want to tune the MAF ONLY if you change any tubing/routing before and or after the MAF our you change the MAF. The MAF is tuned for airflow in the pipe it's located in, not for the engine after it. So if your MAF is going to be installed in the same intake tube and was tuned for it correctly, it won't need adjusted.
Again, the LT1 pcm seems to reference the VE tables differently based each persons car. It is a good idea to tune it anyway even if you notice no difference because if it has a sensor failure and reverts to speed density mode you'll only get a check engine light and not a stumbling bucking back firing engine.
03-18-2015, 04:32 PM
#15
Maybe I will just stick to the 266HR14 which is closer to the original comp cam..also running a stock stall in the 4L80E which may stop me from running the 276HR14 as well.
MAF location is going to change some, I am not sure I can run the F body intake tubing, there may not be enough room in the 51 ford truck engine compartment. But knowing that info I will try and keep the same stuff.
The only reason this is a pain is I do not know of any dyno tuners where I am in NY, so unless I do the tuning I would be hoping it could be done by sending it out. I really want to learn to do the tuning myself but am worried about doing any damage to the engine if I make a mistake.
Time to find some tutorials or compare some tunes that are already done.
As an example, is tuning the MAF a matter of changing one table value, and then testing, or changing multiple values a percentage either way of the original value (s) and then testing? What would I be looking for on the data logger to know i was moving in the right direction? Maybe this is too much to ask here, I will have to do some research and post some logs.
MAF location is going to change some, I am not sure I can run the F body intake tubing, there may not be enough room in the 51 ford truck engine compartment. But knowing that info I will try and keep the same stuff.
The only reason this is a pain is I do not know of any dyno tuners where I am in NY, so unless I do the tuning I would be hoping it could be done by sending it out. I really want to learn to do the tuning myself but am worried about doing any damage to the engine if I make a mistake.
Time to find some tutorials or compare some tunes that are already done.
As an example, is tuning the MAF a matter of changing one table value, and then testing, or changing multiple values a percentage either way of the original value (s) and then testing? What would I be looking for on the data logger to know i was moving in the right direction? Maybe this is too much to ask here, I will have to do some research and post some logs.
03-18-2015, 04:44 PM
#16
TECH Addict
Maybe I will just stick to the 266HR14 which is closer to the original comp cam..also running a stock stall in the 4L80E which may stop me from running the 276HR14 as well.
MAF location is going to change some, I am not sure I can run the F body intake tubing, there may not be enough room in the 51 ford truck engine compartment. But knowing that info I will try and keep the same stuff.
The only reason this is a pain is I do not know of any dyno tuners where I am in NY, so unless I do the tuning I would be hoping it could be done by sending it out. I really want to learn to do the tuning myself but am worried about doing any damage to the engine if I make a mistake.
Time to find some tutorials or compare some tunes that are already done.
As an example, is tuning the MAF a matter of changing one table value, and then testing, or changing multiple values a percentage either way of the original value (s) and then testing? What would I be looking for on the data logger to know i was moving in the right direction? Maybe this is too much to ask here, I will have to do some research and post some logs.
MAF location is going to change some, I am not sure I can run the F body intake tubing, there may not be enough room in the 51 ford truck engine compartment. But knowing that info I will try and keep the same stuff.
The only reason this is a pain is I do not know of any dyno tuners where I am in NY, so unless I do the tuning I would be hoping it could be done by sending it out. I really want to learn to do the tuning myself but am worried about doing any damage to the engine if I make a mistake.
Time to find some tutorials or compare some tunes that are already done.
As an example, is tuning the MAF a matter of changing one table value, and then testing, or changing multiple values a percentage either way of the original value (s) and then testing? What would I be looking for on the data logger to know i was moving in the right direction? Maybe this is too much to ask here, I will have to do some research and post some logs.
03-18-2015, 05:30 PM
#18
TECH Addict
Log it. If you are getting knock pull timing, if not adjust afr through MAF. Then match VE tables. If your MAF mode references your VE tables like mine did, then you'll want to do a speed density tune then a MAF tune.
03-18-2015, 07:06 PM
#20
TECH Addict
Speed density will afr based on the VE tables. MAF will use the MAF calibration tables (or a combination of the two, again this seems to vary per vehicle). If doing a speed density tune use the BLMs to find out your multiplier based on each BLM cell. Google search LT1 BLM cells and check out the images to understand what that means. You could also read everything about this at www.lt1pcmtuning.com/tips/ it's a good place to get started.
Last edited by hrcslam; 03-18-2015 at 08:10 PM.