TBIThrottle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.
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What you guys think?Is this cam enough for a 383 with vortecs untouched just machined for higher lift.The funny thing is I had this cam for a while now and decided to put it in my 383 that had a flat tappet cam failure in 1500 miles.Now Im having second thoughts if I should go bigger.Cam is in engine right now but the intake,rocker,lifters are not installed yet.Springs are good to .540 lift safe.Oh its being fed through 2'' holley tbi,bb injector, 2912 edel intake and 7747 but looking to go ebl.Thanks in advance.
If you are talking about LT4 Hot Cam (P/N 24502586) then it is a hydraulic roller cam designed for SBC with roller camshafts. Advertised duration (intake/exhaust) is 279/287; duration at .050" tappet lift (intake/exhaust) is 218/228; and maximum lift with 1.6 rocker ratio (intake/exhaust) is 525/525. LSA is 112 degrees. I am guessing that your Vortecs have LS6 yellow springs for 0.540 lift. This cam should be OK with your 383 (whats the compression and pistons ???)
Stock 7747 is a poor choice, but EBL will make your job dialing in a straight forward task. If you have a choice get a car ECM - 8746 or 6965 version for EBL conversion. These ECMs have IAS input which allows for easier tuning over wide range of temperatures.
I am questioning your choice of intake manifold - 2912 is not a good choice for near stock, street driven Vortecs. It's power band 3500 to 7000 RPM. Even though stock Vortec flow as well as any factory head they are, after all, exhaust flow limited in stock form. For a street application 2912 will not result in optimum performance, where a dual plane, fully heated intake will do better with TBI. Perhaps you can shed a light on your ride and intended application.
If you are talking about LT4 Hot Cam (P/N 24502586) then it is a hydraulic roller cam designed for SBC with roller camshafts. Advertised duration (intake/exhaust) is 279/287; duration at .050" tappet lift (intake/exhaust) is 218/228; and maximum lift with 1.6 rocker ratio (intake/exhaust) is 525/525. LSA is 112 degrees. I am guessing that your Vortecs have LS6 yellow springs for 0.540 lift. This cam should be OK with your 383 (whats the compression and pistons ???)
Stock 7747 is a poor choice, but EBL will make your job dialing in a straight forward task. If you have a choice get a car ECM - 8746 or 6965 version for EBL conversion. These ECMs have IAS input which allows for easier tuning over wide range of temperatures.
I am questioning your choice of intake manifold - 2912 is not a good choice for near stock, street driven Vortecs. It's power band 3500 to 7000 RPM. Even though stock Vortec flow as well as any factory head they are, after all, exhaust flow limited in stock form. For a street application 2912 will not result in optimum performance, where a dual plane, fully heated intake will do better with TBI. Perhaps you can shed a light on your ride and intended application.
//RF
Im running dish pistons and somewhere around 9.7 cr.I chose the 2912 over the 2116 it had before because there has been alot of talk about this intake being ideal for a 2 barrel tbi.Plus it realy doesn t get cold here in Houston Tx.This is not a dd nor a strip truck.Its a week end truck only.It going to have a 3.73 put in so im really not concerned about bottom end.I want mainly mid range and top end power while not scrificing to much bottom end.Only want to spin to 6500 max also.Oh the spring are not ls6 they are some ultradyne single spring with dampner good to .590 lift.On the 7747 I thought i could pin in iat sensor input if i run ebl.Wil switching to one of those ecm require re pinning.Thanks
OK, thanks for details 383TBI.
I would not go any bigger on cam since you have 9.7 CR and stock Vortec heads. The problem is that you are using stock (un-ported) heads. IMHO your engine will be inlet flow limited by about 5500 RPM as stock Vortecs are only 170cc heads. You did no mention valve size in your Vortecs, but I assume stock (1.90/1.50). Also, higher valve lift does not produce increased flow in stock Vortecs. For the higher RPM operation (5000 to 6500) I would step up to an aftermarket heads (AFR, Brodix. etc ) since additional porting of stock Vortec heads will cost as a much as good after market heads.
On induction side to feed 383 with enough fuel I would step up to 2" or bigger TB and VRFPR (aeromotive) fuel pressure regulator (EBL is a must no if buts or what ever). Based on the brief engine description provided I would expect engine torque peak between 3800 to 5200 RPM with HP peak around 5000 RPM. Back of the envelope estimates would put this combo in 425HP/450 ft-lb range. To feed your 383 at peak HP you'll need to supply 196lb of fuel/hour. Assuming 85% duty factor for each injector which means you need 230 lb/hr total injector or 115 lb/hr for each TB injector. BBC injectors are rated at about 80 lb/hr (at 13PSI) so you'll have to raise fuel pressure to about 27 PSI. The VRFPR should lower fuel pressure to around 15 PSI at idle (high vacuum) to keep injector pulse length from getting too short at idle. There have been posting indicating that (some) BBC injectors do not do very well at high pressures, but IRC 27 PSI is still manageable - do a search.
Stock BBC TBI with 2" bores flows about 645CFM. This may become a limiting factor at 5000 to 6500 RPM.
The reason why I am so interested in your question is that I am also building a TBI 383, but for a street application. For my build I am looking for broad torque band between 2500 and 5000. Just like you, I have started with vortec heads only to discover that the two set that I had (902's) had cracks (or beginning to form) between two inside chambers (4/6 or 3/5). So, after wasting $200 on useless cores I am going with Brodix IK (180 or 200, have not decided yet).
OK, thanks for details 383TBI.
I would not go any bigger on cam since you have 9.7 CR and stock Vortec heads. The problem is that you are using stock (un-ported) heads. IMHO your engine will be inlet flow limited by about 5500 RPM as stock Vortecs are only 170cc heads. You did no mention valve size in your Vortecs, but I assume stock (1.90/1.50). Also, higher valve lift does not produce increased flow in stock Vortecs. For the higher RPM operation (5000 to 6500) I would step up to an aftermarket heads (AFR, Brodix. etc ) since additional porting of stock Vortec heads will cost as a much as good after market heads.
On induction side to feed 383 with enough fuel I would step up to 2" or bigger TB and VRFPR (aeromotive) fuel pressure regulator (EBL is a must no if buts or what ever). Based on the brief engine description provided I would expect engine torque peak between 3800 to 5200 RPM with HP peak around 5000 RPM. Back of the envelope estimates would put this combo in 425HP/450 ft-lb range. To feed your 383 at peak HP you'll need to supply 196lb of fuel/hour. Assuming 85% duty factor for each injector which means you need 230 lb/hr total injector or 115 lb/hr for each TB injector. BBC injectors are rated at about 80 lb/hr (at 13PSI) so you'll have to raise fuel pressure to about 27 PSI. The VRFPR should lower fuel pressure to around 15 PSI at idle (high vacuum) to keep injector pulse length from getting too short at idle. There have been posting indicating that (some) BBC injectors do not do very well at high pressures, but IRC 27 PSI is still manageable - do a search.
Stock BBC TBI with 2" bores flows about 645CFM. This may become a limiting factor at 5000 to 6500 RPM.
The reason why I am so interested in your question is that I am also building a TBI 383, but for a street application. For my build I am looking for broad torque band between 2500 and 5000. Just like you, I have started with vortec heads only to discover that the two set that I had (902's) had cracks (or beginning to form) between two inside chambers (4/6 or 3/5). So, after wasting $200 on useless cores I am going with Brodix IK (180 or 200, have not decided yet).
//RF
Thanks for taking the time to respond.This engine was already running with a 12-262-4 comp cam with the 2116 and 2" holley tbi on top.The cam failed on 1 of the lobes 1500 to 2000 miles after I built it.I went with tbichips cause i didnt research enough when i built the engine.With 3 chips into the tune we were still having surge issues and running rich.Now I know its going to be almost impossible to get it right so thats why I m looking to get ebl when i get this engine put back togather.The engine had alot of bootom end with the 2116.I think i going to leave the hotcam in there just wanted to here some input.The vortecs do have stock valves and i dont want to pull they any time soon for bigger valves or porting.I know I could probably use some bigger cc heads but I ve already spent alot of money.This is just 1 of my projects and Im not made of money specialy now a days.I would like to hear some more plans on your 383 build.Thanks.
Ok now that my truck is running I looking to get ebl.RF you recommended getting an 8746 or 6965 for the purpose of being able to run iat sensor.Would I need to re pin the for any of those ecms?If any body is concerned about the 2912 intake costing you bottom end well its very minor if anything.Im very happy with it.
Ok now that my truck is running I looking to get ebl.RF you recommended getting an 8746 or 6965 for the purpose of being able to run iat sensor.Would I need to re pin the for any of those ecms?If any body is concerned about the 2912 intake costing you bottom end well its very minor if anything.Im very happy with it.
I would chose ECM that was used with 350 CID engine. From memory 16136965 was used in 91-94 B-bodies with 5.0 and 5.7 TBI engines. The 1228746 was used in F-bodies LO3 (aka 5.0L) and also can be found in some late eighties B-bodies (5.0L and 5.7L) The 5.7L 8746 are hard to find and thus are rare. At least in all my JY trips I have not found a single one. As far as pin compatibility the 8746 and 6965 are almost (I have to check my cross pin table) compatible - i.e. all major circuits are basically the same. For my TBI conversions I prefer to use 6965 as it was used in very heavy cars (b-Body is close to 5000 lb! and used 700R4). Surprisingly, this later ECM (6965) has been very reliable.
When you convert ECM to EBL all of minor ECM differences can be addressed through settings. The only thing you need to transfer from your original ECM daughter board a CALPACK module. EPROM become a souvenir for your desk.
BTW I gave up on Vortec heads - both of my sets were cracked (-$390 down into GC). Just placed an order for a pair of Trick Flow Super 23 195.
I would chose ECM that was used with 350 CID engine. From memory 16136965 was used in 91-94 B-bodies with 5.0 and 5.7 TBI engines. The 1228746 was used in F-bodies LO3 (aka 5.0L) and also can be found in some late eighties B-bodies (5.0L and 5.7L) The 5.7L 8746 are hard to find and thus are rare. At least in all my JY trips I have not found a single one. As far as pin compatibility the 8746 and 6965 are almost (I have to check my cross pin table) compatible - i.e. all major circuits are basically the same. For my TBI conversions I prefer to use 6965 as it was used in very heavy cars (b-Body is close to 5000 lb! and used 700R4). Surprisingly, this later ECM (6965) has been very reliable.
When you convert ECM to EBL all of minor ECM differences can be addressed through settings. The only thing you need to transfer from your original ECM daughter board a CALPACK module. EPROM become a souvenir for your desk.
BTW I gave up on Vortec heads - both of my sets were cracked (-$390 down into GC). Just placed an order for a pair of Trick Flow Super 23 195.
//RF
Ok so right now Im running a tbichips chip and besides being rich it runs well.If want to start off with my bin in my tbichips chip what will i have to do.I probably can ask Brian to email me the bin we are working on.Also since doing that will it still matter if the ecm I get is from a 5.7 or 5.0.Thanks
I would get a V8 ECM (not a V6) due to aforementioned CALPACK. Either 5.0 or 5.7L ECM (6965) will work. EBL is shipped with several bin files that can be used as a starting point for a baseline 383 tune. To change displacement in EBL is very easy (in TunerPro) - just change displacement variable in a bin file, save and use EBL HUD to update flash. The whole process can take less than 30 sec to complete from start to finish. Same goes for everything else - makes tuning a straight forward activity.
IMHO, since you are running LT4 Hot cam getting it run leaner will require some finesse - see long running thread: "Tuning with EBL". VE learns will take care of about 75% of your fueling issues. To get things right plan to run heated NBO and if funds permit WBO to get AE and PE where they supposed to be for YOUR engine! No two engines are alike and thus individualized tuning is a must.
(-$390 down into GC). Just placed an order for a pair of Trick Flow Super 23 195.
