383 lt4 questions
Thread Starter
Teching In
Joined: Mar 2015
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From: Hickory NC
383 lt4 questions Hi! This is my first post on here after searching and research for a while now. I Blew a head gasket on my 1995 z28, thus a excuse for a new motor.I am not too versed in engine builing and I came across this engine:
BUILD SHEET: It is a forged bottom end 383. Lunati forged crankshaft (3.75" stroke), Lunati forged I-beam rods, and JE -15cc Pistons. This puts the compression ratio at about 10 to 1. The heads are 195cc GM LT4 heads topped with ported LT4 intake manifold. Camshaft is an LPE L210045087 ( 215/220 .534/.544 HR114) topped with comp cams 850-16 Lifters and Crane cams 1.6 Ratio rocker arms. This is all covered by a set of Canton Racing aluminum valve covers. That were ordered to clear F-Bodies brake booster and master cylinder.
Im going to get it thursday.
I Have long tube headers,ORY pipe,straight pipe to rear, new accel opti, MSD coil, under drive pullies, taylor 10.4mm plug wires, NGK tr55s,New water pump, factory accessories and brackets,Factory fuel rails And new delphi pump, 4l60e, 4:10 posi.
I need help with the rest.
First, Fuel. What size injectors and is the stock pump going to be sufficient?
Stall converter? Lingenfelter reccomends a 2600-2800 stall for the cam. my questions are Whos converter will do the job and hold up without breaking the bank and how long do I get to save before I have to rebuild the 4l60?
What am I forgetting?I plan to have it dyno tuned after the install.
Thanks
BUBBAJONES
BUILD SHEET: It is a forged bottom end 383. Lunati forged crankshaft (3.75" stroke), Lunati forged I-beam rods, and JE -15cc Pistons. This puts the compression ratio at about 10 to 1. The heads are 195cc GM LT4 heads topped with ported LT4 intake manifold. Camshaft is an LPE L210045087 ( 215/220 .534/.544 HR114) topped with comp cams 850-16 Lifters and Crane cams 1.6 Ratio rocker arms. This is all covered by a set of Canton Racing aluminum valve covers. That were ordered to clear F-Bodies brake booster and master cylinder.
Im going to get it thursday.
I Have long tube headers,ORY pipe,straight pipe to rear, new accel opti, MSD coil, under drive pullies, taylor 10.4mm plug wires, NGK tr55s,New water pump, factory accessories and brackets,Factory fuel rails And new delphi pump, 4l60e, 4:10 posi.
I need help with the rest.
First, Fuel. What size injectors and is the stock pump going to be sufficient?
Stall converter? Lingenfelter reccomends a 2600-2800 stall for the cam. my questions are Whos converter will do the job and hold up without breaking the bank and how long do I get to save before I have to rebuild the 4l60?
What am I forgetting?I plan to have it dyno tuned after the install.
Thanks
BUBBAJONES
If you haven't bought that motor already then I'd look elsewhere. Some problems...
10:1 on a NA LT1 is lame and lower than stock. That cam is tiny as hell for a 383 with an overly wide LSA. Those Comp lifters are crap but they only have a shot at surviving because of the dinky cam. LT4 heads as cast aren't all that great considering ported alum LT1 castings can walk all over them. The ported LT4 intake isn't doing much for this motor.
Is this something you're buying or a build that you're stuck with?
10:1 on a NA LT1 is lame and lower than stock. That cam is tiny as hell for a 383 with an overly wide LSA. Those Comp lifters are crap but they only have a shot at surviving because of the dinky cam. LT4 heads as cast aren't all that great considering ported alum LT1 castings can walk all over them. The ported LT4 intake isn't doing much for this motor.
Is this something you're buying or a build that you're stuck with?
Thread Starter
Teching In
Joined: Mar 2015
Posts: 8
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From: Hickory NC
Catmaigne, Thanks for your input, I am buying the engine, it is a steal of a deal so I can afford to send to the heads to LE and get a custom cam from him but what do you recommend for the compression ratio and what lifters do you suggest?
shownomercy, i'm confused, lol remember i'm new to this forum thing.
thanks for the help guys.
shownomercy, i'm confused, lol remember i'm new to this forum thing.
thanks for the help guys.
Are the heads ported at all? With the way this is set up now you'll have hella torque until about 4000rpm and it will then take a nose dive. LT1's with stock bottom end and average heads/cam setups (if done correctly) will be able to walk all over this applicatoin. Is this the LPE cam that is used for the super ram/long runner/TPI type intakes?
On The Tree
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Thread Starter
Teching In
Joined: Mar 2015
Posts: 8
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From: Hickory NC
Just rember i9 didn't build it im just looking at buying it. yes the cam according to lfe is used for tpi, long runner, an ltx intakes. Im not sure if the heads are ported, im going to look at it tomorrow and i'll know more then. would it still be a mean na motor with say LE2 port job on the heads and a more aggressive cam?
thanks
BUBBAJONES
thanks
BUBBAJONES
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Thread Starter
Teching In
Joined: Mar 2015
Posts: 8
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From: Hickory NC
around $2500. the block and intake are ceramic coated, still on engine stand professionally machined and assembled. comes with pcm and edelbrock fuel pump, STAINLESS BOLT KIT, NEW HARMONIC BALANCER, canton oil pan and valve covers.
All is not lost, it's easier to do it now than when its in the car... 
Whats you goals with your car? If your happy with 12s then buy this motor and run as is. If you wana run faster then just build you own. A good stock rebuild 350/355 with good heads and cam will put you mid to low 11s.
Bubba,
This engine is poorly spec'ed from the start. To get this engine where it performs to it's potential, you'd probably have to spend a couple thousand bucks.
As is, this engine will be lazy at low RPMs. If all you want is for the car to get you "from here to there", then fine. For $2500 it's a good deal. But if you expect the car to be high-performance, this engine won't get you there.
WHAT I WOULD DO (and this is just me) is buy the engine and try to get about a $1000 reduction for JUST the short block (no heads/intake). Or.....buy the long block and pull the LT4 heads/intake and sell them separately.
I'd then send off my LT1 heads to be cleaned up, fitted with new springs/valve seals/etc, and install the LT1 heads/intake.
A good tune will make for a 'nice' performing engine that will last 100K miles.
That.....or go with a REAL performance build (lots more $$$$).
BTW.....a Yank or Vigilante TC with about a 2800 stall rating would be really nice behind this engine.
Best of luck whatever you do.
KW
This engine is poorly spec'ed from the start. To get this engine where it performs to it's potential, you'd probably have to spend a couple thousand bucks.
As is, this engine will be lazy at low RPMs. If all you want is for the car to get you "from here to there", then fine. For $2500 it's a good deal. But if you expect the car to be high-performance, this engine won't get you there.
WHAT I WOULD DO (and this is just me) is buy the engine and try to get about a $1000 reduction for JUST the short block (no heads/intake). Or.....buy the long block and pull the LT4 heads/intake and sell them separately.
I'd then send off my LT1 heads to be cleaned up, fitted with new springs/valve seals/etc, and install the LT1 heads/intake.
A good tune will make for a 'nice' performing engine that will last 100K miles.
That.....or go with a REAL performance build (lots more $$$$).
BTW.....a Yank or Vigilante TC with about a 2800 stall rating would be really nice behind this engine.
Best of luck whatever you do.
KW
Thread Starter
Teching In
Joined: Mar 2015
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From: Hickory NC
TravisMcGill2000: My goals for the car in the long run is to run 6.99 or lower in the 1/8th mile ( I bought the car with a cage installed and i want to have to have it.) and still be streetable. this being said i know thats a long way down the road and I have a ton of suspension, transmission, and rear end work ahead of me but first I need a good running strong motor.
KW Baraka: Why would you want stock lt1 heads worked over getting the lt4 top end work that comes on the motor and a new cam?
96capricemgr: I was wondering the same thing. I know i can have the heads milled but idk how much that will help.
A few things i forgot to mention: This is not a daily driver, but I still want to take it out to the shows, test and tune nights, and some of the "mexico" street races and i need it to run on pump (non-ethenol) 93.
thanks again for the help guys, Im a collision technician by profession but this engine stuff makes my head hurt. lol. so many variable and options....
KW Baraka: Why would you want stock lt1 heads worked over getting the lt4 top end work that comes on the motor and a new cam?
96capricemgr: I was wondering the same thing. I know i can have the heads milled but idk how much that will help.
A few things i forgot to mention: This is not a daily driver, but I still want to take it out to the shows, test and tune nights, and some of the "mexico" street races and i need it to run on pump (non-ethenol) 93.
thanks again for the help guys, Im a collision technician by profession but this engine stuff makes my head hurt. lol. so many variable and options....
[QUOTE=Bubbajones;18749764]TravisMcGill2000: My goals for the car in the long run is to run 6.99 or lower in the 1/8th mile
If you only plan on running 1/8 mile, then mill the heads and intake as much as possible to get the compression, (With Loyd), install a more aggressive cam and a lot of gear. Even tho this seems like a deal, you may end up spending more in the long run for this poor setup, As said it will be a torque motor, fry the tires off at a red light then start changing CD's as those other boys are flying by throwing their tacos at you. We are all just stating the facts and trying to help, You never want to be the ones that say,"Dam, I should of listened" Good Luck on what ever you decide, but you still have options with this motor, just going to have to make a few changes..
If you only plan on running 1/8 mile, then mill the heads and intake as much as possible to get the compression, (With Loyd), install a more aggressive cam and a lot of gear. Even tho this seems like a deal, you may end up spending more in the long run for this poor setup, As said it will be a torque motor, fry the tires off at a red light then start changing CD's as those other boys are flying by throwing their tacos at you. We are all just stating the facts and trying to help, You never want to be the ones that say,"Dam, I should of listened" Good Luck on what ever you decide, but you still have options with this motor, just going to have to make a few changes..
Thread Starter
Teching In
Joined: Mar 2015
Posts: 8
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From: Hickory NC
So with no decent heads or block (long story, cracked head sat for 5 yrs with coolant in cylinders,etc) What do you guys recommend I do? Im not dead set on 383 just found that motor and seemed the right price. I would really like forged internals and nice heads and cam. I have about $5k. Help please bc I am supposed to go look at the motor tomorrow. Say I could talk the seller down, How much would make the parts worth starting over with with new pistons,cam,pp heads & intake?
Also another thought. Is 10:1 cr too high for medium boost? Not planning on in any power adders now but its could be in the future.
And before somebody says it....I am NOT doing a LS swap. lol
Thanks
BUBBAJONES
Also another thought. Is 10:1 cr too high for medium boost? Not planning on in any power adders now but its could be in the future.
And before somebody says it....I am NOT doing a LS swap. lol
Thanks
BUBBAJONES
Last edited by Bubbajones; Apr 8, 2015 at 09:58 PM.
Assume the heads are as-cast unmodified LT4s so the chambers are 54.4cc. We know piston volume is -15cc. If this really is a 383 then that means 4.030" bore and 3.75" stroke. The only specs we don't know are piston to deck and head gasket thickness/bore but we can approximate these.
Piston to deck is less than or equal to ~.025 (more likely less than)
Plug all of that into the compression calc and the only conclusion you can draw is that the quench on this motor must be absolute ****. Getting near 10:1 with stock PTD (undecked block) means a head gasket .055 thick (4.125" bore) or thicker w/smaller bore. Not surprised by that at all knowing the top end was poorly thought out.
-15cc dish sounds like a lot but it really isn't with added stroke.
Take .020" off of the heads (3-4cc), swap out for .026 impala gaskets and you'll be in low-mid 11s CR.
This sounds like too much work honestly. Would rather buy something else. If the builder can't spec the motor then how can you trust him to build it?
Piston to deck is less than or equal to ~.025 (more likely less than)
Plug all of that into the compression calc and the only conclusion you can draw is that the quench on this motor must be absolute ****. Getting near 10:1 with stock PTD (undecked block) means a head gasket .055 thick (4.125" bore) or thicker w/smaller bore. Not surprised by that at all knowing the top end was poorly thought out.
-15cc dish sounds like a lot but it really isn't with added stroke.
Take .020" off of the heads (3-4cc), swap out for .026 impala gaskets and you'll be in low-mid 11s CR.
This sounds like too much work honestly. Would rather buy something else. If the builder can't spec the motor then how can you trust him to build it?
The JEs are already a plus.
If you buy that motor. Then take it apart. Deck the block to zero and run a .038 head gasket. Send the heads to le for porting and milling. That should get your compression close to 11.4. Then get him to spec out a nice cam.
