Rebuilt Replacement Engine

[SAATR]

Great combo and lot of power but your mpg's on a good day would be roughly 4/5

I don't see how. I had an 89 Suburban with a carbed 454, turbo 400, and 3/4 ton running gear that got 8 combined, 10 on the highway. A mildly cammed and efficiently tuned EFI 383 should have no problems getting at least 12 to 14 highway, assuming no huge tires and low gears.

 

[jeff's88silverado]

I've been talking to the guy at tbichips.com and he believes with all my mods also with vortec 350,LT4 hot cam,454TBI,higher psi fuel pump. he also said it'll make between 340-350hp and said I should be able to keep my 20-21mpg highway if driven like a normal person would (unlikely )

Also has anbody stuck a LT4 cam in stock vortec heads. I've heard it'll be fine and i've also heard because of the lift it'll pinch valve guide seal if the valve guide is not grinded down a little at a machine shop?

He's also built a vortec 350 with a stock lt4 cam but the stock lt4 is damn near impossible to find.

http://tbichips.com/bluewhale.htm

 

[97c1500]

I don't see how. I had an 89 Suburban with a carbed 454, turbo 400, and 3/4 ton running gear that got 8 combined, 10 on the highway. A mildly cammed and efficiently tuned EFI 383 should have no problems getting at least 12 to 14 highway, assuming no huge tires and low gears.

The LT4 Hot cam is by no means mild cam and the longer stroke hurts MPG's

 

[97c1500]

I've been talking to the guy at tbichips.com and he believes with all my mods also with vortec 350,LT4 hot cam,454TBI,higher psi fuel pump. he also said it'll make between 340-350hp and said I should be able to keep my 20-21mpg highway if driven like a normal person would (unlikely )

Also has anbody stuck a LT4 cam in stock vortec heads. I've heard it'll be fine and i've also heard because of the lift it'll pinch valve guide seal if the valve guide is not grinded down a little at a machine shop?

He's also built a vortec 350 with a stock lt4 cam but the stock lt4 is damn near impossible to find.

http://tbichips.com/bluewhale.htm

I don't see how your going to get 20-21 on the highway with a radical cam a huge TBI setup and more fuel pressure putting out 340-350 if my Stock 97 5.7 Vortec only gets 18 at best on the high way

Also why don't you just put a 6.0 in it those put out 350hp stock and are surprisingly easy to get to 400hp and from what i heard if there left stock and you use a 4l65e or built 4l60e they get a lot better MPG's than you would think

 

[Badass69]

I've been talking to the guy at tbichips.com and he believes with all my mods also with vortec 350,LT4 hot cam,454TBI,higher psi fuel pump. he also said it'll make between 340-350hp and said I should be able to keep my 20-21mpg highway if driven like a normal person would (unlikely )

Also has anbody stuck a LT4 cam in stock vortec heads. I've heard it'll be fine and i've also heard because of the lift it'll pinch valve guide seal if the valve guide is not grinded down a little at a machine shop?

He's also built a vortec 350 with a stock lt4 cam but the stock lt4 is damn near impossible to find.

http://tbichips.com/bluewhale.htm

The LT4 hotcam works fine with stock Vortecs as long as you run Comp 26915 or 26918 beehive springs ( or equivalents). With the corresponding locks and retainers you gain enough stem seal clearance to roughly .550" lift. I have heads both ways, and the subsequent ones I am using have had the guides cut down with LT4 hotcam spings installed. It's up to you but even the LS6 Vette springs are fine for the lift of the hotcam without having to deal with Comp's sometimes questionable quality and breakage.

You would probably be happier with any cam if you lost the 2.73 gears in your truck though. If you junk those and go to 3.73 or so then sure, run the Hotcam or something similar. The hotcam is a pretty mild camshaft but it's not going to be anywhere in it's powerband cruising at the low rpm your truck turns on the highway. That said, no aftermarket cam is going to be really happy with the 2.73's. Even 3.42's would be a step up.

Realistically even with the stock 350 you are being seriouslyt handicapped with that awful rear end ratio. Maybe go junk yarding and try and find a complete 3.42 or 3.73 geared 10 bolt before you even think about an engine change. The gears would wake the thing up like you wouldn't believe.

Don't fear mpg's either with the gear swap. My 96 gets 18-19 mpg easily with it's 3.73's and 29" tall tires. My 94 got around the same with it's at the time stock and dying TBI 350 with 3.42's and 29" tall tires. I recently went from 3.08's to 3.42's in my LT1 powered Caprice and it's a great ratio for that car and 28" tall tires.

I would do gears before an engine swap if I were you.

 

[97c1500]

the LT4 Hot cams rpm range is way to high for a truck if you were racing it I would say go for it but for a Daily Driver its a terrible cam

You should probably call Com cams and have them recommended you a cam AFTER you regear

 

[Badass69]

the LT4 Hot cams rpm range is way to high for a truck if you were racing it I would say go for it but for a Daily Driver its a terrible cam

You should probably call Com cams and have them recommended you a cam AFTER you regear

OP, don't take that advice. Comp will give you advice to buy a grind much like the XE258 cam( or even smaller), especially if you tell them the truck is TBI. Their tech line is an absolute waste of a persons time. You aren't talking to some engine building expert on the other end of the line, just some monkey with little to no engine knowledge telling you what he has written in front of him.

The LT4hotcam is not a racing cam, nor does it do very well as one either............It would do fine in a daily driver as well. Some people are either just scared or don't know.........

 

[SAATR]

The LT4 Hot cam is by no means mild cam and the longer stroke hurts MPG's

The LT4 cam is not a radical or wild cam either, by any means. The increased duration is by virtue of the steeper ramp angles that can be ground into a roller cam, and the lift is perfect for a torquey, street driven 383. The extra 33 cubes will help tame the idle down so that it may have a slight lope, if any. And as far as the powerband goes, with a slight upgrade in converters still maintaining stock lockup capability, will be perfect for a sporty truck, and its fuel economy will be very close to a 350 with the same cam and mods, while being more tractable. I really fail to see where you're getting 4 to 5 mpg from this setup?

Gears will do far more to decrease mpg's in this application than either motor mentioned ever will. The increase in highway RPM's alone will kill it. Perhaps a set of 3.42's would be a good compomise between increased torque multiplication and acceleration and highway manners. That being said, gears would make this cam or one like it a more obvious choice. After all, do your really want your engine to run out of breath at 5000?

 

[97c1500]

OP, don't take that advice. Comp will give you advice to buy a grind much like the XE258 cam( or even smaller), especially if you tell them the truck is TBI. Their tech line is an absolute waste of a persons time. You aren't talking to some engine building expert on the other end of the line, just some monkey with little to no engine knowledge telling you what he has written in front of him.

The LT4hotcam is not a racing cam, nor does it do very well as one either............It would do fine in a daily driver as well. Some people are either just scared or don't know.........

Did not know that comps tech line sucks

If you look at a dyno graph for a Lt4 Hot Cam you will see it starts out low and builds up as the Rpm increase not what you want in a truck that's why I recommended the ZZ4 It give more torque and horsepower at low rpms where you need it most in a truck i'm not hating on the Lt4 Hot cam i'm just saying it's not a very good truck cam

It would do fine in a daily driver as well. Some people are either just scared or don't know

I'm Not trying to start a war so calm down

 

[97c1500]

The LT4 cam is not a radical or wild cam either, by any means. The increased duration is by virtue of the steeper ramp angles that can be ground into a roller cam, and the lift is perfect for a torquey, street driven 383. The extra 33 cubes will help tame the idle down so that it may have a slight lope, if any. And as far as the powerband goes, with a slight upgrade in converters still maintaining stock lockup capability, will be perfect for a sporty truck, and its fuel economy will be very close to a 350 with the same cam and mods, while being more tractable. I really fail to see where you're getting 4 to 5 mpg from this setup?

Gears will do far more to decrease mpg's in this application than either motor mentioned ever will. The increase in highway RPM's alone will kill it. Perhaps a set of 3.42's would be a good compomise between increased torque multiplication and acceleration and highway manners. That being said, gears would make this cam or one like it a more obvious choice. After all, do your really want your engine to run out of breath at 5000?

I Never said a 383 and Lt4 Hot cam would be a bad combo If i remember correctly i said it would be very good because the larger stroke tames the cam but the OP will running a 350 vortec