LT4 budget build
09-29-2016, 09:00 PM
#21
As far as what can be done goes - the LT4 is a pretty darn good starting point. It makes 330 HP base and many people "feel" that Chevy may have understated things a bit with the 350 HP LS1 coming in the next year. However - to me the beauty of the LT4 is it's ability to make 300 ft lb of torque from 1,800 - 6,000 RPM. That is why the car pulls so well !!!
Long tube headers are probably worth 20 HP and aside from cost - have relatively little downside. The rest of the exhaust is pretty decent, and spending another $1,000 on exhaust is not going to give you a lot of bang for the buck.
As other posts have said - think of an engine as an air pump - more airflow = more power.
OK - Having said that - think of the cam as governing where peak torque will be in the RPM Band. HP = Torque/5252, so you make more HP if you move your torque peak higher up in the RPM band. BUT - the ugly fact is that on a street car - torque is probably more important than HP, and your car is operating on the street - you probably don't want to give up too much low RPM torque, as the car will become less drivable. The Hot cam will definitely lope at idle, and will move the torque peak a bit higher on the RPM band. If you pull the heads and have them ported by someone who knows what they're doing - and run the hot cam or something similar - with a good tune you'll probably be about where you're looking to get. Comp Cams, Crane, and others all make good camshafts - and they have people on their tech line that know the products quite well. My suggestion would be to stick to a cam with specs that aren't too different from the Hot Cam. You will need valvesprings that are compatible with the cam, and the heads, and this is one area where I do NOT recommend the GM springs (I've seen two engines with LT4 spring failures - both of which caused very expensive damage. Go with a good set of aftermarket springs.
As for $$$$ - If you figure:
$1,000 for long tube headers and the mods to make them work with the rest of the exhaust
$1,500 for head porting - gaskets etc.
$500 for a cam and springs
That'll get you in the ball park.
Long tube headers are probably worth 20 HP and aside from cost - have relatively little downside. The rest of the exhaust is pretty decent, and spending another $1,000 on exhaust is not going to give you a lot of bang for the buck.
As other posts have said - think of an engine as an air pump - more airflow = more power.
OK - Having said that - think of the cam as governing where peak torque will be in the RPM Band. HP = Torque/5252, so you make more HP if you move your torque peak higher up in the RPM band. BUT - the ugly fact is that on a street car - torque is probably more important than HP, and your car is operating on the street - you probably don't want to give up too much low RPM torque, as the car will become less drivable. The Hot cam will definitely lope at idle, and will move the torque peak a bit higher on the RPM band. If you pull the heads and have them ported by someone who knows what they're doing - and run the hot cam or something similar - with a good tune you'll probably be about where you're looking to get. Comp Cams, Crane, and others all make good camshafts - and they have people on their tech line that know the products quite well. My suggestion would be to stick to a cam with specs that aren't too different from the Hot Cam. You will need valvesprings that are compatible with the cam, and the heads, and this is one area where I do NOT recommend the GM springs (I've seen two engines with LT4 spring failures - both of which caused very expensive damage. Go with a good set of aftermarket springs.
As for $$$$ - If you figure:
$1,000 for long tube headers and the mods to make them work with the rest of the exhaust
$1,500 for head porting - gaskets etc.
$500 for a cam and springs
That'll get you in the ball park.
