Quote:
Originally Posted by Tim M
Heater: Great feedback on you experiences. Not sure about the comment, "produce a little more power due to heat." Possibly I took that out of context, but more heat will produce less power. Possibly the LT1's cam may produce more boost than the LT4...but I'd chalk that up to not an ideal blower cam.
I'm not an expert, but I'd think the cam is not such a benefit to the LT1 with a blower. Yes the intake lift/duration is greater than the LT4, but you have boost benefiting the inflow. Notice the exhaust is less for lift and duration on the LT1 compared to the LT4 - an area that the blower does not help. In other words, the LT4 has a blower cam and the LT1 has a NA cam. How does this impact long term longevity of the engine/cats...
I'd suggest (as others have) the 1.5 point of compression increase on the LT1 is the source of any 'extra' power...I'm not sure a LT4 blown LT1 makes anything more than the LT4. Doing so means the power is made differently with a weaker piston design. Why does Chevy go with a lower CR...reliability, no doubt-just like oldman states on minimal cam actuation/valve springs.
I've asked about better valve springs when going from NA to blower and was told, not necessary. I used to change valve springs out seasonally on my 7200 rpm LT4 (Gen II) motor as they were consumable. I'll probably address in the future as boost on the backside of the valve reduces the resulting spring pressure - I do like to hear those 6500 rpm shifts!
I'm interested in the discussion only because I will be putting the stock LT4 blower on my LT1...may not be the best idea for my application, but can't deny the need for 650 HP!
I'm at 1100 feet elevation so will report back what boost it runs with an OEM LT4 blower/pulled as well as OEM intake setup.
Thanks!
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The LT1 indeed makes more power then a LT4 at the same PSI of boost. As you mentioned, The LT1 has a lot more compression which contributes to the increase. Honestly the LT4 supercharger works better on the LT1 because it doesn't need spun as hard to make power which equals lower blower temps. LT1's tend to dyno around 600whp on 9 psi and not 550whp like the LT4 on 93. The down side is the LT1 runs into a octane wall on pump gas around 10psi. So you need to supplement with Ethanol blend or Meth. LT4 can potentially make a lot more power on 93 octane with it's lower compression.
It's a good swap if you don't plan to go very far. I personally would run a larger 7psi pulley and run a blend of ethanol(E60) with LT4 fuel system. It will soften the hit since the little 1.7 makes a boat load of torque down low and still make the same if not a little more power up top as the 9 psi pulley on 93.