I see a lot of people saying the LT4 conversion is a waste. So what is a good combo and how much would it cost? I want a streetable cam because its a daily driver. My goal would be 400hp if possible.

 

Anyone?

 

I am expecting around 380rwhp with the mods in my sig. To top 400 rwhp you may need to go with a 306 cam or similiar but they aren't as streetable as my cam cause I hear cams with 230+ intakes lobes needing a convertor, gears, tune, ect to have it run decent. I plan on a small 50hp NX shot to bump me over 400rwhp. Going to get it dyno tuned first though before I do this.
It seems that once you get near 430 or so hp that the trans and rear end are weak points.

Jeff D.

 

I think people say that because of the initial cost and not because of their potential. The comparison is taking stock LT-1 heads from your car (free) and having them worked well compared to buying LT-4 heads, intake (around $2000) and having them worked well. When considering money, the LT-4 conversion is not worth it. When considering performance and money is not the main concern, the LT-4 conversion is worth it. The LT-4 heads will flow better then the LT-1 heads.

 

Cost is the factor for the LT4 conversion. The LT4 heads will not outflow a set of well-ported LT1 heads, __unless the LT4 heads have been ported__. You see, the LT4 from the factory flows about 245 CFM peak on the intake side, while a ported LT1 can flow upwards of 275 CFM. Now if you port the LT4 head equally, it will flow upwards of 290 CFM. The flow numbers are not the be all to end all when it comes to head. The LT4 is a better design than the LT1, especially in the exhaust.

One issue to consider with the LT4 is that the intake runners are larger than the LT1 (175 vs 195 cc). This affects low end torque and throttle response. This is one case where bigger is not always better. When choosing heads, you usually want to go with the smallest cc intake runner that has sufficient flow.

My set of ported LT1 heads cost me $1150. That’s about the same as a set of new LT4s. They flow a good deal more than the unmodified LT4s, and come with the springs and valves that I specify. If you will be using a cam larger than the LT4 hot cam, you will need to change the springs (and possibly machine the heads to make the springs fit) on the LT4 heads, which adds cost.

Adding in all the parts that come with a LT4 conversion kit, the ported LT1 heads are still hundreds less, especially since you can reuse the LT1 intake you already have. More flow, meaning more performance, but less money. That’s why people say what they do.

Now if money isn’t an issue, then by all means, buy the LT4s (~$1200), have them ported (another $500 to $1000), and then install the springs and valves you want. By the time you do that, you’ll have $2-3000 in the heads for not that much added performance. The added cost of that added performance is pretty extreme sometimes.

If you are putting the heads on a stock 350 shortblock, then you really are better going with the LT1s. The 350 can’t take advantage of the extra flow from the ported LT4s, unless it is revving pretty high. Now if you are running a stroker or nitrous or a blower, then the equation changes.

There are a number of people here with 350s that put out upwards of 400 hp at the wheels using ported LT1 heads.

 

^ Same as what I said, just more detail.

 

400hp at the crank is good enough for me, thanks for the info