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4.6 block build and differences questions

2K views 8 replies 5 participants last post by  seawalkersee 
#1 ·
I am considering building an engine for my 4.6L Explorer, but wanted to find out which 4.6 blocks would be best as a starting point.

Currently it has the same aluminum block as what a 99-01 Cobra and the Machs have (as its an 03). But I believe the internals are all the same as what an 03 GT would have, correct?

Stock as it sits now, it has I believe 260HP, which I'd like to get up around 300-320 or so if I do this build.

Any thoughts as to what would be the best starting point and recipe for what I want? Using the current block is not an option as its in the vehicle and I still use it daily but instead want to build something on the side.

TIA.
 
#5 ·
He has an aluminum block, and the 96-01 cobras had a forged crank, but the rods and pistons are basically the same as the GTs and other 2Vs.

I thought the explorer blocks were aluminum...If they are not, get one, slap a set of NPI pistons in it, get some good heads and cams. You will need some exhaust to support it.

SWS
They do depending on year, his 03 is still aluminum, at some point they switched to an iron block like the rest of the trucks but I'm not sure when.
 
#3 ·
just do cams long tubes and full bolts ons, should get you 270-280ish to the tire through your auto and awd transfer case. if you want more than that with an auto you need headwork and increase compression
 
#6 · (Edited)
The motor's basically the same as the mustangs but with a WAP block. And 03 Explorers were rated like 240hp and 285ftlbs. Is that 300-320hp you want at the wheels or crank?
You could do cams, exhaust, and tune and get a nice increase or if you want more get another WAP shortblock, swap in NPI or 4V pistons, have them notched for intake valve clearance and do cams, ported heads, exhaust, and tune. Or you could do a blower on your current motor and get more hp than what you currently want.
 
#7 · (Edited)
Thanks for all the responses.

Yes, my current block is aluminum. Aluminum blocks were used in 2002 and part of 2003. I have a January 03 built chassis and it's a Limited, so I am guessing that's one of the reasons it's made its way. This engine is rated for 260 HP, just like the Mustangs of the same era (roughly).

Using this block is not an option though, two-fold. One... I've had some unsolvable coolant loss issues with this engine (It just disappears). We initially thought head gasket, wound up rebuilding the heads and regasketing the whole top end, but I still have some coolant loss (not like I did). Heads were tanked and checked for cracks etc). block was checked for straightness (in chassis). Secondly, the vehicle is operational, I just need to top it off weekly with a few ounces. So, I thought, about building something over the winter and installing it in the spring when the weather is more in my favor.

Long tubes are not an option because of the transfer case and tight clearance. Explorer chassis headers are about $500, so I may order those. I do plan on installing a Magnaflow exhaust system too. Cams are something I am considering too, but also hoping the current Y-pipe won't choke on any increased flow, if so, then a friend of mine who owns a muffler shop do a custom Y pipe and new pipes throughout.

Sounds like the cam and exhaust are going to net me the greatest increase for not a lot of money. Also head porting is an option as my father does that.

I am all new to 4.6's so can any explain the piston variations?

I am also shopping around a little and I only see overbore kits for .010 over. I am assuming its not wise to bore too much on these blocks especially the aluminum ones correct?

Again, thanks for the responses thus far.
 
#8 ·
.030 is the max overbore you want to do on the wap block, a .020 over is common and as far as piston selection at .010 is going to be hard to come by. the explorer also has the aluminum block from 02-05.
 
#9 ·
Wait, you are related to someone who ports heads? You are buddies with someone who owns a muffler shop? And you do not have custom mufflers and ported heads already?
If you are worried about the cost of headers, have your manifolds honed and coat them with some of the heat coatings. Then have some 2.5 down tubes/y-pipe made that goes into a 3" single.

Get some cams and decide if you want to blow it or not.

SWS
 
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