720 Frontier swap

[Robert]

Some may remeber this thread

 

http://community.ratsun.net/topic/56910-my-720/

 

 

I found a really cheap 2001 Frontier engine in great shape. Completely building it like the current engine in the truck that is a 240sx engine. Reasons are the oil pan and mounts will allow the new engine to sit about 2.5" lower while keeping the frame pedistals stock.

 

While disassembling the engine I wanted to compare the two heads. here is what i found and some things I found surprising.

 

Truck head has larger ports on both intake and exhaust. The valve pockets on the truck head were straighter with less valve guide inpedence. Valve springs on the truck head were MUCH smaller and very soft. I could compress them by hand. 240sx springs were shorter, much thicker and I was unable to compress by hand. Of course valves, buckets and everything else was the same. The truck only had 5 cam caps vs the cars 6. The 6th cap on the 240sx heads is basically useless since it doesnt hover over any valves. Trucks exhaust cam is a very short duration but intake is the same. Intake on the truck has no plenum but the runners are nearely the same length and diameter.

 

Here is what I am going to do.

 

 

Use the truck intake and throttle body. The truck has a MUCH easier sensor location for wiring idle valves, injectors, and sensors. All wiring can be loomed above the intake instead of through it. It also allows me to relocate the power steering pump to the passenger side and use stock power steering lines. Currently the car power steering forces me to have very short, and sharp bent lines to the box. I will be using the 240sx cam springs and camshafts. The larger ported head will match those cams better. IMO the 240sx camshaft and intake design narrowed the power band horribly in the 240sx. Long intake runners, camshafts for higher rpms, and small ports were a poor combo. Atleast with the truck head, I will have larger straighter ports matching the camshafts...the long runners are just going to have to stay. I like the wiring and sensor locations with it. I will be keeping the 240sx transmission atleaast for another year....locating a 6 speed Frontier tranny to swap in later. Lowering my final drive to 3.7:1 from my current 4.11:1 allowing better highway RPMs and keeping the easier 1st gear take off.

 

I will be posting photos this weekend of both engines and their differences.

[_chiefjt]

Nice! Good info too.

[RedSquare]

Good info. I'm planning on pulling my 720's Z24 out after I finish my 240 projects.

[Robert]

Ok, here is the update....

 

 

Wiseco Pistons came in yesterday.

Eagle Rods just arrived today.

Have the Bearings, gasket kit and timing chain kit.

 

Assembly will now commence. I have an MS3 with MS3x expansion board with the knock module. I have torn apart a 240SX and seperated all the wires. Took the coil wires off a 2007 honda harness for the COPs. Once I get the motor together I will build the hardness and strip my engine bay and repaint it. Will probably ditch the AEM EMS4 thats in it now and find another project for it.

 

The stand alone AEM EMS4 is a good unit, its simple and clean as far as the ECU. Its a bit glitchy for my taste and the Software is not open source so its not as fun as the Megatune program.

 

I promised photos of the two blocks and heads so I will get them uploaded this weekend.

 

I have seen alot of talk in other forums about the Frontier block being "weak". I will post photos that show the issues people assume will make it weak and let everyone decide on their own. I have yet to see a Frontier Block break from too much power or boost so I cannot say they are stronger or weaker than a 240sx block. Well as a matter of fact, the people claiming they are weak havent seen one break either....so, makes one wonder of the validity of the claims.

 

For the block, it doesnt have a crank girdle, which i wouldnt say adds much strength to the block itself but more of an assembly tool. Crank girdles which are part of the block as in K series motors that are all aluminum do strengthen the block. Also, the frontier block has main caps which are twice the size of the 240sx blocks (much thicker) which would be the weakest part of the whole engine. 240sx blocks handle upwards of 600hp and I guarantee its not because of the mains being part of a girdle. Then there is the issue of the block being weaker since it is narrowed at the bellhousing (I will need to show photos of this to explain it better) but what is not explained is that the truck block is actually MORE than twice the thickness at the bell housing than the 240sx block. This is why the crank shaft is one inch longer and the starter has a longer reach. IMO the bellhousing of the truck is stronger than the 240sx block. Inside the engine they both look very similar except the truck block has an oil galley from the rear pickup to the front cover.....this also adds a fair amount of metal through the length of the block but whether or not it strenghtens it or not is just speculation.

 

To sum it up, there are some 240sx block pushing over 1000hp. Worse case senerio, if the truck block is weaker by half as much, then it should hold over 500hp. BUT I would be confident in saying its equally strong but willing to comprimise with anyone and say it is 50% weaker and will then hold more then 750hp.

 

Anyways, my build will be capable of over 600hp but certainly the limiting factors in building a big hp truck is not the engines block but the truck itself....so, anyone getting bashed on turboing the truck block by people saying its weak (or weaker) compared to the 240sx block, ask them how many truck blocks they know of that have broken. Then point them to my build...lol.

 

Ok, rant off. Photos coming next week.