flatlander757

Alright guys, first off I'm posting here not because I have a GM truck, but because I'm considering using a 5.3L "LM7" in my V8 RX7 swap that I'll be doing this month. I would go LS1, but it's about 3x more expensive and this will be a budget build.

I have been searching this forum for a little while and have basically figured out that the truck intake, oilpan, and accessories are the main external differences from a regular LS1 engine, so I'll be swapping all those. And of course the less bore and iron block.

I need to know what exactly makes putting an LS6 intake on a truck engine such a difficult task? Is it the accessory drive or what? I will be deleting A/C and P/S when I build my car, so I'll only need an alternator, waterpump, and crank pulley.

I've found that the 5.3s have a lower C/R at 8.5 which is less than optimal for a naturally aspirated build. How high can you bump that figure by milling the heads and installing thinner gaskets? And would this make it necessary to mill the intake as well? What is the stock 5.3L combustion chamber size? I've heard that Edelbrock has/is coming out with some 5.3 heads to help flow better. Any info on this would be greatly appreciated!

As for cams, what size cam could I get to get a significant SOTP boost and still stockish drivability? I will be using a T56 6 speed and this car will weigh no more than 2900lbs so take that into consideration.

Let me know what you guys think of putting a truck engine into a lightweight import... I'll keep you guys posted if you like

03sierraslt

iTrader: (22)

Where did you see that the 5.3 had a CR of 8.5-1? I believe it is 9.4-1 or somewhere around that. Being that you are putting this in a light car with a manual you could most likely use a decent sized cam with decent mid and strong top end however I would suggest that you upgrade the valve train if doing so in an effort to get the most out of the cam. Maybe some arp rod bolts as well. I am not a cam expert so others will chime in. Just some thoughts....

flatlander757

Of course valvetrain upgrades will go hand in hand with the cam... I forgot to mention that.

I work for a Dodge dealership so have a bit more automotive knowledge than other 17yo kids

You're right on the compression ratio... I must have heard 8.5 somewhere else...

http://www.carcraft.com/techarticles...s1/index2.html

It is 9.5.

Silver LT

A couple of answers:

Regarding the intake, the truck intake moves the TB up a few inches, compared to the LS1/LS6, to clear the radiator fan. If you have electric fans, there should be no problem making the switch.

As for a cam, you might consider the 2002 and later LS6 cam. It makes about 40 hp more than the stock truck cam (204/218 .555/.551 vs 196/207 .467/.479). There is a compromise though, since this cam makes it's power from 4000 up, below 4000 it makes less torque than stock. One note - this cam has a smaller base circle than the standard cam and will require pushrods that are about .025 inches longer. Don't forget to change the valve springs!

New heads are available from Edelbrock, Air Flow Research, and Dart, but the chambers have more cc's than the 5.3 heads; so these would need to be milled to get back to 9.5:1 ratio. Another, and cheaper option, would be to have the stock heads ported and larger intake valves installed. So far, I have not heard of anyone milling the intake manifold (they are "plastic"), but it would propably be a bad idea since you would be removing the material that keeps the o-rings in place.

If you don't already have a copy, "How To Build High-Performance Chevy LS1/LS6 V-8s", by Will Handzel, would be a great reference book for what you are planning on doing.

goshawk23

well, as far as the ls6 intake, the main things people run into as far as a swap is the water pump and fuel rail. you can use 98 corvette water pump and fuel rails for this. the water pump will get the house neck out of the way so you won't have clearance issues. the ruel rails will get the hose/line in the rear of the intake down low vs the truck intake line. it will stick way up.

if you want an ls1, why don't you bore the 5.3 to make an iron block ls1. you can buy stock pistons for cheap and rings will cost you what 140 bucks. only difference is weight. 60 pounds? i do like your thinking in using a lsx based motor for the build. i am sure some other folks will come in here and provide more info.

litreddevil

iTrader: (4)

well with a car like that i would go with the tr224 cam,put the valves out of the car heads,2.0 ans 1.55 r 1.60 don't remember on that exact size u can shave the up to about 50 ths and b ok,i would not put the motor n with out rod bolts with a 6 speed put some 4.56 in the rear r advance the the cam 2* then another 2* just don't go more than 4* also remember that new parts can make a build slower use the classified ads and ebay

1ImperialSS

iTrader: (5)

since the cam is going in a manual 2900lb car IMO you should go bigger than just a 224, in my 5000 lb automatic truck in going 226 you could probably afford to go with a 226/230 or something decently sized. you'l be spinning high rpm's though so you'll need rod bolts for sure and defintly the car intake will take care of your high rpm problems. you'll need some good head work too WCCH just came out with new 5.3 heads that should help you out pretty good too. im with goshawk, just bore it to 350 and have an iron LS1. thats what you could even name the car

Richard@WCCH

iTrader: (3)

The car intake will have better hood clearance than the truck intake. You'll want to use a car waterpump and alternator bracket to make the conversion work properly. Also fuel rails and injectors from the cars are needed with the car intake.
As mentioned above, we now have a CNC ported head built specifically for the 5.3l engine. The chambers are 2cc smaller than stock so you would see a net increase in compression. Look for cams in the 224º-228º and .560"-.600" lift. Have it ground on a 110º-112º lobe separation. This will make a very responsive engine in a small light car.

Good luck,

Richard

flatlander757

Thanks for all the help guys... I plan on getting the engine in the car and running in stock form first so I won't have as hard of a time pinpointing problems when it is first running.

BTW- the RX7 has 4.10 rear end gears stock so I'll be fine as far as that goes

Can't wait... but I have to I'm waiting for a good Turbo II or GTU model to go for sale in this area... then it shall begin

Hydramatic

There's a red FC vert right down the road from me. I think the guy wants like 4000 tho... Really clean car.