Hey Guys,

Well this is my first post and first experience with the website so I hope you will forgive me for any items that could be found using the search tool. I have spent the last 3 days looking at all kinds of information on the site and I am getting very mixed views on a lot of my items, so I am going to post to see if I can get some answers.

First off so project background:

I am performing an LS conversion on a 1973 Datsun 240z. The original plan was to go with an LS1, but I got a screaming deal on a 5.3 LS from a Silverado with very low miles. This LM7 is stock from oil pan to intake and is complete, less the ECU. I also from the same deal got a set of 243 aluminum cylinder heads.

My goal is to make a streetable 400-450 RWHP on the N/A motor. I plan to turbo down the road, but that is not the case right now and a new topic all together. From what I have read, this is doable, but something has to give on the 5.3.

My questions are as follows:

1. From what I have read lots of people bore the motors to accommodate the larger LS1 pistons to increase the displacement up to 5.7L and basically have an iron version LS1.

Also from my research it seems that I can use the crank and the connecting rods from the 5.3 and just change the pistons? Is this correct?

2. If I do decide to bore out the motor, can I use the 243 cylinder heads on the motor? Should I make any modifications to the heads as I rebuild them, such as LS7 springs and valves?

3. Cam suggestions?

I am always open to suggestions and feedback, so please let me know what you guys think! And again, I have a lot of money to put into the car in other places, so please keep budget in mind as a consideration. Thanks!

 

What's up bud welcome to the dark side. I have a personal love for the Z chassis so kudos.

I know you are talking about staying NA and possibly turbo down the road but....given your goals the cost of converting a 5.3 to 5.7 is likely going to be the same or more than going boost with a cheap setup. Between parts and machining for the conversion I would likely jump right to a small frame turbo like GT45 ($300< on eBay) and stay stock cam or oem LS based cam and so forth. Change head gaskets add china studs possibly some springs...maybe LS7 lifters, and boost it.

Check out the FI section there are a lot of budget builds exceeding your goal for a cost friendly price.

Once again....just my 2 cents given the idea of the bump in displacement.

 

Hey there,

As appealing as a turbo setup sounds to me, I am going to try to concentrate on keeping it N/A and running well until I get all the kinks worked out everywhere else in the car as I am sure I will go overbudget in other areas, such as the Tranny, rear-end, etc.

I would be thrilled if I could get 400 RWHP out of the 5.3 by rebuilding and upgrading the 243 heads and throwing in a lumpier cam, an intake, and a tune, but I'm just not sure if this is realistic, especially since I want to keep it off spray, on 91 octane, and I live in Canada lol.

After I get the car completed and running and driving well.... then I will go boost crazy . If you still think this is the better option though I am open to opinions.

Any thoughts on the upgrades to the heads and cam? I am in Alberta and for as big as the LS motors are in the States, believe it or not, in central Alberta it is hard to find somebody who works on these on a daily basis to get solid feedback from.

 

Good choice taking the 5.3 to an Iron block LS! I just finished building my 5.3. You can bore it out to 3.905" max before you have to sleeve it and then it gets super expensive. I ended up boring mine from 3.780 to 3.899 and running at the very least a 200 shot. Everything is forged but if you have the money I suggest doing it. As far as your bore goes though I would suggest not going to full bore right from the start. If something happens and you need to re-bore, youre outta luck unless youre gonna sleeve it, just something to think about for the future. Hope this helps a little!

 

From another post:

"5.3 Vortec = $500
LS1 intake/rails/injectors = $200
professionally ported heads = $250
Cam/valve springs/pushrods = $500 (still need to research what cam I want)
Sikky long tube headers = $600
high flow cats/exhaust = $300-$400
Good tune = $250

Think this should put me in the 400hp range fairly cheaply and easily."

If you are sticking with NA and a 5.3 243 or 799 (more expensive) heads would help reach your goals from what research I have done.

 

Yes that's very similar to what I am planning on doing. The 243 cylinder heads, a bigger cam, an ls3 tb, long tubes, and a tune. Not sure what I will put down but I'm hoping somewhere in that 400 range. I'm hoping the cylinder heads will bump my compression but still leave it driveable on the street and give me hp I crave lol. If I'm short it'll just have to wait till the Turbo goes on lol. Any last other mods that'll help me teach my goal?

 

$250 "professionally" ported heads may net 400fwhp but not 400rwhp.

 

So if the stock bore is 3.780 and the max is 3.905 how much over did you go? 90 over would be 3.780 + .090 =3.870 the machine shop guy I talked to told me 30 over would be the max (but he was not for sure) I'm building the same engine as we'll and stuck at this part before I get my block done I'd rather ask you since you have done it before

This is my first engine build I'm doing and being a real newbie right no sorry

 

My bore is 3.899" so its .119" over. Did a lot of research and know some people who have gone straight to 3.905. My pistons are 3.898" but I had to go an extra thou over due to the nitrous. Whatever you decide to go with make sure you find all the parts before you do it I.E. crank, rods, pistons, heads. If you have it machined and cant find the parts youre screwed. It took me a little while to put together what I have now just due to the odd-ball bore, but its well worth it.

The pistons I went with were Mahle, cant remember the part # off hand, if you need it let me know.