Mngnt

I have a '90 RX7 turbo ii. Rotary is coming out shortly, putting an LS v8 in.

Hoping to do this is affordably as possible.

I currently have the following:
-LS1 intake
-LS1 241 heads with springs
-LS1 factory camshaft.

Tomorrow I'm hoping to pick up a salvage running 2wd 04 gmc 1500 with lm7 & 4l60e with 100k miles at an auction.

I'm conflicted between a Chinese turbo setup and a good cam (224/232) setup.

Stock lm7 CR is 9.5:1.

If I put the 241 heads on and find flat top 4.8l pistons, CR is 9.7:1, almost the same. Is this worth doing?

Alternatively, should I just use the LS1 cam with factory heads and ls1 springs for a 65hp boost and just run it until I'm bored, then throw a turbo on? Are 241 heads worth anything? I'm not against selling things to fund others...

Help!

Mercier

iTrader: (15)

You will need car front accessories or some cutting/massaging to run a car(ls1) intake with the truck front dress..the truck setup sits further out from the motor. Search for this in the conversions and hybrids forum--a guy did it himself. Otherwise the throttle body will hit the water pump.

If you wanna go NA on a budget for now(I think it will be very fun in such a light car), keep the 862 heads and put LS6 springs($60) and have the 5.3 heads(862s?) machined to accept the LS1 sized intake valve and milled .020" to get you to almost 10:1 compression. You can also use the springs and intake valves off the 241s if you want to save $$. The 862s IMO flow well enough for a LS1 intake when they have the bigger int valve compared to the 241s. That'll get you some power for very little $ at the machine shop. Then you can keep the 241s and slap those on for low compression when you want to go turbo.

What year is your LS1 cam? They are not created equal but are all larger than the LM7 cam. Also keep in mind Gen III and Gen iv motors are different so make sure of what you have.

241s are not bad heads but so plentiful they can be had for $150 or less to the smart shopper.

Mngnt

Thanks for the reply. I'm aware of what's required to make it fit, so I'm prepared (mostly) for that

Didn't get the truck at auction today, so we'll see what I end up with (LM7 or LQ4?).

Cam/heads are from a 2000 firebird.

Are the larger intake valves worthwhile? I was thinking of going with stock 862s, LS1 cam & springs only. No machine shop necessary.

Which leads me to my next noob question - are used heads sold with or without springs? IE - Could I get anything for the 241 heads with no springs?

Thanks

Mercier

iTrader: (15)

Are you anywhere near me? I finally got off my butt and pulled the LM7 out of the Jeep last night. Great motor and in great shape. Found a deal on a low mile LS2 I couldn't pass up otherwise I'd still be running it.

The major restriction on the 862s is the stock intake valve which is smaller than the LS1. Exhaust valve size is the same. My LM7 still ran great in the ~3000lb Jeep and that was with the OLD 5.3 truck intake which is a relative dog. But the LS1 cam is designed with the 2" intake valve in mind. I was going to do the same though with the LS1 cam and 862s but was going to put the bigger valves and mill..have a set of 853s(same as 241 mostly) and was going to rob the valves and springs from them.

Usually used heads are sold assembled. Bare, they are almost not worth shipping. Maybe $50-$100 to someone local that really wants them.

Mngnt

Ah I see, thanks for the info.

Unfortunately I'm up in Canada It snowed today

Mercier

iTrader: (15)

Ha! It's 90 degrees with with 1,000,000% humidity. Wish it were cooler but IDK about snow in early September. We might get an inch in January or so.

wayverippah

iTrader: (1)

I was in a similar situation putting an LM7 into my 280z. I ended up throwing an ls2 intake with fbody accessories on, with 799 heads (milled for compression) and an ls6 cam.

This got me going until I could afford to turbo it. Wasn't all that expensive either. You can avoid milling the heads if you throw in the 4.8 pistons.

RobMinhas

Where in Canada are you? I'm in Calgary, snowed here on the 8th too...

Sorry to derail the thread a bit but I just want to sure I'm understanding right, a 5.3 LM7 can have an LS1 cam and springs swapped in for an upgrade with everything else left alone? No modifications needed?

Mercier

iTrader: (15)

This is what I was planning a few months ago before I changed paths.. I suspect that the LM7 valve springs are similar or same to LS1 units but since nobody want them might as well be safe with the springs that came with the cam. Lifters are fine or you could use this opportunity to upgrade to the relatively affordable "LS7" lifters from GM depending on your budget.

See this page:

http://www.smokemup.com/tech/ls1.php

It looks like as long as you get the bigger of the LS1 cams, you can pick up about 10% lift and almost 10% duration(more exhaust than intake) by swapping to LS1 cam. Should wake it up a little. Not as much as LS6 cam or bigger, but those require LS6 or better springs too.

I've still got the 2000 LS1 cam, springs, retainers, pushrods from a 2000 Corvette I likely won't do anything with now if interested. $60+shipping. Should be the "biggest" of the LS1 cams.

Mngnt

Hi All,

I appreciate the input to this point! I'm happy to say, I'll be creating a "build" thread shortly

Today I picked up a 2002 GMC truck with 90k miles on it. 4.8L (cable throttle) and 4L60 for $350 Salvage truck from body damage pretty much all over, but still starts & runs so mechanically should be OK.

I'm likely going to sell the LS1 cam & heads.

The next big question is whether I should throw a turbo on there right away. Apparently the truck injectors & rail won't be a direct fit into the LS1 intake, so if I go turbo and buy new injectors I'd save that headache.

Which brings me to my next dumb question. I've read about turbo sizes & specs. However most stores list more specs than what people talk about.

IE - "76mm .96 A/R". Is that 0.96 A/R the Turbine (hot) or Compressor (cold) side?