Hey all, I have a 99 C5 with a 6 speed manual. The Engine is mostly bone stock and at about 155k miles. The only modification engine wise I've done is put a Vararam VR-B2 intake on it. Since I bought the car, my plan had always been to just LS3 swap it one day. But it's been like 3 years now and I don't think I'm going to be able to budget the LS3 anytime soon really. So, I'm starting to consider some cheaper immediate upgrades to my LS1. Outside of the engine I've gone through most other parts of the car. Redid all the suspension, put on coil overs, swapped the trans and rear end with one with 44k miles on it (the original one had synchros going bad and I got a good deal on the 44k trans + rear end).

I see a lot of people advocate for a supercharger, but I honestly am worried if that would be a good choice for my engine without quite a bit of other work. My compression numbers are not stellar and kind of all over the place.From 153 to 174. I'm worried if a FI it I'm just got to blow something out somewhere lol. That said, the car does run and drive well. It isn't a slouch and is fun to drive, but I would like a bit more.

I would also like to try to do some smaller upgrades that I can perhaps do in stages.I'd love to eventually get the car into the mid 400 hp range (500 would be amazing but 425 to 450 would be enough to make me happy). It's just a weekend cruiser that I might a couple times a year take to an open track night just for some fun.

So recently I've started looking at what other mods I might can make. It looks like doing LS6 stuff is a good option? I was looking into a set of LS6 heads, but it almost seems like if you do that especially on an engine with this many miles there are quite a few other things you want to do at the same time. And also I wonder if it really makes sense to do the heads without doing the intake manifold, throttle body, and a cam at the same time =/ I've read in some places doing the heads could help improve compression numbers which is what has gotten me thinking about them lately. I might could swing heads, manifold, throttle body in one go, but adding the cam and all the other auxiliary stuff that I'm not thinking about would probably strain my budget right now.

I'm also concerned about tuning with all of this stuff. For one, I have no idea who would be a good tuner that is remotely close to Columbia, SC area. And for two, I imagine tunning with a good tuner ain't going to be cheap either =/

So, what do others think would be a good direction to go here? If I set a current budget at $2k maybe $2.5k, doing all the work minus tuning myself, how far could that get me?

 

I'll be honest with you; I think you should save your money. If your compression is inconsistent like that, I wouldn't be putting money into mods to allow it to perform better, so to speak. I know an LS3 swap isn't cheap but on the same token, your LS1 sounds like its tired and you should put some funds aside to either swap it with something else or rebuild that thing.

 

If your intention is to blow it up so you have to buy a new motor, then proceed. If not, I would leave it alone.....enjoy the car, and save your money for a proper motor swap.

 

When compression varies this much I have to ask if the numbers repeat? I’ve tried several newer gages and had less than consistent results.

 

I'll go the other way and say go for it.

Your compression numbers are within 10%ish.

I would not spend a lot on the LS1 upgrades since you are planning on going LS3 route later. I would get stuff that you could sell down the road for about what you paid. LS6 intake manifold and a freshened up set of 243/799 heads. This would get you Z06 power and maintain reliability and keep the while your in there cost down.( not a lot of gaskets for the heads/intake)
You can also check out the condition of rockers pushrods cam lobes while the heads are off. The cost will go up rapidly if you do the cam. Way more while your in there parts and stuff you need pushrods, springs, more gaskets, oil pump, timing chain and so on.

I would skip the larger throttle body since the intake it would mount to likely won't mate to LS3 heads.

Headers would be another good idea and should work with the LS3 from what I have seen (could be wrong here).

The tune you could do a mail order. you will likely have to invest in the tuning software, but a lot of forum vendors and members offer this service.

Let us know what you decide.

 

So, seems like the general consensus is that none of the upgrades I could do (like heads) would help? It would need a complete rebuild? I mean if that is the route that I need to go, I might look into finding a cheap LS1 that has a good block and just rebuild it then swap it in when it's ready. Would still be quite a bit cheaper than an LS3. But, besides budget, the only reason I have not really been considering that as an option is it looks really difficult to pull the engine in these cars without a lift which I don't have access to currently. And I enjoy working on the car as a hobby too much myself, plus don't want to pay the labor for someone else to do it lol.

As for the consistency, yeah I took each reading 3 times dry and 3 times with a bit of oil in the cylinder. They were fairly consistent on each cylinder between all the readings.


I appreciate the feedback, it kind of confirms my worry that this engine is just too tired to be worth doing anything with. But it is what it is.

 

Between Engine Masters and Richard Holdener YouTube videos there are far more than a few examples of motors in similar condition making serious power. I apologize if I missed it, but did you provide oil pressure numbers to go with compression? Lower compression will lead to more blow by, oil consumption, and slap, but bad oil pressure can be
much worse.

 

Oh yeah, mentioning oil pressure would've been good. According to the instrument cluster, when I'm cruising in 6th gear around 1k RPM it's around 35 - 40. If I'm accelerating hard 3k+ RPM it gets up to around 60.

It doesn't burn any oil, never see any blueish exhaust smoke. And the level on the dipstick is very consistent. I also park it in a garage on concrete and never see any oil on the floor.

Last oil change (less than 500 miles ago) I put 10w-30 full synthetic high mileage mobil 1 in it.

 

Of course upgrades will increase HP/TQ. Heads, cam, intake manifold, headers, tune. Maybe you get away with a fun street car ...but you want to track the car too? ....that's just borrowed time. It all depends on how many times you want to spend the money, tear it apart, etc. If you blow it up on the track, and can't afford to drive it for months......is it worth it? All depends on your tolerance for spending money twice, your time, and down time.

 

Sorry, I meant that it wouldn't help improve the compression numbers. I know that upgrades would help to improve HP lol =/

As far as if I do blow it up, not a big deal. It's not my daily or anything. If I had to park it for a while, it would suck for sure, but the fact that I might have to deal with waiting on the side of the road for someone to come pick me up to go get my trailer bothers me more than having to work on it more :P

 

Sounds like you've got it all figured out. Good luck with your choices.

 

Haha, I wish...

No, that is why I came here to post to see what others would suggest as an upgrade path if I did start doing upgrades. But, I'm also willing to accept that my engine might not be able to handle them as well. I'm a shadetree / youtube hobbyist, not a professional expert mechanic. I didn't come here saying that I'm ready to blow the engine up, I merely responded to your statement about if blowing it up would be worth it to say that ultimately it's not a big deal to me if I did blow it up.

So, I would still value opinions on the best upgrade path in stages, or further opinions that it isn't a good idea on this engine. So that I can decide if it would be worth upgrades on this engine, or trying to figure out a way to pull the engine if I went a rebuild route.

 

With all of the external mods you've done it sounds like you've put together a fairly nice car, it just has an engine with moderately high miles. Maybe do headers, tune and some additional cooling for oil. Get out on track (HPDE) and see if that's a segment of the hobby you'd like to delve into. Finding another LS engine to build for a future swap sounds like an excellent idea to me as you can build it as robust as needed depending on your power desires.