Hello everyone. I have a 2003 SS with the L36. I was wondering if the stock 180,000 mile block would be able to handle a topswap + an XP cam? Would it be best to get a lower mileage block from say, the scrapyard and refresh all of the gaskets? I also have a tranny that was rebuilt at 150k, but was looking into a possible 4T80e swap from a Deville, as I feel like it would be cheaper and more reliable than a built 4t65e trans. Would it be better to stick with the 4t65e or swap in a 4t80e? Let me know what you guys think!

 

IMO the engine should be fine. Id do a leak down + compression test first just to make sure things the rings are still holding up ok and send it. These engines aren't usually the weak point - its usually rust, a wreck, or the transmission thats the issue. Tons and tons of examples of 200k++ 3800s if one of those 3 doesn't take it out.

A lower mile junkyard engine could be better of course, but there's a bit of a gamble too as occasionally you'll get one that wasnt well maintained. Assuming you know your engine's history fairly well, I think you've got a good bit more life left as is.


As for the transmission, I wouldnt even remotely consider a 4t80 at that power level. A lot of people talk about it (mostly from the LS4 side), but the number of people that have successfully done this on the 3800 is pretty low - I think under 10 as far as Ive seen. At least a couple of those swaps aren't even running anymore today.

IMO the 4t80 is a route to consider for someone on the high end of 3800 power where they'd really want a 4t65 build using the discontinued GMR parts for longevity. When you're talking about dumping $5k++ into a transmission to hold together, thats when diving into the 4t80 starts to become appealing.

But at the power level of a XP/top swap car - a 4t65 can handle that all day without all of the hassle of a 4t80 swap. Even a stock 4t65 should last awhile if you aren't beating om it hard all the time.

 

I unfortunately do not know much about the history of the engine in the past year that I have owned it, other than me physically seeing that it has been neglected. The first oil change I did I'd say about ~2-3 quarts came out of the engine, and it was very dark. Then I drained the coolant, which didn't even have a gallon in it. Tranny fluid checked out seeing how it had been remanufactured at 150k but the car has likely been neglected since 2011, a time where it got in an accident that rendered it as a salvage. My brother who owned it previously also drove it hard, pretty much flooring it on cold starts and speeding at like 100 mph on the highway. Otherwise, the frame is great and has no rust seeing how it has likely been in the Albuquerque region for most of it's life. I'll do a compression and leakdown test sometime this week to further see the condition, but it runs really well after doing all of the much needed maintenance and I've noticed no issues commonly associated with low compression. Another question is tuning. I'm certain I want to tune the vehicle myself, but where would be a good starting place to learn how to tune these engines? Let me know, thanks.

 

That's a tough one - sounds like you're rolling the dice a bit either way. Personally I'd pull the engine either way doing those kind of mods - assuming you do them together, youre stripping the engine down to the bare bottom end anyways, so it wouldn't be a ton more work to slap a different bottom end in it. But if the compression is good on the current engine and there's no metal in the oil, the current one would probably be fine too. Id probably add tossing a straight edge across the cylinders while you've got the heads off for the top swap due to the coolant level, just to be sure its straight.


As for tuning, theres really only one new option for full tuning these days - HPTuners. Theyve got a good bit of 3800 tuning posts / content on their forums, so Id probably start reading there. The bad thing with 3800s is there isn't a really good, singular guide Ive ever come across.You may find "Jerrys Guide" from back in the DHP Powrtuner days (a gm v6 specific full tuner thats long since been discontinued), but its got fairly outdated methods in it (and isn't written for HPT so the menus aren't the same). I learned from reading hundreds of threads on the old DHP boards, but I think those are long gone too at this point (and were password protected to people who bought DHP, so likely inaccessible with wayback machine).

Realistically, the fundamentals aren't really different from generic LS tuning- its just a matter of learning what these engines like. You'll obviously have to flash the L67 stock tables for the top swap and that'll be enough to get you up and running/driving. From there its just the typical dialing in fueling via wideband and then optimizing timing. Iterative processing of reading AFR and fuel trims at each fuel cell and modifying to hit the targets you want.

The big thing with these is knock / KR, especially with stock pistons. If you've got areas of more than a few degrees of knock, you need to fix it before moving on or you'll end up chunking pistons. These aren't nearly as tolerant as the LSs are (due to boost) so its critical to eliminate KR.

 

Just picked up a compression test kit at AutoZone, will post results soon for the compression test. Is there a good magnetic drain bolt that you would recommend that would allow me to better see metal fragments that could be coming from my engine? Let me know.

To be on the safer side, would it be a good idea to run the stock 3.8 pulley until I get the tune dialed in? Or would it be acceptable to run a pulley size acceptable for my mods (scanning for knock of course) and just not getting on it? I don't want to pop a piston and have to go through the pain of pulling the engine out for a second time and replacing the block.

 

TBH I bought my 3800 drain plug probably 20 years ago, so I'm not sure what's available these days. When I recently got one for our new Traverse, I bought the brand "Gold Plug". It was overall a bit shorter than stock, but the magnet was crazy strong.

Honestly though a magnetic plug isn't a great way to check for bearing condition as some of the metals in bearings aren't magnetic. I usually just do a visual look through the oil to look for "glitter". A more scientific approach would be to get a Blackstone Lab Analysis - their standard $35 report includes a spectral analysis which tells the exact ppm of all kinds of common metals.


Either way works. If you do the latter, I'd either disable the BBV or remove the SC belt until youre ready / have a scanner hooked up. Keeps you from accidentally forgetting or getting into part throttle knock.

I will say for a top swap the 4.2" is usually the starter pulley for no knock (and no mods), so even just keeping the stock 3.8" on there is a good upgrade with the increased compression. One thing to keep in mind as you mod is to try to balance timing and boost. A 3.4" with 18 degrees of timing and good fueling would destroy a 3.0" car with 8 degrees of timing running 10:1 WOT AFR. Power rolls off pretty quick when you have to neuter timing and flood it with fuel to keep it from knocking itself to death.

 

I'll just go with this option. If compression checks out and there is little to no glitter, it would likely be fine.

Knowing this, I'm confident to put a 3.8 pulley on there considering I'm camming it and already have a 3.0 downpipe with an intake, front plog and other small mods ready for installation. Thank you for all of the information thus far. You truly are a 3800 wizard

​​​​​​​Compression test results coming tomorrow!

 

Nice - sounds like you've got a good start with mods! Refreshing to see - so many people approach this the other way - slap a tiny pulley on it then rush to throw mods at it until the knock goes away.

 

Thank you bumpin. Just want to use common sense especially when applying boost to a high mileage block.

As for the compression test, I was only able to finish the front 3 cylinders before I lost the 14 mm thread hole adapter somewhere in the engine bay. I ordered a kit of my own but otherwise, front three cylinders have a compression of 120 psi. I'm not sure what the compression level is on brand new L36's, but surely these close ratings are good? Let me know

 

Honestly I've not seen a reading like that before. The L67s I've done (granted with about 0.9 less compression ratio than you have) seem to be up around 150-200 (obviously not that whole span on one engine, but the total range of several engines).

I have seen low readings before, but its usually way lower- ie 5 cylinders at 150/160, 1 cylinder at 40. I can't say that I've ever seen consistent low 100s. Did you crank it over several times for each cylinder?

The upside at least is theyre consistent and you don't have major damage.