High Compression L36 bottom + L67 SC (Corey's Engine Build)

Hi Corey, I merged your posts with another thread by another member, also named Corey, who tried what you're considering. So yes, it has been done. Read through when you have an hour of free time.

However, do listen to what's being written in this thread. High static CR + added boost compression = a spark knock machine if not controlled. So what if it makes power? If that power isn't reliable, the engine becomes a time bomb. Think of it this way: if it were as easy as just increasing static CR, there would be no need for superchargers - you could just run 20:1 static CR and call it a day. But it's not that easy, because detonation gets in your way.

Recently, we've seen some manufacturers doing exactly what is being suggested in this thread. BMW for example is running twin turbos on a 10.5:1 compression engine. VW, Ford, Hyundai, and GM have tried similar ideas over the past year or two. But it's important to note they are using a new technology called direct injection in order to make it work. Direct injection cools cylinder combustion temperatures by pumping relatively cold fuel into the mix after the air passes the intake valves. Why? To eliminate spark knock associated with combining boost + high static CR. Now we can have the power from super-compression without creating a massive amount of detonation.

Certainly as a Mechanical Engineering major from GM's own Institute in Flint, MI back in '01-'05, I'm partial to respecting the physics of combustion chamber dynamics... but in this case, there's more than just what was mentioned, involved in how these engines gain performance. The results, from everyone in the market, top performers to basic modders, have maintained the benefits of using L36/26 blocks under boost.

It is certainly a finer line, when it comes to margin for error, when adding too much boost or going lean. The tried and true paths are very safe, when proper scanning, and sensible pulley choices are used for the top swapped setups.

I've personally built and/or tuned/tweaked at least 15-20 N/A-block 3800's with s/c's swapped on them, with no trouble over the last 5-6yrs of doing so, starting by swapping my own & seeing a great result before going into others' cars to do the same. Typically, before I left for the AF almost 2yrs ago, I'd have owners include a moderate cam and headers with the top-swap parts they'd bring me with their cars to build. By using a VS or S1x cam, and a set of headers (~$1,200 swap parts cost total), I did 5 or 6 swaps for guys in about a year, with all of them happily still driving to this day (aside from Corey's car scrapped for a newer vehicle). They can run a 3.4-3.5 pulley with a clean mid-high 11 a/f ratio on wideband that I used on all of them to scan/tune.

Nothing elaborate was done in tuning these to perform, other than knowing to walk before running with the throttle usage, as the initial driving showed what the vehicle wanted, before forcing boost down its throat. Many of the people who chip pistons after swaps, do not take care to see if the tune/pulley is even in the ballpark for what their new setup can handle right away. Some others claiming failures, simply spin rod bearings due to not flushing coolant out of the oil valley during the work, causing contamination that kills lubrication soon after the fire-up.

Didn't mean to post an essay, my bad. Just saw the subscription alert from the thread merge, and wanted to re-assert some very experienced input (as I'm not the only 10+yr veteran of this engine platform who has benefitted from the L36/26 block usage for maximum s/c performance).

Hi Dave,

Thanks for stopping by, and for clarifying what can and can't be done re: L67 + L36/L26. Your track record for building 15-20 blown L36/L26 engines is certainly respectable. I don't think anyone doubts your ability or knowledge on the subject, as you've proven it can be done.

But you have to admit there are other, possibly better ways to skin this cat, as demonstrated by every auto maker who's sold a high compression production engine with power adder. Direct injection seems to be the way to go. Or am I missing something - in your opinion is there not a good reason to go DI?

The most recent comments in this thread were intended to steer the new guy, curious about mixing high compression and supercharging, in the right direction. Other than having an expert such as yourself do the build, I can't see any practical or safe way for the average DIYer. The idea that this is safe for "basic modders" can be misleading. As another member of our forum found out, adding a high compression block to his supercharged top end ran for a short time, then ended in catastrophic failure. In that case, the member used someone claiming to be an "authority" on building and tuning this kind of set-up.

As you can surely understand, Dave, this type of build isn't as straightforward as some would like to think, as we've witnessed the consequences first hand. We've seen a Riviera equipped with a supercharged high compression block go "boom" in short time. What we have not seen are many (if any) Riviera engines failing on the conventional mod plan: using the factory provided design and carefully adding boost, advancing timing, and modifying for better breathing. Your method shows another way, but some, including myself, believe it presents a higher degree of risk.

Direct Injection is an option, only if someone decides to go to a whole different engine platform. If you have the means to convert a Series 2/3 3800 to that style of fueling, you're not really seeking much in the way of "newbie" advice, I'm sure. I can think of the things required to tap into our engines to do so, and it would be an undertaking well beyond the basic conversation we're having in this topic.

I'm 50-50 when it comes to suggesting someone new-ish, go for a top-swap vs. doing an L67/32 swap. If the person has enough experience with this engine already, in boosted form, to know how touchy they can be, even with the 8.5:1 block, then the L36/26 option may be on the table. When it's someone completely new to digging into their own engine bay, it's definitely less of a hassle to leave a complete L67/32 together (aside from clean-up/mods), and have a little more of a buffer zone with the pressures being dealt with.

In the grand scheme of things, our engines, even in N/A form, are still considered "low compression" compared to most modern engines. For example, when I helped my friend with his LS1 (now LS6) '00 Camaro SS set-up a Procharger centrifugal supercharger kit, he went from the stock 10.5:1 engine, down to a commonly used 9:5:1 forged setup in a new LS6 block as many others utilize in that market for "low compression" for boost. Many even install the kits on the stock engine, and enjoy them with more moderate boost levels (typically A2A I/C'd 5-8psi pulleys with or w/o cam upgrade).

Overall, I'll agree that a minimally experienced builder/tuner should probably shy away from doing the N/A 3800 block under an M90, without having some X-factor that may assist in ensuring it's done correctly from the start. If there's someone looking for an edge in their modding potential, wanting to squeeze another few tenths and some HP out of their setup, they most likely have enough sense to find a fresher N/A engine & cautiously integrate it into their build with success.

I'm in the process of building an M90 L26 setup that should be running in around a week or so. There's a couple premises that made me go this route. I'm not planning on doing anything beyond the limits of the M90 in terms of the power adder and with that being the bottle neck, higher compression makes more sense in the efforts towards power. If you could see a turbo in the future that could create virtually any amount of power via boost, then a low compression set up makes much more sense. Secondly, I know that between James and myself, we will be able to get the tuning straight and make it reliable.

Hmm, so starting with intake, exhaust and finding an m90 supercharger out of a junkyard is probably a good idea just to start with, and will probably get me around 300 ft lbs of torque, and maybe 250-260hp?

would I need to drop a pulley size from the engine being a 9.4:1 compresion ratio, or would there be an inexpensive way to reduce KR enough to have stock pulley size?

and how much would the m90 supercharger be off a wrecked buick or grand prix gtp, what have you, in a junkyard? I have no idea on junkyard prices, but a guy I know claims he got GT40 cylinder heads off one for $150 for his 91 mustang which I believe is complete bull. I don't know how to find junkyard prices at all, but these superchargers have to be a dime a dozen on wrecked cars methinks, so if I pull it out myself, cost?

take a look at

http://www.horseheadspickapart.com

they post prices on a price list for their pull parts, if they have it in the yard they will pull and ship to you for a fee on top of those (low) prices.

Albertj

Are all the parts the same cost? Like ANY engine is $200?

c0reyl wrote:

Are all the parts the same cost? Like ANY engine is $200?

Yeah. If it is in the yard and you can pull it that's the price. There are pictures of the cars newest to the yard and you can phone in to ask about others, or about parts. They are affiliated with a recycler (place that pulls parts and warehouses them) and can get lots of stuff that is not in the yard. For instance one time I needed an OE wheel for a Subaru I used to own. They got me one at a decent price, I think $20 - $25 - it was a new pull from a Subaru that a buyer had bought alloys for & did not want the wheels.

If you can't pull the part yourself, say that engine, then the price goes up by just the labor charge to pull it. I forget the rate but it's posted and not unreasonable. The yardmen drive a ratty school bus with an acetylene torch and a bunch of tools. I have helped them pull things from time to time when I was in the yard looking for odd parts and not having much luck. Once they get to know you, if you're not a jerk they will point out to you where stuff might be that you are looking for.

Can someone supply a list of parts I'd need to put a supercharger on my L36? My engine only has one belt, the L67 has two.

I need the Eaton supercharger, lower intake manifold? And what for the belt? Brackets? I want to add the supercharger before summer if possible.

http://shop.zzperformance.com/store/p/1017-L36-Supercharger-Kit.aspx

Is it possible to buy all that WITHOUT the brand new supercharger, as in buy the supercharger out of a junk yard then buy the rest of what I need on that site?

c0reyl wrote:

Is it possible to buy all that WITHOUT the brand new supercharger, as in buy the supercharger out of a junk yard then buy the rest of what I need on that site?

You should add the year of your car to your signature. If you have a '95 no. If you have a '96+ yes.

If you are N/A (Naturally Aspirated) now, you would be better off to buy a complete L67 engine (S/C). The supercharged engine has a lower compression ratio. Adding a supercharger to your engine is possible, but adding a supercharger to the high compression engine will require extremely careful tuning work. If you get a supercharged engine to begin with you will need the PCM and wiring harness (or add a wire to your harness, not that bad). The extra wire is for the "Boost Bypass Valve", something the N/A motors don't have. Technically the wire to the valve is not necessary, but you might get a check engine light if you don't have access to a tuner to disable it.

You would need a tuner to change your VIN as well. You may be able to buy a pre-tuned PCM with those little changes done for you, depending on the year of your car and donor setup.

I'm well aware of the 9.4:1 compression my L36 engine has vs the 8.5:1compression pistons in the L67. That site says on the supercharger kit he linked that they tested NUMEROUS L36 blocks at 500+HP.

All I have to do is be careful about KR and keep an eye on pulley size and ill need bigger injectors if I go smaller.

I am NOT gunna throw away my perfect fly fine engine when all I have to do is add a few bolt one and its better than a stock L67 with the same amount of boost.


So, I ask again. How would I go about buying a used supercharger for maybe 200 and getting the rest of that kit?

http://shop.zzperformance.com/store/p/173-L36-SS-M90-Install-Kit.aspx

AA wrote:

http://shop.zzperformance.com/store/p/173-L36-SS-M90-Install-Kit.aspx

Thank-you! So all I need is that, the supercharger, and lower intake manifold?

Also, does that work for only the Gen III, or would an Eaton Gen V work as well? :3

What year is your car? That pcm will not work with a 4T60 trans.
Aside from that kit you may need to look into HD diff and trans parts. (you WILL need that if you plan to make 500hp)
Belt routing is different for G bodys vs W bodys so the belt sizes will be different from those supplied in the kit.
I also believe the throttle bodies are different between the L67 and L36.
If you can wait a little while i will have a gen V supercharger for sale, fully ported too

May be better off buying a used L67 from Ed morad and pulling parts you need. Then sell the short block and L36 part when done with it.

I have a 97 with a 4T65e.

c0reyl wrote:

AA wrote:

http://shop.zzperformance.com/store/p/173-L36-SS-M90-Install-Kit.aspx

Thank-you! So all I need is that, the supercharger, and lower intake manifold?

Also, does that work for only the Gen III, or would an Eaton Gen V work as well? :3

'

That kit works for Gen III or V superchargers, but in addition you will need the correct harmonic balancer and belt tensioners/pulleys. You also want the Riv specific tensioner and idler pulley standoff for the SC belt or it won't clear the front engine mount. Other applications with the front engine mount are acceptable donors for those parts too.

Used superchargers come up for sale in 3800 specific forum classifieds all the time, or you could get one from car-part.com. This forum isn't as active in the FS department as some others, clubgp is known for their classifieds being useful, but there is a lot of other garbage at that forum, at least in my experiences. Maybe not as bad today, most of the riff raffy types have probably moved on to other cars by now. There are a lot of part outs/complete engines there. You may be able to find a complete engine with a cam etc already installed and skip a few steps, then resell your engine to make up the difference. "Numbers Matching" is really not a big deal these days.

I know too many people who top swapped (what you are suggesting) and then a few months later had a chunk come off a piston ruining their 'perfectly good engine'. Yes this can be avoided with careful monitoring and tuning, but I am strongly advising against it, especially as you seem new to these motors. For one with a lot of experience and has been through a couple engines already, it's a different story.

What you have is a perfectly good engine, but not a supercharged engine. Changing it to a supercharged engine without getting the low compression bottom end puts you at very very high risk for blowing up your perfectly good engine.

c0reyl wrote:

I'm well aware of the 9.4:1 compression my L36 engine has vs the 8.5:1compression pistons in the L67. That site says on the supercharger kit he linked that they tested NUMEROUS L36 blocks at 500+HP.

All I have to do is be careful about KR and keep an eye on pulley size and ill need bigger injectors if I go smaller.

I am NOT gunna throw away my perfect fly fine engine when all I have to do is add a few bolt one and its better than a stock L67 with the same amount of boost.


So, I ask again. How would I go about buying a used supercharger for maybe 200 and getting the rest of that kit?

Corey,
It's possible to do this, but I just get the feeling you think it will be relatively easy to do. It will not. You will likely run into a few roadblocks along the way. If you have the patience and you are willing to follow this through, I wish you luck. Document everything, and take pictures. As far as I can tell, you will be the first one on this site to attempt this.

Mr.Riviera wrote:

What year is your car? That pcm will not work with a 4T60 trans.
Aside from that kit you may need to look into HD diff and trans parts. (you WILL need that if you plan to make 500hp)
Belt routing is different for G bodys vs W bodys so the belt sizes will be different from those supplied in the kit.
I also believe the throttle bodies are different between the L67 and L36.
If you can wait a little while i will have a gen V supercharger for sale, fully ported too

May be better off buying a used L67 from Ed morad and pulling parts you need. Then sell the short block and L36 part when done with it.

I don't think I'm going to make 500 horses anytime soon, rofl.

I'm more aiming for a little over 300 in the distant future, maybe more if I can get enough CFM into my heads.

Ehh, wih the higher compression, I might as well grab a Gen III because I can get more power with the same amount of boost.

You guys realize this HAS been done before right? and if I do blow up my motor, oh well, I can replace an engine, lol.

But.. I don't see how that's gunna happen when I'm not going to let my motor have KR. I seriously don't see how it's possible to bust my pistons like you all say if I manage my KR. I'm not going to basically throw a bunch of bolt ons, forcing my motor to kill itself. I'm only going to allow as much boost as my motor setup will allow with max power, maintaining low knock. even with a smaller pulley, the higher compression will make more power than the L67, so I don't mind.


I just need the parts mostly. so you said different throttle bodies? I might want to just grab an LS6 throttle body, assuming it's compatible without a ton of other parts, I think I saw an L36 Camaro with an LS6 throttle body :3

c0reyl wrote:

All I have to do is be careful about KR and keep an eye on pulley size and ill need bigger injectors if I go smaller.

How are you going to do this exactly? This is the important piece, and if you don't already have some tuning experience it will be a very big challenge. If you have some tuning experience then by all means go for it.

Please keep in mind, I am not trying to discourage you from doing a top swap. But it is NOT an easy thing to keep in tune. You don't just "keep an eye on KR and pulley size". There is MUCH more to it than that. I'm done with warnings. Please take the message to heart.

You should be able to buy a supercharger from car-part.com, or you can pick up a ported Gen III. Places to shop -

If you are looking at a place like car-part.com for a supercharger, a '96 - '04 supercharged 3800 will get you a Gen III supercharger. Applications abound, GTP, RegalGS, Park Ave Ultra, Riviera, Impala, MonteCarlo are most of the choices. An '05 or newer L32 will get you a Gen V supercharger. With a GenV supercharger you will need a different throttle body as they switched to drive by wire. Most people use the cadillac Northstar V8 throttle body, typically referred to in the 3800 community as an N*. ZZP sells an N* kit as well.

Also any 3800 forum generally has superchargers in the classifieds. A few of the big ones are clubgp.com and 3800pro.com. You can also pick up a harmonic balancer there. You might want to look for a local W-body or 3800 club. There are a lot of part-outs going on right now.

Good luck!

deekster_caddy wrote:

c0reyl wrote:

All I have to do is be careful about KR and keep an eye on pulley size and ill need bigger injectors if I go smaller.

How are you going to do this exactly? This is the important piece, and if you don't already have some tuning experience it will be a very big challenge. If you have some tuning experience then by all means go for it.

Please keep in mind, I am not trying to discourage you from doing a top swap. But it is NOT an easy thing to keep in tune. You don't just "keep an eye on KR and pulley size". There is MUCH more to it than that. I'm done with warnings. Please take the message to heart.

You should be able to buy a supercharger from car-part.com, or you can pick up a ported Gen III. Places to shop -

If you are looking at a place like car-part.com for a supercharger, a '96 - '04 supercharged 3800 will get you a Gen III supercharger. Applications abound, GTP, RegalGS, Park Ave Ultra, Riviera, Impala, MonteCarlo are most of the choices. An '05 or newer L32 will get you a Gen V supercharger. With a GenV supercharger you will need a different throttle body as they switched to drive by wire. Most people use the cadillac Northstar V8 throttle body, typically referred to in the 3800 community as an N*. ZZP sells an N* kit as well.

Also any 3800 forum generally has superchargers in the classifieds. A few of the big ones are clubgp.com and 3800pro.com. You can also pick up a harmonic balancer there. You might want to look for a local W-body or 3800 club. There are a lot of part-outs going on right now.

Good luck!

Thank you for advice, and I'm not trying to mock you.

but I was seriously thinking if I had less boost than stock L67, and slightly more power from compression, I wouldn't have to worry about my engine exploiding. I don't plan to get anywhere near 300 horses until I have everything I need to completely eliminate any KR I might have, but seriously, 260 horses would still blow my engine up with a supercharger? If this is the case, then I will focus on breathing mods first instead, and obtain 260 horses naturally aspirated before even slapping on a supercharger.

Thank you for your help.

I think the missing piece here is with the higher compression and adding boost you have the potential to boost stack quicker and have spikes of KR faster than with the same boost in a L67.
There is a reason the factory lowered the compression when the added forced induction.

Not trying to scare you off. Plenty of people on clubgp or regalgs have boosted L36 motors. Read some of their trials and tribulations before making a decision to buy a kit. Im guessing this riv is your daily driver and not a weekend toy.

Yeah its my daily driver. I might just get forged 8:1 pistons in that case while I'm gunna upgrade the cam anyway. I'm thinking this would solve my problem.

Assuming I got stage 1 cam, ram air intake, new valve springs, forged pistons, how much power would my L36 take, how small could the pulley go?