okay, just a quick comment/question here... why the hell does the L67 not have dual overhead cams? i mean the only thing better than a 12v s/c monte is a 24v s/c monte....

 

Because this engine was designed in the 1960's.

It is very old technology, but these engines are unbeatble workhorses.

-Riggs.

 

yea i am just ticked lol no big deal, these motors really do rock though... i saw someone posted that the bottom is so strong it can still be fine with up to 700 hp... i don't know if that is true, but it seems plausible..

 

Why would it have DOHC? Those engines are more expensive, tend to be less reliable (especially belt drive), and would require an extensive engine redesign. Plus, the 3800 was designed to be a cheap, reliable powerplant to run everything from taxi's to police cars to regular commuter cars. The key was to have a nice broad powerband, with a nice low torque peak. For what it was designed to do, dohc would've been a detriment- not a benefit. Not to mention, the vehicles that got the 3800 and 3800 sc weren't really 'performance' vehicles- none were really ever used or intended for racing, they didn't even offer them with a manual trans in recent years to take advantage of a high revving manual anyways.


Not to mention, at the time GM had been having terrible luck in the DOHC V6/V8 department and chose to focus its efforts on 2v engines. I'm sure no one at GM would even think to suggest dumping all the R&D money into the 3800 platform after the 3.4 dohc was dropped after such a short period of time.

The 3800 community was pretty close to getting a 4v set of heads. There was a group buy and everything set up on clubgp. This company was all lined up to make custom heads with special, split rocker arms- so that the standard cam could run all 4 valves w/ just two pushrods.

It is impossible to say at this point- literally no one has ever broke a 3800 series 2/3 bottom end from too much power. There have been failures due to manufacturing defects, overheating, lack of oil, knock, wear, etc- but never due to too much power.

The crankshaft can theoretically take 1000 crank hp, and there have been two cars to come pretty close to that number that I can think of.

Really, the durability of the bottom end is a pretty moot point- what difference does it make if the engine can take 1000 hp if the transmission breaks with 300 hp? Sure there are built transmissions out there- but if you look at pretty much all of the hardcore street and strip only builds, most of them either rebuild their trans regularly- or have replaced multiple transmissions. Thats probably the #1 reason why a lot of the big turbo setups demod shortly afterwards- you can't put on a wide enough street tire to hold the power, but when you switch to a slick or DR, then you start eating trasnmissions.

 

thanks chad that is really great info

as far as our tranny goes... how much hp/torque can it take?

 

Thats really hard to say- it seems to depend on 3 main things:

-how much and where you race it (ie strip or street)
-what mods you have
-bad luck

It only takes a lot of any 1 to kill the trans. I've seen them come apart on totally stock cars with little-no racing (lots of bad luck), and I've seen guys racing around for years with all kinds of mods and no problems at all. The bad thing is, the first two seem to go hand in hand- most people won't sink a ton of money into mods if they don't even race.

I'd say for the average person, I'd trust a stock tranny to the basic bolt on level for an L67 (so about 300 crank hp or mid-high 13s depending on altitude). After that, I'd be socking money away for a built tranny. It also seems like a bolt on, basic turbo kit is fine as well (makes more power and quicker 1/4 mile, but has a smoother transition into the power band). Coincidentally, this also happens to be about what the 5.3L V8 LS4's make, and you can see how many of them have these similar tranny problems (and their trans has some upgraded parts, so its not 100% the same as ours).

Beyond that I'd get wary again with a full on L67 build (big cam, IC, headers, tiny pulley, etc- which ends up about 350-400 whp) or a pretty serious turbo build (really anything 400+ whp, getting real bad the closer it gets to 500 whp+)- because IMO you're starting to push even a built tranny to its limits. This goes back to what I said before though, if you're in this category- your regular street tires won't hook for anything, so many upgrade to slicks/DR's- and that obviously kills the life of the tranny too.

Thats the one major upside to RWD vs FWD, with a RWD setup, you're usually just an adaptor plate away from running something stronger and stronger- turbo 400, powerglide, lenco, etc. With FWD, there really isn't any stronger transmission that is easy to go to. The 4t80e is a stronger trans, but no one really has pushed them to their limits that I know of; and the tranny parts are significantly more massive, so your drive train loss is a good deal greater.


One interesting thing to note, there is only one group I've seen that has had great sucess with the 4t65- and thats the GM Racing Team. They run it in thier 1000+ crank hp drag cars and claim it to be 'reliable' (this is actually where all the hardcore 3800 people got their 1" drive chain- which I believe is now discontinued). If you search on the internet for "gm sport compact performance build book" (its a pdf)- you should find it. It deals with different builds on the Ecotec 4 cylinders, as well as 4t65 modification to handle that power.

However, there are a couple of important points to note. First is that they claim doing 'extensive modifications' some of which aren't listed- and no one is going to be able to top their level of technical expertise on the 4t65 (they have access to all the gm engineering data for all the parts). So its not like any regular performance shop is going to be able to build anything perfectly comparable. Second is thier race and drag cars are significantly lighter. Even stock for stock a cobalt is a good bit lighter than any W-body, and add to that lexan windows, CF pieces, and a gutted interior- and you end up having to move a lot less weight. Third is how they're making thier power, with a DOHC turbo 4 cylinder- so all their power is in the upper rpm band (yes I realize they're coming out of the hole on a transbrake, but I bet low end torque at launch is just as high if not higher for some of our 3800 drag cars w/o a brake).

 

jeeez chad that is awesome info, i am actually saving that to a word file lol... i am already putting money aside for a new tranny just because i have had bad luck in the past.... i blew the 700r4 that was in my firebird and i converted over to manual and put a t5 racing tranny in it.... keep in mind i wasn't pushing that much hp to the wheels even i was just being a jackass 17 year old...

 

links to 4t65 GM build:

http://tunersource.gmblogs.com/Racer...trans.pdf/view

links to the rest of the chapters (unrelated, but its kinda cool to see what goes into a 1000+ crank hp ecotec other than a massive turbo):

http://tunersource.gmblogs.com/Racer...nce-build-book