VETDRMS

I'm trying to find some info about the 81 L-81 engine. I recently got one and wanted to know some more specific info, such as cam, type of lifters, compression ratio, heads, ect and so fourth.
If anyone has any info about these lack-luster performers, PLEASE
let me know.
I did find that compression ratio was 8.2:1, could i possibly up this by
just getting different head gaskets, or would new pistons, ect be needed?

Sorry its all a bit general, i'd just really like to know,
thanks :D

45ACP

http://www.l81vetteregistry.com/

UKPaul

Hi,
I'm trying to get some more out of my L81. The CR is apparently 8.2:1 & from what I can tell the heads don't flow to well, so skimming them to up the CR may not be the best way to go for max performance (but it should help). Aftermarket heads would be much better - but that involves a lot more hard cash :(
I did have lifts/durations for the std cam, but can't find them now. Basically, it's pretty naff, so I'm about to fit a Crane CompuCam, which works really well with the ECU. Have you still got the ECU fitted? If not then the guys here will point you in the right direction involving cams, etc.
I'm also going to fit a Performer manifold (once Customs let the cam through :cuss ).
Fitting 2 1/2" dual pipes (no cats) & open mufflers gave mine an improvement that was really seat of the pants noticeable (sounds brilliant as well :D ). A high output coil & cap along with new Moroso leads also made a big difference.
Mine has all the emmisions stuff removed. It definately goes better than when I got it, but it seems that cam, heads & CR are the way to go to really wake up an L81. After that it's a case of the normal stuff: double roller timing chain, roller tipped rockers, etc.
Hope this helps in some way (I also hope it's correct coz I'm now spending out lots of money on it :lol: ),
Paul

VETDRMS

Thanks for the info :)!
You wouldn't happen to know how much lift the stock valve springs can take do you? Cause i wouldn't mind just upping the compression, adding a nice roller cam, and the open exhaust is a definate. I wanted to just put a set of vortec heads on here and i'm assuming the 64cc chambers would bring the compression up at least to 9.5? How stout is the bottom end on these engines? I don't currently have the ECU, so a compucam probably wouldn't be the best choice for me. I did manage to find that the stock cam had .3900 lift intake and .4100 lift exhaust, i'd like to take those numbers closer to .5000, just not sure how much the stock heads can take.
Anyone got any more info on cam, ect?
The input is highly appreciated, this forum is a undespensable resource :)
Thanks Again.

Ganey

Bottom end is no problem. Stock valve springs max. safe lift is .460. Check the head casting no. for which heads.
What's trans. - needed for cam.

:cool:

Ganey

PS You might want to rebuild if the engine has a lot of miles.

UKPaul

Without a confuser fitted then don't even consider a Compucam - there's plenty of alternatives out there (Ganey should be able to sort you out with what you want). 64cc heads seem to be a popular choice & are what I'll eventually get for mine. One day!
:cheers:

VETDRMS

Ganey:

These are the heads on the car 462624.....75-86...350/400......76cc chamber, 1.72/1.5, 1.94/1.5 or 2.02/1.6 valves. I'm pretty sure the L81 had the 1.94/1.5 valves. And the block is 14010207...350...80-85...2 or 4
This is an L81 engine, so i'm assuming its a 4 bolt main? The transmission is a TH-400, the rear end is 3.70 The engine has about 27000 original miles on it, and it runs really good.

UKPaul:

I was curious as to what the 64cc chambered heads would do to compression, you wouldn't know would you? Would the vortecs bolt right on?


Thanks again for the valuable input :D

Ganey

The 624 are lightweight smog heads, so you need better heads. 76 to 64 will raise over 1 pt. C/R so about right.
Comp Cams XE262 will work if you drive hard.

:cool:

VETDRMS

Thanks! :)

So would the L31 vortec be a good choice with this cam as well?
I didn't want to get too much invested, but would this route be ok:

L31 Vortecs
Roller Cam
1.52 or 1.6 roller rockers
Performer RPM Airgap Vortec

I do want to go with the roller cam, despite the cost.
Cam seems to be ~$299 and lifters ~$170
Would the gain in HP be worth the cost over a standard hydraulic?
How much power would i see from this combination?
any estimates?

Thanks :cool:

VETDRMS

Anyone got any Info on that previous power combo???
:blueangel:

UKPaul

As far as I know 64cc heads will be in the 9.5:1 region, which is about the max I'd want to run with iron heads. Could go to about 10:1 with ally heads without pinging - but it all depends on the quality of your fuel: ours varies from place to place so I don't want to go too high eg I filled my daily driver with fuel last week & it's been pinging & rattling merrily until I filled up at a different place yesterday, when it started running as sweet as a nut (holing a piston or blowing big-ends out of my daily driver would just be inconvenient, doing the same to my Vette would be horrific!).
From reading this forum it appears that vortec heads will drop straight on, but you'd have to get a vortec compatible intake manifold to go with them. Apart from that hiccup people seem really happy with them :)
With only 27000 original miles on the motor I'd just go for it without stripping it down (and hope those miles weren't done in 1/4 mile increments :lol: ).
Paul

john's '81 mouse

OK, sounds like you've got an L81 engine in a non-'81 vette, correct?

Stock L81 engine used the factory steel shim head gasket with compressed thickness of about .017", so you can't improve compression by using a thinner head gasket. Although I am running them, the 624 S/B chevy smog heads are said to flow badly, be prone to cracking if engine is overheated, and are NOT recommended for performance applications.

Vortec heads are a great choice from what I've read. You must use the self alinging rocker arms with these heads, and in stock off the shelf form, are limited to maximum lift of approximately .480", before you'll have valve spring coil bind.

I don't think roller cam/lifters is of any significant advantage, unless you modify the valve spring pockets of the Vortec heads to accept springs capable of higher lift camshaft, which is one of the major advantages of running a roller camshaft/lifter set up. If it were me and my money, I'd run a good dual pattern hydraulic flat tappet camshaft, with you set up, something like Comp Cams XE262. (Will require higher stall torque convertor, if you have an automatic)

I believe you will find that the Vortec Performer RPM Airgap intake manifold will cause clearance problems under your stock hood, unless you already have a high rise type hood. You MAY be able to get by with a drop base air cleaner type system, but this may cause some restriction, and will not be as good as factory type fresh air systems, which provide more horsepower by pulling in cooler air from front of car.

Vortec heads will require purchase and use of center bolt valve covers, which you probably can purchase from local salvage yard for $30.

I understand that 'out of the box' stock Vortecs, will flow better than any of Chevy's older style 'performance' small block heads, plus the Vortecs use the smaller valve sizes, which means your engine will still have great torque, while gaining significant horsepower increases from such a head/cam/exhaust change.

VETDRMS

Wow, thanks for all the VERY helpful info, this looks like a mod that i'm definitely going to do in the comming months :)
*sigh* its just so addicting, just installed all new exhaust (ceramic coated headers, 2-1/4 duals with x pipe into dual flowmaster 40 series), replaced all my u joints, had the half shafts and driveline balanced, redid the ignition, adding a crane HI-6, camaro seatbelts, new paint and completely restored fiberglass, {{{ 17x8 Torq Thrust II's }}} :D:D:D:D:D, she's comming along quite nicely, i REALLY need to update my sig, she doesn't look like that any more! Oh, completely new suspension too, going to front transverse, and possibly rack and pinion....now the engine....its quite a hobby, but one i LOVE.

My thanks and gratitude go out to everyone on this forum for making it such a great place to get and share information with fellow enthusiasts, THIS site should be put in the new corvette car manuals as a resource ;)

Dalannex

Hey UKPaul, what are the specs on the CompuCam that you are looking at? I think that so long as the cam you are running gives you 15 hg of vacuum the computer won't give you a problem. I went with Ganey's advice and put in that Comp Cams 260H and couldn't be happier. For those of you that don't know I have true duals, no cats or cross pipes, and an automatic, but Paul already knows that, we've been through it. ;) I had a local engine builder tell me that the car would never run with that cam, and that I had to use the appropriate CompuCam because the carb is so picky. Well, either I'm a master E4ME tuner, (not hardly) or the computer works just fine with it once it's set up. Oh yeah, mine is bone stock, other than the Comp Cams 260H and the true duals with no cats. The charcoal filter inside the air filter disappeared too.

UKPaul

Hiya Justin,
Apologies for my silence – up to my elbows in Vette :D
The cam I’ve gone for is the Crane CRN-114132 (known as the 2040) from Summit. Specs are 210/216 & .440”/.454”. Info on it from Summit & my good friend Gator81 are:
16” of Hg at idle
idles smoothly at 600rpm
good throttle response
Max torque of 390 lbs/ft at 3500rpm, with about 80% of that available
from below 2000 rpm to over 5000 & a good curve.
Greater duration and valve lift than std, but with very steep opening and closing ramps, to minimise overlap & maximise exhaust purging while keeping the vacuum high.
Still meets emissions regs (not that I’m bothered!)
And I’ve lost the HP specs!!!! There are cams that will give more HP, especially at the top end (eg the 2050), but I still want good all round driveability. As we say over here, "I'll suck it & see".
Really need to up the CR & improve flow through the heads to get full effect, but one thing at a time (or I’ll end up on 1st name terms with the Bank Manager!).
What charcoal canister? ;) Hope the painting went well – is it finished (having a total 'mare with mine)?

Wrong post for this, but it looks like it’s just us that would have gone for that $1000-00 wreck. Me, I would offer the seller a ridiculously small amount & let him haggle me up to about $500 (the hood, glass, diff, etc have got to be worth that, and if the frame is good well, what a bonus). Then use it as spares to build up a car in much better condition. And if you know people into restorations (like on this forum), you can help them out with parts that you don’t need (& recoup some cash). I’ve bought total wrecks of bikes in the past (bought a heap of spares on Monday night!) & it’s amazing how many times that those parts have been needed by me, or somebody else, to build up another one. Seems sensible when you consider that these spares will just get harder to find (or more expensive) as time goes by.
Maybe I just enjoy filling my house with old iron :)
Take care
Paul