My current (non-original) engine came with the car, and performs respectably. It is a 440ci with a 427 crank, high-rise aluminum intake, L88 cam with solid lifters and L88 air intake, Holley 670 street avenger carb (sorry Lars, I bought it before I was aware of you!), headers & sidepipes, unknown iron heads, and not much else modified that I know of. Compression is about 10.5:1 according to the guy who built the engine, and his estimate was 425 hp (but I guess I'll never really know for sure).

Next winter I'll be pulling the engine for a rebuild if I can come up with some heated shop space by then. Supposing I wanted to achieve a nice round 500 hp on pump gas (93 octane is the best I can get around here), what might be some options I could consider? I hope to use my current block, I assume I'll need new heads, and everything else is negotiable.

Jughead, if you're reading this, your setup is downright inspiring! If I could convince myself to drop the same $$$ you have, that's probably the ballpark engine I imagine. How many hp do you calculate you'll be putting out once that bad boy is transplanted?

Thanks in advance all, go ahead and spend my virtual dollars and tell me what you'd build!

-Roy

 

I would think that a good set of aluminium heads would get you over 500HP.

The motor should not be a sleeper with what it already has in it. Have you had it on a dyno? Ever been to a professional tuner to see what they can get out of it?

Get some gasket matching, and a port and polish while you have it apart.

 

I would immmediately try a 800+ cfm mech sec carb if you have not, that little 670 is choking it if the eng has the cam you think it does. Just make sure you have some depends on for the first test drive.

 

Unless something is wrong you should have 500hp already- stock L-88s have 560hp. Find a good Chassis Dyno shop that knows how to tune a carb and see what you have.

I don't have all the specs for my engine, but It has a hydrolic roller cam, and is 468ci using a 454 crank. I have 495 hp and 540 tq, or 404 rear wheel hp, and 440 rwtq.

This is a very mild cam designd to give a lot of torque. My engine builder insisted that touque is all that matters in a street engine. He said that one you start aiming for peak HP your TQ curve narrows. Low end tQ is what makes a street car feel fast.

There is a lot of debate over solid lifters. Beside needing an occasional adjustment, some people are concerned that they don't get enough oil at low rpms.

Do a lot of research and be prepared to spend a ton of money if want a significantly better engine :)

~Jay

 

Sounds like you have a beast in there waiting to break loose !

If you indeed have an L-88 cam then it's fairly 'radical' compared to most. The lift on that should be somewhere between 0.561 intake & 0.585 exhaust. Post the # on the cyl. heads (stamped on the heads under the valve covers) and we'll look 'em up for ya ! :thumbs:

A good carb. in the 800cfm range (double pump. / mech. sec.) would help that beast breath more ! :reddevil
And a complimentary set of aluminum heads will do wonders !

You can use the GM specs for the L-88 to model your parts list. However, keep in mind that original L-88's had 12.5 : 1 compression to build 550 Hp :eek:

 

Thanks all so far. Don't be misled, the thing will jump and roar as it is, definitely NOT a sleeper. I can't guarentee the cam is what I've been told, but it certainly sounds like it now that I have the idle properly adjusted (sounds MEAN).

To also clarify, the engine itself is NOT built to L88 specs...lower compression and iron heads being the biggest differences that I know of. I agree that more low-end torque would be more of an advantage than absolute horsepower (except for braggin' rights...500hp just sounds good :D ). Generally speaking, it doesn't break loose the tires when I step on it unless I put the clutch in and rev up a little first. I REALLY feel the power in the 50mph to 120 mph range...it'll do that jump in about 4-5 seconds, and I run out of nerve long before the engine runs out of RPMs.

If nothing changed at all, I wouldn't be entirely unhappy. I just feel like I ought to be able to squeeze more from my setup than I'm getting now with some mods, and I'f I'm rebuilding anyway, why not?

-Roy

 

I would put a good set of heads on it and more carb. Then stick it on a dyno and tune it. I don't know much about the L88 cam but cam design had come a long way since then. A wise man once told me..."power is in the heads...so put your money there"

 

I got the L88 cam with the solid lifters in my engine and everytime I floor it I get goosebumps.(After 4 years )
The only disadvantage is the rough idle and not much going on until it reaches about 2500 RPM, above that it really hauls. The cam is probably not intended for regular street use, but lots of fun on open roads.
I never dynoed my car, but I would guess its in the neighborhood of 500hp.

 

Grinchia:
First thing is first. I'd ditch that 670cfm carburetor and go for an 800-850cfm Holley. The carburetor is holding back the motor's topend capability big time. That 670 should be used on stock/mild 350 and 327 small blocks....not 427ci big blocks. Here are some other questions and suggestions. How often do you adjust the valves on this motor? If you haven't checked the valve lash in a while it would be a good idea. When valve lash loosens up it robs you of topend horsepower and is also harder on the camshaft. What kind of mufflers do you have in your side pipes. At any rate, if they are the glass packs or the reverse flow mufflers they are robbing you of some major horsepower. Get a pair of JCL spiral mufflers for them. The above suggested ideas should really wake up the motor. What is the casting number on your heads? To find this remove one of your valve covers and it will be cast into the heads. This is important because the heads are basically the heart of your motor and is the easiest way to pick up some horses.
The 454 that I built went a best of 12.1 @ 118MPH with GM iron oval heads, Comp Cams 294S solid flat tappet cam, 10:1 compression, Holley Strip Dominator Intake and Holley 850 DP.

 

Hey Grinchia >>>
I might be willing to trade ya my Edelbrock 750 double pump for your Holley 670. I have the rod/jet kit for it also. It's too much carb for me, until I find the funds for a major re-do on the block & new heads.

 

Grinchia,

The combo you have is a bit of a mismatch in that the compression ratio is really too low for the L88 cam. L88 specs is good for an easy 550hp at the crank. Mine made 483 at the rear wheels. Iron heads really won't hurt your power if you have the large port design. Tell the cam manufacturer your setup and they can spec one out for you that will really wake the motor up.

You are right the the sound of the L88 cam is something special. Above 2500rpm with 12:1 compression, there was no doubt I had a serious engine under the hood. My current solid roller gives me pretty much the same feel, but is a bit more civilized down to 1800rpm.

Chuck

 

Morning!

java0881: I'd have to agree, it's over 2500rpm where it really roars and pulls.

bence13_33
: I'll get the number on the heads when I adjust the valve lash (?maybe this weekend...I have a lot of irons in the fire for this weekend, so no guarentees). Opinion on this forum is unanimous that a bigger carb is in order, so I'll have to add that to my list. I'd like to do the aluminum heads too, and am open to suggestions for the best bang-for-buck for pump-gas compression range and a fairly radical cam. I could change the cam too I suppose, for more low-end torque, but I haven't decided yet.

BacaBill: Too early to call on that one, I won't be doing the rebuild until winter, and I need something to drive with NOW. If/when I do upgrade, I'll likely go with the Lars philosophy and get an 800+cfm with mechanical secondaries :D

Chuck Harmon: what cam are you running? I don't really mind the rough idle...it scares people :D ...but I'd like to start feeling the pull closer to 1500-1800rpm. I'll never got to 12.5:1 though, my goal is to get by on pump gas. Even at 10.5:1 I add a little lead for insurance, although it's mostly to protect primitive valve seats.

-Roy

 

My view: Bigger carb first, also if you have aftermarket setup where your air filter get hot air from engine bay change that into "original" l-88 setup with airbox etc and get much power more due to cold air at least around low speeds. They dýno tune. And if not enough get alu.heads :party:

 

Again, get the 850 DP. I prefer Holley but a Grant will do. Why are you going to rebuild the engine? It sounds like its real strong now.

Brett :thumbs:

 

I have the L88 hood which should be sucking colder air from outside, and it matches the tall manifold and L88 air cleaner well.

I'm rebuilding for a number of reasons:

1. I bought the car as a project, and wished to learn all the ins/outs of restoration and the good ol' internal combustion V-8, and one learns by doing!

2. The oil blackens up pretty quick...I haven't done a compression test yet, but I suspect I'm getting leakage around rings +/- valve guides.

3. The valve seats are not hardened, and if I ever want to get away from adding lead, I'll have to get 'em re-done.

4. The whole engine compartment is a MESS, and once the engine is out, I'll clean up and detail a little. I'll also paint the block!

5. I want to know for certain what's REALLY inside there, and make it a certifiable 500hp car :D

6. I'm almost due for a clutch.

I'll let you know what I decide when winter comes, and post pics!

-Roy


[Modified by Grinchia, 9:21 AM 4/15/2004]


[Modified by Grinchia, 9:46 AM 4/15/2004]

 

I agree with the thought that your carb is way too small,go with 850 dp,if you like the L88 cam,and dont mind not having much low end power,then your cam is actually more streetable than people think. Depending on what heads you have now,(open or closed chamber) you can run OVAL port ulum heads and make more power.And save some poundage off the nose of your car. Alum heads also allow you to bump your compression higher without engine detonation.You could run 11. to 1 compression and it will seem like 10.to 1.Engine dyno is a must! I have never spent better money,(200$ for 4 hrs). Having built a L88 engine from the ground up,I cant imagine NOT spending the few $ extra to properly break in, set timing,play with jetting,find some hidden HP that you didnt know was there! :) You can make 500HP real easy,You likley have close to that now!

 

Clearly I have more research to do! It's reassuring to hear so many of you think I'm close to 500hp already...the guy I bought the car from was not exactly an expert, but felt it was 425-450 hp. The guy who built the engine (before someone else switched to the L88cam and MAYBE increased compression to 11.5:1...I doubt it, because I don't ping with 93-94 octane gas) thought about 425. The guy I bought it from mentioned that the heads are rectangle port, but as I posted earlier I'll note the casting numbers when I adjust the valve lash.

Initially, my greatest cause for doubt about the estimates I was given was lack of low-end power, which as someone has noted is what I want for the street. Although it's fun to be able to slam your copilots head back into the seat from 90mph to 120 mph, realistically I can't drive that way often, and shouldn't drive that way at all... :D

What would be nice is to have some more rubber burning capability off idle.

I live in a small town and have no clue where the nearest dynomometer lives, I'll have to do some asking around. It makes sense to get things checked and tweaked after a rebuild. I'd hate to be disappointed with the numbers though :(

Out of curiosity, how would an 850 cfm Holley affect gas mileage compared to the 670 I'm running now? Lars assures us that the power is impressive, and that the driveability can be sweet if properly tuned (...translation: drop-shipped to Colorado :D ), but I've never heard him discuss gas mileage for normal driving with big carbs. Face it, I don't drag race, and would like to do a big road trip to visit my brother the Cop in Toronto! 1200 miles one way at 7mpg is a painful thought. My current carb seems to be giving me 12-15mpg, maybe even a little better when I don't roar too much. I don't think the 20mpg someone was dreaming about is realistic with my setup, even if I put a 5-speed overdrive unit in. But if I could maintain 15 mpg driving politely I'd be content.

If anyone cares to take a stab at the fuel economy question between big and small(er) carbs, please do!

-Roy

 

Tuned well you can get close to 15mpg with 3.08 gears on the highway if you keep your foot out of the secondaries. The dyno session is absolutely a requirement for both mileage and power. Use someone who knows what he's doing.

Chuck