keithl1967

Not asking for head advice on which to buy, just a question about parts I have on the shelf already.

Car is now bone stock L48, 1977, except the exahust--curently 2 inch pipes (true dual, into glasspack mufflers...coming off of stock manifolds...

I will be pulling the motor just to clean up, paint, re-seal, etc. Figure while its out, there are a few changes I am am making.

My plan is to swap intake form stock to edelbrock performer, and upgrade to holley 650 DP (sometime int he future, I may go EFI, but for now, let's assume not). I will be adding Hooker coated headers and 2.25 exhaust pipes, into Dynomax super turbos...

My real question, is:
I have a pair of 461 heads on the shelf--64cc chamber, no port work or anything. Obviously it will bump the compression a tad, and flow better than the boat anchor 882's...

So--what kind of difference do you think I will see by changing out the heads, and the other parts previously mentioned?

Team Lazy

I couldn't offer any ideas and obviously the best you're going to get is a guess. But I will say if you are going to all that trouble, you would be silly to not do a cam. All those parts can be made to work together optimally with a cam, otherwise they are just parts thrown at a problem. IMHO.

cagotzmann

Is the car still running in the stock form. If it is I would take the car out to your local track to get a baseline where it started.

Get some 1/4 mile runs and focus on 1/4 mile MPH. ET depends a lot on lauching and MPH is a good measure of engine performance.

In stock form you should be around 16 sec 1/4 mile ET and around 88-90 MPH. This will depend where in the world you are.

Intake ,Heads & carb change / exhaust change my give you a little more, but I wouldn't expect a big change unless your current setup is not running correctly.

You may get the car similar to a L82 Version of the car but slower (still needs a cam to get L82 range). Which is a 15.5 sec 92.5 MPH and this is with a 3.73 rear ratio. If you have the 3.08 rear maybe 15.9 @ 90-92 MPH.

Will you notice the change yes but it may not give you the "WOW" factor.

The only real change that helps is the heads and exhaust. A little with the intake but the carb change is like a color change. Looks different. ( assume your quadrajet is working correctly.)

cardo0

The L48 is basically the same GM "Good Wrench 350" they have sold for decades and the GM 350 "Target Motor" before that.

There are 2 books that cover all performance upgrades for the low compression L48 better than i ever could. How to Build a High Performance Small Block Chevy on a Budget by David Vizard for 20 bucks. The other one is Small Block Chevy Engine Buildups by HP Books for Chevy High Performance magazine - only like 10 bucks on Amazon.

Good luck and let us know how it works out for you.

bluedawg

With a little work and no cam maybe 20 horse maybe a hair more If you used .015" shims. the 461's have to flow better than 882's, but by how much. Add a cam and headers you might hit 50 or 60 horse. The thing about the L48 and the 882's is that just about any part you add makes more power. I'd also go 2.5" on the duals (true duals for folks that don't understand the word dual). You going to do any dyno work?

mrvette

I used to have a '87 vette, sold it and bought my '72 L48.....

one of the earliest things I did was put on serp drive from 88 vette....

and electric fan, at first mounted in stock shroud...today I have spals on there....

and I went L98 #113 heads.... and L98 TPI induction speed density computer 1227730

~5 mpg improvement better starting, smoother running, better torque, better idle.....like a whole new engine.....

keithl1967

not really planning any dyno work, but figured if I had the parts on the shelf anyway, I'd see if I can put them to use to give the car a bit more umph. I'm not so deluded to think it'll be a Humongous difference, but it I could squeeze a little more performance, why not...

ajrothm

If the 461s are in good condition and the valves are sealed well, they would likely pick up some power..both from the slight compression bump and probably flow a LITTLE better. I would expect much but....IF you have them, why not?... Make sure they have accessory holes.

I'd definitely put a little cam in it as well. A mild cam like an L79 or L82 (or a more modern version preferbly), new valve springs etc. Make sure to keep the lift under .480" so you don't have problems pulling the studs out of the heads.

Between then heads/cam, I figure you can pick up an honest 30-40hp assuming the rings are still sealed well, maybe more. You could also use a steel shim .026" head gasket to help with the compression as well.

I did a 327/350hp rebuild with some 461s ( I THINK), ported them slightly and used a Crane Z274-2(224/230, .473/.486")hyd flat tappet and it came out really nice...sounds good, good vacuum and mild lobes are quiet on the valve train. I did install screw in studs though as the lift is up there. This was in my dad's 66' L79 4 spd car with 3.70s and it ran pretty decent.


On my 71's L48, it was re-ringed/bearings, stock heads were valve job'd/ported slightly, L79 cam, Edelbrock Performer intake, Q Jet, 1 3/4" headers and 2.25" exhaust. The car ran 15.0@91 with a T400, stock converter and 3.08 gears.. Still pretty weak. Probably would have gone 14.80s in winter air but... I pulled the motor and went another route.

cagotzmann

Then take it for a run at your local track to get a before and after test

At least you will know if th changes help

NewbVetteGuy

$0.02:

Your exhaust plan sounds great, from L48 intake to Edelbrock Performer sounds good, too, BUT...

Sell the 461s, sell the Edelbrock Performers; Keep the money you would've spent on the Holley carb and keep the Qjet.


Use the money to buy used Vortecs & Christmas money for a Vortec style intake. Get an appropriate cam to go with it when you can.

Make sure your timing chain isn't stretched out (if it's the original, get a new one) and change that retarded cam to either straight up or advance it 2 degrees and she'll get perky and between the efficient chamber Vortecs, the extra CR, the headers and fixing the cam timing you should see a couple MPG increase in fuel economy to go with your dramatically perkier Vette, too. (Plus the headers you've already planned will make it SOUND perkier to boot.) The vortec style intake will drop the exhaust cross-over so you'll get a little boost from the cooler air charge, too.

Save the EFI for next Christmas after this Christmas's "Beta testers" work out the bugs from the Holley Sniper $899 system and get extra driveability and another mpg or two depending upon how well tuned your Qjet is. -Assume that you'll sell the Qjet to help pay for the TBI EFI.


Adam

NewbVetteGuy

Oh yea and if / when you do go with 64 cc ports, be sure to get the FelPro 0.015" gaskets -if you go with a standard 0.045" you're leaving 0.5 CR points on the table. (Yes, a shocking, but true statistic.)

Krystal

I know you said weren't looking for advice .......so just take this as my own opinion and why I chose a different route for my '79. I realize you'll likely dismiss this because it does come off as advice......but really if you haven't spent $ yet.......it really is the alternative view that you should want to hear and should at least consider BEFORE spending the cash....

So here goes.....

......"wake up" an L48?........and really let's not forget the L82...... I'm amazed that anyone sees these motors any differently all these years later. Both are products of the same dismal period in time for performance.

I fully realize you and most everyone here reading this knows what I'm going say already.......but really sometimes it just needs to be said again.......

It's still true......."you can't polish a turd" ........ and "throwing good money after bad" are both expressions that would seem to apply here pretty quickly if you aren't absolutely certain that you will be happy with a finished job that can't produce even 300HP.

Today it's hard to make a case for reviving or attempting to "wake up" a smog motor if your goal is anything more than what I think should be a bare minimum power level for any Corvette that can't be victimized by a new Honda Civic in an acceleration contest these days.

If it's originality you want to keep? This one is a tough argument to make too. Unlike that 1970 LT-1 that would lose value in a big way on motor swap ....even super low mileage, perfect examples of any Corvette from the late 70s commands such a very weak resale "bump" for originality of it's engine.......there is no case I can make that suggests you should even attempt to "wake up" this L48 engine or the very weak upgrade from back-in-the-day an L82.

The sad truth......both motors are hopelessly tied to the smog era and the engineering was just so focused on beating the tough new tail pipe testing rather than making power....... it would require new heads, a different cam, intake, carb and exhaust all told changes that don't come cheap........ by the time you add it all up.........it's hard to make the case for the work.

Today there are simply too many roller cam, crate motors with warranties attached that just make so much more sense.

Jonz79

I guess we should take: every post-72 Vette, Trans-Am, Z/28, Monte-Carlo,......toss all the "turds" and replace them with crate engines, or LS's?


Please. Can we stop the essays espousing such nonsense?


Take ANY GM 350, $3K, some ingenuity, and access to some careful planning, and perhaps some used parts, and you can make decent power.


These cars were decent, relative to when they were built. BTW, the market for all mentioned is growing, and fast. So keep telling the 79 TA, or Vette owner that his 403, or 350 is a turd. BTW: I define "decent" as a car that simply gets down the road with a nice pull, positive shifts, makes a great sound. If we are all chasing 11 second "weekend cruisers"......lol, I stand corrected. Wait,....then again, there is always forced induction.

Jebbysan

I would not waste the time on the 461's unless you port them well.....and install quality backcut valves with a primo 5 angle valve job.....

As a previous poster mentioned....I also had a 66' 327/350 with highly ported 461 heads....L-79 cam w/1.6 rockers....Edelbrock 650AVS and Performer intake....through manifolds with sidepipes it ran consistant 13.90's w/ a 3:36 and 4 speed wide ratio. It was a midrange power.....lots of fun.

Buy a pair of 180 Iron Eagles new or second hand......install a nice cam/intake/carb package.....curve the distributor....a pair of headers and hold on......It will pull very well.

Jebby

Old55

Keith, I will honestly answer your question best I understand it.
You will for sure have the new Hooker Headers pipes and good mufflers. Good stuff!
Changing carbs will get you nothing IMO save your money.
Changing heads you have on hand now will provide a very modest bump.
Swiping to a free flowing intake will help but only just a very little bit not worth the money due to your cam and heads.
So that is an honest accurate answer to your exact question.
If that is only what you want to do I respect that. If it were me would take part of the money you saved on the carb and buy a quality aluminum water pump.

Keith think of your engine as a pump. Its a sum of its parts.
You need a plan. Are you going EFI or not? If yes then do the above only until you decide on the EFI.
The key is flow as all the others stated. Without a cam and effective heads not much can happen but IMO figure out EFI first then choose cam heads and intake that matches the EFI or carb of your choice Edelbrock performer is a good carb an AFB copy I think.

I like very much what newbvetteguy (local guys rock!) said. The books Mr. Cardo0 called out are very helpful. Lots of great advice here.

keithl1967

Much appreciated on the advice guys... I will likely have a motor build several years down the road--this is more a hobby for me, and am in no rush to get everything done...Car was a solid original runner when I bought it, but had its issues as you could imagine. Slowly working through them--already re-done the interior, got all of the gauges working, the HVAC controls, etc, etc...

Was just wondering what parts might be worth the effort while I had it out--specifically parts I have on hand--all of the above mentioned I have on a shelf (heads, carb, intake, exhaust)...While I did purchase the exhaust specifically for the project last year, all else were just stuff I've had sitting around, so no real additional OOP expense.

Sounds like I might just leave well-enough alone for now, pull the motor, clean it and the bay up, swap the exhaust (and likely the intake and carb--I get the Q-jet responses, but I have always been a "Holley Guy.")

As for EFI--that questions was as much for my '67 Camaro as it was for the Vette...just thinking of drive ability/reliability--not so concerned with racing applications...

Patro46

Many of these suggestions will have you spending enough money to DO an LS based swap, leaving to door wide open to pretty much anything you can vision....

cooper9811

Patro46 - How is an LS swap as cheap as swapping intake/heads? I'm not trying to be argumentative, but if it can be that cheap, I want to know how you sourced parts and would honestly start to plan for one.

My belief is that too many other things also have to change to make it as cheap as a gen 1-based top end (which is what the OP was actually posting about).

I agree that once it's done you have a great platform for performance - but aren't the total modifications required to run an LS in any C3 rather extensive?

Jebbysan

I love the LS engine.......but the biggest deal killer for me is how it does not at all look like it belongs in a Vette.......I cannot totally explain it but Vettes were showcases for the best Chevrolet engines of the time......a statement that is true today......but the heart that beats in a vintage Stingray is vintage itself......
Just my opinion....and the reason I spent over 6k building a kick butt 406 that looks like is suppose to go there. My car would not be the same with a LS deal in it. Depends on the theme.....
Anyway...carry on

Jebby

jb78L-82

I agree about the LS swaps..not my thing since to me that engine just not fits the theme...depends what you want though..its your car though to do as you please. I feel the same about 383 conversions but going to a 406 is a different animal

FWIW-my understanding from the engine builder (he builds big HP chevy engines and has done MANY) who did my bottom end of the L-82, commented that the .015 head gasket I used is good for about .2 compression bump, not .5.