jaycall88

68301 Hedman Headers
350-3701 Edelbrock Performer Intake Manifold
K12-210-2 268H Camshaft "Complete Kit"
350 60909 Edelbrock Aluminum Cylinder Heads


Hello
So far these are the modifications that I plan to have on my L48, I was wondering what do you guys think of this combination? Again these upgrades will happen during the summer as I do more research before then.

Once again thank you for your help!

SanDiegoPaul

ditch the Edelbrock heads get AFR's or brodix. For carburetor use the Quadra jet if you need to be smog legal. Get the car dyno tuned when done, so that your carburetor and distributor are properly configured.

fauxrs

The AFR street 180 heads p/n 0916* are superior to the edelbrocks in flow at all lifts other than .200 so this is a good reccomendation. They have a 65cc combustion chamber which will also up your CR a little bit offsetting somewhat your dished pistons in the L48.

That should be a good buildup for a smog legal motor. Run a qjet as opposed to an edelbrock carb, I simply cannot recommend their carbs for performance use.

jackson

dunno if smog legal??? but they oughta be ...
alum heads as found on late 80's-early 90's GM L98 sbc in vette, camaro & fbird w/ TPI. Also on ZZ4 crate motor.

58cc chamber is better match w/ L48 dish piston ... 58cc makes about 3/4 of a whole point more compression than 64cc.

qwank

I think the AFR heads will still be a better choice because they will still outflow those early aluminum heads

jaycall88

Cool lots of information to research!

Once I have read through and researched everything I'll do a write up since alot of the useful information out there is spread out amongst different threads.

Oh BTW

Will this setup give me more low end torque? I'm looking for quick acceleration feeling. I rode in my friends 500HP Lancer Evo and man, I felt like I was in a roller coaster that thing accels super hard!

Shark Racer

The compression ratio part is spot-on, but these heads flow very poorly and do not have egr passages in the head. EGR on L98s is routed through the exhaust manifold. Not a legal route.

I agree. 180 will keep the torque up and be more than enough head.



As to the 500hp Evo - it's hard to beat an AWD launch, and if it's a true 500hp, it will be VERY hard to get there while remaining street legal, unless you go to a modern motor mill. You can do things to a G1 small block and pass smog, but you'll be on the ragged edge and definitely will have trouble with the visual.

jaycall88

What HP/TQ can i expect from this build ?

jackson

No doubt afr flows more; $more$ too.
But L98 flow is not bad ... and unless OP plans for more cam than 268H, I doubt he can use much (if any) more port flow than L98 provides. And its small chamber>increased comp is significant. And $less$.

Comp 268H cam
268° Intake / 268° Exhaust
218° Intake / 218° Exhaust
.454'' Intake / .454'' Exhaust

perhaps OP has confirmed his primary usage & smog plan & performance goals? etc etc ... and will post same?

cv67

disagree the 180 AFR heads will kill the L98s at every lift level even with that cam and remain smog legal. PLus more efficient combustion chamber to boot, ligher valvetrain. Totally worth it.

hit up tpi421Vette for a great deal on a set in the C4 tech section.

jaycall88

Would my stock transmission / rear end be able to handle these upgrades?

fauxrs

yes, you will not be producing any kind of power that would be a threat to the tranny or rear end.

jaycall88

I'm guessing these mods would put me around 350hp-ish?

Cheeseoreno

I used AFR Aluminum Heads shaved (as per their suggestion), Retained my manifold (I found out it is exceptional on Corvettes), A high lobe short duration roller cam, roller rockers & tappets to avoid Smog issues (overlapping cams have much higher contaminant output). I stated to watch your Headman CARB Legal (if you are in CA) Headers because they have 1-3/8 exhaust ports and many Aluminum Heads DO NOT have that small a port. So it will, most likely, not seal properly as told to me from the Headman Tech.

Big tip....if you own a Corvette with rear gears of 3.09 or there abouts you will get the great seat-of-the-pants pull with a better gear ratio like I did BUT you will probably have to go to a 5 speed transmission to tack less than 3500 RPM at around 65 mph. The combo may save you a LOT of money and stress at the Smog Station. It may save you money because you may not have to tear into your engine with your other mods but, of course, we never have enough power or speed.

stingr69

The specified cam kit has too many parts in it to work with pre-assembled heads. You would not need the extra valve springs, retainers, keepers etc because the heads are already assembled.

Cheeseoreno

I think you replied to my post (I am new to the Forum and finding my way) but I did get the double coil Springs etc due to my selection of High Lift short Duration cam. I didn't want valve float or "bumping". Tolerances were critical while in higher RPM operation. I researched this pretty deeply as I was terrified after putting in all the time and money for my 383 Stroker to fail at the Smog Stations in California, where I live. My other strategy was to lower the temperature by eliminating as much friction as possible, which I achieved in part through my roller hydrolic tappets and Roller Rockers. All-in-all it worked for me as I have passed smog for over 20 years now. If you have a modified engine and live in California you always live in fear.

TedH

Probably closer to 300hp than 350hp. Retro roller cam would provide better performance and still meet emissions. See my sig for the Comp Retro Roller kit I installed.

The 68301's have 1 5/8" ID exhaust tubes. The only difference from the 68300 (non-smog) and 68306 (non-smog, HTC coated) are the air tubes at the ports.

stingr69

Nope - I was replying to the original poster. No need to double up on parts.

calwldlife

could you supply some specs?
comp/ratio
cam
carb?
and what it failed on?
nox?
c02?
lack of oe smog equip?

hard to build a motor without specs.
smog wants more heat at idle with retarded timing
but that is heat and nox goes up.

Cheeseoreno

Sorry and Thanks for answering back so I get used to knowing what I am doing wrong on the Forum.