I have read about performance upgrades for the L48 on here in the past and I have not been able to find anything on my search.


I have a 78 with the L48. It was a California car when I purchased it.


It has a performer intake and someone in the past also installed a cam as it sounds much different than the stock L48. I just don't know what cam is in it and guessing it must be something that allowed it to pass CA smog checks.


I have removed all the smog equipment and found a noticed increase in performance. That may just be from eliminating a belt and the fan.


It has stock configured exhaust with Magnaflow mufflers. I will change it to true duals and long tube headers.


What I would like to know is what can I do with a cam, heads intake ect.


Would the 64cc chambered heads raise compression from the stock heads. I have ideas but would like to hear what works with out going into the bottom end for know.

 

64cc heads will raise the compression.Go aluminum.
Intake is fine.
Fix the exhaust first.
After the exhaust and maybe heads it may very well be fast enough without changing the cam.
Without knowing the current cam it is hard to suggest going bigger/smaller.

Exhaust upgrade and heads would make a night/day difference.

 

Yes, with 64cc heads you'd gain just over 1 CR over that had with 76cc ones, which the L48 severely needs. So, if you actually have 8.5 now you'd have ~9.6:1 after the swap.

I'd suggest you perform a cranking compression check (all plugs removed) and leak down test before cracking it open. This will give you an idea of how well (or poorly) matched is your current cam/CR combo, as well as how healthy are your cylinders. Wouldn't be a bad idea to drop the pan and check the front main and 1-2 rod bearings either, as well as to consider swapping in main studs for some added insurance should you intend on flogging it regularly.

And, in any event, tho it isn't necessarily the holy grail of engine design, for this CR range I'd definitely do your DCR* maths before pulling the trigger on the cam to be used with whatever else you elect to do. Very easy, it is, to over-cam and end up with a real slug. For a 9.5'ish CR pump gas mill, I'd probably aim for ~8 to 8.25 tDCR, erring on the lower side with iron heads.

Excuse me if I refrain from suggesting a specific cam, but FWIW while narrower LSA cams may yield slightly higher peak HP, wider LSA cams (say 112* v 108*) will typically have a flatter TQ curve and generally display better manners. (IMCO a thumpy idle isn't always the best criteria by which to judge a cam.) I will say that AFR 180s would definitely be among candidate heads I'd consider here. My $.02






*Theoretical DCR (tDCR), as typically utilized for such evaluations, is based solely on an engine's trigonometry at the point of intake valve closing. Actual DCR = static CR x VE% at a given RPM, but isn't readily calculated unless you already know a particular engine's VE% curve. The more efficient and/or higher performing is an engine, the more likely higher will actual DCR be relative to static CR, the higher will be peak cylinder pressures, and thus the less relevant a tool will be tDCR maths.

 

Thanks for the refresher. I just couldnt be sure about my thoughts on a budget up grade for the L48.

This car has 63k in miles. It feels and drives like 63k. The engine runs great and seems crisp. No leaks. Just low on the performance.

I do believe the engine was out or the car at done point. It's painted black and has a cam that's not real lopy but sounds nice. Being from California I would guess someone has camed it just enough retaining smog passing.

I will drop the pan and check the compression. I think the suggested heads are a great choice.

So heads, long tube headers, split the exhaust out and it should run nicely.
Thanks!