Looking at keeping my 73 instead of going with a hot rod. Factory original L48 with TH400. In doing so, I decided to beef it up a bit. I am looking at a set of 041 heads that have been converted to 2.02 with screw-in studs. Looking for input on a cam to match. I already have headers and chambered exhaust. Already tweaked the timing, carb (Q-Jet) and removed smog equipment. I also have a polished Edelbrock Performer to put on when I do the swap.

Car only has 20k miles now, so a rebuild is not in order.

Looking for the best cam to match this setup. I want a lopey idle so it sounds badder than it is with the chambered exhaust. I just cruise in mine, but still want a mean sound. Guessing I will be looking at a 3000rpm stall as well. ?

Thanks!

 

Going to need to know your CR to get an ideal what cam can be used and your goals for the power delivery.
Do you want good low end torque with a 5500 rpm top or do you want to sacrifice low end for more top end rpm and power?
The 2101 is geared for low end torque so I would guess that is the range you're more interested in.

 

Always match your cam to your compression. Once you get the replacement heads ready you can measure them with liquid then after you take your old heads off you can measure the above piston volume to. Yes you can measure that volume with the block in the car. Just look up REEL8VTER as he did it and I believe measured 22cc above the piston on his stock L48. This gives a very accurate c.r. as any professional can measure.

Next you want to match your cam to your trans and rear gearing. BTW I didn't know the L48 ever cam with a TH400? I thought they were all TH350.

Let's us know what you find.

 

I currently have 993 heads (76cc) on my 350 and the compression ratio as stated by the factory is 8.5 to 1. The 041 heads are 64cc. My corrected compression ratio should be a little over 9.5 to 1 I believe.

Looking for strong low-to-mid performance.

TH400 was the only auto in the C3 until 75 or 76 I believe. L48, L82 or 454.

 

If you are going to go as far as changing the heads, get a modern technology design like AFR180. Do some research. Yes, those 993 heads are junk for performance.

 

I am on a little bit of a budget, and I have a fresh set of 041 heads at my disposal. Otherwise I would. Not trying to make max HP with my setup, just something nicer then what I currently have.

 

186 casting numbers are more abundant. I would also look into Dart iron eagle

 

I'm not an expert, but I believe that your two goals are mutually exclusive / at odds with eachother: if you want a "lopey" big cam sound, you need to chose a large/long duration CAM; these cams, by definition will sacrifice low to mid performance (torque) for high-end HP. -You can tame the oversized CAM with Rhoads lifters if you're sticking with hydraulic flat tappet cams, which will give you more low to mid end torque; BUT that kind of gets rid of the lopey idle.
-You're ultimately going to have to choose trying to focus on low to mid performance or the lopey idle because they really are mutually exclusive options.

Having said all that, a high stall torque converter will help there as you can take off closer to the top of the powerband. You can also play with advancing your cam timing to give you a slightly better bottom-to-mid end.


You could also scour Craigslist for a set of used Vortec heads that will probably perform better for the money; but that's assuming you bought the intake new and can return it to swap for the Vortec version of the Performer. (Or look at ProMaxx aluminum Chinese heads, if you want to save 50 lbs of weight and don't mind going with import options---there are strong opinions on this subject...)


What are your rear end gears? -That'll also be a major factor for low to mid perf.

 

Last thing: the lopey big cams like higher compression (you'll lose less on the low end) so don't forget to go with the super thin FelPro 0.015" thick gaskets. The diff between the thick 0.045" gaskets and these is 0.5 CR point (shocking, but true; plug it into a CR calculator).

Adam

 

There a couple challenges as I see it.
First the L48 came with a true CR of below 8.0. This is due to the volume of the piston and the heads were not a true 76 cc's. More like 80cc's.
With the 64 cc heads and a stock 4.0" bore with the pistons .025" in the bore (stock) you get 9.02:1 using a felpro .015" shim head gasket.

The heads you intend on using I would cc them. You can do it at home easily.
Check out this thread. Plexiglass a drill set, some grease, and a syringe is all it takes. You may find they are bigger than 64cc's.
Your pistons are in the 17cc range for volume.
With the 64 cc heads 17cc pistons, and a stock 4.0" bore with the pistons .025" in the bore (stock) you get 9.02:1 using a felpro .015" shim head gasket.

https://www.corvetteforum.com/forums...er-size-2.html

Second is those pistons provide no real quench/squish for combustion turbulence.
Which means detonation is more likely for a given CR. Instead of 9.5:1 you may need to stay lower depending on the cam you choose as the cam will directly effect cylinder pressure.
Use a DCR calculator to get an idea of how the cam effects cylinder pressure. The higher the DCR the higher the cylinder pressure.

https://www.jeepstrokers.com/forum/calculator/

Too high and you get spontaneous combustion (detonation) due to lack of mixture motion (turbulence) in the chamber to provide a good fast burn or you end up dialing the timing back, enrichening the fuel etc,etc to try to prevent detonation, all of which reduce power.

 

Enriching the fuel/ going with higher octane fuel is the only option that would allow him to run at the higher CR WITHOUT reducing power, right? -It'll cost more money every fill up, but it won't actually lose you power, will it?


Adam

 

Yes it will. Just like economy, power is achieved at an optimum fuel mixture. Being forced to make it excessively rich reduces power.

Getting a higher octane fuel (race fuel, or mix pump and race) can stave off detonation and provide power, of course at a higher cost for the fuel.

 

I found this web site that has a short video. It's talking about AFR values but still supports what were talking about in lean vs correct vs rich.

http://www.safrtool.com/SAFR-AFR-values.asp

 

So I will probably forgo the lopey idle for better low end then.

 

Full disclosure first; I'm a fan of 108 LSA's. So if a guy is looking for a fun cam with decent bottom great mid-range and ok top I would go with something like this.
http://iskycams.com/cart/index.php?m...roducts_id=270

I have a 108 LSA roller cam with 270/270 duration. Very fun the way it comes on in it's power range.

 

Thanks again; I misunderstood what you meant by "enrich the fuel" -I thought you meant increase the octane by adding octane booster; you meant enriching the air-to-fuel ratio so that it has a lower air to fuel ratio and was therefore less likely to cause detonation. -I totally understand now.


Adam

 

that cam he listed with the cr will work Ok
Compression makes it more efficient think premium pump will be Ok
Recurve the distributor for best results
Youll still hear a little cam with that Isky. not radical but youll know its got something in there and make good torque. Old line but work good, like them myself. If I had to buy a store bought FT cam would get another in a minute, ran good never went flat either.
Some 1-5/8 headers will help you too.

 

20K on car? Assuming original mileage on body and motor no rebuild. If 20K is on motor only then may have been rebuilt with flat tops if bored over.

I agree that Isky Mega 270 cam is an older grind but a good all round performer with some lope.

 

The link shown is the 264 Mega cam with 214-214 450 lift 108 lsa. I used this cam in a stock 76 l82 with a turbo 400. Had much better low and mid range than the l82 cam. Nice throaty idle. The Isky 270 mega cam has 221-221@ 050 470 lift on a 108 lsa. Might be too much cam unless you had a stall and/or decent rear gear. Isky still makes great cams and I am running an Isky solid flat cam in my 455 65 Gto and one in my carbed 84 C4 with no problems.

 

20k on car, engine, drivetrain, etc. Original and untouched, until now.