Hi, I have a 350 and the guy I bought my 73 vette from doesn’t know what cam is in the engine just knows it’s a mild cam definitely not stock, but I still have stock heads, can I just throw a pair of aftermarket heads to try and gain some power if so how would I know which ones to get, or do I have to pull the cam and put a new one and match it to a pair of heads? I hope to hit 400+ horsepower.

 

400 HP is doable with the right combination of parts. Any good set of heads will be an improvement. Good long tube headers. proper dual exhaust. a good intake manifold. And yes. the right cam. not hard to pull the cam and ID it when you have the heads off.

 

You are starting out with what? 190-200 horse? To add another 200 is not likely going to happen with 9:1 compression, more like 8.8 :1.
New heads & cam kit will not add 200 horse. If it did, the factory would have done that 40+ yrs ago.

Heads come in a wide array of quality, flow rate, compression and price. You can get a pair, fully loaded for less than $600 a pair.
Or you can get heads for $2,000 . . . . . . . . . .EACH !

So, you need a budget.

To identify your cam specifications does not require head removal.
However, fan, belts, water-pump, timing cover, timing set, will have to be removed. Cam part number should be on the end of the journal.

Its more common to match the cam to the heads than to match heads to the cam.

 

Have you driven a vehicle with 400 horsepower? I have and they can get squirrelly in a heartbeat.

 

Get a timing tape, dial indicator. Takes removing the plugs and 4 screws.

Put the tape on the DAMPER.

Pull the plugs and rotate the engine with the dial indicator. first on the intake, then the exhaust valve rocker.

Now you know the cam... Cost is less than $50 and takes less than an hour.

 

-I don’t have 9:1 comp rn I have flat top pistons in so the comp is higher, and when I replaced my timing gears and chain I didn’t see any numbers on the end of the cam?

 

and you not only know what your cam is. you hadda learn camshafts. opening and closing events. overlap. all that good ****. and you own a dial indicator with base...

 

Of course aluminum heads will add a lot of power ... You get a modern combustion chamber that's happy at 32 to 34 degree timing instead of 38 to 40 , you get ports that flow more as cast at .300 valve lift than ported cast iron flow at .500 valve lift . the 64 cc chamber will add a full point of compression ... I put Promaxx 183 cc intake port with 64cc combustion chamber on my 80 L82 , added a performer intake , headers and a Comp XE 262 which is a modern version of the L82 cam . If my car don't make 400 horsepower then it's close , 13.6 at 102.79mph first pass on a 1/4 mile right off the street

 

- so would you recommend those heads for a car with a mild cam?

 

Just fyi, I checked 2 sites to calculate HP using trap speed vs car weight. Using 3600 lbs (car plus driver) and 103 mph both yielded 307 hp (at the flywheel). So unless you weigh 600 lbs, you're not making 400 hp. Neither am I, btw.

 

-with the right stuff you could easily make a 400hp out of a 350 or 383

 

This cam and heads will do it

 

BK , it sure isn't going to have 400 RWHP

 

not with a 262 cam.

 

Once a camshafts duration specs starts climbing to 280, you better have lots of compression to go with it.
The O.P. and the former owner do not know what cam is in there now. Nor does anyone know what slugs are in the bores.

To make some serious H.P. you need slugs & matching chambers squeezing at least 9.7 or more C.R. And that is just static C.R.
The more important Dynamic C.R should be 8.0 - 8.5. That's where the power is made, Dynamic C.R.

A 400 horse mill has a lot more involved than just slapping parts on blindly. Someone can state they have Dish Pistons, Flat-Top Pistons or Domed Pistons. Without knowing the exact SCR and the DCR, the piston data is all for nothing.

Good luck.

 

400 HP you’re gonna need CR 10:1 or very close. Good aluminum heads that flow a good 240 CFM on the intake, or more. Double the flow on the intake side and that is the rule of thumb for the potential HP from those heads. However that’s in an optimized combo. That kind of optimization is usually not affordable or achievable by most of us. What can you afford? No less than 180 cc runners, may want to consider 195cc if your near sea level.

a roller cam with a 110 LSA and 225@ .050 duration or better on intake, or 108 LSA and 220ish or better @ .050 duration.
advertised duration of 280ish or better. More duration will net more HP, but you will be sacrificing low rpm torque and HP.
Get the best heads you can afford. Better flowing heads require less duration on the cam to get the same power. Of course 195 cc heads will flow more than 180 cc heads due to the volume increase, but the velocity of the flow will be reduced, so cylinder filling at low rpm will be less meaning les torque and HP at low rpm in order to gain at high rpm. Depends on what you’re looking for. And what gearing the car has.

pay attention to the squish distance. .037 to.045 in where you want to be. Stock 350 has the pistons .025 in the hole at TDC. So a .015” felpro shim head gasket is perfect. If the block has been zero decked then a .040- .041 is perfect.

good dual plane intake with lots of flow, performer RPM or air gap. Standard performer has small runners and will be restrictive at high RPM unless you can port it out.

what kind of internals in this engine? If stock L-48 then it’ll all need to be changed. If it’s an L-82 then they can be used. L-48 comes with junk cast dish pistons and cast crank. L-82 has all forged internals and flat top pistons.

Then the intake needs to be unrestricted, not choked up with a single snorkel stock L-48 intake.

exhaust needs to be true dual. No less than 2” . Long tube headers 1 3/4” primaries with that system, NOT stock cast iron manifolds.

these things will get you to 400+ HP. Otherwise you’re gonna reside in the sub 400 realm.


you will gain some HP just getting modern heads just due to better flow of those heads. However to optimize them you will need to make other changes to support that additional flow.

 

- that is all very useful thank you for responding looks like I have some work and decisions ahead of me!

 

Just remember that any high rise intake manifold will cause hood interference problems. Also the air gap manifold is a terrible choice unless you live in a warm climate and it's still a bad choice. probably the best flowing stock sbc intake manifold is the one used on 67 Z-28's.

 

First of all, according to Edelbrock, the Air Gap is a medium rise. Its only around a half inch taller than stock.

Second, anytime you can keep heat, hot oils and the like off of the bottom of the carb base area, is a win-win situation. Especially in the tight and overly hot confines of a C3 engine bay.

And a drop-base air cleaner is a simple solution to hood clearance.

 

Are you running an air gap or know anyone who has? They have a tendency to freeze up in colder weather. They might be great on the drag strip but on a daily driver not so much.