[jjacks01]

Im cleaning up my engine bay and engine in my 1966 A code convertible. I believe the engine is original based on casting dates. I've pulled the cam and found this....

base circle dia......1.4815"
max cam dia .........1.7110"
cam lift.............. .2295"
total lift @rocker.... .3672" (1.6:1 stock rocker arm ratio)

I'd like to wake this engine up slightly, but keep solid durability and the original heads and setup. This lift seems small.

What was the stock cam lift?
Any recommendation for a wake up cam? I'd like to stick with crane or a major name. Carb is holley 600, intake original 4 bbl (though I have a performer RPM avaiable from my boat)

Thoughts appreciated.....

 

[Huskinhano]

Pprobably a cam such as the Edelbrock Performer would be a good choice for a stock engine. Check with your favorite cam company for the best info on selecting a cam

 

[jjacks01]

Is there a known limit on lift with the stock heads and valves?

 

[70sportsroof]

Stock heads and valves also means stock springs and retainers. You have two things to think about from a purely physical fit perspective. First, there is valve to piston clearance. The general wisdom is that with factory flat top piston with no valve reliefs, total lift (lift at the cam times rocker ratio)can safely reach .500 without worrying about clearance. Others have gotten more lift than that without fitment problems. I ran .512 on the exhaust side, which is a smaller diameter valve when compared with the intake.

The second thing to think about is coil bind. This is the point where the valve spring is being asked to compress beyond what the coils can accomplish at a specific rpm. Thus, with factory springs you don't want to use a cam designed to make peak power at 7,000 rpm. The coils will bind and not allow the valves to operate.

For these reasons, when thinking about cam specs you need to consider the need for notched or recessed pistons (which will lower your compression ratio - dished more so than notched)and different valve springs. With the higher cam lobes, the valve springs are being asked to do more work. Hence you will need higher seat pressures, both in open and closed position. In addition, you need the correct spring height to avoid coil bind within the operating rpm of the cam.

This has to be figured out by specific application. The cam manufacturer can recommend the correct springs. After having some difficulties with CompCams in obtaining correct valve springs for a cam grind they sold me, I now recommend Crane for cam/spring combos.

Remember, the cam is the brain that tells the lungs how deeply to breathe. If you have a cam that is asking for more air (inhale), you will restrict it where the engine will run poorly if you run the factory intake. It is the synergism of parts - the manner in which they operate together - that builds an efficient engine. Parts that operate well individually do not necessarily work well together. That is why some folks like the Total Performance packages from Edelbrock, or a comprable "kit" from Trick Flow, as they have taken the guess work out of matching parts. (kits are cam, heads, intake, carb)


good luck.

 

[VictorII]

Summit has a Performer clone that is very reasonable. It is a split duration and comes with lifters. They told me it is gound by Crane but I really don't know. It might be a good idea to call them and tell them what you have in the way of valve springs. I think they will work with stockers and the lift is higher. The idle is smooth but there is more punch. I have had mine for way over 100,000 miles and remain happy with it. It is a good idea to consider a new timing chain set as well. Summit has their own brand that is also not all that expensive. They hve both single and dual row. I use dual row. It is not a true roller but acts like it. After all these miles it is still pretty tight....

 

[CAponyboy]

For stock heads I would recommend a dual profile camshaft or custom grind of the same....

I would decrease the LSA a bit (keep it at approx 112)
Don't exceed valve duration of 220 @.050" but do favor the duration on the exhaust side since the exh ports are tiny on the 289 stock heads.

Do match valve springs to the cam specs. Do install a new oil pump when going with a better profile cam....preferrably a performance unit to keep things well oiled.

Now would be a good time to get the heads serviced with new guides and seals along with 7/16's screw in studs for roller rockers.

regards
R