Cylinder head and cam question

[qkcuda]

My 66 Charger has the original 361 engine. It runs smoothly and has great low end torque. It has become apparent that the valve seals are probably shot. Lots of smoke on cold start up. I believe the engine has 70,000 original miles on it, and there is no evidence the heads have ever been off. I will be changing the intake this winter, and will either have to change the valve seals on the engine, or pull the heads.

Now for the question. If I have the original 516 heads rebuilt and change out the small 1.60 exhaust valves for 1.74 versions, and have a plunge cut done on the intake and exhaust, will it make any appreciable difference in performance if retaining the stock cam? What about if I add a small cam under 450 lift with low overlap? I am trying to retain the low end torque and street manners, but if I have the heads off for a valve job anyway???

 

[vance.dykes]

remember that an engine is an air pump so the more air you can move the better the engine will run more efficient for power and better response but all must be equal to big in one part you wont be happy. call a cam company and tell them what you want and they will tell you how it will work together. or replace valve seals and replace the valve springs and you will see a improvement.

 

[PRHeads]

Without removing the heads to see what kind of shape they’re in....... and wanting to still have a clue as to their condition to make an informed decision about removing them or not.......my suggestion would be to remove the rockers and put a straight edge along the tops of the valves.
What you’re looking for is evidence of exhaust seat recession.
If the exhaust seats are noticeably “sunk”, the exhaust valve tips will be noticeably higher than the intakes.
If they’re all still pretty even....... just replace the seals and keep driving.

 

[69a100]

I have 516's that have been cut for the 1.74 valves with a pocket port job and upgraded to a Hughes 2330 cam and made a huge difference. Keep your cam no larger than 10% over stock duration and no more than .050" of lift over stock and you'll have a sweet street car that can retain it's stock converter. Good Luck

 

[yella71]

also what kind of exhaust is on the car? single or duel? manifolds or headers? opening up the heads wont make any differance if the rest is just as restrictive

 

[qkcuda]

This is all good advice. Although the engine is original internally it has been upgraded with dual 2 1/4 exhaust to 2 inch tailpipes off stock manifolds. It also has a performer intake and 625 street demon carb. I am not sure about changing the cam, mainly because of all the A/C stuff hanging off the front of the engine. The part that makes me nervous is the 54 year old timing gear. If I have to change it a new cam will go in. The stock cam is only 390 lift

 

[PRHeads]

If you do pull the heads, I’m not sure how much difference you’re going to see with the 1.74 exhaust valve....... with the heads on the small bore of the 361.

 

[qkcuda]

My second reason for thinking of the 1.74 valves is in case the valves have sunk you are cutting a new higher seat. I don't think I will put enough miles on it to warrant hardened seats

 

[PRND21]

I don’t believe 361s had plastic cam gears, all I’ve ever seen were steel, somebody correct me if I’m wrong. Chain will probably have a little slop though.

 

[qkcuda]

If the cam gear is steel I will feel better. I hope I will be able to see a bit of the gear when I get the intake off.

 

[Don Frelier]

It should have steel gears.

 

[padam]

Old timers say that if you improve your heads, specifically the valve seats, you will probably start to see more blow by of the piston rings.

 

[Don Frelier]

hope I will be able to see a bit of the gear when I get the intake off

The timing chain and gears won't be visible with the intake off, they are on the outside of the block.
But I suppose you could try turning the crank and see how far it rotates before the cam rotates.
I know the timing marks will jump pretty badly on a really stretched chain, I've seen that before.
But you say that your low end is strong thats a good sign because when the chain is stretched/worn excessively they get soft on the low end since it's retarded.

 

[qkcuda]

There is a bit of a window in the front of the block by the distributor drive. I figured I might be able to see some part of the gear through that, or at least get a magnet in there?

 

[PRHeads]

If the heads come off, and there is any sign of ex seat recession...... just put seats in.
It’s not that expensive, and then it’s done.

Also, if the recession is fairly deep, the 1.74 valve won’t really solve the problem.

Last year I had two sets of heads come through the shop with the most severe exhaust seat recession I’d seen in 30 years.
Some had valves that were down into the head nearly 1/4”(not exaggerating).
A set of 1967 GTO heads, and some mid-60’s 289 Mustang heads.

Installed new ex seats and they were as good as new.

 

[Runcharger]

I had a 383 in a 70 Adventurer that had a couple exhaust valves receded and it ran rough (imagine the loss of spring pressure), he says this car runs smooth. I think you will be very happy with what you are planning to do.

 

[qkcuda]

Update. Looks like the heads will be coming off. Did a compression test today and all cylinders were between 125 and 140 EXCEPT number 6 which was at 60. I went to another cylinder and came back to it just to make sure, and exactly 60 again. Oh well, hopefully it is just a valve, and not a ring problem. I will have to recheck the plugs tomorrow but as I took them out I didn't notice any oil fouling, just that it has been running rich, which I already knew.

 

[Don Frelier]

You should try it with some heavy oil in there BEFORE you pull the head.
If it comes up a good percentage then you have decisions to make.

 

[qkcuda]

It was lucky I had the lift or I wouldn't have been able to get the tester screwed in. I had to do most from underneath. I tried to add some oil and test again, but I could not get the oil can in there. I thought my big block a body was tight but between the stock manifolds, power steering and A/C lines it was major PITA

 

[qkcuda]

I may try again tomorrow to get some oil in there and retest. I was done for today.