Putting 6X heads on a 1970 455 Pontiac engine.

Hey Folks,
Wanting to put this set of rebuilt 6X heads with hardened valves on my 1970 455 4 bolt main Pontiac motor, but am not sure if I can just remove the existing ones and bolt these on, or are there some things I need to do to be safe??  I dont know alot about these heads, but I bought them about three years ago for $200 and put them in plastic bags after having oiled the begeebeers out of em.  They say KO66 on one head, and KO86 on the other.  The have the letters D-N and G-M on both. Any ideas guys or can I just put em on and runem!!! Thanks, JB    

What is the stamped number on that little machined pad below the valve cover bolt hole? Depending on whether it is an 8 or a 4 tells you if they have 101cc or 96cc chambers respectively. The 6X's are functionally identical to the 1975-only 5C's which I'm using on my 75 455. I just posted a video on the "Knights" thread of mine running on the test stand this afternoon, they are 5C-8's.
Steve  
A little help... 'cause we don't all have to learn the hard way!

The -8's give between 8.7 and 9.0:1 depending on deck height, overbore and milling on a 455.  
A little help... 'cause we don't all have to learn the hard way!

Hey Steve, its an 8 on both of em. Is that good?? JB  

That's the larger chamber size which puts you right around 9.0:1 CR, they're a decent head for a budget build, I swapped out the bottle neck studs for 7/16" studs and COMP roller tip rocker arms to make them adjustable.  
A little help... 'cause we don't all have to learn the hard way!

So Barney do you think I am okay with just doing the swap and firing her up??? JB  

depends on what cam you have. the valve springs should match to the cam. and you should remove the shrouds under the spring retainers befor they break and end up in the wrong place! otherwise bolt them on and enjoy the power.

by the way what heads did you have on the 455? #64s were stock. i know a guy looking for a 70 ys 455 for a 70 gto.  
76 455/4spd TRANS AM
69 GRAND PRIX 406/5SPD

hello

The price is right however here's the problem. Just because the are clean and possibly rebuilt to some degreee you did not have them rebuilt so you have no idea if they are good or not. I would strongly recommend you take them to a reputable head shop and have them inspected unless you want to possibly take them off again right away. The guides could be worn or knurled the valve stems could be worn the seats could be improperly installed in which case they can fall out etc. You also need to see how much they have been milled if any. Any more than .025 will cause the intake to fit improperly.

The springs are likely stock and need replacing for a performance cam as mentioned above.  

+1 on what Rowsley and 70Bird said!  
A little help... 'cause we don't all have to learn the hard way!

Rowdy, 70 Bird, and Barney, Thanks for all the awesome direction and I will do exactly as you say and have the heads checked out.  My good friend, Idrive said some of the same stuff but encouraged me to ask the forum to be safe! How do I find out what cam I have?? Sorry to be ignorant about this stuff. I will take the heads to our local machine shop. Also, I will check and see what heads are currently on the 455.  Also, my understanding is it is out of a 1970 GTO!! JB  

jb would you be interested in selling or a trade for another 455?  
76 455/4spd TRANS AM
69 GRAND PRIX 406/5SPD

Finding out what cam you have could be a booger, JB. I think they are only marked on the ends. Nobody usually knows what the marks mean and even then theres no guarantee what lobe profile the cam has, even if you measure the lift. The way I see it- if you want to know what cam you have, you need to replace it. If you replace the cam, you need to know what pistons you have, the deck height, and combustion chamber volume of the heads you plan to install. You must measure ("cc") them to find that out. Once you know exactly which pistons it has and the head chamber size and valve size, then you plug in the rest of the facts about the car to arrive at a range of cam choices. Then you buy a cam, and then you know what you have.

But wait, you're not gonna do all that and not have a peek at the crank bearings are ya? Gee, why put it back together with the stock bolts, lets add ARP rod studs and resize the rods ... because you didn't know which cam you have. And of course your block has bore wear so now we need boring and pistons. By the way now you can choose valvesprings. Oh and once you buy all the parts, you can't trust that any of them are good so you'll need to check everything with a micrometer, etc. See how it piles up and why I stay away from engine talk completely now? If you don't know what cam you have, basically you need to blueprint the whole engine and install a new one. At least thats what I have gathered from a few years of forum use. Don't forget- even if you get a new cam, you can't trust that its the one you ordered even if the box says so.

Bottom line, JB? It gets complicated real quick and real deep. I can't give a simple answer. Be glad you don't know TOO much! If you're like me, you'll end up just running what ya got until theres a problem, even though you may have better stuff than whats on it, just laying around.  

Hello Jbmacneil

I just saw your question on determining what cam you have. If you want to know simply so you can determine if you need new springs then it's easy, all you need to know is the lift approximately. If this is the case which by your comments I'm guessing it is then you can do a few things.

1. Use  venier calipers and if you don't have those then use a cheap old tape measure that has 1/16 graduations on it. Now after you stop laughing put the valve so it is closed and measure from the head to the top edge of the retainer. Now watch the valve and have someone rotate the motor untill it gets to the lowest point  and measure it again.This will give you your lift within 1/16 of an inch if done properly and this is all you need in your specific case. The duration is not really relevant unless your car had a nasty lope to it, in which case it obviously has a huge cam and you may have the right springs on your existing heads anyway so just have the machine shop compare and install the better ones. Anyway, big lift typically means big duration. Tell us what it is and we can help you with spring pressures etc.

You can also do this slightly more scientifically by starting at number one tdc etc.

If you want to know exactly what the cam is if the marks don't tell us then you need to put a degree wheel on the crank unless the timing cover is off then use the cam itself.

You don't want more than 120 lb on the seat.  

Hi Rowsley, I am putting it in my 1969 GTO, but I would be happy with a 400 4 bolt just the same.  Its not a numbers matching car anyway, so it doesnt really matter. You can pm me and see if maybe I can help you.  I have from carb to pan and it was a runner when pulled with no oil loss or noises.  I just want to put a good strong motor in my 69 GTO so I can enjoy her!! I eventually would like to put a vortech supercharger on the motor. In time! Ive also thought about putting a FAST fuel injection system on it, also eventually JB  

Matt, matt matt!!! You are supposed to make things easier for me!!! Just kidding pal.  I know what you are saying.  I may be trading the motor for a 400 so who knows anyway, the point may be moot!!! JB