on cam kits

[doug 351]

I figured you'd get it. I've had some of the same kind of Duh moments myself. I did oversimplify it a bit-they can't just make a cam fire whenever they want. The piston goes to the top of the cylinder twice but only fires once. With the cylinders that are switched, those that were on the compression stroke on the original firing order are now on the exhaust stroke.
I first heard about changing the firing orders with a cam many years back. It was on a SBC and IIRC they switched the 3 and 7 cylinders. They found that the motors did a better job of scavenging exhaust gases with the new firing order.

[doug 351]

My most recent Duh moment- I got to thinking- why if a 351w's rotating mass is heavier than a 302 would a 351 have a 28 ounce imbalance and a 302 a 50 ounce imbalance? Took days for it to dawn on me that the 302 would also have less room to spin counterweights and therefore lighter crankshaft counterweights to offset the piston and rod weight.

[302]

Tonight, I just check the compression. My results where very bazzar.
Cylenders Compression
1-30
2-105
3-70
4-30
5-30
6-0
7-80
8-0

What does this mean? Is my timing betwen my crank and cam off? Are my valves not seating? I'am completly lost on this one. I know my piston rings can't be bad. The engine never smoked or burned oil. It only has 77,000 miles on it. That's not bad for 20 years old.

[jonmark1985]

Those numbers mean its time to crack back into the engine. When I had similar problems on my Firebird I had the rocker arms down to tight, You don't have adjustable valvetrain, so this hopefully is not the case. Double check your timing chain, make sure you have it lined up right. If this is the case, check the pressure on the pushrods when their respective valve is closed. Usually you want to be able to slgihtly twist the pushrod. Check for bent pushrods, broken springs, binding lifters, and all any other things that seem odd with the valvetrain. Then comes the scary part of piston to valve clearance, the standard output motor has no valve relief, this will probably mean pulling the heads.

[302]

This may sound like a stupid question, but what is valve relief?
I'am not sure how I'am going to check to see if the cam and crank are lined up right. Because last weakend, I had to change the timing between the crank and cam, because they wheren't coiniciding properly. The problem was that the cam is for a HO, wich has a differant firing order. I checked, and relized the pistion was coming up for compression when the intake valve was open. And when it came down for intake, both valves where closed. I don't know how it even started at first. So when we timed it, we based it off of cylinder 6, because it coinsides with cylinder 1, just on the oposite stroke. Or did we mess something up even worse. I think I turned the crank 1.25 turns without the cam moving to time them. Then put a timing wheel on it.

[jonmark1985]

Valve relief Is the notches cut or cast into the top of the piston. The heads put on the standard 302 in later years had the valves placed higher up. This design along with the smaller and steeper ramped hydraulic roller camshaft allowed the pistons to be cast with no valve relief.

Piston to valve clearance theoretically should always be checked when the camshaft, heads, or camshaft timing is changed.

From what I understand even putting a HO camshaft and hO heads on a standard output block can mean piston to valve interference.

Regardless of what firing order you use you want to put the timing chain marks at the right points. Pull the cover back off and line up your marks, and just because the piston moves down doesn't mean its on the intake stroke, it could be on power stroke.

[302]

I was woundering if the heads on a 89 mustang 5.0L HO are the same as mine on my 89 CV 5.0L? I'am asking this because I found a valve spring upgrade kit for OEM small block ford heads. They say there for a mustang though.
I took the driver side head off tonight, and found that my valves are bent. I figured if I got the money, while I have the heads off, and replacing the valves. To put better springs on it while I'am at it, that I know will handle the lift. The discription say's it will allow a performance cam of up to .542" lift. My cam I put in is .530" lift. So if the springs will work, the springs should be fine. If anyone knows if they will work, please let me know. Thanks.

[jonmark1985]

On the bottom of the intake ports should be a number, something like E7TE or E6SE. The E7 number is the HO head for 87-93, the other is the standard output head.

You have to check your installed spring height, the outside diameter of the valves springs, and inside clearance around the valve seals.

The next question you have to ask yourself, is "how did those valves get bent?" Did they float when you revved up the engine? Or did the valves smack the faces of the pistons. I'd stick 1 new intake and 1 new exhaust valve in the head, put some "Play-Doh" on the top of the piston, put the head back on, and just pushrods on the new valves, and then crank over the motor by hand, pop the head back off, and check how much "Play-Doh" you have between the valves in piston. Cutting slots in it with a razor to get a profile will help you determine how much clearance you have. I think Speed-Pro reccomends .1 inches.

[302]

Today I just took my heads to a local machine shop. I have them all stripped down, and I looked over my valves. All of them appeare to be straight, but he is going to test them to double check. But the valve seats had a lot of carban build up on them. Some of the build up hardend and prevented the valve from seating properly.
I should get the heads back by thursday. I'am having a complete valve job done, completly cleaned, seats re-ground, heads re-surfaced, and the valves cleaned up. I'am also having new, stronger springs put on. That should help.
I'am still confused though on how it got off time in the first place? Especialy with a new timing chain on it. I returned the timing chain though. Because after only one time running, before it stalled and something bad happend. It was already streached to .5" deflextion. I have a new one on the way. But this time I went with edlebrock, and not Zoom.

[jonmark1985]

Ask your machinist what they think about the piston to valve clearance.

Cloyes, Speed-Pro, or Melling make good quality timing chains. The Edelbrock unit is probably a re-boxed Cloyes.

The last chain probably stretched when the pistons hit the valves.