If on TDC, is there still a chance the valve will fall down? Deck height is stock and valve notches are maybe a little bigger than standard because I had to get the compression down a little with 462cui and 72cc heads. Still they are not massive... I think the pistons have -12cc or something like that.

The rope seems to be a good idea, since air pressure would force the piston down.

Even with a dished piston, but with a 72 CC chamber size the valve should not drop out at TDC.

Thats good news. The pistons are -15cc.
The only number I have not is the deck clearance, but it should be around .020 since the block was stock and we didn't zero deck it. So I should be around 10.4:1 and 10.6:1 CR. (10.24-6.80-2.125-1.295 = 0.02 deck clearance)

Would be pretty bad if a valve drops since I only bought the spring compressor tool to avoid removing the heads.

As Steve said generally they will not drop in most cases.

the air psi needed to hold the vale up will definitely not push the piston down. the main benefit to using air is it holds the valve all the way up nice & tight & makes adding the locks & new spring while using the spring compressor tool much easier.

im sure the rope works ok but the air is quick & easy & wont even budge the piston.

the air psi needed to hold the vale up will definitely not push the piston down. the main benefit to using air is it holds the valve all the way up nice & tight & makes adding the locks & new spring while using the spring compressor tool much easier.

I agree. Sometimes the seal holds it good sometimes it slips down getting the locks back on is a pain.

Sounds like I will have a lot of fun changing the valve springs :rolleyes:
But I'll use compressed air and get the pistons on top just in case something happens.
Hope I can feel the difference when it's all done :)

I changed from SFT to SR springs in the car. 72cc E heads. Did get harder to rotate as more cylinders got the stiffer springs!

You may not notice any difference until 20K miles down the road when the springs are still doing there job just fine!

So I did it... it wasn't just a cam and spring change in the end... I did:

- changed the xe276hr to the OF cam from Butler
- replaced valve springs (with Edelbrock 5845.) using the Proform 66784 tool.. wasn't too hard with engine in the car
- replaced valve seals
- gasket matched the RPM intake
- build new wires and connectors for the EFI

Because of bad weather I couldn't do much testing, but it clearly feels stronger and it runs really nice...idling at 800rpm without any issue and no problem with vacuum.

If anyone with a 455 is wondering, if the old faithfull cam is too big... don't worry... I'm pretty sure a tighter LSA would also be streetable.. mine has 236/242/114.

What is the valve lift on that cam?

I used that pro-form valve spring compressor and didn't like it. The fork angle is not correct for a Pontiac head. It can work, but was dicey on some.

If I had it to do over, I would get a LSM one or weld something to the fork to make it flat to the spring.

Here are the LSM ones:

https://lsmproducts.com/collections/...ng-compressors

236/242, .521/.540, 114 LS

I forgot to mention... I had to bend the fork... took me 30 seconds max :) If the fork is flat, it works really well. And it locks when the valve spring is compressed... which is pretty comfortable.

Glad it went well!

Me too, wasn't so sure when I started but in the end my biggest problem is a thermostat housing which will not seal. I found out the mounting surface is bent... after trying the O ring = leaking, then a paper gasket = leaking and finally silicone with paper gasket = still leaking.

It was also necessary to remove the support bracket for the horns, to have enough space to remove the cam... but after that (3 or 4 bolts) it was very easy to get it out and the new one in.

Sadly some water ran into the oil pan after removing the timing cover... but I had to change the oil anyway.

If the O ring type does not seal up then I would say your your two hold down bolts are too long and bottoming out.

Add a washer or two to each.

I have leveled off a warped housing by sanding it in a figure 8 pattern on soapy water lubed up wet or dry 180 grit sand paper.
It takes a while, but it works if the housing is not warped too much.

That is a mild lift compared to the real OF cam offered by SD. Butler doesn't call this the OF cam do they?

Butler uses Comp XE hydraulic roller lobes. In the linked cam here the only similarity to Dave Bisschop's Old Faithful cam is the same 236 degrees intake duration and the same 112 LSA.

https://butlerperformance.com/i-2503...tegory:1272239


.

Yup,
Here are valve lift traces for both (1.65 rockers) using a few hundred data points from Comp. Real OF intake is the lighter.

That said, the smaller lobe will often run very low 11s with a well built 455 combo / 300 CFM head. Using 110 LSA if people think it matters.

https://i.imgur.com/ZAmUhuk.png