I am thinking very hard on putting as fresh engine in the car, rebuild one. Two reasons, one my cooling fan was not working for the first 2 months had car, engine got way hot alot, 2nd I am going to keep the car and do some more body mods and want to be able to have a little fun, why not? I am asking is it better to use a NA block or a SC block. Part two of the qestion can the top end of a NA be used on a SC block.
Qestion/idea number 2 the SC block if can be used, would raise compression since used is in a NA platform.

I am wanting to rebuild block then install on in summer, late summer I am nor going for 12 or anything like that I have 20'* on car and have no plans to remove them, so fast qt not the goal here. I would how ever have to do some stuff to it, PEM and PLIM. Some other but we are still in the early part here.

Both Series 1 engines are the same compression, 8.5:1. The L27 and L67 both.


Do a compression check. Let us know the numbers for all 6 cylinders. Don't even consider replacing that motor again until you do at least that. Please also let us know what your oil pressure is on cold start, warm idle, and WOT.

I am on it, will do CT on Monday at work and check oil pressure also. Thanks

Ok compression check is as follows
1 139
2 156
3 145
4 150
5 152
6 141

Oil pressure is 50-60 on start up cold, 75-80 on idel warm, and 80-85 WOT, this is kinda estimate from looking at gauge in car. So what have I learned and what next?

I dont think there should be that much fluctuation between the cylinders

#1 is definetely weak. Looks like #6 isn't doing so hot either. Variance tells more than overall numbers. It could just be bad valve sealing, it could be a head gasket just about ready to give it up, or it could be weak rings. Ideally you want all cylinder pressures to have no more than 5% difference.

It'* not a head gasket. If it is, I'll buy 'em. And find me a half a handful of blown head gaskets on this Forum in the last 5 years and I'll buy the cars for you.

It'* more likely valve seals than rings or cyilnder wall wear. Replace the valve seals. It can be done on the car.

Your oil pressure is great. Swapping motors now will be too great a risk. You don't know what you're getting. Even rebuilt.

Willwren, if it'* valve sealing, valve seals themselves won't help. They're just for oil control. The valve faces and valve seats themselves have to be reground, he'd have to remove the heads to do that. At which point he'd need to replace the head gaskets anyhow...

Try dumping a little bit of oil down the weak cylinders and do the compression test over. If you get higher numbers, your rings are on their way out. If not, I'd put my money on valve sealing.

Pontiacs, the point we're trying to make here is that these motors are brutally tough and hard to kill. As long as oil pressure is good, these things won't quit.

Doing what you suggest for such a minor issue is a waste of time and money.

I'm not suggesting anything, it'* his car and he can do whatever he wants with it. I just pointed out an issue and possible causes for it.