[DaleO]

I had a pair of 670's built 15 years ago. For many reasons I've been unable to install them. They have been inside the house in a completely controlled environment the whole time. I'm ready for them now. Are my seals dried out? What else do need to consider? (they are destined for a 1969 400).

[mgarblik]

If the seals are Viton, they will be fine. If they are just the tiny black O-rings inside the retainers, I would upgrade. Much better seals have been developed in the last 15-20 years.

[25stevem]

Are you also running a 69 intake and carb?

[DaleO]

It is a 1970 intake and quadrajet. And for the bigger picture it is a 1969 400 with 46 heads which I want to replace.

[25stevem]

All good!��

[Goatracer1]

I'm doing the same thing using heads that have been sitting 25 years. I have checked everything and even though the seals appear good I will change them (they are cheap, under $20) and hand lap the valves.

[25stevem]

If you have them all apart it would serve you far better to get the guides topped for positive .530” Viton type seals, then eliminating the oil splash shield and then installing a .015” shim under the valve springs .

[25stevem]

Dale, also note that those closed chambered heads might want richer full throttle AFR mixture then the open chamber 46 castings especially if your 69 carb was not secondary jetted / rodded for a ram air Cam, and or your also running a bigger Cam then that Carb was original mated up with.

[geeteeohguy]

I see you're up in WA so it's nice and humid/damp up there, so you may be ok running 670's up there if you have stock flat top pistons. Otherwise you will need 95+ octane fuel to keep it out of detonation. The 46 heads you currently have are a great choice for a street 400. But I don't know what pistons you have, so I'm just throwing stuff out there. I was unsuccessful trying to run 670's on my stock '67 GTO for years, switched to #12's, still no luck, and now am running #15's with an 87cc chamber. But where I am, all the gas is 10% alcohol and the highest octane is 91. And it's hot and dry. Back in the '80's, my GTO STILL pinged with the 670 heads running 92 and even 94 Octane.

[DaleO]

Originally Posted by geeteeohguy

I see you're up in WA so it's nice and humid/damp up there, so you may be ok running 670's up there if you have stock flat top pistons. Otherwise you will need 95+ octane fuel to keep it out of detonation. The 46 heads you currently have are a great choice for a street 400. But I don't know what pistons you have, so I'm just throwing stuff out there. I was unsuccessful trying to run 670's on my stock '67 GTO for years, switched to #12's, still no luck, and now am running #15's with an 87cc chamber. But where I am, all the gas is 10% alcohol and the highest octane is 91. And it's hot and dry. Back in the '80's, my GTO STILL pinged with the 670 heads running 92 and even 94 Octane.

Good point. The piece of the puzzle which you wouldn't know is that the 400 has the 8 eyebrow cast pistons. I've not run into any problems with the lowest octane gas with this setup. The way I'm figuring it is since the engine with these pistons work for the 10.5 rated 46's I'd be fine with the 670's which I believe were also rated at 10.5. And if I might have compression issue though I have a couple more octane points to get at the pump.

[qoute 25stevem Dale, also note that those closed chambered heads might want richer full throttle AFR mixture then the open chamber 46 castings especially if your 69 carb was not secondary jetted / rodded for a ram air Cam, and or your also running a bigger Cam then that Carb was original mated up with.]

My cam is a baby Engle cam, 210/.440 lift I, 216/.455 lift E, 112 deg.

I don't know, maybe I shouldn't even goof with it as it runs great and it is just a cruiser. I originally had the heads done for the 428 in my '67 GTO. (I have two cars, 1974 LeMans with the 400 and a 428 in the GTO). The 670's would be right to see with hood open but I went with a pair of Dave Bisschop's 240cfm 6X-4's instead for the 428. So now I have these 670's sitting there and I started thinking why not? There must be a little performance gain going from the small valves to large.

At the same time of head rebuild I purchased a set of cast iron headers which I also didn't use as I went with Hookers. So I have these sitting there also and I thought they would be cool to go with the head swap. I wish they were the larger collector version as I'd put them on the goat, but that is another story,

Thanks for all your inputs, I really appreciate it.