[Qball]

Okie dokie, here goes. My engine is a 68 YS 400 bored .060 over with stock 3.75 inch stroke. Stock 670 heads, log manifolds, '67 iron intake. 600 cfm edelbrock carb but I do have 2 quadrajets, a '68 and a (I think) a '74. HEI distributor. Th 400 transmission w/stock converter.

Okay, that said, what I'm looking for is great low to mid range torque. My GTO has power brakes, air conditioning and a pretty tall rear gear. I don't know the exact ratio but to put it into perspective, at 60 mph, I am turning @ 2000 rpm on 215/65/15 tires.

This car is strictly a street car. I do like to get on it on back roads and I like to take it on ro ad trips (Power Tour) so mileage is a concern, as well.

I want to stay with a hydraulic flat tappet cam. The rpm range that this engine will live is off idle to 3500 with occasional blasts to 4500. Also, with whatever cam is recommended, what valve springs would work best?

I hope I gave enough info to get an informed answer.

Thanks.

[72LuxuryLeMansLa.]

I'm no expert but it sounds to me like the Pontiac 068 grind would work for that.......

[b-man]

Originally Posted by 72LuxuryLeMansLa.

I'm no expert but it sounds to me like the Pontiac 068 grind would work for that.......

This.

Latest technology? Of course not.

But it's a good match for your combo.

Nothing wrong with using a proven factory performance cam that was used in everything from 350s to 455s.

[Qball]

Awesome. This is where I was leaning. Thanks a bunch.

[b-man]

Probably less likely to wipe a lobe with the comparatively gentle action of the factory cams, not a bad thing.

[Qball]

I like the sound of that. What valve spring pressure should I be looking to run. Stock springs, I suspect?

[b-man]

Any good brand of new stock replacement springs will be fine.

I have a set of H-O Racing VS-11 springs that I've been saving to use with my 068 cam. Same cam grind that was factory issue for my 1964 421 HO, the part number at that time was 9770543.

[Blued and Painted]

Is this a new Build. Have the heads been installed.
If not I would have them set up for full roller 1.65 rockers.

The Summit 2801 would be a small step toward the wild side.

[Qball]

This isn't a new build. The engine is fully assembled in my car and does run. I have a ton of valve train noise and it's time to do some freshening up so I figured why not step it up a bit.

[rexs73gto]

All new springs of a stock pressure with the seat pressure no more then 125 lbs. Along with the new 068 cam you'll see a big difference in the way the car runs now. Most rebuilders will tell you the valve springs are worn out at 60k miles. By changing the springs & cam it will feel like a new car. I would also recommend new rocker arms to possibly roller tip rocker from comp as they tend to be much closer to what the 1.55 ratio that is advertised & not just hit & miss like the factory rockers are. Factory rockers can be any where from 1.49 to 1.58. There just a quick stamping & not always on.

[77 TRASHCAN]

My question to those approving of the 068 cam...This engine is more than likely over 10:1 compression wise. Will the 068 suffice??? I've asked here, and heard from others about suing the Crower 60243 or Summit 2802 cams in a 10:1 400, and this one is .060 over. Even though it's a cruiser, is this thing going to be a pinger???, wouldn't want that!!!

Just asking...

Qb, has the engine been zero decked???

[Tom Vaught]

Based on post #1 you have been driving this thing on the gas out there today for some period of time. So I am going to assume that when you step up for example to the 65 389 TRI-Power camshaft, (068) the engine will only be happier compression wise.

Sounds like good recommendation to me.

Also I agree that a roller rocker set-up would improve valvetrain durability on the valve stems. You really do not need the lift for your HP goals but if you can get the 1.65 rocker for the same price as the 1.52 rocker and you have the right installed height springs you should be good either way.

TV

[Stan Weiss]

Originally Posted by Qball

Okie dokie, here goes. My engine is a 68 YS 400 bored .060 over with stock 3.75 inch stroke. Stock 670 heads, log manifolds, '67 iron intake. 600 cfm edelbrock carb but I do have 2 quadrajets, a '68 and a (I think) a '74. HEI distributor. Th 400 transmission w/stock converter.

Okay, that said, what I'm looking for is great low to mid range torque. My GTO has power brakes, air conditioning and a pretty tall rear gear. I don't know the exact ratio but to put it into perspective, at 60 mph, I am turning @ 2000 rpm on 215/65/15 tires.

This car is strictly a street car. I do like to get on it on back roads and I like to take it on ro ad trips (Power Tour) so mileage is a concern, as well.

I want to stay with a hydraulic flat tappet cam. The rpm range that this engine will live is off idle to 3500 with occasional blasts to 4500. Also, with whatever cam is recommended, what valve springs would work best?

I hope I gave enough info to get an informed answer.

Thanks.

I do not know what rear gear ratio you have, but it calculates out to 2.58:1

Stan

[geeteeohguy]

Qball, I'm running an 068 in a 9.3CR but otherwise bone stock .030" 400 in my '67 GTO convertible (original engine, TH400) and a lazy, 2.56 rear gear. It runs very well in spite of the lazy gear, and is an absolute joy to drive on the open road. 20-21 mpg at 75-80 mph. Your car, being a factory AC car, most likely has the 2.93 gearset, which was standard in AC GTO's that year. IMO, it's the ideal ratio for a TH400 equipped GTO....plenty of power, but great high speed drivabliltiy. My O68 has been in there for about 70,000 miles and is going strong.

[Qball]

Originally Posted by 77 TRASHCAN

My question to those approving of the 068 cam...This engine is more than likely over 10:1 compression wise. Will the 068 suffice??? I've asked here, and heard from others about suing the Crower 60243 or Summit 2802 cams in a 10:1 400, and this one is .060 over. Even though it's a cruiser, is this thing going to be a pinger???, wouldn't want that!!!

Just asking...

Qb, has the engine been zero decked???

I have no idea if this engine has been zero decked. It was built around 20 years ago and has maybe 18k miles on it. I never had any of the specs on it. My dad had it built but I don't think he would remember any of those details and being the cheap ass he is, I doubt he would have that done.

[rexs73gto]

It was designed for higher comp. as most of the cars back when it was designed all the cars were a higher comp. format. So you'll be fine & it won't be a pinger unless you turn the timming up to much.

[Qball]

I've been looking at valve springs and holy cow there's a TON of choices. Was leaning towards the Comp 988 spring. Through my research, it seems to do what I will need. Assuming my spring seats haven't been cut, will I need any shims to achieve proper valve seat pressure?

By the way, I have just ordered a Melling spc-7 cam and a set of Hylift Johnson (hydraulic) lifters. Thanks PDude!

[PunchT37]

I`d be game for the Crower 60240 or the 60918

http://www.crower.com/media/pdf/2008b/126-128.pdf

[PunchT37]

By the way, I`d dump the Eddie 600 and run one of your q-jets, set up properly.

[Qball]

Originally Posted by PunchT37

By the way, I`d dump the Eddie 600 and run one of your q-jets, set up properly.

You and I on the same page