[67Lemons]

I have a ‘68 400 that I’m going to replace the cam in this winter, looking to install it in my 1967 LeMans. The car is a cruiser that may hit the track a few times for tuning but otherwise just a weekend toy to cruise around. I’m building a TH350 that will need a new converter & have a 3:23 gear set to install.

Currently the motor is completely original, about 40k miles on it with factory #15 heads so pressed in studs. My fail safe cam pick is an 068 but wondering since I’m starting from scratch maybe I should up the cam size a little. I realize that the press in studs are the limiting factor so I guess I have to look at having screw in studs installed at a machine shop if I go bigger than the 068? I’ll also need new springs, locks & retainers obviously.

Some cam choices are the Summit 2802, the Crower 60916, maybe something else from another supplier or custom ground if it’s a real improvement in quality? Budget is the key so no roller cams but I also realize the issues with HFT cams so I want to put my best foot forward with quality parts like US made lifters, etc.

[b-man]

Well those were the first two cams I would have picked.

The 60916 is a great 400 cam.

[JB Eng Wis]

Would you UP the valve size in those #15 heads?

[PAUL K]

068 with 1.65 rocker arms would be the next step up and work excellent. Compatible with factory style springs.

[b-man]

If budget is key then stick with the 068 cam which will play nice with your press-in studs more so than anything else, but that means sticking with the original 1.5:1 rockers.

You’ll probably be floored when you see the machine shop bill to tap 16 holes for 1/2-13 (its either that or 7/16 Heli-Coils) and the cost of the conversion studs with 1/2-13 bottom threads (around $100) or just the normal kind that are 7/16-14 bottom threads ($65). Plus they’re going to charge you to pull the old press-in studs out.

I once converted a set of #66 455 heads to screw-in. I made a tapping block to guide the tap In straight that I could bolt down using the old stud adjacent to the one I was tapping 1/2-20. After pulling the first press-in stud using a stack of washers and an old rocker nut and tapping that hole I used a 1/2-13 bolt to hold the tapping block in place and pulled the stud next to it and tapped it, repeating until all the holes were tapped.

It was a bitch to do by hand, plus I needed another bottom tap along with a regular tap. Then I had to grind about 1/8” off all the studs and deburr them because they’re a bit too long, otherwise they would bottom out before they could be tightened. It’s easy to see why shops charge as much as they do when you start to understand what all goes into it.

And yes the studs went in straight and didn’t look like a bunch of old trees in a forest.

[4zpeed]

Originally Posted by JB Eng Wis

Would you UP the valve size in those #15 heads?

^^^ This ^^^

A set of big valve screw in stud heads aren't that expensive, probably some in your area if you look.


Frank

[b-man]

I don’t see the 1.96/1.66 valves as being some kind of performance killer or worth spending money on to upgrade.

Budget build.

It’s not like all the later 389 heads with 1.92/1.66 valves didn’t have plenty of get up and go on the GTO 389s and also during that time the big Pontiac 421s that shared the same heads.

[ta man]

075 then its a 3/4 race cam..Sorry guys had to do it

[SD455DJ]

I’m really pleased with the Summit 2801 cam in my 400. I have a ’70 XV code 400 (330 hp) in a ’70 Tempest that was rebuilt and dyno’d a few years ago. It has the ’70 small valve #16 heads (1.96 in/1.66 ex) with 78 cc chambers after a truing cut (no porting). The block is well built with forged rods (RPM 4340) and .030” over pistons (Icon) that are .0015” in the hole with .039” Felpro 1016 head gaskets for .0405” quench. The compression is 9.94 to 1 and the ports are untouched. It runs the cast iron 4-bbl intake with a 7040268 Q-jet and cast-iron log manifolds. It has the Summit 2801 cam & lifter kit with CC-990 springs with 1.5 factory stamped rocker arms. We just pinned the pressed-in studs to keep them in place ($95 in 2019).

On the dyno, it made a corrected 384 hp @ 5200 rpm (best) at 454 lbft @ 3600 rpm (358 hp/425 lbft uncorrected) with 2.5” Pypes headpipes. It makes over 18 in. vacuum at idle in neutral and operates the power drum brakes without any problem. It has run a best of 13.18 at 104 mph in the heat and humidity (DA 3200’) with 3.42 gears, TH400 trans, full dual exhaust at 3800 lb. race weight. The TH400 is programmed to shift automatically at 5600 rpm. It drives easily on 93 E10 gas on the street with a good 4-core radiator and factory flex fan.

With the #15 heads from the '70 YH 455 (std. engine in Bonneville's), your compression is in the upper 8's with the 90 cc chambers (86-87 cc AMA specs).

[4zpeed]

I guess it depends on how much one wants to put in a set of heads
and how far they may go in the future, invest that money wisely.


Frank

[PunchT37]

Originally Posted by SD455DJ

I’m really pleased with the Summit 2801 cam in my 400. I have a ’70 XV code 400 (330 hp) in a ’70 Tempest that was rebuilt and dyno’d a few years ago. It has the ’70 small valve #16 heads (1.96 in/1.66 ex) with 78 cc chambers after a truing cut (no porting). The block is well built with forged rods (RPM 4340) and .030” over pistons (Icon) that are .0015” in the hole with .039” Felpro 1016 head gaskets for .0405” quench. The compression is 9.94 to 1 and the ports are untouched. It runs the cast iron 4-bbl intake with a 7040268 Q-jet and cast-iron log manifolds. It has the Summit 2801 cam & lifter kit with CC-990 springs with 1.5 factory stamped rocker arms. We just pinned the pressed-in studs to keep them in place ($95 in 2019).

On the dyno, it made a corrected 384 hp @ 5200 rpm (best) at 454 lbft @ 3600 rpm (358 hp/425 lbft uncorrected) with 2.5” Pypes headpipes. It makes over 18 in. vacuum at idle in neutral and operates the power drum brakes without any problem. It has run a best of 13.18 at 104 mph in the heat and humidity (DA 3200’) with 3.42 gears, TH400 trans, full dual exhaust at 3800 lb. race weight. The TH400 is programmed to shift automatically at 5600 rpm. It drives easily on 93 E10 gas on the street with a good 4-core radiator and factory flex fan.

With the #15 heads from the '70 YH 455 (std. engine in Bonneville's), your compression is in the upper 8's with the 90 cc chambers (86-87 cc AMA specs).

There were 15 heads in `68 also. More like a 75 to 78 cc chamber.

[67Lemons]

Originally Posted by PunchT37

There were 15 heads in `68 also. More like a 75 to 78 cc chamber.

Yes, exactly, my 15 heads are from 1968, supposed to be 75 to 78cc’s as mentioned

[67Lemons]

All very good points above, I’ve been looking around for some big valve heads with screw in studs but haven’t found anything locally yet. I also agree with the thought of how much do I really want to invest in the heads for what I want to do, we all know about mission creep. Bringing the heads to the machine shop for screw in studs would mean at least a valve job or replacing the valves with bigger valves & more machine work, screw in studs meaning more machine work, etc etc.

[PunchT37]

What Paul said above is a budget way to go. 068 with 1.65 rockers. That will give you .448 lift. With 212/225 at 050, that will be a decent step up without going to big valves and screw in studs.

[b-man]

1.65 rockers will put stress on the studs, perhaps enough to cause them to snap off at the bottleneck.

Personally I wouldn’t do it unless I had BBC style 7/16” screw in studs.

This was recommended in Pete McCarthy’s book, so when I ran some good used RAIV 1.65 stamped rockers with the 068 cam I converted the heads to screw-in ARP 7/16” studs.

I don’t like pulling off one of the valve covers somewhere out on the highway to see where that nasty noise is coming from…..

[67Lemons]

It sounds like the 068 is about as big as you can go with pressed in studs?

There are a pair of #62 heads available locally but they have 72cc chambers which would probably be too much compression for the street with my stock pistons in the ‘68 short block?

[Cliff R]

Pressed in studs are prone to breaking off and in rare occassions pulling out of the heads. Seldom if ever happens with stock low lift cams and stock spring pressures but upping the game there increases the risks, so it is simply like upgrading to forged rods over stock cast rods.....if nothing else you'll sleep better at night.

Don't sell small valve heads short and there is no need to install larger valves in those heads for what you are doing.

About 15 years ago we had a pretty high-end 455 rotating assembly ready for some SD Performance CNC ported KRE heads and one of his custom solid roller cams ready to finish and stuff in a car in time for Norwalk. The order was delayed so I walked into the parts room and grabbed a used Crower cam left over from another project, and a set of #46 heads from a 1969 428. I modified them for screw in studs, touched the seats, ground the stock valves (45 degree intake seats), added bolt holes to the ends of them (not drilled/threaded) and a good set of springs. Not a grinder or sanding roll touched them anyplace.

We quickly finished the engine, topped it with a 1978 Oldsmobile carb, stock HEI with a positive stop welded in it, and into the car it went.

The car was a 1981 FB, TH350 (built here with a custom converter) added some DOT's and off to Norwalk it went. I was expecting maybe mid to high 12's out of it.

Right off the trailer it went high 11's in the heat of August!

So for sure if the big 455 didn't care much about small valves in the heads your' little 400 woln't either......

[SD455DJ]

Originally Posted by PunchT37

There were 15 heads in `68 also. More like a 75 to 78 cc chamber.

Thanks! I forgot about the '68 #15's! They looks very similar cc-wise to the small valve '70 #16's which measured 78 cc's +/- after a minimal resurfacing. As Cliff said, don't underestimate these higher compression small valve heads! I'm certainly a believer! I would modify with BB screw-in rocker studs with anything more than the 068 cam, or with more than .450" lift.

Dennis

[Jay S]

Keeping with 1.5s, with no jump in lift against a 068 is the Melling SPC-3 (744). It does not have the dwell over the nose of the old 744 cam, and doesn’t require extra spring pressure over a Melling SPC-7 (068).

Lee on here has the biggest cam I have seen successfully using press in studs, is in a 455. IRC…about .445” lift and 222*@.050 intake, just over .43” lift and 240* ish on the exhaust.

[Cliff R]

Agreed, the 068 cam fits the bill nicely here, plus you can run stock spring loads on it, light weight stock retainers, stamped steel rocker arms, etc. This takes away some of the things I feel are killing a lot of flat tappet cams these days. Running big heavy retainers, rocker arms, and KILLER spring pressures just aren't needed for most of these builds. For sure there is a time and place for that stuff, but the end user shouldn't be surprised if they don't get very many miles out of their flat tappet cam build with a BUTT LOAD of seat pressure and enough open pressure it's like having 16 big fat guys standing on your pushrods!.........