400 sbc heads and steamholes? add them or?

[Coley]

I was wondering if anyone knew much about the extra steamholes (coolant holes?) issue in the 400 sbc heads?
I have heard that guys have used other standard (non 400) sbc heads and simply drilled and added these holes to run on the 400 sbc engines.
Does this not ruin those heads for non 400 sbc applications?....drilling into them?...anyone ever done this successfully?....or unsuccessfully?
Or...what has happened when you run regular, non-drilled heads on the 400 sbc engines? ...are they quick to heat up or only under heavy duty use or?

Just thought I query the many experts we have here on this site about this issue.

Many Thanks!
Coley

[68Gold/white]

The holes HAVE to be there if used on a 400 block, period!!!

There are exceptions, all are racing super-de-duper high HP applications that have nothing to do with what you or I will ever do with one of those engines!!!

YES, the steam drill heads CAN be used on any other non 400 engine, like a 350!!!

The 400 block has siameased (spelling?) cylinders that need the holes to help with cooling...ALL other small blocks do NOT have this feature (old school small blocks).

400's are AWESOME engines!!!

[Coley]

Interesting.....
so how do you use a sbc head that has had holes drilled into the water jacket without it affecting that (non 400) sbc engine?
....just curious as to the risks of leaking coolant under pressure through those new holes?

All good
Coley

[B. W.]

the theory is that without the steam holes the coolant doesn't flow in the pockets created by the siamese cylinders so it kinda sits it the pockets and creates hot spots. If I build a 400 I drill the holes but I have run a 400 with aluminum heads & no steam holes with no adverse effects. I'd still drill them though.

I don't know why you couldn't run drilled heads on a 350, the head gasket would seal them but, I haven't done it.

[68Gold/white]

The steam holes on a 350 are exposed to the head gasket, it seals the holes, no problems...

[Coley]

hmmm....

Here is the backstory:
I have a chance to pick up a very inexpensive 400 sbc complete short block assembly.
One of the reasons its cheap is that it has no heads.

Now, in my part storage I have a set of really good 1.94 heads complete with all valves/springs/etc ready to go....nothing fancy or high compression....but in near new condition, gathering dust.
I paid $50 for these through a very lucky deal....and given the low investment in them I was wondering if they might be a good risk and candidate for the 400 that needs heads.

Regardless....I don't want to ruin them necessarily....if I don't have too....so first, I am gathering information on this 'drilled steamhole' addition angle.

Again, just thinking on this....the risks, the rewards....etc.
All in all a low budget, fun side project opportunity maybe?

All good
Coley

[68Gold/white]

Do you have any background on the 400???

A stocker? been rebuilt? bored? Raced?

The best ones (to me) are stockers that have been pulled from the original vehicle, that no one has gotten their hand on yet and screwed anything up on it...yet...

What exact heads do you have? They need to be large chamber heads to work on a 400, to keep comp ratio within reason.

[A1971Blazer]

Look around and find some good 400 heads.....you can also put a healthy cam in a 400....they respond REAL well.....if I wasn't all in on the LS1.....I would be looking for a good unmolested 400......

[Coley]

I think the motor is in all stock form....been in storage for several years, its available for inspection etc because the heads are off of it.
The heads I have are a set of 74-76cc heads with the 1.94 valves in them.
I think they were taken off a stock crate 350 engine with very low miles to upgrade to HP aluminum heads or vortecs.
Based on the info I have on it, I think the 400 was in a 77' or 78' Blazer...to my recollection.

All good
Coley

[68Gold/white]

Originally Posted by Coley

I think the motor is in all stock form....been in storage for several years, its available for inspection etc because the heads are off of it.
The heads I have are a set of 74-76cc heads with the 1.94 valves in them.
I think they were taken off a stock crate 350 engine with very low miles to upgrade to HP aluminum heads or vortecs.
Based on the info I have on it, I think the 400 was in a 77' or 78' Blazer...to my recollection.

All good
Coley

Cool!!!

Man if that short block is anything near what you describe, I'd bring it home. Typically 400's are only good to .030 or .040 over bores. I have not heard of many folks that used a .060 400, or had to. I would prefer not to...

The 2 bolt main blocks are preferred. The outer bolt holes on 4 bolt main blocks can crack out (I've heard...never seen a problem with one though...)

[Eddie H.]

# of the holes need to be drilled at a 30 degree angle, and 3 are drilled straight.

[GRX]

Originally Posted by Eddie H.

# of the holes need to be drilled at a 30 degree angle, and 3 are drilled straight.

^^ that. Back in the day we charged $30 for that operation.

Would not take a SBC 400 block more than 0.030 over. Not a fan of these siamese blocks personally. Using gauge bore in worn cylinders one can see how they distort in ways 350 blocks do not. Which leads one to wonder how much power is lost by ring blow by.

[68Gold/white]

Originally Posted by GRX

^^ that. Back in the day we charged $30 for that operation.

Would not take a SBC 400 block more than 0.030 over. Not a fan of these siamese blocks personally. Using gauge bore in worn cylinders one can see how they distort in ways 350 blocks do not. Which leads one to wonder how much power is lost by ring blow by.

The 400's that my engine builder built were all honed with a torque plate. I've heard of other folks that built them that DID have problems, not using a torque plate...

My engine builder was/is a sticker for details. Just wish he was still doing regular street type engines. He had some life changing stuff going on about 15 years ago, marital status and other stuff that warranted him to move to to different part of state, and change his business focus. When he was still married, he taught his step son ALL the engine building and machining techniques that we all desire how to do. That step son doesn't even work on engines these days....

[GRX]

Originally Posted by 68Gold/white

The 400's that my engine builder built were all honed with a torque plate. I've heard of other folks that built them that DID have problems, not using a torque plate...

Indeed. Torque plate are great for simulating cylinder distortion when assembled but do nothing by way of reproducing thermal expansion differentials unique to these blocks, which is what I was referring to in my last post.

[Coley]

I'm still in a negotiations with the guy on the engine....but he is away skiing for a few days so I've got a bit of time to consider everything around this, including the hole drilling operation in those spare 76cc/1.94 heads that I have.
(note: probably pricing is about $200 for the short block assembly complete with pulleys, balancer, ring gear/flywheel, etc....just no heads)

I can't help but think tho'....that drilling holes in those heads will ruin them for a regular 350 block usage......
Will a regular head gasket re-mount on a 350 keep those from leaking coolant? or?

All good
Coley

[davepl]

I think the 400 is a great motor if you shoot for torque and put a torquey cam in it. When it all goes bad is when guys try to make "horsepower" motors out of them and overcam them and spin them too high.

I'd think a 400 block with 1.94 heads and a 204/208 cam would be great street truck!

But higher RPMs are not it's thing. The rods are so short relative to the stroke that they barely reach the crank when the piston is at TDC ;-)

[palallin]

Originally Posted by Coley

(note: probably pricing is about $200 for the short block assembly complete with pulleys, balancer, ring gear/flywheel, etc....just no heads)

As far as I know, the pulleys, balancer, and ring gear/flywheel are worth that. Even without a set of heads, I'd be trying to get it.

[Rickysnickers]

$200??? What are you waiting for??? Seriously, the heads can be used on another SBC even with the holes drilled into them.

Originally Posted by Coley

I'm still in a negotiations with the guy on the engine....but he is away skiing for a few days so I've got a bit of time to consider everything around this, including the hole drilling operation in those spare 76cc/1.94 heads that I have.
(note: probably pricing is about $200 for the short block assembly complete with pulleys, balancer, ring gear/flywheel, etc....just no heads)

I can't help but think tho'....that drilling holes in those heads will ruin them for a regular 350 block usage......
Will a regular head gasket re-mount on a 350 keep those from leaking coolant? or?

All good
Coley

[67_C-30]

Originally Posted by Coley

I'm still in a negotiations with the guy on the engine....but he is away skiing for a few days so I've got a bit of time to consider everything around this, including the hole drilling operation in those spare 76cc/1.94 heads that I have.
(note: probably pricing is about $200 for the short block assembly complete with pulleys, balancer, ring gear/flywheel, etc....just no heads)

I can't help but think tho'....that drilling holes in those heads will ruin them for a regular 350 block usage......
Will a regular head gasket re-mount on a 350 keep those from leaking coolant? or?

All good
Coley

No, the gasket will the steam holes if you run them on a 350 later.

[68Gold/white]

Originally Posted by GRX

Indeed. Torque plate are great for simulating cylinder distortion when assembled but do nothing by way of reproducing thermal expansion differentials unique to these blocks, which is what I was referring to in my last post.

I follow you, but the 400's my builder produced, had no issues with ring seal. I have no idea why. Maybe the torque plate helps...

[Eddie H.]

I've been running a small block 400 in my 69 GMC for more than 20 years now with no issues whatsoever. I Built it mildly as a low rpm, high torque engine with a .020 overbore and a mild Crane 260H cam. I just used the stock 400 heads with a little port clean up. In my opinion, it is a great little truck engine, and should have been put in these trucks from the factory. I've never had it on a dyno, so really I have no idea as to actual HP and torque numbers, but from the seat of my pants, it feels much stronger than any 350 powered truck I've ever owned.

[68Gold/white]

Originally Posted by Eddie H.

I've been running a small block 400 in my 69 GMC for more than 20 years now with no issues whatsoever. I Built it mildly as a low rpm, high torque engine with a .020 overbore and a mild Crane 260H cam. I just used the stock 400 heads with a little port clean up. In my opinion, it is a great little truck engine, and should have been put in these trucks from the factory. I've never had it on a dyno, so really I have no idea as to actual HP and torque numbers, but from the seat of my pants, it feels much stronger than any 350 powered truck I've ever owned.

LOL, I've told folks about the potential of Small block 400's in the past. THey all doubted that a 400 had much more power potential than a 350, I don't argue about much, that just leaves more 400 blocks for me!

A good friend had my mentioned builder build an econo 400 of sorts, this was in early 80's. He used the stock short rods (not much was available back then to make much else, at least on a budget), cheapest forges Sealed Power foged pistons, 441 heads that were touched up by the builder, an early Edelbrock Performer (the early ones had larger runners than later units), a Comp 268H cam (high energy, not XE), a Holley 3310 750 carb.
It had 1-1/2 O.D. headers, which sound too small....

The absolute net dyno numbers were 300HP and 400 Ft/Lb torque. Mind you these are S.A.E. net numbers, power at the flywheel, which makes it sound just O.K.

It was put in a 66 C10, LWB, 3.42 gear (out of an 80's pickup), and a Muncie M20 4 speed.

I rode in this pickup many times, it was a fun ride every time. It had sooo much torque, but also revved very quickly.

He sold the pickup around 1995, and I did not know about it, man I would have bought it...it had zero oil use issues.

I have a similar 400 waiting to go in my 67 C10, but makes 100 more HP, can't wait!

[Wizo]

FWIW: I used a set of 1985 194 truck heads from a 350CID. Before I used them i turned them into 2.02/194 with stainless valves and LT1 springs. I used felpro head gaskets specifically for a small block 400. You MUST drill the steam hols in the heads for the 400cid application which I DID. I kept the rocker arm ratio stock (1.5/1) but went with the roller tipped stamped rocker arms. A 268XE cam works really nice. Lumpity, lumpity, lumpity. A holly 3310 sits on top.
I agree with the rest of the guys, the 400 is an awesome motor. Mine lays some pretty *****'en scratch marks. BTW my slush bucket is a built THM400. I can beat on that thing all day. Final drive is 3.73 12 bolt.
Summers coming; Happy Cruz'in.

[Coley]

Good info here on these 400's so far...

How accurate do those drill holes need to be?....+/- 1/32" or tighter?....good for a machine shop or this possible with standard 'home shop' tools?

Part of the project element for me would be perhaps a 1 year time frame?...basically a simple evening project with some renewal or light duty rebuild to get the engine ready as a temp replacement in my truck.
...maybe check the bearings, etc.....hone it and re-ring it?.....not sure yet.
Maybe a cam upgrade would be nice....perhaps topped with a performer manifold and a quadrajet.
I appreciate an engine with power....but to be quite honest, as a realist...the odds of me using excessive power around the neighbourhood on a daily basis are maybe 5%.
I think 300hp is a great number....but I'm more interested in bottom end torque because I do most of my driving from 1500-4000 rpm...and again, like most very rarely over that for the better part.

Now, that said I am fortunate to still have the original/factory 350 in my truck...which i think was rebuilt 20+ years ago by the previous original owner
Its been a very good motor, it runs very well...starts great, very reliable, very smooth but its getting down a little on compression and is starting to use a little oil.
So if I was to pull it to do a rebuild, I would want a good substitution while I took that on so I could still use the truck.....hence the 400 sbc.

One of the attractions of this 400 sbc motor for me is its identical size to the 350 sbc and other sbc engines which makes it a very easy swap out.

Then I got wondering....if I swapped it out, I might not want to put a 350 back in it afterwards...lol.

Coley

[GRX]

"How accurate do those drill holes need to be?....+/- 1/32" or tighter?....good for a machine shop or this possible with standard 'home shop' tools?"

Hole locations must be very accurate to ensure proper gasket seal. Very possible at home with good drill skills. I have done more on the workbench than a mill.

Best method is driving alignment dowels from the block into the heads to place gasket at proper location. In lieu of that you could use some head bolts with washers.

Lightly tap with hammer using your nice sharp center punch. Once you are confident those are centered with holes in head gasket, hammer harder to give yourself a nice divet to drill on.

As for hole sizes, start with 1/8" on both straight holes (exhaust side) and angled (intake side). You can leave it at that if desired. If confident you can open them up to approximate factory sizes. 1/4" on the straight, and 3/16" on the angled.

Once you experience the 400 you won't want to go back to a 350. The 3.75/4.125 stroke/bore combination can make some decent power. Interesting to note that the Pontiac 400 is virtually the same (3.75/4.120) yet has a very different power curve because of their head and valve design. And unlike the SBC 400, they are internally balanced. But that is getting off topic.