I was told a "333 and 690 head provides virtually same compression ratio".

[1964SuperStocker]

Please forgive me for asking what seams like an overly simple understanding (by anyone that can see) but I was told I am spreading misinformation about 333 heads knocking compression down by almost a point over a 690 head. Seems like a safe bet considering how many people complain about 333's knocking compression down, Then he claims there is only 15cc difference between 333 and 690 heads. ANYONE here know how big of a difference 15cc creates in a combustion chamber? My 400sbc came with 70cc heads and I strapped 65cc chamber heads on that 400sbc. Let me tell you, 15cc is a pretty big kick in the pants in compression. So tell me, am I spreading miss information or is my buddy Chad lost his mind?

 

[1964SuperStocker]

Here is Chad's quote "Please Please Please stop spreading misinformation. I'm not sure why I have to do this but here are the two heads (he posts a couple general photos of each head surface) a 690 and a 333 head. They are virtually identical. Within 15cc's so that is what 0.2 or 0.25 in compression ratio."
These are his words specifically, not mine.

 

[Ishiftem]

4.312 bore and 4”” stroke. If it is 11.4:1, adding 15 cc of chamber volume would drop it to 10:1.

4.312 bore and 3.5” stroke. If it is 11.4:1, adding 15 cc would drop it to 9.8:1.

Compression rounded to the nearest .10

 

[boxerdog]

Not to mention the port size difference.

 

[La Hot Rods]

15 cc will have different effect on different engines depending on bore and stroke.

 

[SSpev]

Chad is an idiot.

 

[Don Jacks]

Yes Randy you're wrong.There's little to no difference in compression between those heads.THINK about it.The SAE AND NHRA sspec for the area around the valves and spark plug notch is 15-16 cc's,the same as the ''combustion chambers'' on the 333 head.How can there be any compression loss? Fun fact;Edelbrock's heads are built to tthe same spec,but Bob Walla's heads spec out at 5cc's,so you get a little more ccompression there.

 

[MRHP]

And thats what I remember as well Don. I have a bit experience with 333 heads and compression.

 

[1964SuperStocker]

Yes Randy you're wrong.There's little to no difference in compression between those heads.THINK about it.The SAE AND NHRA sspec for the area around the valves and spark plug notch is 15-16 cc's,the same as the ''combustion chambers'' on the 333 head.How can there be any compression loss? Fun fact;Edelbrock's heads are built to tthe same spec,but Bob Walla's heads spec out at 5cc's,so you get a little more ccompression there.

Don, not sure you are understanding this correctly. The claim is there is a 15cc difference between the 333 and the 690 and that difference between them makes little difference in compression. The difference between the two is the key. I can CC a couple virgin heads and post it up the results here. There are countless posts on this forum that discuss how the 333 heads drop compression by about a point due to the chamber. In one post Cecil discusses how when the 333 head came out in 1962 with the chamber, they stopped adding a notches to truck blocks to drop compression. I'll get my fancy new Titrette Digital Bottletop Dispensor and see what we get for cc on a 333 and 690 to help this discussion along.

 

[Don Jacks]

I will await the results of your tests.I could be wrong,but I've never heard of that kind of difference.

 

[hrlykngt]

I had a 333 head laying here I just picked up a set Friday. Here is a pic showing the 333 head having a small combustion chamber compared to the basically Angle Cut Valve Job Chamber on the 690's (w 2 heads in pic) & Edelbrock Aluminum head. Sorry pic I had of heads was dirty but you can make it out.'. Harley

 

[hrlykngt]

Here is a better pic of a 690 Head up close and my 333 Head. 690 Pic from Ebay, Day Automotive has these for sale.

 

[61BUBBLE348]

Isn't all about port size and runner shape and length.
the 333 are small port. ie 348 and low HP 409

 

[1958 delivery]

Isn't all about port size and runner shape and length.
the 333 are small port. ie 348 and low HP 409

combustion chamber size has nothing to do with runners. If the chambers are 15-16 cc larger then it will drop compression

 

[MRHP]

The 333 heads should have about 16cc and the 690 should be about 8cc.

 

[Ishiftem]

The 333 heads should have about 16cc and the 690 should be about 8cc.

Sounds right going by looks. I would like to subscribe to your magazine and/or newsletter.

 

[nana1962409]

When I ccd my 690 heads I got 15cc. The valves have a decent amount of dish to them.

 

[1964SuperStocker]

Isn't all about port size and runner shape and length.
the 333 are small port. ie 348 and low HP 409

Just covering the difference in "chamber" from 690's and 333's only. How and why they produce power based on port size and runner shape, length is a different topic for a different day.

 

[1964SuperStocker]

When I ccd my 690 heads I got 15cc. The valves have a decent amount of dish to them.

Nathan, any idea if that head of yours has been milled down at all? I have maybe one 690 that hasn't had the surface milled and I know I have several 333's that haven't been milled yet. I'm trying to go by factory castings that are unmodified. a 333 can be milled right down flush with the top of the valves to bump up compression (I've seen it) but not sure that would be ideal.

 

[nana1962409]

They were milled .020 to clean them up.