[AIR RAM]

My 69' 350 came with notches however my 72' 455 has no notches (that I recall)... I will take another look at it when I get it back from the machine shop... but Im fairly sure there are no notches.

When I added the EDL PERF RPM heads to my .040 bore 350 I had to increase the size of the existing notches to clear the larger 2.11 intake and 1.66 exhaust valves.


SPEED SAFE, NICK

[steve25]

Yes, Running those heads on a 350 demand’s valve notches and even more so on the exh side then if you where running iron heads with 1.77” exh valves.
This is due to the E heads having the exh valve moved over .040” from stock .

My 71 455 2 bbl block was taped for 4 bolt mains and had no valve notches, but I added them.

[biz421]

Do the notches (bore chamfer) ever become an issue for stroked motors? It looks like the piston rings are shifted higher on the stroker pistons and might get close to the chamfer.

[PAUL K]

Yes they can be an issue. Specifically on the 67 400 blocks.

[performerrpm]

didnt see a reason to start a new thread, ill post in this one.


i have 2 455's both are 71 yc code. 1 has notches 1 does not. 1 is standard bore without. the other was standard bore with.

is this common?

[steve25]

My thoughts are that the 455 motors ordered with a 2 bbl did not get the notches since a 1.96” intake valve did not call for it.
I had two 485428 blocks and neither had the notches .

[performerrpm]

Originally Posted by steve25

My thoughts are that the 455 motors ordered with a 2 bbl did not get the notches since a 1.96” intake valve did not call for it.
I had two 485428 blocks and neither had the notches .

thats really the only idea that would make sense, except both mine are the same code and most likely came with the same heads and carb. i guess as long as it works is all that matters.

[STEELCITYFIREBIRD]

To The engine builders in the group;
Would you add them if not present?
And if so, at what bore size if any?
🤔

[mgarblik]

More than once, I have bolted a head on a bare block with the camshaft installed and 2 lifters, test springs, rockers and push rods. Turned the block upside down and just observed the areas around the valves as they open and go through their cycles. I want a nice, clear path all the way around both valves. If notches are needed, I put them in.

[steve25]

I would say this, it will never hurt to have them , if you have the compression to spare then I would add them.
Of course on the other side of the coin if you need to drop compression then adding them is a start.

[sdbob]

Here I go with my experience. When Arnold Hines was doing my SD he asked if I could find some 455 blocks without chamfers. His reasoning was boring block oversize for Superstock car increasing compression is what I was told.

[steve25]

The rule of Thumb I was privy to and said to me by a well known local pro stock engine builder was this.

If you have enough compression for the Cam being used then never sacrifice airflow for the sake of compression.
There’s a point of very diminishing returns once a full on race motor has a compression of 12.5 to 1.

[srmmmm]

Len Williams built my stroked 350 using my 1970 block and 1977 6X-4 heads. Both only had minor clean-up surfacing done taking .010 off each. Pistons were Ross flat tops set at zero deck height using 6.8" rods on the 4.25" crank.

Len confirmed no issues with chamfer size and relationship to top ring position. He did say that the .502/.510 lift on the cam was getting close to the limit though.

[MarkS57]

Originally Posted by Jay S

<snip>

The oily photo is from a 75 350, exhaust chamfers only with no valve reliefs <snip>

Interesting, didn't all 350 / 400 / 455 have 2.11 intake valves 75 up?

[steve25]

Yes, other than the 301 all V8 heads had the 2:11” valve starting in mid 75.

Then there was the odd ball 350 head that had a 1,96” intake and a 1.77” exh, which I believe was in 72.

What I story that might be to hear!
Just think of the possibility of machining mistakes that could have lead to that because I do not think it was intentional.

[Gary H]

What's the consensus on the CC size of the chamfer? I would guess around 1 cc

[steve25]

I have to look thru my notes which a have on this.

But If you have a block with a chamfer and the tools to check for CCs along with some clay then make a mold of the chamfer and drop it in the CC burette.
I tend to think in terms of a chamfer for a 2.11” valve that 1.5 CCs is more like it, but that hinges on what you have for a bore diameter.