Valve overlap

[FireSale]

There's a difference between engine math (which I understand) and it's effect on performance (which I don't always) and I think the performance part is what you are after. Lunati has a nice explanation of what it means in terms of performance on their tech site. Link below.

http://www.lunatipower.com/Tech/Cams/CamSpecTerms.aspx

BTW: Those block photos you sent Brian were helpful. Now I understand why I cant easily run stocker heads on my M6010 block.

[west coast]

So it looks like there is no real standard of what lift you should measure valve overlap. Since i have a comp cam i will kind of fallow them. It sounds like you should use the numbers for tappet lift done during advertised duration which is .006. i found the web page that had the formula's that John Dinkel posted on here which work if your cam card reads valve timing at advertised duration which mine doesn't it is at .050. So now on to understanding all the theory's behind all of this.

Dale hope my costly mistake will save you money. Its hard to explain the problem but a picture is worth a thousand words that will leave you speechless sometimes.

[FireSale]

Read the Duration section of this link. It explains a bit more about the effects of duration and why cam grinders use 0.050 lift. It's a bit too long to post.

http://www.austincc.edu/wkibbe/camtheory.htm

Also this from the HotRod network:
http://www.hotrod.com/articles/ccrp-...amshaft-power/

Also: I'm going to just keep my AFR 1399 heads with the 1.9/1.6 valves that they come with. No fit issues with the BOSS302 block. If I declare the car for SS/CS I can run the Combo legally. Aluminum heads any valve size 10.5 lbs/cid. The index sucks O2 (10.30) but I have thrown t he book at my car over the Winter.

[SSDiv6]

Originally Posted by FireSale

Read the Duration section of this link. It explains a bit more about the effects of duration and why cam grinders use 0.050 lift. It's a bit too long to post.

http://www.austincc.edu/wkibbe/camtheory.htm

Also this from the HotRod network:
http://www.hotrod.com/articles/ccrp-...amshaft-power/

Also: I'm going to just keep my AFR 1399 heads with the 1.9/1.6 valves that they come with. No fit issues with the BOSS302 block. If I declare the car for SS/CS I can run the Combo legally. Aluminum heads any valve size 10.5 lbs/cid. The index sucks O2 (10.30) but I have thrown t he book at my car over the Winter.

Sorry Dale, you cannot run aluminum cylinder heads in SS/CS class, only cast iron, inline/wedge heads only.

[FireSale]

Originally Posted by SSDiv6

Sorry Dale, you cannot run aluminum cylinder heads in SS/CS class, only cast iron, inline/wedge heads only.

OK. I read this revision as "Aluminum heads OK. No billet in modified classes except CS"

2017 revision:
Aftermarket aluminum cylinder heads permitted (no billet) except in CS.

I'll take the car to ETI in March and see. I'm beginning to not care any more.

Back to camshafts.

[SSDiv6]

Originally Posted by FireSale

OK. I read this revision as "Aluminum heads OK. No billet in modified classes except CS"

2017 revision:
Aftermarket aluminum cylinder heads permitted (no billet) except in CS.

I'll take the car to ETI in March and see. I'm beginning to not care any more.

Back to camshafts.

Dale,
The rule can be confusing.
What the rule change should say is that any aftermarket aluminum head, except billet heads are allowed.
Still, SS/CS class is NHRA approved cast iron cylinder heads only.

Prior to the current rule, it was required to run approved cylinder heads that had an OEM part number.

As applicable to your Mustang, would be the Ford N351 cast iron cylinder head casting.The N351 head, as cast, just with port matching, will outflow the AFR 165 heads by a mile.

[Adger Smith]

Comp Cams Chart
http://www.compcams.com/Pages/413/ca...ion-angle.aspx
Might give you some added info