Angle milling benefit

General engine tech -- Drag Racing to Circle Track

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DCal
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Re: Angle milling benefit

Post by DCal » Mon Mar 12, 2018 5:47 pm

OP said he can only cut them .030 so the he gets more compression benefit from flat cutting than angle milling plus he doesn't have to re-spotface the head bolt holes or cut his intake manifold flanges.

athomp
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Re: Angle milling benefit

Post by athomp » Mon Mar 12, 2018 6:50 pm

Tech has no way to measure how much has been cut so the .030 really means nothing. They CAN measure CR so that's what counts. There's no tolerance over 8.5:1.
DCal wrote:
Mon Mar 12, 2018 5:47 pm
OP said he can only cut them .030 so the he gets more compression benefit from flat cutting than angle milling plus he doesn't have to re-spotface the head bolt holes or cut his intake manifold flanges.

ZIGGY
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Re: Angle milling benefit

Post by ZIGGY » Mon Mar 12, 2018 7:46 pm

How are they measuring cr?

Keith Morganstein
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Re: Angle milling benefit

Post by Keith Morganstein » Mon Mar 12, 2018 8:33 pm

Sanctioning bodies are usually measuring CR with a Whistler.
https://m.youtube.com/watch?v=wL-SJMdtL1c
Automotive Machining, cylinder head rebuilding, engine building. Old school shop, semi-retired moonlighter. Can't seem to quit #-o

Keith Morganstein
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Re: Angle milling benefit

Post by Keith Morganstein » Mon Mar 12, 2018 8:38 pm

athomp wrote:
Mon Mar 12, 2018 6:50 pm
Tech has no way to measure how much has been cut so the .030 really means nothing. They CAN measure CR so that's what counts. There's no tolerance over 8.5:1.
DCal wrote:
Mon Mar 12, 2018 5:47 pm
OP said he can only cut them .030 so the he gets more compression benefit from flat cutting than angle milling plus he doesn't have to re-spotface the head bolt holes or cut his intake manifold flanges.
What savvy tech will notice is how thin the edge of the cylinder head is. A .125” angle mill is obvious. I don’t see any point in angle milling with those rules. If they have a Whistler, your going to have to keep it honest.
Automotive Machining, cylinder head rebuilding, engine building. Old school shop, semi-retired moonlighter. Can't seem to quit #-o

athomp
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Re: Angle milling benefit

Post by athomp » Mon Mar 12, 2018 8:42 pm

Whistler
ZIGGY wrote:
Mon Mar 12, 2018 7:46 pm
How are they measuring cr?

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Re: Angle milling benefit

Post by athomp » Mon Mar 12, 2018 9:01 pm

I don't think our tech has ever been accused of being savvy. What they check and when depends on who they want to win.

[quote=What savvy tech will notice is how thin the edge of the cylinder head is. A .125” angle mill is obvious. I don’t see any point in angle milling with those rules. If they have a Whistler, your going to have to keep it honest.
[/quote]

Krooser
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Re: Angle milling benefit

Post by Krooser » Mon Mar 12, 2018 10:36 pm

Forgot to mention we angle milled that .080 off the heads. Yes it's noticable but I see a lot of that despite the rule.

No we didn't have to spot face the heads... seems the studs seated OK. My engine guy sez he has never spot faced them... been doing them that way since the 70's.
Last place in the B-main is better than anyplace in the grandstands...

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Re: Angle milling benefit

Post by racinnut15xm » Mon Mar 12, 2018 11:07 pm

Warp Speed wrote:
Mon Mar 12, 2018 7:16 am
JoePorting wrote:
Sun Mar 11, 2018 2:58 pm
I think it's a waste of time and money, and you'll be ruining a set of heads. Anytime you mill a head and cut into the 35 degree top intake angle you will lose intake flow. Typical lose is around 10 CFM across the lift range.
"Ruining"?
That's kinda funny, as every performance cylinder head I have worked on/with for the last 25+ years has been cut into the valve job. LOL
I was reading all those responses saying angle milling was the devil and was for sure scratching my head :?:. I feel like flow is nothing without compression, i'm sure its not that simple but goes hand in hand.

But on his limited compression ratio class i agree with most of the responses probably not worth anything. Or you could be of the thought process that they are rarely checking and you aren't worried if you get caught, and when you do throw a thicker head gasket on.

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Re: Angle milling benefit

Post by ZIGGY » Mon Mar 12, 2018 11:33 pm

Couple or three comments: IME many Saturday night bullrings don't have a Whistler(I agree they're very accurate
when used correctly) or are too lazy or ignorant or too big a hurry to use. I'd let my (good) head guy decide if the angle cut is
desirable.
Krooser wrote:
Mon Mar 12, 2018 10:36 pm
No we didn't have to spot face the heads... seems the studs seated OK. My engine guy sez he has never spot faced them... been doing them that way since the 70's.
X2. Done many claimers that way, sometimes using hardened washers with the head bolts.

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Re: Angle milling benefit

Post by pamotorman » Tue Mar 13, 2018 4:15 pm

the whistler were originally used by GM when building engine in mass production to make sure the CR did not go over the build specs.. katech adapted it for use at race tracks. it is very accurate as i disqualified a winner for being .25 point over the CR spec and he protested and i poured the engine and it was what the whistler said it was. it cost him $10K the first place payoff. i told him to sue the engine builder.

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Re: Angle milling benefit

Post by Warp Speed » Tue Mar 13, 2018 5:34 pm

pamotorman wrote:
Tue Mar 13, 2018 4:15 pm
the whistler were originally used by GM when building engine in mass production to make sure the CR did not go over the build specs.. katech adapted it for use at race tracks. it is very accurate as i disqualified a winner for being .25 point over the CR spec and he protested and i poured the engine and it was what the whistler said it was. it cost him $10K the first place payoff. i told him to sue the engine builder.
They are accurate to +/- a couple of tenths, that is it.

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Re: Angle milling benefit

Post by pamotorman » Tue Mar 13, 2018 5:54 pm

that is why builders stay .4 / .5 under the spec. what happened was the engine spun a cam nearing the first night out and at the rebuild the shop clipped the heads because of the head gasket fire ring recess in the heads. he had built the engine too close to the limit originally. he admitted the original build was only .2 under.

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Re: Angle milling benefit

Post by groberts101 » Tue Mar 13, 2018 6:06 pm

Lol.. no serious class racer or builder I know leaves .5 on the table.

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Re: Angle milling benefit

Post by Warp Speed » Tue Mar 13, 2018 8:04 pm

pamotorman wrote:
Tue Mar 13, 2018 5:54 pm
that is why builders stay .4 / .5 under the spec. what happened was the engine spun a cam nearing the first night out and at the rebuild the shop clipped the heads because of the head gasket fire ring recess in the heads. he had built the engine too close to the limit originally. he admitted the original build was only .2 under.
.4-.5 under?!?
That's no way to build an engine!!! Hahaha

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