Milling A460 heads to increase compression

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Post  CDMBill on May 6th 2019, 7:44 pm

We are trying to step up our Drag Week program a bit without breaking the bank. After reading the long SR-71 thread the question is how close could we get to Jon's 1200HP with the existing 598"/A460 3X TFS Tunnel ram setup with a cam change and compression increase.

So with the A460 3X Heads that have been cleaned up once with a .005 cut, how much more can they be milled to increase compression which is 12:1 now with a flat top JE piston? Current chamber volume is 82cc. Current cam is 282/294/113 installed at 109 .462"/.451 lobe lift, 1.85 rockers.

I asked a related question about the A460 3X cross sectional area.

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Post  Lem Evans on May 6th 2019, 8:02 pm

CDMBill wrote:We are trying to step up our Drag Week program a bit without breaking the bank. After reading the long SR-71 thread the question is how close could we get to Jon's 1200HP with the existing 598"/A460 3X TFS Tunnel ram setup with a cam change and compression increase.

So with the A460 3X Heads that have been cleaned up once with a .005 cut, how much more can they be milled to increase compression which is 12:1 now with a flat top JE piston? Current chamber volume is 82cc. Current cam is 282/294/113 installed at 109 .462"/.451 lobe lift, 1.85 rockers.

I asked a related question about the A460 3X cross sectional area.

The heads can be milled much more. Valve to piston clearance is the 1st issue. Intake fitment would be the next issue......which is easy to resolve.

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Post  c.evans on May 7th 2019, 12:12 am

With the "D" shaped chamber of the A-460 heads, it takes .0055" of milling to reduce the chamber volume one cc. That's 5 and a half thousandths,
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Post  litshoot on May 7th 2019, 10:20 am

Dont know if its any help. I have a set of motorsports a460 heads witha a 63cc chamber, from what i can find they started mid 80s cc(82, 85,87) sounds like it can be done.  The intake was ported to match so not sire if they shifted ports or shaved gasket surfaces

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Post  dfree383 on May 7th 2019, 4:58 pm

I’d seriously consider domed pistons if your after 1200 hp gonna need the squeeze to make the cheese

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Post  CDMBill on May 7th 2019, 8:10 pm

Lem Evans wrote:
CDMBill wrote:We are trying to step up our Drag Week program a bit without breaking the bank. After reading the long SR-71 thread the question is how close could we get to Jon's 1200HP with the existing 598"/A460 3X TFS Tunnel ram setup with a cam change and compression increase.

So with the A460 3X Heads that have been cleaned up once with a .005 cut, how much more can they be milled to increase compression which is 12:1 now with a flat top JE piston? Current chamber volume is 82cc. Current cam is 282/294/113 installed at 109 .462"/.451 lobe lift, 1.85 rockers.

I asked a related question about the A460 3X cross sectional area.

The heads can be milled much more. Valve to piston clearance is the 1st issue. Intake fitment would be the next issue......which is easy to resolve.

With Charlie's input on the effect of milling .0055" cut = 1 cc its pretty clear pistons will be in order to hit the compression ratio target. Is there a P/N you guys sell that would be the best fit to the "Lem" chamber on these particular heads? I'm sorry If I am mis-attributing the design change to the TFS A460 3X, but that is how I recall it. I normally work with JE.

If I do all the compression increase with piston and only cut the heads a little or not at all I preserve the ability to easily go back to the pump gas deal. Will I end up with too much dome?

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Post  kjett on May 8th 2019, 8:17 am

Diamond has the right dome piston you need to fit that chamber. I'm sure Lem can hook you right up too. Cool

Oh, and I cut my 83cc A heads down to 75cc chambers. Had to cut my new intake down to make the ports line back up, but works well. My 618 with flat tops pistons is almost 15:1 Twisted Evil
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Post  litshoot on May 8th 2019, 8:42 am

kjett wrote:Diamond has the right dome piston you need to fit that chamber. I'm sure Lem can hook you right up too. Cool

Oh, and I cut my 83cc A heads down to 75cc chambers. Had to cut my new intake down to make the ports line back up, but works well. My 618 with flat tops pistons is almost 15:1 Twisted Evil

that's a good point, what compression are you looking for. My stock a460 head, 8cc dome and .051 gasket gets me 14:1.

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Post  Lem Evans on May 8th 2019, 8:53 am

CDMBill wrote:
Lem Evans wrote:
CDMBill wrote:We are trying to step up our Drag Week program a bit without breaking the bank. After reading the long SR-71 thread the question is how close could we get to Jon's 1200HP with the existing 598"/A460 3X TFS Tunnel ram setup with a cam change and compression increase.

So with the A460 3X Heads that have been cleaned up once with a .005 cut, how much more can they be milled to increase compression which is 12:1 now with a flat top JE piston? Current chamber volume is 82cc. Current cam is 282/294/113 installed at 109 .462"/.451 lobe lift, 1.85 rockers.

I asked a related question about the A460 3X cross sectional area.

The heads can be milled much more. Valve to piston clearance is the 1st issue. Intake fitment would be the next issue......which is easy to resolve.

With Charlie's input on the effect of milling .0055" cut = 1 cc its pretty clear pistons will be in order to hit the compression ratio target. Is there a P/N you guys sell that would be the best fit to the "Lem" chamber on these particular heads? I'm sorry If I am mis-attributing the design change to the TFS A460 3X, but that is how I recall it. I normally work with JE.

If I do all the compression increase with piston and only cut the heads a little or not at all I preserve the ability to easily go back to the pump gas deal. Will I end up with too much dome?

What is the compression target? I can get the dome to be what ever you need.

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Post  Lem Evans on May 8th 2019, 8:55 am

x

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Post  CDMBill on May 8th 2019, 11:42 am

Lem, the target is between 15:1 and 16:1, and I'll race on C16 or Q16 with the 1.85:1 or 1.9:1 rockers, drive on E85 and 1.7:1 rockers. It's simple to change the tune in the ECU and I have plenty of tuning support. The current flat tops weigh 639g with 172.5g pins, rings and locks 58g. I anticipate needing a bit more valve relief if I end up with a .482 or slightly larger lobe. The current .462 lobe has .125" P2V with a measured .831 lift at the valve with zero lash and the 1.85 rocker. RPV .060"-.075"-.090"

Ring pak has been JE Hellfire (n2O) .043/1/16th/3/16 maybe I can go a bit thinner with something form Total Seal?

I may be kidding myself, but I still think I can get close to Kaase's 1200 HP with his 598" with the SR71 heads, tunnel ram and two carbs, vs. my 598" with the fully CNC's A460's and similar compression, CNC'd TFS tunnel ram and two 2200 cfm TB's. . I am talking to Cliff about cams too.

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Post  Lem Evans on May 8th 2019, 12:08 pm

Change the ring package for sure. How much crankcase vacuum you running?

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Post  CDMBill on May 8th 2019, 5:33 pm

I have it (Peterson Wet-Vac) limited to 12 in." at the moment. I think it will pull about 16" maximum.

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Post  Lem Evans on May 8th 2019, 7:04 pm

CDMBill wrote:I have it (Peterson Wet-Vac) limited to 12 in." at the moment. I think it will pull about 16" maximum.

Yep, we need to talk about the ring package.

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Post  cool40 on May 9th 2019, 12:37 pm

I’d cut the head and use least amount of dome possible to get where I want. It should be easy with that cid. Diamond has a standard dome for that head.
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Post  CDMBill on May 20th 2019, 1:08 pm

I am working with Lem on those Diamond pistons. And were going to leave the heads alone and do it with dome, about 22cc worth and still not half as tall as the typical BBC. The ring package will be Total Seal and those guys concur with Lem's recommendation, nothing crazy AP .043 top and second, 3mm oil. By leaving the heads alone we avoid too deep a valve relief and I I ever decide to go back to the pump gas setup its an easy cam and piston swap.

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Post  Lem Evans on May 20th 2019, 3:20 pm

CDMBill wrote:I am working with Lem on those Diamond pistons. And were going to leave the heads alone and do it with dome, about 22cc worth and still not half as tall as the typical BBC. The ring package will be Total Seal and those guys concur with Lem's recommendation, nothing crazy AP .043 top and second, 3mm oil. By leaving the heads alone we avoid too deep a valve relief and I I ever decide to go back to the pump gas setup its an easy cam and piston swap.

Are you sure about that 22cc dome? I didn't come up with near that much dome.

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