Compression question

[DuceAnAHalf]

I have the oprotunity to buy a set of AFR 185s but they have 54cc chambers, i figure that will give me about 10.8:1 compression with a .041" gasket. is that too much compression for hyper pistons and regular rings? What about a thicker gasket, maybe a Cometc?

[mrltd]

Sure WAY too much. I'll trade you for my GT40's

[DuceAnAHalf]

Sure WAY too much. I'll trade you for my GT40's

Oh yeah, he only wants $900 for them.

[Tiggie]

Not to much for the pistons or rings, but too much for pump gas unless you run a cam that bleeds off about 50psi.

[mrltd]

tI'll trade off a 94 civic for 'em...and then give the heads to slydawg...

[Mercracer]

I have the oprotunity to buy a set of AFR 185s but they have 54cc chambers, i figure that will give me about 10.8:1 compression with a .041" gasket. is that too much compression for hyper pistons and regular rings?

If you are going to run those heads, this is not Grandma's car anymore. You will have gears and a converter. You should have no problems with a conservative timing curve and premium pump gas. MSD distributor and ignition time. Compression is your friend.

[DuceAnAHalf]

If you are going to run those heads, this is not Grandma's car anymore. You will have gears and a converter. You should have no problems with a conservative timing curve and premium pump gas. MSD distributor and ignition time. Compression is your friend.

3.55 gears, 3000 stall, MSD billet distro, MSD 6al. Aeromotive street rod fuel pump, fuel cell. 325/50R15 drag radials, heavy shocks stiff springs. My car does not even have a radio. It is a long way from a grandma's car.

[Tiggie]

What type of cam are you planning to run? Your gonna have to have a large one with around 50 Degrees ABDC @ .050 to get your dynamic cranking pressure down to 195 psi, about max for pump gas. The 3K stall is abuot what you're gonna have to run with at least 3.73s, or 4.10's to make the car driveable.

[DuceAnAHalf]

What type of cam are you planning to run? Your gonna have to have a large one with around 50 Degrees ABDC @ .050 to get your dynamic cranking pressure down to 195 psi, about max for pump gas. The 3K stall is abuot what you're gonna have to run with at least 3.73s, or 4.10's to make the car driveable.

http://www.cranecams.com/?show=browseParts&action=partSpec&partNumber=443941&lvl=2&prt=5

that is my current cam. It is kind small. but i have 1.72 rockers which gives about .522/.543 lift at the valve. unfortunatly they are pedastal mount so they cant be ran with the AFR's

this looks to be a better cam choice.

http://www.cranecams.com/?show=browseParts&lvl=2&prt=5&Vehicle_Type=Auto&Cylinders=8&Engine_Make=FORD-MERCURY&Year=1989&Engine_Size=302-351%20C.I.&partNumber=440881&partType=camshaft

[Mercracer]

What type of cam are you planning to run? Your gonna have to have a large one with around 50 Degrees ABDC @ .050 to get your dynamic cranking pressure down to 195 psi, about max for pump gas.

You can't be serious...

[Mercracer]

What type of cam are you planning to run? Your gonna have to have a large one with around 50 Degrees ABDC @ .050 to get your dynamic cranking pressure down to 195 psi, about max for pump gas. The 3K stall is abuot what you're gonna have to run with at least 3.73s, or 4.10's to make the car driveable.

Do you understand what you typed? What did you read and try to type?
When describing valve timing, you typically see valve duration listed in degrees @ .050 lift so that cams can be accurately compared to other cams on a level field. When you are seeing numbers quoted in degrees ABDC, you are typically looking at intake valve closing geometry. If your intake valve starts closing at 50 degrees ABDC, you will build much more cranking pressure than you will with a cam likuceAnAHalf referred to which begins closing at 67 degrees ABDC. If we look to his current Crane cam specs listed under @ .050 , it is actually only 35 degrees ABDC when the valve begins to close which isn't far from one of the the Crane high compression cam I would recommend which begins closing at 39 degrees ABDC according to the timing specs listed under @ .050. The TFS Stage 1 cam starts at 38 degrees and the Stage 2 cam is also at 39 degrees

......that is my current cam. It is kind small. but i have 1.72 rockers which gives about .522/.543 lift at the valve. this looks to be a better cam choice.......

Although your current cam is a little small, the second cam is insane for your application.
This would be a better choice... Good Cam Specs

Your configuration fits right into its specs. It makes power from 2200RPM's -6000RPM's. The large one you linked to doesn't start making power until 3200RPM's and is made to run to 6800 RPM's. Way beyond a good street car.
To save money and still have a great cam, you could also probably get away with running the TFS Stage 1 cam with 1.7 rockers. A reasonable street cam which makes a pile of power. If you want a more wild car, then the TFS Stage 2 cam will serve all of your needs and more without being stupid big. Either cam is less expensive than the Crane cam.
TFS Cams

[DuceAnAHalf]

Thanks for the cam recomendations. But i cant use the TFS cam i dont believe, im using a flat tappet cam in my Windsor.

*EDIT* i noticed that the one you recomended was an X303 cam. would that work in my motor since it is flat tappet? id think the ramp rates were too high.

[Mercracer]

Thanks for the cam recomendations. But i cant use the TFS cam i dont believe, im using a flat tappet cam in my Windsor.

*EDIT* i noticed that the one you recomended was an X303 cam. would that work in my motor since it is flat tappet? id think the ramp rates were too high.

The X303 cam is a FRPP cam, not one of the Crane or TFS cams I listed. Crane lists their cam as an upgrade/replacement to the X303 cam.
It would be worth your time to get a set of the retrofit roller lifters so that you can run a roller cam. They run between $250 and $300 on the web. You can not use flat tappet lifters with a roller lifter cam.

[Chevyguy]

I would split between the two cams, this should bleed off some DCR and make some good power with the AFR heads. This is a nice flat tappet cam

LUN-61003LK


Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,800-6,200 RPM
Intake Duration at 050 inch Lift: 227
Exhaust Duration at 050 inch Lift: 233
Duration at 050 inch Lift: 227 int./233 exh.
Advertised Intake Duration: 268
Advertised Exhaust Duration: 276
Advertised Duration: 268 int./276 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.522 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.538 in.
Valve Lift with Factory Rocker Arm Ratio: 0.522 int./0.538 exh. lift
Lobe Separation (degrees): 110

http://store.summitracing.com/default.asp?target=egnsearch.asp&N=115+400421+310650&autoview=sku

[Tiggie]

Do you understand what you typed? What did you read and try to type?
When describing valve timing, you typically see valve duration listed in degrees @ .050 lift so that cams can be accurately compared to other cams on a level field. When you are seeing numbers quoted in degrees ABDC, you are typically looking at intake valve closing geometry. If your intake valve starts closing at 50 degrees ABDC, you will build much more cranking pressure than you will with a cam likuceAnAHalf referred to which begins closing at 67 degrees ABDC. If we look to his current Crane cam specs listed under @ .050 , it is actually only 35 degrees ABDC when the valve begins to close which isn't far from one of the the Crane high compression cam I would recommend which begins closing at 39 degrees ABDC according to the timing specs listed under @ .050. The TFS Stage 1 cam starts at 38 degrees and the Stage 2 cam is also at 39 degrees

Yes, I do understand exactly what I typed. Notice I said 50 degress at .050. With the intake valve closing at 39 degrees ABDC, their is more air/fuel mixture to be compressed than if the intake valve was closing at 50 degrees at .050. With you're recommended cam, you're still looking at around 205psi of cranking pressure. You'll never get it to run without predetonation on pump gas, regardless of the aluminum heads. At the very least, a cam with more than 45 degrees ABDC at .050 is going to be needed to run this thing on the street.

I've run a 390 with a cam of 23 degrees ABDC at .050, and 9.4 compression. It would not run on anything but 93 octane, still with predetionation and retarded timing. It only had a cranking pressure of about 180psi.