Piston deck clearance

[05stroker]

I know the factory spec is .008 and for N/A you want almost 0 , but for a high boost S/C setup what do most engine builders set it at ?

Mine is at .017 average (varies .015 - .018) The highest piston rocked all the way over measured .009. I measured both sides of the piston at the sides and averaged the to sides to get the actual deck clearance for the piston in the bore .

I'm about to put the heads on my new motor and am trying to decide which set of gaskets I want to use . I have a set of Ford gaskets that spec .036 compressed and a set of Cometic that spec .045 compressed. I had bout the Cometic set for the last SB because of some minor piston to head contact , but after finding the piston to wall clearance was the problem so I rebuilt with a new block .

As is sets if I use the Ford gaskets I will be in the 8.96/1 range and the Cometics will put me in the 8.81/1 range

 

[lito]

What are you plans on boost levels and fuel to be used?

Also which bore size is the cometic, 92 or 94?

Actually if you share more data on your build, heads, piston dish size, etc. it would be good.

 

[05stroker]

What are you plans on boost levels and fuel to be used?

Also which bore size is the cometic, 92 or 94?

Actually if you share more data on your build, heads, piston dish size, etc. it would be good.

Manley 18cc dish pistions, and ported heads still with 51cc cambers.

Cometics are 94 mm and the stockers are 92mm.

Will run 93 oct with 16 or so psi on the street and 24-27 psi with c16 on the track with a small N20 shot later .

Motor is a 302 stroker with 3.75 stroke and 3.582 bore

 

[05stroker]

I guess another question would be , how accurate is the readings Im getting without a tq plate or head installed ?

 

[lito]

I've just read you have a procharger, I would even would went with an slightly higher CR for it. In your case I would use the stock gasket. For pump gas and 15-16psi you could have went with 9.3-9.5.

Also if you are going to use aftermarket cams it would help.

I have a customer running 14psi+ on a paxton on the stock engine on our shitty 91, car pulls strong and I had it a little retarded up top and has about two years going strong. I did not wanted to work with that pulley but customer insisted (he already had a 323cid motor bought just in case, we are fitting in this week)

 

[05stroker]

I've just read you have a procharger, I would even would went with an slightly higher CR for it. In your case I would use the stock gasket. For pump gas and 15-16psi you could have went with 9.3-9.5.

Also if you are going to use aftermarket cams it would help.

I have a customer running 14psi+ on a paxton on the stock engine on our shitty 91, car pulls strong and I had it a little retarded up top and has about two years going strong. I did not wanted to work with that pulley but customer insisted (he already had a 323cid motor bought just in case, we are fitting in this week)

Forgot to mention that I do have aftermarket cams . Comp custom grinds that spec as follows.


Int. Exh.

Gross valve lift .491 .501

Duration @ .006

Tappet lift 261 265

Valve timing Open Closed

@ .050 INT. 3- BTDC 45 ABDC

EXH. 47 BBDC 1- ATDC

These specs are for a cam installed with a 114.0 centerline

Intake Exhaust

Duration @ .050 222 226

Lobe lift .4910 .5010

Lobe separation 114.0

 

[lito]

Those are pretty mild cams, they will idle close to stock ones.

I would go with the stock head gaskets.

 

[05stroker]

Those are pretty mild cams, they will idle close to stock ones.

I would go with the stock head gaskets.

Yes , but with more lift and power .

At 20 psi they made 702/686 rwhp on c16 . What do you think the Comp 127550 would pick up with the same setup ?

If the Comp 127550s were used would they require the pistons to be cut for clearance ?

I did decide to stick with the Ford head gaskets . Just trying to degree the cams now with the Trick Flow crank gears now. The cams I have call for a 114 centerline and the stock cam gears with lockouts at full advanced were at 104 centerline . So far It looks like 2 deg retard will get me where I want to be .

Is there a way to figure they cam centerline with the same setup with the cams locked at full retard?

 

[lito]

Yes , but with more lift and power .

At 20 psi they made 702/686 rwhp on c16 . What do you think the Comp 127550 would pick up with the same setup ?

If the Comp 127550s were used would they require the pistons to be cut for clearance ?

I did decide to stick with the Ford head gaskets . Just trying to degree the cams now with the Trick Flow crank gears now. The cams I have call for a 114 centerline and the stock cam gears with lockouts at full advanced were at 104 centerline . So far It looks like 2 deg retard will get me where I want to be .

Is there a way to figure they cam centerline with the same setup with the cams locked at full retard?

I have a car with (I assume) your same pistons (platinum 18cc for 3.750 stroker and 5.850) with a custom cam somehow similar to 127550 (550/550 lift) and they clear perfect, also have another customer with 127550 and diamond 14cc coated and they clear no problems too.

With this customer car I can tell you soon, it has a F1R with a 9.3 livernois pro shortblock and 127550, we installed a wastegate so to use pump and C16 with the same pulley, I published some graphics here:

http://www.s197forum.com/forum/showpost.php?p=626005&postcount=22

We got to flatten the boost curve around 15-16psi but had problems with it getting closed for full boost, waiting for some WG springs to test but we expect about 25-26psi @ 7000. We are targetting for 800.

Fully advanced 60 degrees? or limited to 20? I seriously would lock those gears.

 

[05stroker]

I have a car with (I assume) your same pistons (platinum 18cc for 3.750 stroker and 5.850) with a custom cam somehow similar to 127550 (550/550 lift) and they clear perfect, also have another customer with 127550 and diamond 14cc coated and they clear no problems too.

With this customer car I can tell you soon, it has a F1R with a 9.3 livernois pro shortblock and 127550, we installed a wastegate so to use pump and C16 with the same pulley, I published some graphics here:

http://www.s197forum.com/forum/showpost.php?p=626005&postcount=22

We got to flatten the boost curve around 15-16psi but had problems with it getting closed for full boost, waiting for some WG springs to test but we expect about 25-26psi @ 7000. We are targetting for 800.

Fully advanced 60 degrees? or limited to 20? I seriously would lock those gears.

Mine are locked full advanced now . Thanks for the info . I was thinking about the 127550s in the future to get a little sound out of it along with some power . The cams I have now make good power , but the duration is short. While good for making boost , there is a pretty smooth idle . I would love to have the extra .050 of lift though.