Steel Shim Gaskets or Fel-Pro?

[deputycrawford]

    Many have heard my 383 comboin the past but I'll make it short. I have 9.35 to 1 comp with my 906 heads at 75 cc chambers, 23 thousandths deck and 40 thousandths head gasket thickness. I will be running an Engle Solid .575 cam and am worried about keeping the low end responsive. I was thinking about going back to the .020 steel shim gasket to get around 9.78 to 1 comp. I have to keep this thing on pump gas, but am looking for a peppy part throttle thing. Will giving it more compression to blow off at idle make that much difference? Is it recommended to stay away from shim gaskets when rebuilding? I have the engine apartright now but will be putting it back together in the next 2 or 3 days. Any thoughts are appreciated. Thanks.

[firefighter3931]

Dep, is that the Engle grind we talked about awhile back ? If so, i would keep the static comp at 9.35:1 because that cam will build more low end cylinder pressure than your old xe 285 hydraulic.    When you're looking at solid flat tappet profiles you have to account for the effect that lash has on what the motor "sees" in terms of valve timing events. The duration numbers will be ~5* smaller than what the cam card is showing. That custom grind we talked about was to be ground on a 108* lsa vs the old xe's 110* lsa so that will have some impact as well...

Overall, i think you will be very happy with the new cam. The idle quality/street manners should be very similar but it will pull harder and hold on longer than your old "juice" stick.  Don't forget the Rotella 15/40 diesel oil and a bottle of GM EOS for the breakin. 



Ron

[deputycrawford]

Thanks firefighter. That is the custom Engle I had made. I had already thought about the Rotella oil but you say to get GM EOS? I will get some. I also have removed the inner damper springs from the valves for break in. They do have 160 lbs on the seat at 1.9 height with the dampers. I thought that was too much for the break in. Am I in the right direction? I will keep the Fel-Pro's then. That should garantee that I won't have a ping going on in there on 93 Octane.

[Chryco Psycho]

sounds right to me , the inner springs can be a pain to instal later but it is worht the effort

[deputycrawford]

Ok Chryco. I don't want to flatten a cam so I will have to do the two stage spring thing. Man, I hope the cam holds up the spring pressures after the dampers are in.

[firefighter3931]

Ok Chryco. I don't want to flatten a cam so I will have to do the two stage spring thing. Man, I hope the cam holds up the spring pressures after the dampers are in.

If you're worried about the lifters....there are a couple of options. The ceramic base Schubecs are expensive but bulletproof. You don't even have to break them in...just fire it up and go.

The second option is the new EDM lifter which has an oil feed hole drilled into the face to pressure feed the cam with lube instead of solely relying on the splash method.  The set sells for less than $200.00 and is well worth it.


Whatever lifter you decide to run : make sure that they're rotating in their bores. You'll have to mock up the valvetrain, set the lash and turn the engine over by hand. If the lifters aren't spinning then you will have problems. After the mock up is completed remember to re-coat the lifter bases with the moly lube because most of it will be scrubbed off during the rotation test.


Fun stuff huh !  



Ron

[John_Kunkel]

I have 9.35 to 1 comp with my 906 heads at 75 cc chambers,

Have you actually measured those chambers? 75 cc's sounds awfully small for heads that average around 90 cc's. (Unless milled .060"+)

[deputycrawford]

Thanks for the responses guys. My heads were hacked around .050. They were measured at 75cc after that. I wanted good flame propagation. I think thats how you say it. Oh, I tried to separate the inner springs from my heads and didn't have any luck. I am going to break it in with full pressure, 160 lbs on the seat at 1.9 height. That should drop to around 150 or so after break in, I hope. I have to set the lash tomorrow and put in my new high volume oil pump. My other high volume pump looks really bad after the thrust bearing went through it. I have most of the long block together now and will set the lash later today. The solid mounts go on it next and I drop it in. I hope to have it running in a couple days. I hope the cam breaks in with full pressure. My valve springs are double springs, not a spring and a damper. Let me know if I'm way off here. Oh, I torqued the head bolts to 65 ft pounds in two stages. Is that good enough or do you suggest something else? Thanks again for all the replies.

[Chryco Psycho]

Heads should be torqued to 70-75 lbs
I would run a High pressure pump ONly unless you have a deeper pan on the engine with 8qt minimum

[deputycrawford]

Ok, I have 7 qt pan with 1 qt filter. I will retorque to 70 ft pounds in the morning.