andrews 26 cam in 95 build

[Fisherking]

A squish band is where a piston and head surface come in close proximity of each other at TDC. There are several types of squish bands. Some heads have an angled surface machined or cast into the inside perimeter of the head gasket surface. The piston has a matching area. In the case of a stock twin cam, the head has a bathtub shaped combustion chamber. The flat sides of the chamber extending from the head gasket surface make up the squish area. As the piston (flat top for a stock twin cam) reaches TDC, the AF mixture that was in this area gets forced out. The amount of squish effects how violently it is forced out of that area. When it is forced out of the squish area and into the combustion chamber the AF mixture creates turbulence in the combustion chamber and helps promote a more complete and quicker burn as well as reduce chances for detonation. The squish is determined by 2 things in a stock twin cam configuration, the deck height and the head gasket thickness. For example, if the stock deck height is .010" down in the hole then the piston is .010" below the head gasket surface of the cylinder. If the head gasket is stock it measures about .045". Add those 2 numbers together and you have your squish, in this case .055". Now if the deck height is set so the piston is .005" down in the hole and a .030" head gasket it used, the squish is now .035", a more desirable number. This is what dolt is talking about, I hope it helps you

Yes it does help ty. It nice to understand the prosses.ill probly have to read it a cupla times lol
So it maters were the piston pin is placed for piston deck hight . This will affect the squish band as well soin the calculator it figures that in or is it a rough estimite with the dome cc s ?
Thanks , F.K.

Ps the big boys compression calculator

 

[dolt]

FK-
Headwork
BigBoyz offers a "street" port for $299 but that does not include measuring chamber volume which is obviously required; decking for compression which is not required with your domed pistons and drilling/tapping for compression releases which I would recommend. Bean retains stock valves and springs if in good condition, does a multi-angle valve job, installs new guide seals and will mill the heads removing almost no material just to insure a flat deck mating surface. There is less porting to do on the '06 heads as most of the improvement on the earlier head results from working the floor of the exhaust port and the port size which the MoCo addressed with the upgraded '06 heads. The cost for the BigBoyz street port, measuring chamber volume and machining for compression release will run about $375, plus out and back shipping which will probably run $50 each way.

Head Gasket
You have bounced around between machining the dome to set compression to retarding the cam timing, so I am not sure what your plans are now. If I was building the motor, I would mill the piston dome down to 5cc, use a .030" head gasket and call it good. That would set static CR right at 10:1, corrected CR at 9.33 and CCP at 188psi at 1000' above sea level; the motor should be happy there and I would expect you will see very similar numbers to those I posted earlier; probably a bit more with ported heads. You will need a good fuel management system like the TTS Mastertune or Powervision; the Cobra system will not get the job done with this motor.

 

[dolt]

Yes it does help ty. It nice to understand the prosses.ill probly have to read it a cupla times lol. So it maters were the piston pin is placed for piston deck hight . This will affect the squish band as well soin the calculator it figures that in or is it a rough estimite with the dome cc s ?
Thanks , F.K.

Piston pin has nothing to do with deck height. Deck height, which Jack explained, is the difference between the top of the piston and the top of the cylinder/deck. If the piston is down in the hole, the deck height is positive as it adds to the squish band. If the piston is above the top of the cylinder/deck, the deck height is negative as it reduces the squish band. I have never seen a TC with negative deck height; always down in the hole. The early TC88s, like yours were typically down in the hole .003" to .005"; some more but those dimensions are typical. The pistons in the later TC96s are typically down in the hole .005" to .007", some more but those are typical.

I used .003" and .005" in my calculator to come up with the compression numbers in my previous post.:s

 

[Fisherking]

Follow On Post

Ok ic . So will the domed pistons have the same deck hight as the stock . ? Or is that something we check as I put it together . Or will CP have that included in there instructions ?
F.K.

Ok sounds like 4 cc off the pistons . Will I still be able to put the stock push rods in if i used the 0.030 Cyco head gaskets ?

 

[dolt]

You will need to measure deck height. When you get the pistons and cylinders back from the machinist (BTW, he should also check ring gap and file rings if required-CP can provide recommended ring gap for their pistons) you will need to wash the cylinders, pistons and rings in some warm, soapy water until you can wipe the wall with a with a white cloth and not see any gray or black stuff. Sometimes it takes 4 or more wash/dry cycles to remove all the machine dust and grit. When done, liberally apply WD40; the ductile iron cylinder walls will start to rust before your eyes.

You should "mock up" the top end before final assembly. Install the top ring on both pistons, no need to install the pin retainers to check deck height. It's going to be a bit tricky with the dome but your indy should know what to do.

Stock pushrods will work; how much you remove from the dome doesn't make any difference.

 

[dolt]

Easiest way I have found to check deck height is with two pieces of .030" resin core solder; .020" if you can find it. Cut two pieces about 1" long and place them on top of the piston at the flat area, not the dome. I use a small piece of painters tape to secure them in place. The solder pieces should directly opposite one another so the piston won't "rock" when the solder crushes. Secure the head to the cylinder without the head gasket and torque to say 25 ft.lb. Slowly rotate the crank via the rear wheel and when the solder makes contact with the head, you will feel the resistance but should be able to continue rotating the crank and crushing the solder. Remove the head and measure the thickness of the crushed solder with a set of accurate digital vernier calipers; that is your deck height. Add the thickness of the head gasket and you have your squish band measurement. If you can set squish so that it is less than .040", call it good. Cometic makes a .027" head gasket as well as a .030" gasket.

Some builders prefer acid core solder but it's messier as the acid core should be removed and it will crush easier. A little extra work but a bit of a pain in the neck.

 

[Fisherking]

Ok I undrestand all that . It makes sence .
I was asking about the 0.030 gasket and the stock pushrods off the tappits .
Thanks F.k.

 

[dolt]

Ok I undrestand all that . It makes sence .
I was asking about the 0.030 gasket and the stock pushrods off the tappits .
Thanks F.k.

As I said in a previous post, if the thinner .030" or .040" head gasket is the only change in the valve train stack up height; stock pushrods will work. However, if you change cams, now or in the future to higher lift with smaller base circle, or deck the heads; the stock pushrods will not work and adjustables will be required. I like adjustables because should the valve train be a bit noisy, more preload can be applied to the lifters to quiet things down. Andrews cams are typically not noisy; soft ramps and with the little bit of extra preload from the .030" head gasket valve train noise should not be an issue.

 

[Fisherking]

Ok kool . I thought u just referd to the 0.040 head gaskets so I asked about the 0.030 . Just to make shure
Thanks for the follow up .
F.K.

 

[stray dog]

be careful with p/r's. I think the stock cam lift is .473 and the 37's are .510.
also gasket thickness plays into the dimensional stack up.

I wasn't referring to the springs, I was concerned with the push rod length in respects to the lift of dif cams. You are correct "bolt in cams" in respect to valve springs.

Dolt has you covered in the last post regarding the p/r length.

Ok I undrestand all that . It makes sence .
I was asking about the 0.030 gasket and the stock pushrods off the tappits .
Thanks F.k.

F.K. I think I muddied the waters with post #44.
Somehow my mind got off tangent thinking the two different cam lifts entered the equation for push rod length. THAT WAS WRONG...it is the base circles of the cam that matter. Dolt refered to this and somewhat subtly corrected this, he should've spanked me harder on this one.
Sorry for the confusion!