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Topic Review (Newest First)
10-08-2013 10:57 PM
vinniekq2 after decking the pistons are down the hole .035?
10-08-2013 06:37 PM
BaySox1
Quote:
Originally Posted by techinspector1 View Post
I agree. Make sure he checked the mains for being round and parallel.
OK--I asked Bill, machinist, to check the mains to insure that they are round and parallel. Not sure if that was correct because he looks sort of confused The other guy that is there, looks like perhaps the owner as he is always in the office, responded, "no problem".

So>>>>I picked up the engine today and it looks pretty good. The pistons are now .035 in the hole. I think I mentioned that I'm having the stock heads worked by a local guy that does work for the racing crowd. As I explained everything that I've learned here about the heads he nodded and said no problem.

So>>He is cutting the heads, installing 2.02/1.60 valves, guides, porting the heads and intake, springs and retainers. Estimate was about $750.00. I need recommendations on assembling the engine, (gasket type and thickness etc) what cam and are my stock injectors going to be OK?

The guy doing to heads said he would give me some recommendations re: cam etc, but I've come to realize that some of what I hear "in the street" is BS. The information I get from you guys puts me in a better position to make the best decision for my motor.

Thanks so much
09-30-2013 02:15 PM
techinspector1
Quote:
Originally Posted by vinniekq2 View Post
$100. to deck the block is very fair.Make sure you bring a bottle of whiskey/bourbon or w/e to smooth things over.well worth the few extra bucks
I agree. Make sure he checked the mains for being round and parallel.
09-30-2013 02:11 PM
vinniekq2 $100. to deck the block is very fair.Make sure you bring a bottle of whiskey/bourbon or w/e to smooth things over.well worth the few extra bucks
09-30-2013 01:39 PM
vinniekq2 when the engine performs well,go back and praise him for a good engine.He will be happy for good news.He might learn something for future customers???Not every machine shop does high performance engines,and stock engines will run fine as long as the fitment is all "close enough".
Your next engine you will be better equipped to do a better more powerful engine. Next time you will take the same care custom fitting piston to wall clearances and ring gaps for even more power
09-30-2013 01:34 PM
jokerZ71
Quote:
Originally Posted by BaySox1 View Post
Tech, thanks so much for the education. It would have been EXTREMELY useful today when I took the engine back to the machine shop. I was, however, armed with the squish, quench rate, knowledge which was a great help in my argument.

They, Bob at the machine shop, really didn't want to take the block back apart and deck it because I had not specifically asked that it be done. My first argument was, "well at the very least, I should have received a phone call" Bob just shrugged his shoulders and stuck with "the gasket will seal that".

So I posed the quench rate argument for about 2 minutes. I got a blank stare and he said, "bring it back in and I'll disassemble and deck the block for $100. I felt, particularly with my dearth of knowledge, further argument would only hurt me so I agreed. I don't think I'll be dealing with them anymore.
Which is when you should have replied<"I didn't request it becuz I didn't know you were gonna use El Cheapo Pistons ". Good deal tho>Glad you are getting it took care of.
09-30-2013 01:21 PM
BaySox1
Quote:
Originally Posted by techinspector1 View Post
Most everyone, including David Vizard, agrees that the tighter the squish, the more power the motor will make. Mr. Vizard tested a tighter and tighter squish on a small block Chevy and didn't encounter a piston to head collision until......I believe 0.027". That's why you will see a range of 0.035" to 0.045". That range allows for the piston growing taller from the heat of combustion, the connecting rod stretching a little and the crankshaft bowing a little at speed. I agree with Jay that over 0.050", you begin to lose the squish effect. Your example of 0.073" squish might better be termed a "lack of squish".

Tighter than 0.035" could get you into a piston/head collision situation and looser than 0.045" will not be as effective as a tighter squish. The idea is to blow the mixture across the chamber by squeezing it out from between the crown of the piston and the flat area of the cylinder head opposite the chamber, homogenizing the mixture and eliminating any rich or lean pockets of mixture so that they will burn completely. I generally try to spec a piston that has a generous amount of flat area on the crown to accomplish this squishing. If you get the squish right, you can generally use a lesser grade of fuel without suffering detonation.

Here is an example of a flat-top piston that would work well.....
http://www.summitracing.com/parts/su...0-30/overview/
Here's a D-Cup piston with a generous flat area on the crown to mate up with the underside of the head....
http://www.summitracing.com/parts/ue...make/chevrolet
I don't use pistons that have a thin ring of crown material all the way around the perimeter and a shallow dish. Not enough flat area to effect a good squish. I couldn't find a photo of that type of piston right away.

I have little experience with blower motors, but I'm told that they will not benefit so much from a tighter squish as a naturally-aspirated motor will. The mixture is homogenized by the blower on the way in.
Tech, thanks so much for the education. It would have been EXTREMELY useful today when I took the engine back to the machine shop. I was, however, armed with the squish, quench rate, knowledge which was a great help in my argument.

They, Bob at the machine shop, really didn't want to take the block back apart and deck it because I had not specifically asked that it be done. My first argument was, "well at the very least, I should have received a phone call" Bob just shrugged his shoulders and stuck with "the gasket will seal that".

So I posed the quench rate argument for about 2 minutes. I got a blank stare and he said, "bring it back in and I'll disassemble and deck the block for $100. I felt, particularly with my dearth of knowledge, further argument would only hurt me so I agreed. I don't think I'll be dealing with them anymore.
09-28-2013 11:38 AM
techinspector1 Most everyone, including David Vizard, agrees that the tighter the squish, the more power the motor will make. Mr. Vizard tested a tighter and tighter squish on a small block Chevy and didn't encounter a piston to head collision until......I believe 0.027". That's why you will see a range of 0.035" to 0.045". That range allows for the piston growing taller from the heat of combustion, the connecting rod stretching a little and the crankshaft bowing a little at speed. I agree with Jay that over 0.050", you begin to lose the squish effect. Your example of 0.073" squish might better be termed a "lack of squish".

Tighter than 0.035" could get you into a piston/head collision situation and looser than 0.045" will not be as effective as a tighter squish. The idea is to blow the mixture across the chamber by squeezing it out from between the crown of the piston and the flat area of the cylinder head opposite the chamber, homogenizing the mixture and eliminating any rich or lean pockets of mixture so that they will burn completely. I generally try to spec a piston that has a generous amount of flat area on the crown to accomplish this squishing. If you get the squish right, you can generally use a lesser grade of fuel without suffering detonation.

Here is an example of a flat-top piston that would work well.....
http://www.summitracing.com/parts/su...0-30/overview/
Here's a D-Cup piston with a generous flat area on the crown to mate up with the underside of the head....
http://www.summitracing.com/parts/ue...make/chevrolet
I don't use pistons that have a thin ring of crown material all the way around the perimeter and a shallow dish. Not enough flat area to effect a good squish. I couldn't find a photo of that type of piston right away.

I have little experience with blower motors, but I'm told that they will not benefit so much from a tighter squish as a naturally-aspirated motor will. The mixture is homogenized by the blower on the way in.
09-28-2013 08:40 AM
jokerZ71 Standard deck hgt on an SBC is 9.025.This is the measurement from the center of the crankline @ BDC to the top of the deck.Removing more than .025 from the deck could start causing fitment/alignment issues with the heads & intake.It can also cause valvetrain geometry issues requiring different pushrods etc.
09-28-2013 08:34 AM
jokerZ71 After .050 or so,you lose the benefits of quench.Your engine will be down on power & more prone to detonation.You also won't have an efficient & complete burn of your fuel.The advertised gasket thickness is the actual thickness after torquing head down.That is the actual compressed thickness.Your engine will run as is,but,the effects of a proper quench are well worth the effort.My main concern in your case is gettin a good seal with the condition of your deck.So if your gonna have the deck cleaned up,it won't be any harder to go ahead & set the proper quench distance.You know your .045 deep now,so,have the shop remove .025 from the deck.
09-28-2013 08:17 AM
BaySox1
Quote:
Originally Posted by GMC boogie View Post
Have the decks cut to a 9.00 deck height. This will leave you around .020 in the hole. Use a .028 gasket.
Quote:
Originally Posted by techinspector1 View Post
That would work fine in my opinion.
OK>>pardon my ignorance, but a 9.00 deck is measured from what point to what point? So .020 and using a .028 gasket, wouldn't that give me a quench of .048? Or is that .028 the gasket thickness prior to torquing the heads therefore giving making my quench much lower?

So I can better understand, and gain some perspective, can you explain what the effects of for a larger quench, ie. I'm currently .045 down and I go ahead and use an .028 gasket and result in an .073 quench?

Thanks All
09-27-2013 08:57 PM
techinspector1
Quote:
Originally Posted by GMC boogie View Post
Have the decks cut to a 9.00 deck height. This will leave you around .020 in the hole. Use a .028 gasket.
That would work fine in my opinion.
09-27-2013 08:40 PM
GMC boogie Have the decks cut to a 9.00 deck height. This will leave you around .020 in the hole. Use a .028 gasket.
09-27-2013 07:54 PM
techinspector1 I'm a fan of using the tallest piston I can find, resulting in the least material off the decks to engineer a good, tight squish, 0.035" to 0.045" with the piston at top dead center and the head gasket in place. I have a fear of cutting too much off the decks, because you begin getting into fitment problems with the intake manifold. The more you take off the decks, the narrower it is between the heads when they are bolted on. One of the most critical things in a build, to my mind, is the sealing up of the ports between the heads and intake manifold. That's why I suggest bolting the motor together, torquing everything down just like you're finished with it, waiting until the next day and removing the intake manifold to inspect the intake gaskets for sealing up all the way around each and every port. If the port is gapped open on the top side, you will probably be able to find a vacuum leak with a combustible spray. If the port is gapped open on the bottom side, you will never find it with a combustible spray and the motor will be pulling in oily vapors every time the intake valve is opened. That's where oily plugs come from many times. If the gasket is pinched all the way around each and every port and you can witness that there is a seal, use another set of the same part number gaskets, bolt it back together, torque and you're done, knowing that the motor is sealed up.
09-27-2013 06:51 PM
jokerZ71 If you deck the block,your current pistons will be fine.Just use the correct gasket thickness for the proper quench.I've never decked a block anymore than to get a clean level surface,but,ppl 0 deck all the time.I have heard that when using the shorter piston combined with 0 decking,will keep the ring Pak cooler by placing it closer to the water jacket @ TDC.
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