Thread: Is quench always important?

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I have a set of heads I intend to bolt on the 383 I am building. They are 2.02/1.60, 74CC. They were given to me for free (they came off of may Dad's race car). Is obtaining the proper .040 quench as helpful on these heads? I will be running flat top pistons, about 10:1 CR and would like to do all I can to reduce any detonation.

Originally posted by Randall
I have a set of heads I intend to bolt on the 383 I am building. They are 2.02/1.60, 74CC. They were given to me for free (they came off of may Dad's race car). Is obtaining the proper .040 quench as helpful on these heads? I will be running flat top pistons, about 10:1 CR and would like to do all I can to reduce any detonation.

Quench area is one of the most important details often overlooked by engine enthusiast. A good quench is important for detonation control in any engine. It also produced more power because of a better air/fuel mixture caused the swirl. I normally will zero deck my block and use a Fel-Pro .039 Hi-Perf. gasket. I get away with some pretty high compression, cast iron headed engines on the street using pump gas.

Yes, quench is very important if you want to avoid detonation. If your block is stock with the pistons .025 in the hole, you will want to find a head gasket with of thickness between .015 and .019 for proper quench. And you should be sure to find out your DCR with the cam you are considering. You will want to keep your DCR under 8.0 with iron heads if you want to run pump gas.

In my opinion, quench is the cornerstone of an engine build. I also will use a piston with a flat crown like this....
http://kb-silvolite.com/performance....tails&P_id=222
instead of a production-type Chevy piston with a dish and 4 valve reliefs to maximize the area of the squish pad.

If I have to use a dished piston to reach a certain c.r., I'll use a piston which has the dish offset like this KB, so that, again, I'll have maximum area for the squish pad instead of a piston with a concentric dish and a small, narrow band to squish against the head....
http://kb-silvolite.com/performance....tails&P_id=224

The second most important area of building, again, in my opinion, is matching the static compression ratio to the camshaft. I see it over and over and over where youngsters come on here with some double-throwdown long cam in their stock c.r. motor and expect the motor to be a world beater.

YOU MUST KNOW YOUR EXACT STATIC COMPRESSION RATIO BEFORE YOU CAN CHOOSE A CAMSHAFT. NO EXCEPTIONS.

And as my buddy Dave Severson keeps hittin' on, use the cam companies. They have technical experts waiting to talk to you on the phone and their advice is F-R-E-E. Write all your specifications down and call up your favorite cam grinder for a recommendation.

If you don't know how to figure the c.r., use my suggestions here...
http://streetmachinesoftablerock.com...opic.php?t=124

I used to stress the importance of the quench doctrine but in the past few years have diluted my conviction on this matter, especially in the area of most street cars. However, in all out race cars and high compression engines, yes, it is of the utmost importance.

From what I understand, most engine blocks are only out at the most by .015" from one corner to the other. If you take this number into consideration, you will be able to calculate the difference in c.r. to be less than .25 of a point. So if you are running a 9.5:1-10:1 compression motor and use 92-94 octane, it is easy to see that a quarter of a point of compression will not cause you grief. Add to this, if you have a large overlap cam, this reduces the compression even further. As for the difference of h.p. at the lower compression piston, depending on the overall h.p. rating, but it would only be a matter of 1-2 h.p. less per piston. So the hp loss is not a big issue and neither is pre-detonation.

On the other hand, if you build an engine to the tightest tolerances, where you might want to run 87 octane and have 9:1 compression, and if pre-detonation was to occur at 9.1:1, then yes, you should have the engine square decked.

Myself, I square deck and true bore all my motors. For the cost involved, it is a small price to pay. But if you are on a tight budget and you have room to play on the cr., then don’t bother.

Originally posted by techinspector1
I see it over and over and over where youngsters come on here

I would probably be considered a "youngster" to most here at 32, It has been about 15 years since I built my last motor (did I say 15, wow) and that was just a mild Pontiac 400 street motor. This is going in the 32 I am building and I want to do it right.

I have been closely monitoring the forum (thanks to all for your vast knowledge) to get advise. Your formula's for CR were very helpful tech, I had already figured I would be between 9.5 & 10:1 when I called Comp and Lunati cams. Your formula worked out to 9.78:1.

I am currentlt looking for a machine shop in Columbus, Ohio, any advise what to look for?

Other than having the block bored, honed, align-honed, & possibly decked (Tech, I read your post on bringing the block home and installing the crank and 1 piston in 1,2,7,&8), what else should I have the machine shop do?

First, have the block magnafluxed to determine if you have a valid player or not. Then measure the bore and determine if you will overbore and if so, how much. Order the pistons and take them to the shop so they can set the piston/wall clearance when they bore the block. Have it bored and honed to size and washed off. Take it home and do the deck measurements. Back to the machine shop to cut the decks, remove the cam bearings and give it a final wash. Have them install new cam bearings and you're ready to bring it home for assembly. Make sure all threaded core plugs are in place, including the one under the rear main. Use brass Welch plugs on the outside of the block. Use a little sealer around the edges and then stake them in place with a punch and hammer.

The bore is stock @ 4.00, I plan on boring .030 over. I already have the rotating assembly (Eagle crank, rods, & Speed Pro pistons). I also have thread chases to clean up all of the threads.

The rotating assy. is sold as a balanced kit, should I still have it balanced @ the machine shop?

I am still not sure how to determine what machine shop to use. What questions should I ask to find out if they are capable?

Originally posted by Randall
I would probably be considered a "youngster" to most here at 32,

Ya think that's a "youngster!" sorry man, that sounds pretty old to me, i'm only 16.

Originally posted by Rico
Ya think that's a "youngster!" sorry man, that sounds pretty old to me, i'm only 16.

It's all relative.

I might be twice your age, but I am sure there are some on here twice mine.

Knowledge comes with age as well, so they (those older than myself to be politically correct) also bring most of the information to these boards.

While quench is important I would not try to (break the bank) to obtain it.Someone has posted about building a (zero deck height engine).I would never build a street engine like this for any reason.If you have any warpage or any other deck problems a ( zero deck block) becomes a very nice boat anchor. Get it close and call it good.Keep in mind, like I said before thousands and thousands of blocks of come from Chevy,Ford and Dodge without even checking this.

A guy doesn't necessarily have to zero deck the block to achieve 0.035" to 0.040" squish. You can juggle head gasket thicknesses to get there. For instance, Chevy makes a shim gasket that is 0.016", so you could have the piston down in the bore 0.024" and still achieve a squish of 0.040" and have 0.024" of deck to take another cut later if need be. There is also a 0.028" gasket from Chevy where you could have a deck of 0.012" and still get the squish where you want it. Even if you do cut the deck at zero and have to cut it again later, just use a thicker gasket to keep the squish at 0.040". I know there is a 0.051" gasket and probably a 0.060" that would allow you to pop the piston out of the bore and still get 0.040" squish.

I hope I'm making sense to you. It's clear to me.

Originally posted by techinspector1
A guy doesn't necessarily have to zero deck the block to achieve 0.035" to 0.040" squish. You can juggle head gasket thicknesses to get there. For instance, Chevy makes a shim gasket that is 0.016", so you could have the piston down in the bore 0.024" and still achieve a squish of 0.040" and have 0.024" of deck to take another cut later if need be. There is also a 0.028" gasket from Chevy where you could have a deck of 0.012" and still get the squish where you want it. Even if you do cut the deck at zero and have to cut it again later, just use a thicker gasket to keep the squish at 0.040". I know there is a 0.051" gasket and probably a 0.060" that would allow you to pop the piston out of the bore and still get 0.040" squish.

I hope I'm making sense to you. It's clear to me.

Yes,you make sense to me.I just don't want people going out there and spending money to obtain perfect (quench).Yes, Cometic makes gaskets all the way up to .125

W

What kind of disaster would cause you to have to cut the block down again and not bust the rest of it. IMO if you have a motor failure that needs to cut the deck down to fix, you have major problems. There is nothing wrong I can see with choosing thin gaskets and shims if that's the way you choose to quench. I like to zero it because it trues the block and I like Fel-Pro's hi-performance gasket #1010. I have had no problems with this set up. It's just a personal preference. It is more important than line boring the mains to me unless you change fasteners.

GM has let a lot of tolerances go unchecked, that doesn't mean it was a good move on there part. A 5.565 rod in a 400 came straight out there plants. We know that a 6" rod is much better. They are into production of numbers so therefore have production tolerances. Look how much core shift comes out of all stock blocks.

Proper quench has little to do with just getting the numbers squared for equal HP on all cylinders.

PROPER QUENCH IS WHAT KEEPS A STREET ENGINE OUT OF DETONATION. WITHOUT PROPER QUENCH, A 10.1 CR WOULD NOT MAKE IT ON PUMP GAS.

I am in the process of building another blower motor now that I couldn't get a inverted dome type piston for. I had to use a dreaded soup bowl. At 9.0:1, I would not set this motor up for
6 lbs. boost without water injection. I run 9.0:1 with 6 lbs boost with no problem on my engine with INVERTED DOMES AND A 0.039 QUENCH ON PUMP GAS. I don't think it would be possible without the quench set right.