You buy him books and buy him books and still he cant read!

Quench = piston to deck clearance at TDC + head gasket thickness.

Example from my motor:

Pistons are .012" below deck at TDC. Head gaskets are .020" thick.
Quench = .012" + .020"
Quench = .032"

 

deck clearence and quench are different measuremets, deck clearence is from the top of the piston to the block deck. Quench is from the top of the piston to the head, it includes the gasket thickness, the deck clearence has nothing to do with the gasket.

Get the .020 shim, spray it with copper spray, its a small can that costs $6. Or put the standard fel pro's in if you are so scared.

 

i know i understand kurt, but wouldn't a .030 gasket go better with .025 deck clearance than a .040 head gasket which would be less quench?

 

the desired quench is .035-.060 max. the closer to .035 the better and the more benefit you will get.

.025 plus .020 gasket is a nice .045 quench
.025 plus .030 gasket is getting borderline at .055, anything over .060 is of no advantage, it starts to hurt you.

On the other hand, .035 is a general mininum, due to rod and piston expansion.

 

What part of this aren't you understanding? You add deck clearance to gasket thickness to get quench distance.

More quench distance = more ping.

You're trying to run the piston as close to the head as possible, with the limit being about .030".

So again I ask, why on earth would you run .030" thick gaskets when .020" gaskets are available? You'd be going backwards.

 

gotcha gotcha...failed to explain that i'm leary of using the .020's for cause of possible leaks....sorry sorry guys...lack of online communication.

 

so again (hopefully the last) if i use the .030 which will compress down to around .025 or maybe safer to say .028 plus .025 is .053 which is plenty to work with correct? i really don't want to have to deck my block for the simple reason i'm bout out of money but if you think it will be a hard thiing to run low grade with the .053 quench then i'll have to do it and come up with the money.

 

the gasket thickness is the compressed thickness, i measured a set of FE or 335's gasket and they were .047 and the compressed spec is .041.

So, this .030 turning into less may be unrealistic. Like, i said if you really want you can run the fel pro head gaskets.

Now, this would require a longer pushrod possibly, the lifter preload spec is .020 to .060. The thicker gasket moves the head up and therefore shorten the lifter preolad. If it were still in spec no big deal.

You would also loose all the quench benefit, I have a .070 quench area on the 901 camshaft. I am running a 160 thermostat in order to keep the engine temp to around 180-185 in spring, summer, and fall.

I also, recommend reworking the timing, there's inital, mechanical, and vac advance. The timing needs to be under 40 degree at full advance. Its best to use an adjustable vac cannister and turn it down so it does not pull as much timing. Inside the dizzy are springs and two slots. You should see, the weights stamped something like 10L,13L,16L,21L etc. Most, FE dizzys that I see have 16L and 21L. Usually the slot is hooked up with the 16L, and that is too much. It will pull 32 degrees of mechanical advance at 3500-4000 rpm. The 16 is doubled because the dizzy is run off the camshaft and it turns at half the speed of the crankshaft.

You either replace, the setup which is a PITA or put a piece of windshield rubber hose on the tab. The decreases the 16L be about 2-4L or 4-8 degrees of crank timing.

DO NOT replace the springs with lighter ones, it will pull the timing in faster and will ping. Leave the stock springs in there.

Now, the vac advance depends on the level of engine vaccum. This will pull more timing. I don't feel like writing a book about it but I have a lengthy post on this section that explains the timing in more detail.

And set the carb using a vac gauge not anything else, and set the timing using a light, NOT EARS.

 

heres a copy from a previous post. Btw, if using the 901, i do not know your cam. 89 octane is best, if you have the 343941, 87 may work.


OK, there is 3 phases so to speak. Inital is what your balancer says and it is what is set via basic timing light. Typically 6-14 btdc and the goal is to build peak cylinder pressure and then ignite. As rpm increases you need to fire the plug to compensate for the increased speed of the piston.

Inside the dizzy is a piece that has 2 weights,and a tab and comes in the following combos 10L/15L, 13L/18L, 16L/21L etc... The tab that is hooked up is the amount of centrifugal or mechanical advance. For instantance 16L would equal 32 degrees. This is because the cam turns at 1/2 the speed of the crankshaft. So the readings are doubled. Mechanical advance is the 2nd phase of the timing. AS rpm increases the amount of mechanical will increase. This is controlled by the tension of the springs inside the dizzy. A lighter spring will let the timing come in sooner than a heavier spring. EX. a light spring may let full advance it at 2800rpm while a heavier spring may be 3700rpm. Mechanical is added to inital so if you had your timing set to 10 dgrees. You would have 42 total.

A race setup would be something like 16-18 inital with16-18 mechanical in by 2500rpm or so fot a total of 32-36 depending on situation. NO VACUUM ADVANCE!!!

Now for the 3rd phase is vacuum advance. Like I mentioned earlier it adds advance to the motor. Say we have 10 inital again and are 16L tab, you know you have 42 total already and 36-40 is ideal for iron headed motors.

Lets say the motor is idling in the driveway at 700 rpm. So right now we have 10 before top dead center firing. AS you go to drive down the road, the throttle is opened and vacuum advance will add timing, for examples sake 17 degrees at 1500 rpm. Now as you increase your speed, the amount of vacuum advance and mechanical will increase and that is added to the starting 10 btdc. Lets say you cruise up to 2200rpm the vacuum and mechanical will increase some more so for ex. 34 btdc. So as you are going down the road the engine is firing at 34 degrees btdc. Lets say you step on it and you are at 3000rpm. Well, we got more rpm so more advance well lets say we are pulling 48 degrees btdc. Now this will or may cause the engine to "ping" denotate. Meaning the air fuel is ignited and the force slams the piston back down as it trying to come up. This causes damage. Can be very severe. Well then continuing, lets say you see a chevy 1500 and mash the pedal to pass him. So, your ar at WOT, so the vacuum advance is no longer an issue. You have you starting 10, plus the 32 at 4000-4500 rpm for a toal of 42 btdc. This is less than the previous 48 is easier on the engine.

The problems arises at part throttle conditions because the vacuum is strong and the engine doesnot need to be fired that soon. For ex. you are at 2300 rpm, you have 10 inital, are pulling 20 degrees from vacuum adavnce, and have 14 from mechical. So that is 44btdc at 2300 ouch!!!! the engine doesn't need to fire that soon and its causes the preignition, ping, etc. If we can run at 4500 rpm with 42 btdc why the hell would we need 44btdc at 2300. We don't, it causes problems.

So, we tweak the igniton to say 6 inital, use a 10L tab, use and adjustable vacuum cannister(the piece to the dizzy). So with this combo we have a very conservative 26 total. But at say 2300 rpm we might have 6 +14+10 for 30 degrees btdc at 2300 which is much better than the previious 44 btdc. Which is less prone to preignition,ping, etc...


I hope this helps a little.

 

wow finally a detailed explanation of something. i've got experience with the mechanical weights on the inside as we had to replace one of the plastic clips that the weights sit on. My dad also got a rebuilt dizzy years ago for his 351w and they just threw some random weights in there from the rebuild factory...she didn't like that. so we've had our share of mechanical weight issues but this is a great explanation of what to do. thanks fordeverpower! now still does anyone know who ROL is that i can get those gaskets from or at least check into them?? thanks

 

the rol site is www.rolmfg.com

you might get them on ebay, summit, jegs, or other outlets, i will look for a part number after i get another beer.

 

i buy my ROL kits from www.partsdinosaur.com Bruce is a great guy to buy from.

 

ford390- I called rolmfg today and they do not have a .033 head gasket for any FE. Their gaskets only compress down to low to mid .040's (can't remember exact number he said). So does anyone know for sure a supplier that has a head gasket with a thickness thicker than .020 but thinner than .038? I wouldn't have a prob using the .020 b/c i know my heads are straight coming back from the machinist but the block has 5,000 miles on it and i could check it but i'm not sure how prone these things are to starting leaks after driving for a while. Not fearful, just don't have the time to be pulling intake and heads after i build this thing and get it back in the truck. Just wanted to pick ya'lls brain on this one a little more and see what ya'll think. thanks