Oh yeah, one more thing that worries me. When I removed the head bolts from bank 1 (the lower head bolts) water just spewed from them. I noticed water in the lower bolt holes of bank 2 also
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Oh yeah, one more thing that worries me. When I removed the head bolts from bank 1 (the lower head bolts) water just spewed from them. I noticed water in the lower bolt holes of bank 2 also
Bolts go into water jackets, so that is normal. thats why you always put sealer on all head bolts on a sbc
462624 1976-1979 350 with 75.5 cc chambers
Unfortunately, the 624 casting are probably the worst of the GM castings for cracking. They are prone to cracking across the exhaust seats and thru to the heat crossover. They’re not good candidates for any decking either.
Mortec says they are from a 75-86 350 or 400, 76cc chamber. They were manufactured with 1.72/1.5, 1.94/1.5 or 2.02/1.6 valves
If they have the 1.72/1.5 or the 2.02/1.6 valves and they are perfect – they may be worth drilling steam holes. If they are the small valves or (as is very likely) show any cracks, I’d start looking for new heads.
If you have any budget, the Vortecs are a good way to go. This means a new intake manifold as well, but will definitely bring the 400 alive. GM Part Number 25534421 ($1100 a set or less on ebay) is a great head, 185cc runners and 66cc chambers. They’ll need steam holes drilled.
Good Luck!
Glenn
We really need to know more information about the block and pistons before you jump and buy different heads. What is the piston crown configuration? Can you post a pic? Is there a part number stamped on the top of the piston? With the piston at TDC, how far is it down in the bore? You can measure this with a set of feeler gauges and a straightedge ruler. What I'm getting at is that you have a fairly short cam in the motor now and with the large chambers of the heads you have now, the static compression ratio works out ok on pump gas. But if you go with smaller chambers, you may exceed the match-up of static compression ratio with the cam timing you have now and you'll be tearing back into the motor to change the cam. Let's try to make this work the first time. Post the info I asked for.
You mentioned going with 305 heads. I can't think of a worse combination than 58cc heads on a 406 with a short cam and unknown squish. Detonation City.
With the short block on a stand, get a buddy to stand in front of the motor and turn the crank with a socket and long bar on the harmonic damper retaining bolt head. This bolt is torqued to 65 ft/lbs, so it will not unwind if you turn the crank backwards easily. Roll the crank around so that the #1 piston (driver's side front) is at approximately top dead center. You will be standing at the side of the block at #1. Stand your ruler up on edge and span across the cylinder bore about a half inch from the edge of the bore. You will place the ruler at either 3 oclock or 9 oclock position. Placing it at noon or 6 oclock will allow the piston to rock on the wrist pin and give you an erroneous reading. Start with 0.025" or so and slide the gauge blades under the ruler and all the way to the cylinder wall. Have your buddy rock the crank back and forth so that the piston is coming up to TDC and back down in the bore just ever so slightly. If the piston doesn't push the ruler off the deck, then use more feeler gauge blades and try again. Maybe go 0.005" at a time until you find how far the piston is down in the hole at TDC. This is called the piston deck height. We must know this dimension before going any further. And don't forget the pic of the piston crown.
Quote:
Originally Posted by glennsexton
I made another post but I guess it evaporated. Anyway, all I know about the heads is that they have been machined and have new valves so there should not be any cracks. I'll measure the valves tomorrow when I drill the holes. Thankx
STOP! Don't do anything else until you have read and understood post #45.Quote:
Originally Posted by Bigbzc
Yup - what Tech said - I was a bit premature in a head recommendation. It was my mistake to "assume" stock pistons and deck height. We might still get to the same place (i.e., Vortec heads) but it is really important to get the details of the PDH and squish.
I don't plan on using different heads as I am out of money for this project. I will drill the 350 heads I have tomorrow and hope to have them in by the weekend depending on the weather
make sure you use the 400 gaskets
Yes sir! lol Gottem loaded in the truck to take to work tomorrow. I was hoping to see "paths" on the head or gasket from where the water leaking but there were none. I guess this could be because they were not on there very long. I do see the point that it CAN leak because there is not much of a seal in the steam holes of the gasketQuote:
Originally Posted by cffisher
after looking at the gaskets carefully I noticed that there were no traces of water from the steam holes. What I did discover is that the cylinder seal of my gaskets are overlapping the coolant ports that are just beneath the spark plugs. So, now what?
http://i706.photobucket.com/albums/w...c/IMAG0006.jpg
http://i706.photobucket.com/albums/w...c/IMAG0005.jpg
http://i706.photobucket.com/albums/w...c/IMAG0004.jpg
I think I figured it out. Measured the diameter of the bore on the gaskets and it measures 4.180" This block has NOT been bored and it's diameter is still 4.125" Looks like they gave me the wrong gaskets. Let me know if I am correct
No--gaskets are correct---the heads are wrong
Can you take a couple close ups of the head and post them? Is either a bad picture or something nasty happened in the machine shop.
I was thinking that they shaved to much off the heads. The pics I posted are not bad, what yo see is what it is. See the notch in the coolant port in the 1st pic? That is where the biggest leak is but ports on other cylinders over lap the compression ring on the gasket and leak into the cylinder.Quote:
Originally Posted by glennsexton
Ok I had my personal guru (who just happens to be a Master Machinist and Master tech) look at the heads and he said they have been angle milled and too much. That they would make great boat anchors. He also looked at my 305 heads and told me that he would use those since I am looking to make more torque. They cam off a 86 transam and are the H.O. heads with 68cc chambers and 1.84" valves. Casting number is 14014416. Looks like this will be the rout I am going to try
There are two schools of thought in regard to using 305 heads on a 400 – one says “with a ton of work, they can be used”. The other school says, “don’t use them..”
I’m in the second school – The steam holes are the least of your problems. The heads you have (14014416) are 58cc (not 68cc) and that’s a big factor. With your all stock engine and a .040” head gasket you’ll be pushing close to 12:1 compression ratio with these heads. Couple that with the small valves and relatively short runners (165cc/59cc) and you will end up with a dog that will only run on premium fuel - anything over 10:1 starts to be touchy with pump gas.
The 400 was designed for torque, but it still needs to breathe. Remember that an engine is really just a big ol’ air pump and the 400 was designed to move a lot more air through its stock heads than even HO 305 heads can supply.
Your “stock” bore 400 is 4.125” and a 305 is 3.766” – do the math and you’ll have .359” of cast iron hanging over the cylinder area. You’ll play hob trying to get 400 gaskets to seal so you’d have to use 305 gaskets and they do not have provisions for steam holes.
Probably not what you want to hear – but I think your frustration will be compounded if you bolt those heads on your 400.
Check out this thread from several years back:
http://www.clubhotrod.com/chevy-smal...s-400-sbc.html
We really do want to help you here –go back to Tech’s post #45 and get the measurements let us help you determine what a good head would be for your engine.
Regards,
Glenn
Bigbzc------
When angle milling cylinder heads was a more or less common thing to do to raise compression so as not to need a large piston dome sticking up blocking the flame front---on a sbc they welded up those slots in the heads and then redrilled a hole to line up with the one in the block.
Now , shortly , since you seem to have a blockage of anything any of us have posted, I will be deleting my posts later tonight, and I would highly recommend that others do the same thing>
Ok, in regards to what you have all told me, we did a little more research and found that you are correct. A race engine builder told me that I would have to use racing fuel if I use those heads because of the high compression. Sorry that I have been stubborn about this. I just am over my budget and really can't afford new heads. I will get those measurements Tech wants tonight
I think all of you are doing a great thing trying to help this guy out. There's a lot to learn and that's all he's trying to do.
I agree he needs the proper heads for the job. He's learning and so am I.
Thanks. It's nice to see someone help.
Well…. It’s what we all want to do – help others. Sometimes it’s hard because we all tend to have our own ideas about what is the “best way” to do something. I know I do – however; when it comes to engine building, I listen up to Jerry, Pat, Tech and some others here as they’re a storehouse of knowledge brought about by a lot of years of hands-on experience. I’ve built my share, but I’m not a machinist and I want to keep learning until the day they lay me to rest.
Ask me how I know about steam holes and 400 SBC? Been down that road because I thought, “those tiny little holes can’t possibly be that important…” Well, let me tell you – they are! The machinist I was working with was gracious and gave me a “Heat and the Siamese Cylinder Block 101” lesson after hours in his shop and then he and I found a solid set of cores and he showed me the correct way to drill holes. You don’t soon forget those experiences and hopefully, when people come to CHR and have questions they’ll realize there is a lot of smart men (and brilliant women too - Barb!) who are passionate about what they know. Listen up, process the responses and make a decision. We’ll always support someone who wants to learn. Know-it-alls, eh –not so much.
Ok, the squish is .041" THe piston clearance is greater than .030" my largest filer gauge is .030 and it slides freely. these are also dished pistons
In case you didn't know, you can stack feeler gauge blades one on top of the other to make any thickness you want. How did you arrive at 0.041 squish? Squish is the piston deck height plus the gasket thickness.
Thought it was just the thickness of the gasket. Deck height is .036 so that makes squish .077Quote:
Originally Posted by techinspector1
Piston clearance????/how did you measure that???I know you said feeler guage but how?????
Jerry, you must have a lot on your mind today because I know that sometime in the past 50 years of hot rodding, you've checked piston deck height with feeler gauges and a steel rule. I explained to this OP how to do it in post #45 and he is reporting back, saying that he has a squish dimension of 0.077" (0.036" piston deck height and 0.041" compressed gasket thickness).Quote:
Originally Posted by jerry clayton
Do you understand that 0.077" is pretty much unacceptable and that it needs to be between 0.035" and 0.045"?Quote:
Originally Posted by Bigbzc
I'll try to measure it again. It is in the truck so it makes it very hard to measure. However, the thickness of my gasket after being torqued down (compressed) is .041" which according to your specs isn't giving me much to work with and I know there is more than .004 deck hight. Maybe we are misunderstanding each other somewhere?Quote:
Originally Posted by techinspector1
OK Tech
I reread it---I was taking it that he checked piston to wall like above the ring land--I've had people do that before not understanding that the pistons are much smaller up there than the skirts.
Have a good week end
Jerry
Perhaps. Let me go through it for you. When you assemble a motor, you want a flat part of the piston crown to come up against the underside of the cylinder head with just enough clearance to squeeze out the fuel/air mixture from that area and "jet" it across the chamber just as the plug is firing. This creates turbulence in the chamber and homogenizes the mixture to prevent rich and lean pockets where the mixture would burn inconsistently. Tests have shown that this tight "squish" dimension (0.035" to 0.045" including piston deck height and compressed gasket thickness) will allow the motor to operate without detonation on lesser quality fuels than a motor with a wider squish or no squish at all, as in the case of the '72 Ford D2VE cylinder heads. Ford had to drop the static compression ratio down into the 7's to prevent detonation on that motor. Needless to say, they only used that head for one year. The following year, they cast up the D3VE heads, using +/-95cc chambers and a squish pad. The clearance is just enough to prevent a piston to head collision at high engine speeds. You are setting the clearance cold with the motor at rest, but at speed, the crank flexes a little, the rod stretches a little and the piston compression height gets a little taller from the heat of combustion. David Vizard has done exhaustive experiments with the SBC and reports that he experienced contact between the piston and head at around 0.026" squish.Quote:
Originally Posted by Bigbzc
The best piston configuration you can use is a flat-top with valve reliefs cut into the crown. Next best, if you need to lower SCR, is to use a D-cup piston that has a generous squish pad on the piston opposite the chamber side. Either of these designs will make the best squish.
Look closely at this piston crown, the one at the top where it starts off "For budget or stock-style rebuilds". You can see that there is insufficient material on the crown to mate up with the underside of the head. The piston is cut into a "dished" configuration with no squish pad. I would not use this piston on a demolition derby car, much less a daily driver.
Sealed Power Cast Pistons - SummitRacing.com
Here's another example of a piston with no squish pad....
Sealed Power Z536NP - Sealed Power Cast Pistons - Overview - SummitRacing.com
Here's an example of a piston with a D-cup. See the nice squish pad on the left of the piston in the photo?
Keith Black/KB Pistons KB138-030 - Keith Black KB Performance Pistons - Overview - SummitRacing.com
And you don't have to spend a lot of money to get pistons that will work. Here's a flat-top for a 350 that has the proper 1.560" compression height and also a generous squish pad for under 100 bucks for the set ot 8. That is a deal!
http://www.summitracing.com/parts/SUM-17350-30/
Now, here's the way it works. The block deck height on a SBC is nominally 9.025" from the centerline of the main bearing bore to the decks where the heads bolt on. When choosing parts, you try to put together the tallest stack you can that will fit into that space. Let's use a 350 to keep it simple. The stroke is 3.480", so the crank radius is half of that, or 1.740". The rod is 5.703" center to center and the piston has a compression distance (centerline of the wrist pin to the flat crown of the piston) of 1.560". Added together, we find a "stack" dimension of 9.003. Fitting this stack into a virgin block where the decks have never been cut produces a piston deck height dimension of 0.022". If we know the decks of the block and the decks of the heads are good and flat, we can use a 0.016" compressed thickness shim head gasket and reach a squish dimension of 0.038" (0.022"+ 0.016"). You can't use these shim gaskets with aluminum heads though, so you must cut the block decks to reduce the block deck height so you can use a thicker gasket to prevent brinelling the aluminum.
So, in summation, you could use a 0.022" piston deck height with a 0.016" gasket or you could use a 10105117 GM composition gasket that compresses to 0.028" together with a piston deck height of 0.010" or you could use a 0.039" gasket with a zero piston deck height (you have to cut the block decks 0.022" in this case).
Well, as I have said over and over, that the bottom end including the pistons is stock and that is the way I plan to leave it. This means that the pistons are dished, just the way they come from the factory. Now your telling me that this will not work which is why I'm getting confused on what you are asking of me. I do not plan on racing this engine and am not seeking 500 hp out of it. At most, it will be used to tow my rock crawler.
it will work fine with the right heads find a set that are not screwed all up drill them for steam holes . bolt them on run it use a good RV cam .as for the stock re build i used cast pistons and deck them . i trim the deck to get better squish and the stock deck can be off and a bad finsh. i done many cast piston engine s for stock to very mild use .i seen one thing i will add stop using them phucking 3m wheels on flat parts engine deck intake heads less you want some thing not flat when done them small wheels remove metal. 80 grit long boad stick it paper on a long board works better if your not milling
Excellent post explaining squish and the relationships between the pieces, Tech. I really enjoy reading and learning more about these things from your experience base, and you're a good writer.
The one thing that jumped out at me is the gasket thickness - it seems that you could pick up ten to fifteen thousandths by using a thinner gasket, getting you down into the .055 to .060 range. Pat, you mentioned a long board and some 80 grit. Would it be possible to keep things flat and take off another .010 to .015 with elbow grease? Too much risk of getting it crooked? Just wondering after reading both yours and Tech's posts. May not be worth the risk for a basic stock rebuild where the decision has been made that the lower end is not being touched (no new pistons).
Very Interesting post humm!!!
I agree Tech. This is very valuable info, but it just doesn't seem so for this build. I have another project after this one that I will use this teaching on because it WILL have flat top pistons (I already have them) and a pretty large cam that I have also. It will be a 350 using my 305 heads and will go in my daily driven S10. In this thread I needed to now why I was getting coolant in the cylinders of my 400sbc which I have figured out and I now know that I need another set of heads that will workQuote:
Originally Posted by rspears
Here's a thought of an idea, (please bare with me on this), What if I did put the 305 heads on the 400, achieved the high compression, and run it on E85 fuel? I know that I would have to at least everything rubber in the fuel system, but I also know that E85 loves high compression and that the alcohol would help keep the cylinder cool. (just a thought to keep from having to buy new heads that I can't afford)
By the way, my carb is a Quadra-junk. I know they make carbs for this such as the Quickflow but was wondering if this setup will work if I can find a rebuild kit to allow E85 to work in the "junk"
no you will never get 008 or .015 off a deck with 80 grit paper your arms will fall off before that will happen. i leave a sleeve up about .003 up and flat file it to the old deck if not milling the deck that the only time i file a deck. as for head gasket cometic 027 with steam holes c5877-027Quote:
Originally Posted by rspears
I think I remember researching this for another member here and found that you could run up to 15.0:1 on E85 if you built the clearances correctly.Quote:
Originally Posted by Bigbzc