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Big Block chevy heads casting 3946074

31K views 23 replies 13 participants last post by  Scott McMullen 
#1 ·
Hi all need some info on Big block gm heads casting numbers 3946074 aluminum rectangular open chamber heads used on L88.ZL1 engines whats the the pros and cons on these heads was there any problems with the casting was thinking of picking up a set for my drag motor thanks in advance
 
#3 ·
IF you have them, the 074's, and they don't need much work, they can make some power. YES there prone to cracking and are usually welded.

Depending more on application and WHY you would be using these? There are a lot of BETTER heads for the $$$ usually then these for making power. If it was going to be a mild build, street/stripe type of deal, then maybe, but I wouldn't go out and buy these heads unless your doing more of a "restoration" type of build. They usually want good $$$ for them, and needing work. Better off getting a set of Dart 320's or something older/smaller that would be about the same $$$ anyway, and be a better, tougher head.

Now if you HAVE a set, ready to go, and you want power and performance, I think I would try to sell them. YES they WILL make power, but you are better off with a stronger (NEWER) casting.

John
 
#6 ·
I have a set of the #077 "Snowflake" Heads 2.25 In-1.88 Ex Open Chamber-119 c.c.These heads DO MAKE POWER.My motor in the Bantam is just a little ol' 427 & these Heads Work awesome.I agree there are Heads out there for the money that are better & make more power than the old 074 & 077's as mentioned before..Dart 320 etc.It all depends on what you want to do(Power Wise Etc).I must have been one of the lucky ones.I have never had a stud etc "Brake" on me.The only issue I have ever had was I had one tiny little hairline crack on the seat.I guess when it was cut for a larger spring it just touched through.Its funny that this thread came up because I am thinking of selling mine.Of course the Aluminum back then is a totally different material than it is today.Good Luck! :p
 
#8 ·
Hi all thanks for the replys the heads are on a 427 it not an L88 short block was gonna buy the whole motor has 10.5 com camp cams solid cam 580-600 lift 256-266@50 motor was street driven has about 10 hours on it guy did 1 pass when't 10.70 1/4 mile thinking of buying the whole motor
put it in my chassi use it for drag race only. i'm just worried about having problems with the heads should i buy this motor or pass on it ? persons asking $4000
 
#9 ·
Hi all thanks for the replys the heads are on a 427 it not an L88 short block was gonna buy the whole motor has 10.5 com camp cams solid cam 580-600 lift 256-266@50 motor was street driven has about 10 hours on it guy did 1 pass when't 10.70 1/4 mile thinking of buying the whole motor
put it in my chassi use it for drag race only. i'm just worried about having problems with the heads should i buy this motor or pass on it ? persons asking $4000
Sammy lets put it this way...It does not sound like a bad deal $4000 is not a bad price...but you know how it goes.You never know what your getting if you didnt build the motor yourself.Will he pull the pan & let you inspect everything?What Rods,Crank & Pistons are in it?I know you say he said it has about 10 hrs on it.About how old is the Rotating Assembly?There are a lot of questions to ask before you purchase one.Theres always the "Do's & Dont's" when buying a used Bullet.Good Luck!
 
#13 ·
Well... if nothing else if the heads have a nice Date Code ( under the valve cover ) of say anything before 71 you could sell the heads to a restorer for some good coin that would probably pay for a better set of heads. the rods will sustain 7500 rpm , if you want more RPM 7/16 Boron bolt rods or aftermarket stuff will be required, overall sounds like a decent price if it is healthy..
 
#14 ·
4000 dollars sounds a little steep for a two bolt, stock rod, engine. TRW pistons are certainly nothing to celebrate either. They will work, but I don't think I would use them in a track only engine. Unless this guy knocks about 2800 bucks off his price, I think I would pass on this engine. Just my .02!!
 
#15 ·
Sorry if I steal the thread.But I was wondering on what aftermarket heads were derived from the L88/ZL1 heads.

Which ones would be closest to the overall design.......GM performance,Dart,AFR,Trick Flow?

What are the stock port volumes of these heads?
 
#16 ·
was there any problems with the casting
They work fine until you hurt them. I had a valve drop and totally wipe out one chamber, I had a couple of local shops try to weld and re machine to no avail then sent them to brodix and they couldn't do anything either. Everyone said the aluminum was to nasty/dirty and no weld would stick worth a crap. I don't know if the heads I had where just a bad set or all the old aluminum's are like this.
 
#17 ·
Sammy, I don't think I would "jump" at the deal on the motor! Could be a bargain, but could also be junk. Like Bantam said, you just never know.

IF you can get it cheaper, then might be OK to spend a bit and go through it again, and possibly sell the heads. On that note, just being "snowflake" and date code heads don't mean there are worth 1500-2000? Been in that "game" for about 10 years now too. Those $2000.00 heads are date code, FRESH and not modified,repaired at all. New valve, spring, guides, surfaced, the whole deal. Many a seller get the "Barrett-Jackson" on the 074's and think there ALL worth $$$. Hell, I've been offered a bare set that have a gasket match and repaired for $300.00 03-69 dated. And this IS from a restorer, that's why he's dumping them, he had a few sets at the time, along with some Reynolds ZL-1's AL. blocks that also aren't with shit.

Just be cautious when buying used and check it out the best you can. BTW what intake with this motor?
 
#18 ·
As the other guys said, they are good for mild performance. Small roller cams and solid flat tappet stuff are the max as the aluminum is soft and pull tower threads out easily. Stuff with lighter spring pressures. Some of the spring pressures we use today would pull the threads right now. The seats do come loose in them also. They are light though, only weigh 26lbs.
 
#21 ·
This has absolutly nothing to do with this thread (SORRY), but as long as we are on the subject of rare factory big block stuff, I watched a numbers match LS6 454 on our local dyno a couple weeks ago, 505 hp and like 490 something on torque!! The only things that were not 1970 issue were the cam, and distributor. I couldn't believe it made that much power!! It did have a reproduction cam, so the specs were original. Not bad for a 40 year old bone stock engine!!! Sounded pretty fuckin cool too!! Anyone have any idea what this engine might be worth?
 
#23 ·
Depending on the amount of "love" you put in them. But 700hp is NOT out of the question. I have a set of "dated 1970" 074's that will go well north of that on the size motor your asking.

Just pay attention to details and think a bit outside the box in way of longevity
 
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