will 400cui stock heads fit on a 350 cui block and will they be an improvement against L98 stock cast iron heads which are fitted on my 350 cui now.
My L98 is carb converted.
I will be getting these heads for next to nothing.
Worth it or not???:lala:

 

They will be either 882 or 624 castings in all likelihood...

They are among the worst possible heads you could put on any motor. DO NOT pay any money for them beyond the current value of scrap iron (around $.05 per pound, or roughly $5 per set of heads, minus the cost of hauling them to the scrap yard). In fact, if it appears unavoidable that someone is going to force you to accept delivery of them, pay him not to give them to you. If he sneaks up in the middle of the night and leaves them on your property anyway, have them melted down as soon as possible, to erase this disgrace from the collective memory of automotive enthusiasts.

They will be a massive step backwards. You'll be taking off some of the better heads and putting on some of the absolute worst.

Catch me sometime when I'm in a bad mood and I'll tell you what those heads are really like.

 

Listen to RB he really knows his ****!!

 

The L-98 heads are better than any of the old 76cc heads that came on 400's.
You would loose compression and power.

Your heads have lots of performance potential
with larger valves and porting. If you want better performance and need to use a factory head then your L-98 heads are the ones to use. casting number ends in 083.

 

I'd still try and find out what casting numbers they are. You might be lucky in the past someone may have swaped the heads in the past.
If they are the original heads of a 400 there's a good chance they are cracked.

 

I too have a set of these 400 heads on hand.. but in my case yhje question is wether the 400 heads are any better than the standard lg4 ones?

 

On a 305? Absolutely not.

On a 350? Absolutely not.

On a 400? Well, you're going to have to control compression ratio one way or another, but if you do that, then the 305 heads are still better.

 

I looked at the set I pulled off a 400 a while back. They actually have 1.88 intake valves. They wouldent even be good for a blown setup. Trash them and move on. The heads are the main reason stock 400's dont make any power.

 

I was thinking of swapping in the 400 shortblock, but wondered if I'm to keep the 400 heads or put in my lg4 ones. Both suck I guess, just wanted to know whick sucked the least. Guess compression would be up at least with lg4 ones, right?

Think I read that lg4 heads have 54 something cc combustion chambers..

 

The factory made three different compression ratios for the 400, let alone the aftermarket. You'll need to see what pistons your short block has.
400's tend to run a little warmer than other small blocks, that might shorten the life of your light weight casting lg4 heads.

 

400's tend to run warmer than other small blocks?

FALSE....

With a properly funcitioning cooling system, and a properly built engine, the 400 runs NO Warmer than a 305...or a V-6 for that matter.

For YEARS I heard how 400's run hot, warmer etc...

One thing is that alot of bonehead "mechanics" replaced cylinder heads on the 400's and did NOT drill the required steam holes that the 400 needs to keep cool. Unlike other small blocks, the 400 has siamesed bores, so there are no coolant passages between the cylinders...this is why GM used "steam holes" drilled into the block and correspondingly the cylinder heads.


The other problems come when someone replaces a weak, high mile 305 or V-6, with a built 350,383, 400 and doesn't touch the factory cooling system, which is probably as old as the car, and in need of maintenance in the first place.


My last 400 based motor in a 3rd gen was a 408 / T5 combo in a '85 Trans Am. I converted the car to dual fans before the 400 swap...with a stock alum radiator, and a decent water pump, and a 180 thermostat, that car never ran over 190, even with the AC pumping in 90+ degree weather.

 

Notice how the myth about 400s running hot is always brought up by people who don't have one. Typical personality trait exhibited by humans, to pretend to be an expert on something they have no experience with. I must confess, for as long as I've lived among them, I have hardly begun to understand that species.

 

Well, I did have a problem with my 400 running hot once. When the lower radiator hose burst and dumped all the coolant.

Was driving on I-805 at the time. When we exited the freeway, noticed various vapors coming up out of the hood. Cut off the burst portion of the hose, hooked it back up, let it cool down while we ate lunch, filled it back up with water, went back to work.

A couple of years later, I gave the car to my brother. He took the engine apart and discovered 7 of 8 top piston rings broken. He replaced them, put in new bearings, had the valves cleaned up, put it back together.

Oh, the engine had about 200k miles on it when the hose broke. No cracks in the block or heads. Stock bore.

Those 400's are so unreliable...

 

you guys gotta realize alot of power can be made with 882s and 641. you just have to do it right. I agree that they will not really flow well above 4000. if pick out the right cam for low end power, and about a 600 cfm carb, they make an assload of low end power, the top end is weaker, with out a doubt, but they can be made to run descent, as long as the shifting is done before 4500. they work damn good in that situation....

 

If you were trying to bait me it worked! Just for he record I have owned two 400's. both were mildly modified. Yes they did have steam holes in the heads and I even drilled the steam holes in a set of 186 fulies when I ran them. In my experiance with at the time what I considered an adequate cooling system, both motors ran about 10 degrees warmer at idle over what I had with a 350. These were in a tighter engine bays than third gens have.
I also have a friend who had a FC Holden with a 400 in it, when he canged to a 350 he noticed it idled a little cooler than previously.
So while I appreciate there are many variables that can affect idle temperature I was just stating my experiance.
I've also owned and raced mild to wild 350's,383's and now I'm down to a 305. The one thing I will always remeber about the 400's was the instantaneous low down torque they had.

 

Oh no my 400's running hot! Actaully I do notice when you install them in other vehicals with a insufficent radiators they do run warmer but not hot. Last one I worked on was a 77 4x4, the factory radiator was toast so we replaced it with a smaller more avalible 350 radiator which held about a gallon less coolant. It did run warmer on a 108* day but it wasent hot hot its going to blow.

Useful tech cooling info, 4 OEM radiators were avalible for trucks 454 & SB400 shared the same radiator.

 

Anyone know of some shops building and selling honestly priced and built 400 shortblocks?

Seems to be hard to find one where I'm at, at least a built one.

 

from what i hear 400 only had a short production line and are some what hard to find.

 

Just found some at http://www.coasthigh.com/assembly_index.html
They sell 406 shortblock's assemled and blueprinted for $2799

Would be nice to find some other to compare it to though.

 

i thought you where talking about finding one at a junkyard.

 

Well, I'm considering both actually, but the guy's at the yards consider their 400 block's to be gold, so it would actually be cheaper to buy a complete shortblock, and not have to risk getting a block with progressed core shift.

Only 400 block I found they wanted $1080 for it, and then THey wouldn't even tell e me if it where 2 or 4 bolt, if it had been rebuilt or not. They hadn't looked into it, and I had to buy it unseen also. Not that great a deal.

 

Another piece of info I found on 400 blocks is the 2 bolt 400 blocks are stronger than the 4 bolt block (2 bolt has more webbing). Best case with the 400 is to get the 2 bolt and have it splayed.

 

Don't buy just a 400 block or engine.

Get the local trader / recycler / classified whatever...

Look for 72-80 Impala's, GM trucks, Van's, Station wagon's etc

Last 400 I bought was running well w/ 120k on it. Cost me $400 and it came attached to a 1975 Kingswood "woody" estate wagon. Sold the Turbo 400 for $100, And sold the rest of the car for scrap for $100.

 

Problem is, where I'm at, a running 70'ties stationwagon in nice shape would go for a minimum of $5000

But a good tip for all the others. I'm going to sweep all of scandinavias wrecking yards this summer looking for one.