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I'm back... 400 SBC Build (I have questions!)

DokWatson

DokWatson

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I gave the Blazer I was building back to yellowk20 and am going a different direction. He's granted me access to all the stuff we have laying around to build a DD/tow rig and light wheeling rig.

I traded some guns to yellowk20 for a 1979 400 SBC. It ran when pulled so we were planning on cleaning it up, checking bearing wear, and letting her rip. I tore it down today and found the heads are mismatched according to a couple websites... I'm not 100% sure though. Maybe one of you can help me out there as well.

http://www.73-87.com/chevy_ids/sbheads.htm
According to the casting number this one is for a 350SBC and its 1.72/1.50


This one is also for a 350SBC and its 1.94/1.50


There are some vortec heads in the shop, and I'm wondering what I have to do to run them, other than getting a vortec intake. I've read the compression ratio would be too high for pump gas. I'm really not looking to dump a whole lot of money into, just something nice to drive with some torque.
 
Too bad you are not a little closer, I have a pair of heads, and I have a good 400 long block.:dunno:
DokWatson said:
I gave the Blazer I was building back to yellowk20 and am going a different direction. He's granted me access to all the stuff we have laying around to build a DD/tow rig and light wheeling rig.

I traded some guns to yellowk20 for a 400 SBC. It ran when pulled so we were planning on cleaning it up, checking bearing wear, and letting her rip. I tore it down today and found the heads are mismatched according to a couple websites... I'm not 100% sure though. Maybe one of you can help me out there as well.

http://www.73-87.com/chevy_ids/sbheads.htm
According to the casting number this one is for a 350SBC and its 1.72/1.50


This one is also for a 350SBC and its 1.94/1.50


There are some vortec heads in the shop, and I'm wondering what I have to do to run them, other than getting a vortec intake. I've read the compression ratio would be too high for pump gas. I'm really not looking to dump a whole lot of money into, just something nice to drive with some torque.
Click to expand...
 
Double posting my bad... but now I am confused! This website says the specs are the same for both heads. http://outintheshop.com/faq/casting/heads.html

However, it does say they are 350 heads... I thought I read somewhere 400 heads are different. I guess if it ran, it ran. Help me out!
 
On a side note, was your old truck in the stuck section of Petersen's this month?
 
The difference is 350 heads need the steam holes drilled.

Theres a trick to it but I cant remember.

Id still probably go vortec if the option was there, and yes its only the intake thats different.
 
400 heads have a steam port drilled between cylinders 3&5 and 4&6 (due to "Siamese bore"). You'll need to make sure that whatever heads you use have these steam ports drilled out (as well as the correct head gaskets with steam hole).
 
79rustyk10 said:
The difference is 350 heads need the steam holes drilled.

Theres a trick to it but I cant remember.

Id still probably go vortec if the option was there, and yes its only the intake thats different.
Click to expand...

I've got a lot to learn about gas engines :doah: Thats what I am thinking too. I don't trust myself to do it though, shouldn't cost too much to get them done at the machine shop.

I'm still wondering about compression ratio... I really don't want to spend 300$ on pistons if I can avoid it. So far I've read a stock 400 with vortec heads directly swapped comes out to 11:1 and won't even run on the higher octane pump gas :dunno: Someone school me on compression ratio.

If I have to spend money just to get it running, I'd rather that money go towards rebuilding it and destroking it to a 377 street machine and scratch the wheeler.
 
if your pullin heads then pull them and see if valves are same size.

if same smack it back and run it. as lots of remans use diffrent castings but redo valves to match sizes.

if not find a set or do vortec swap.

and trick is 1 new head gasket for 400 sbc and few bolts to center it on the head. mark the holes to drill and remove.

then drill the hole's out and watch the depth you go. otherwise bolt on and run.
 
I wouldn't run anything above 10.5:1 with iron heads on pump gas.

The stock 400 has some decent torque, why mess with it too much for a light wheeler, DD, and tow rig? Keep low compression, clean it up and run it as is...
 
manchildau65 said:
I wouldn't run anything above 10.5:1 with iron heads on pump gas.

The stock 400 has some decent torque, why mess with it too much for a light wheeler, DD, and tow rig? Keep low compression, clean it up and run it as is...
Click to expand...

Its a DD, wheeler is a separate rig... and I only have 350 heads if the ones on it aren't going to work. I have vortec heads, and 'regular' 350 heads, along with whats on the engine... which may not be right to begin with.

sweetk30 said:
if your pullin heads then pull them and see if valves are same size.
Click to expand...

How do I go about doing that? I need it broken down barney style, lol. (Measuring valves, I can pull the heads.)
 
Should be good then, don't get too hung up on drilling steam ports, as sweetk30 said, use head gasket as template and drill... If you do a quick web search it'll tell you the size, depth and angle.
 
manchildau65 said:
Should be good then, don't get too hung up on drilling steam ports, as sweetk30 said, use head gasket as template and drill... If you do a quick web search it'll tell you the size, depth and angle.
Click to expand...

Still doesn't solve the compression ratio issue. Anyone else have input on that?
 
if you dont use vortec heads then no change in ratio basicly.

and 350/400 all used large cc heads for lower compression.

and as i said just drill the holes even if its on 350 heads.

as to measuring the valves its easy with a tape measure tool. :doah:
 
sweetk30 said:
if you dont use vortec heads then no change in ratio basicly.

and 350/400 all used large cc heads for lower compression.

and as i said just drill the holes even if its on 350 heads.

as to measuring the valves its easy with a tape measure tool. :doah:
Click to expand...

Got it, thats what I figured :thumb:
 
Pulled the rear main bearing and a rod bearing, everything looked surprisingly good. Still need to pull the timing chain cover, waited till I could immobilize the crank to do it. Get that done tonight. Going to re-seal the rear main and run it.



We are going to run the vortec heads, and maybe a slightly hotter cam. I found that the engine has the biggest factory dished pistons available at the time (No valve reliefs, 18cc I think) Will run fine on pump gas, Checks out on paper... I got 9.8:1.

http://www.gtsparkplugs.com/CompRatioCalc.html
 
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do your self a huge favor get the felpro 1 peice gasket and install it since motor is out and upside down for fast easy install.

and its reusable and has anti crush sleaves built in to it also.
 
I ran the block number when i pulled it. I could've dug deeper had Gus said something. If you decide to scratch the vortecs I can find you a matched set of 1.94s. But now the BIG question.... What trucks is it going into?
 
plyr2k said:
I ran the block number when i pulled it. I could've dug deeper had Gus said something. If you decide to scratch the vortecs I can find you a matched set of 1.94s. But now the BIG question.... What trucks is it going into?
Click to expand...

Its getting the vortec heads, and I don't know what truck its going into yet.
 
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