Looking for some input i own a 92 z28 with a lb9 305 ... i hate the 305 in it and have recently found a 400 4 bolt block like new for 400$...its got all machine work done and is like new..my question is is it worth puttin in my camaro after all the 400 is the bastard of small blocks due to the fact thta i hear most small block parts will not work with it...so is it worth gettin the 400 and buyin aftermarket parts or just goin with the 350? Or is there any way some what inexpensive to still use the 400 block...and yes my car is TPI...thanks for all the help in advance...





Mike
Light'em up

 

Wanna run that one by me again? What won't fit? (hint - it'll all fit).
Don't ask a question then state a fact that isn't true. A lot of people seem to be asking about 400's, if they should use, etc, then continue by saying "because I know the 400 has cooling issues", or something along those lines. Well if you KNOW that, then why are you asking about the 400 block, since you seem to know so much about it??

err, cough, sorry, that wasn't directed at you, so much as the many people who make statements like that.

Anyway, try a search, this question gets asked a lot. All your parts will transwer over, but a stock 305 TPI setup chokes the crap out of a 400 block. (like driving diesel trucks?)
So you'd want an aftermarket injection setup like a HSR or something, or a cheap carb setup. Everything else will bolt over.
Side note - the 4 bolt main 400's were made when GM wasn't doing a great job at making the 400's. When they made them with 2 bolt mains they also added more metal to the main webbing. So the 4 bolt ones aren't condusive to racing, ie, extended high RPM usage. As long as you're powerband isn't planned to be 3500-7000RPM you should be ok though.

 

ditto that for the 400 4 bolt; no good...

A 2 bolt 400 is a great place to start. If you have to have more then you can buy splayed four bolt main caps to install at the machine shop.

You really shouldn't use the 305 heads on the 400, either. If you use a set of 350 TPI heads with the steam holes drilled in them you will be fine.

You also do need a different intake. Yours will work but you will choke the engine. The HSR is good, the GM ram jet intake is good, the accell is okay, all are available second hand (ebay) now so if you are patient you can get one for less than new.

 

Well, there is some truth to the "400's are different" thing. Different main bearing size, different rod length, different bore, heads had steam holes, flexplate/flywheel & damper have a counterweight - all things different than 350's, 305's, 327's. The intake manifold and waterpump are the same, though. Starter too, I guess. And exhaust manifolds. Maybe even the dipstick (but different than 3rd gen dipsticks).

4 bolt main blocks are weaker because the holes for the outer bolts reduce the web material in a critical spot were there already isn't much material - not because they cast them with less web material. 4-bolt main 350's have the same issue, except the main bearing size being smaller gives the web more meat.

I would agree, though, that a 400 TPI would be a poor idea.

 

unless you might be good at fabrication. I think it would be neat if you used the stock style tpi and made say 550 rwhp. would take alot though. I wish I had a tig welder.

 

400 chevy motors are awesome especially with a 4 bolt main. The more main the more power. Anyways, 400 chevy's are really good otors to start off with when building power. I would find a set of matching 400 heads for it though because stock 305 heads just don't seem to cut it when you want to make power. Chevy high performance calls them smog restrictors. My brother has set of ported chevy 400 heads on his 350 and they really gave the motor some grunt. Definetly use the 400 because there are a lot of parts easily accesible for it. Tpi would make it a poor motor. I would just go out and find a used holley to sit on top. That would really help the whole package.

Good luck

 

I don't see any reason you can't do this in stages.....
Has this block been magnafluxed? If not, don't buy it until it has. If it checks out ok, then your priority is building a good short block. I have run several 4 bolt 400's with no problem. Use main studs on the main caps and the block is good for 450 horsepower. Scat sells a very reasonable cast steel crank for less than $200. Even a good standard stocker cut to .010 would work. Use 5.7" rods from any 350. If your on a budget, use the "O" or "X" condition rods. These will have an X or O cast into the cap. Have them reconditioned with ARP rod bolts and let the machine shop know they are for a 400. Ask them to machine the bolt for clearance. There are tons of varieties of pistons for this rod....even more than the stock 5.565" rods!! You'll need a sizable dish to keep compression in check. I would choose the best piston you can afford. I always use deck plugs and drill a good size hole. Deck plugs stiffen up the deck and keep it from cracking.
TPI 350 heads are cheap and a decent start. Don't foget to steam hole them. Choose a cam for EFI applications. Keep it reasonable. You can always change it when you can afford more intake. There are a few good websites on how to home port your TPI intake. This will help for a while but you'll need to go aftermarket on the base and runners eventually...not necessary right away though. Get your self a set of about 26 lb. injectors, an adjustable pressure regulator and at least a 350 TPI chip....better if you got a custom and you will have to get a custom eventually to extract the most power.
Headers, good exhaust are mandatory. If your beginning to see that the plan is almost exactly the same as for a 350 swap, that's the point. If you were going to a hot 350 then the drill is exactly the same. This is because TPI was designed for the 305 and not even for the 350. My plan gets you up and running with good torque. Then buy your bolt ons as you can afford them.

 

That's a fine build for a 400, but it doesn't address the fundamental problem - the TPI itself. I chokes a 305, imagine what it does when you increase the displacement by a third. Can you make TPI work on a 400? Of course, but it is going to cost you some serious change.

Stock 400 heads are garbage. You'd be better off working over the 305 TPI heads. And, the # of main bolts has nothing to do with how much power you make.

cityspud117, "somewhat inexpensive" is a pretty subjective. $4000 would be "somewhat inexpensive" to some people - is it for you?

 

305 heads will work fine if you port them well enough. If you stay with these heads, you may as well stick with the TPI. You can do alot of work to the stock TPI unit to get what you want out of it, at minimum you should port the snot out of the base and plenum, it would probably be better to siamese it. On an engine of this size it's a good plan to kill some low end and move the power band up. Really it comes to what you're wanting to do with this engine. In my mind there are really 2 ways to go when putting something like this together, work the crap out of the stock parts, or convert to carb. There's always the more expensive ways to go like stealth ram, LT1 intake conversion, etc. but to me those are more exotic and not the most direct route to the ultimate goal. BTW a 400 block under your worked 305 heads even with a stock TPI will be KILLER to drive, but just so you know your tires will hate you and as mentioned before the engine won't want to rev very high. A siamesed base and decent cam should feed the engine up to 5000rpm or so and that should agree well with the 4 bolt 400.

 

Point well taken, five7. What I was trying to convey was if he went my route, he wouldn't have to take the $4000 hit right away. By porting what he has, it would make the combination fun until he had the money to upgrade to something that would be more compatible.

http://members.tripod.com/~Proformula/porting.html

http://sethirdgen.org/TPIbase.htm

Port your plenum and your base. Start saving for runners. Pick up a good used set in the classified section of this website. There is not a week that goes by that there isn't a set for sale. Then start saving for a base...better heads, etc. If you port your plenum, it's good for high performance applications. I like the suggestion to stay with the 305 heads but you will need about a 30cc dish like a KB 126 piston.

Also, five7, I didn't mean to imply that the four bolt mains would make 450 horsepower....just that the block could handle up to 450 horsepower.

 

Funny thing is, 2-bolts will take more. If you start with a 2-bolt, and have splayed main caps installed, that's your best combo. But, by that time, you might as well be considering an aftermarket block, and then you're certainly beyond the "somewhat inexpensive" realm.

The factory didn't make 4-bolts mains to take more power. They made them to prevent cap walk, which is hard on bearings and cranks. It is more of a problem with heavy loads, but for whatever reason they put them in their "performance" engines like Vettes and 4-bbl 350's prior to the 3rd gen era. They even put them in 305's in vans (only heard of them north of the border, though).

Back to the originator's situation - Go ahead and put it in, remember you're going to need the weighted damper and flexplate; weighted flexplates are typically 168 tooth, so you need that kind of starter, which sits out farther from the center of the engine, often interfering with 3rd gen headers. And, don't expect barn burner performance - although it will probably be better than the 305 was.

And, you're going to have to do some PROM tuning, because speed density doesn't take kindly to having its assumptions changed.

 

My advice on the 168 tooth starter is just to buy a dual pattern mini starter from the get go. Thats what I did and I've never regreted it. My 350 came with the weighted 168 tooth flywheel. I have Hedman Long tubes and they fit like a charm with my generic mini starter *purchased from eBay 3 or 4 years ago*.

 

I'll concur with the ministarter w/168-tooth part, but just want to clear up something about the "weighted flywheel" part - 350's don't use a "weighted" flywheel in this context. The one-piece rear main seal flexplates/flywheels have a weight on them, but it's not the same thing as a 400 flexplate/flywheel with a weight on it.

The 400 weight is for balancing, the one-piece RMS weight is to make up for the counterweight that 2-piece RMS cranks had built into them outside the RMS.

It's confusing, I know, but (or "so") we need to be clear what we're talking about.

 

I never knew that and appreciate the information.