I found a guy in my town that says he has a "Chevy" 1970-1976 400 Small Block with the crank and rods. It's never been bored and the block is perfect.

What do you guys know about this engine, I thought only Pontiac made 400 small blocks? Is this one just as good? What can I stroke it too? Can you go TPI on it like the Pontiac 400's? How much is it worth?? This engine would be for a 1991 GTA with all the goodies like supercharger, 1000cfm TPI system, etc

Thanks.

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[This message has been edited by 92GTA (edited June 21, 2001).]

 

Chevy definitely made a 400. There are 2 block castings; the early one is 4-bolt, clearly identifiable from all other SBC engines by having 3 freeze plugs down the side of it; the later one is 2-bolt and looks externally like any other SBC. If you are looking at a naked block, both kinds have steam holes between the cylinders. The harmonic balancer and flywheel / flex plate are "unbalanced" since there isn't enough room between the pistons and the crank for enough counterweight to internally balance it.

The Pontiac 400 is not a "small block", nor is it a "big block". All Pontiac motors have the same bore spacing, so the terms "small" and "big" have no meaning when applied to a Pontiac.

It is at least as "good" as a Pontiac motor, better in some ways. It weighs quite a bit less for one thing; SBC parts fit it for another; and it will install in our chassis without much grief at all.

It has a 4.125" bore and 3.75" stroke with 5.565" rods. Compare to a 350 at 4.00" bore and 3.48" stroke with 5.7" rods.

It can be stroked. I built one for a friend not too long ago with a 4" stroke instead of the stock 3.75"; and 6" rods instead of the stock 5.565". In a .030" over block, this gave a 434.

You can put a TPI on it, unlike a Pontiac block which you cannot put a TPI on. (I can't imagine what you'd have to go through to adapt a TPI to a Pontiac motor.) Personally I would not waste a perfectly good motor doing that to it, since the stock TPI chokes a 305, and totally strangles a 350. I've never heard of a 1000 CFM TPI, can't begin to even guess how you'd get there; people struggle mightily to get anywhere close to the same flow out of a TPI that you get from a 750CFM carb. Some of the TPI "replacements" such as SuperRam and MiniRam would actually work on a 400, especially the MiniRam, unlike a stock TPI. (For a good primer on how inadequate TPI is for high horsepower, look how hard it is to get one to run with a LT1; or, to look at it a different way, how little you have to do to a LT1 or LS1 to keep it ahead of any TPI motor.) Best choice for a hot 400 would be a single-plane intake fitted with injectors, and a 4-barrel throttle body. Look at the Accel Pro Ram. That's what we put on the 434 I mentioned above. Of course, none of that is street legal out here, if that matters to you.

The heads the factory put on the 400 are pure and absolute crap, usually 882s. Keep in mind that to have the same torque vs. RPM curve as a 350, the 400 would have to have heads, cam, intake, & exhaust that flow 15% more than a 350; the 434 I mentioned would need flow #s 25% greater than a 350 for equivalent RPM characteristcs. That's alot of flow. Since we all know that heads are everything as far as making horsepower (HP = flow, pure and simple), no kind of stock heads are adequate, unless opened up as far as possible.

The 400 I have in my 83 has a Comp XR282HR cam currently, 186 heads with race valves and some port work, etc. It runs OK, for mostly just a bunch of junkyard stuff. It hasn't lost to a Mustang on the street yet, not even to sprayed ones, in the 10 years I've had this motor in various configurations in that car.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Dude, sweet! This sounds like it may be the block I've been looking for, I'll just stick with the 4" crank and do a 427. Thanks man...

 

Is it a 2 or 4 bolt block? If it is a 4 bolt, I'd stay away from it. The 2 extra holes in the block remove some of the internal webbing, which greatly reduces the overall strength of the block. I haven't had any personal experience with this, but I have read it all over when I was pondering the idea of a 406 in my RS, which is in the works now...

 

So I should only get it if it's a 2 bolt main?

 

Hey man, Great motor, in my oinion! I had a 1973 400 small block built mldly in my 1971 Chevelle. It ra awesome Get the numbers off the block (located right behind where the distributor goes) then go to this site www.mortec.com
it will tell you what year block, and any info you might need like (4 bolt, or 2 bolt etc)
Take care
Mike

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Smokin 1989 GTA- Bone stock except for exhaust. (no catalytic-stainless pipe into Flowmaster 2 chamber).

 

You want to get a 2-bolt block then have it splayed for 4-bolt mains. This is what I was advised to do when I was looking into a 406 for my car.

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89 RS 350 TBI auto Hooker SC/LT headers Open element 3in K&N CVT protorque mini-starter

Daily driver 91 RS auto LO3 63k

 

Some other concerns......

The 400 block has siamesed cylinder bores. (no space between cylinder wall casting for water to go around....) This sometimes leads to cooling problems, but, with a good cooling system, should not be a real problem.

You CAN use 350 heads on this block, but, you have to drill the steam riser holes in them. ANY part that will bolt onto a 350, will also work on the 400. (gotta love GM)

I have a two bolt block out in the garage that is currently being reworked to replace the aging 350 in my Formula, cant wait to test drive that one........

 

oh no alex what are u thinking??????????????????? your GTA would be sweet with that setup

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Tony

 

Ok, I called the guy and it is a 2 bolt thank god BUT the guy will only sell it with the crank and rods and he wants $300!!! I've seen it and it is in like perfect condition and it totally factory still.

Is 300 too much??

 

$300 is entirely reasonable. Snag it. Try to get the balancer and flex plate.

I was accustomed to pay $250 in Memphis where they are still fairly plentiful.

AFAIK there are no cooling problems with 400s. That is some kind of urban legend that probably got started by the circle track guys so that everybody else wouldn't want them. I have had a number of them over the years and had no problems any different from any other motor, in fact alot less than some others. In my 83 I am running the stock single electric fan; a stock replacement plastic & aluminum radiator for some later IROC; stock fan switch; 180° thermostat; stock hood with hood blanket; A/C; and a Stewart Stage 2 water pump (the stock one worked fine as far as temp went, I was just tired of replacing them). Living in 100°/100% RH Memohis, with the A/C on continuously for 6 months out of the year, I had no trouble with it.

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"So many Mustangs, so little time..."
ICON Motorsports

 

Thanks, I found a local shop that will give me $75 for the crank so that will bring it down to only $225

 

one problem with a 400 block is that you are going to need a speical harminic balancer and flywhell/flexplate. Like it was mentioned befor they coulden't get enough weight on the crank so you need a balencer and flywhell/flexplate (by the way i don't think chevy even made a flywhell for a 400 -I havent seen one yet)

 

400 flywheels are out there. The 3/4 ton and larger Chevy and GMC trucks (up to about 1980) that had 400s were available with 4-speeds (not the performance 4 speeds).
jms

 

Theres nothing wrong with building a 4 bolt block 400. I wouldnt pass on one umless it was for an all out race motor. For a hot street car like most on this board they work fine. Ive had both 2 and 4 bolt blocks,and never had any problems with the 4 bolts. Even if they are weaker in the main webbing. Oh well.. more 4bolt blocks for me.

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Black 90 IROC, L98, A4, 323 gear. SuperRamed 406 in the works!

 

Hey RB, just wanted to say you shouldn't totally rely on the three freeze plug theory. I bought a 72 400 engine a long time ago with three freeze plugs in the side, and it was a two bolt block. As far as the overheating myth goes, the version I've always heard is that if you bore a 400 .060 or more, they can experience overheating. There again, I've also heard as long as you have a good cooling system, it's not an issue.

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89RS w/350 TPI; 69RS/SS w/450 HP 350/Muncie 4-Speed "Too weird to live, too rare to die."

[This message has been edited by Pat Hall (edited June 24, 2001).]

 

I had to have steam holes, a Becool radiator and 2800cfm of electric fans to keep mine below 200. It runs 190 with one fan on when sitting at a light in 90 degree temps. The other fan will kick on at about 205.