[footjoy]

I am thinking about building or buying a engine. I am looking for dependability, runs cool and good everyday performance. Just a driver.

326 - 400 What year if it makes a difference.

Thanks

Greg

[gtofreek]

400's are damn good engines and make the best of both worlds IMO. You can lots of power with them, and decent mileage, and can be very dependable. The 400 would be the cheapest bang for the buck, and the cheapest to build. There are not much choices for pistons for the smaller engines, but the 400 has all kinds of stuff avaiable without going custom.

The 326, 350, 389, 400 all have the same 3.750" crank stroke, the only difference is the bore. 3.720", 3.875", 4.062", and 4.120" bores, respectively. So if you were to build one, you might as well build the biggest, and most popular for parts. Plus the 400 engine parameters are great. Big bore, short stroke makes a good combo.

[GRX]

Good question. Had access to any factory displacement I wanted as a base for my total blueprint project. Chose a 400 for the reasons Paul mentioned. Have always liked them for an all around street engine.

[Squidward]

350 or 400.

400 for the reasons Paul gave.

350 because almost nobody wants them, but they can run. They can perform almost as well as a 400 for a street build, as long as your "street" build hp definition doesn't start with a 4. Head gasket and piston choice is slim. But I like the idea of running high compression 400 heads on a 350 to get some good pump gas streetable compression.

Most everyone would say you would be wasting your time with a 326, but there are those who have made them run. Hell... most people say don't waste your time with a 350.

Choice could be impacted by the chassis the motor will go into for motor mount reasons.

If a 400 opportunity comes along for the right price, do that as first choice. But if a nice 350 rolls across your driveway looking for a good home, I wouldn't turn it away.

[steve25]

The 350 can not even be bored up to the size of the 400 come rebuild time and if you get to the point of wanting a big increase in power that will mean ported heads or aftermarket heads and either way even a over bored 350 limits the total air flow gain you could have had with a 400, and stroking a 350 to try for more torque makes 100% no sence!

The 400 blocks made from 1967 thru 74 are the ones to look for and any 400 motor / block that has a no full size balancer and bolt on timing pointer stay away from if you can!
A 389 block is just as good as any 400 block and many if sonic checked can go .090" over to get you up to the 412 CID that a .060" 400 would have been if your really hung up on CID .

The 389 blocks have the intake valve notch in the wrong place for 67 and up heads, but since you will need to control the compression ratio these extra 2 CCs or so will make that easyer and allow you to shoot for a tight deck clearance when rebuilding the motor which helps Octane tolerance !

[mgarblik]

All things considered, a 400 is the best choice. Of all the displacements you listed, more kits and parts are readily available for the 400, Pontiac made a zillion of them, and you get the most HP per dollar from a 400. You didn't mention the car it was going in but if it is heavy, a 455 is still a good choice too. They made allot of them, total cost probably $500-1000 more than a 400 to build, but an almost automatic gain of 40-50 HP and 60-80 Ft. Lbs. of torque, all things being equal. The time worn saying of "no replacement for displacement" still rings true. Good luck with your choice.

[CROCIE JR]

455

[Half-Inch Stud]

Always boils down to HP/ LB, and BSFC. That's why I Build the 455 + 030 or 060.

The parameters are at odds with each other until the heavy car is factored-in.

Yet the 400 may be the most fun on the highway and faster MPHs

[footjoy]

It would be for a 1965 Tempest for just cruising with air conditioning and overdrive.

I don't want to dedicate a life time to get it to run 190 degrees.(been there)
It needs to be able to run on pump gas.

Thanks for the good ideas.

Greg

[ponyakr]

Here you go.

http://lenwilliamsautomachine.com/400_Long_Block.html

Get him to build it with no more than 9:1 CR, and less cam, like maybe an 068 clone, or even a Summit 2800, if you just want to cruise, under 5000 rpm. And go with a GOOD electric choke Q-jet & either stock '72 intake or Performer, and a good HEI, such as a DUI brand.

https://www.summitracing.com/parts/d...w/make/pontiac

Make sure he does not use a 557 block. Any 400 block that came before the 500557 is OK. The '71-early '75 481988 blocks are probably the most common, good, 400 blocks.

I'd want SP forged pistons & 5140 RPM forged rods, minimum, with H-beam rods & light pistons preferable.

If the extra cost is not a consideration, I'd prefer a 455 or 400 block stroker, either 4.00", 4.21", or 4.25" stroke. With this extra low end torque, you have plenty of power, even when running highway gears, like 2.41, 2.56, 2.73, a stock converter, and even the overdrive you mentioned. Hey, with 2.41 gears + overdrive, a 455 wouldn't have to run much above a fast idle at highway speeds.

Alum heads are also a good extra cost option to consider. Alum heads + alum intake will make the engine lighter. Plus, you can run more compression, safely, with pump gas. The D-port E-heads, have the exhaust heat riser holes, like stock heads. So, if you use an intake with the heat crossover, this will provide warming of the air/fuel mixture, intake, & carb, for cold weather driving.


"...I don't want to dedicate a life time to get it to run 190 degrees..."

There are lots of things you can do to make sure your Pontiac engine runs cool. There have been lots of cooling threads, and much good info on the subject. But, you can't expect to just throw it together, with a stock 3 row rad, 4-blade fan, no shroud, and a huge water pump impeller fin to divider plate clearance, and hope it'll run cool. Ain't gonna happen. You gotta do it right. Need the correct parts, and the correct tune.

[Blued and Painted]

The 400 is most common, versatile, and imo the standard for pontiac excitement. But if you run across a buildable 455 first, Get It. Cost about the same to build, plus a but load more torque.

[GP67]

455 with 400 heads. CR 15:1
Use race fuel. Screw domestic pump crap.
I know. I owned one.
That will be my next build again someday with any luck.

["QUICK-SILVER"]

Originally Posted by footjoy

It would be for a 1965 Tempest for just cruising with air conditioning and overdrive.

How much overdrive or how low of a cruise rpm?

A bone stock 71~73 455 will run on about any fuel you put in it. And has plenty of torque right off idle to pull the car at low rpm's. If rpm's aren't that low, similar year 400's would get the job done.

[b-man]

Out of all of the choices the 400 without a doubt.

I had a very mild 400 in a '69 GP, 8.2:1 compression with 6X-4 heads, Summit 2800 cam, stock Q-jet and intake with log exhaust manifolds and a 2-1/2" dual exhaust. the GP had a TH400 and 3.23 open rear as originally equipped.

It was a strong runner, I took a friend for a ride (we both bracket raced 455-powered 12-second cars) and he couldn't believe it was only a 400.

The 400 is a very underrated engine, they're too often overlooked for a 455.

Surprisingly enough, the 400 is supposed to be the 'gas mileage champ' out of all the 3.75" stroke V8s.

[gtofreek]

400's can also be very torquey. Just look at the 400 I just dynoed. Made an average of 487 Ft. Lbs. of torque from 2700-5500 RPM. This is with iron heads and stock iron intake. It made 443 FT. LBS. at 1800 RPM. That will get the job done! Just put the right cam and heads in it.

[hurryinhoosier62]

I ran 400s for years. They're great street engine. 455s and 428s in decent condition are becoming somewhat difficult to find unless you spend a LOT of money.

[92GTA]

A 400 with the 461 stroker kit

[Half-Inch Stud]

Originally Posted by b-man

Out of all of the choices the 400 without a doubt...........
The 400 is a very underrated engine, they're too often overlooked for a 455.

Surprisingly enough, the 400 is supposed to be the 'gas mileage champ' out of all the 3.75" stroke V8s.

OMG, 2.56:1 posi rear and we had over 20 MPG with a 68 400 HO in 70 GTO with dearborn 3- speed.

[steve25]

Wow , really GP67?
You know I should have looked in that 15 to 1 direction years ago as I have some 1200 gallons of VP116 on hand !

[71 T/A]

Originally Posted by GP67

455 with 400 heads. CR 15:1
Use race fuel. Screw domestic pump crap.
I know. I owned one.
That will be my next build again someday with any luck.

More like 12:1, which will still require race gas.