Misunderstood Mopar tech 400, Thermoquad etc.

[DeltaV]

...but there are verifiable reasons for a sbc 400 to be "second fiddled" that don't apply to a Mopar 400 or 360.

1- no 4 barrel version ever offered. Not true of the Mopar 400 and 360.
2- oddball heads that don't interchange. The Mopar 400 does have different heads, but they are no worse than 383 heads and do interchange.

I'm NOT a chevy scholar, but those are the two that I know.

I am a "knuckle dragger" when it comes to Chevy, but was the sbc 400 really a 400? I ask because my coworker back in the day had a 1972 Chevelle SS 396, but it was actually a "402".

 

[YY1]

The way I've understood it-

If you ordered a "400" in a 1972 truck- you got a 402 big block.

If you ordered a 400 in a 1972 car- you got a 400 small block.

 

[BearDodge67]

I am a "knuckle dragger" when it comes to Chevy, but was the sbc 400 really a 400? I ask because my coworker back in the day had a 1972 Chevelle SS 396, but it was actually a "402".

Yes it was..SBC 400 came with a bigger bore but shorter rod than the 350. Like a Mopar 400, it had the biggest bore of that engine family (4.125 vs 4.0 for a 350).. the only reason GM kept calling the BB 402 a 396 in 70 was for marketing reasons because it was so popular, but they did eventually market it as 402 as my friends 71 Chevelle SS had it on the air cleaner. The change was to help offset the lower HP ratings. (He now travels the country authenticating SS's being sold).

 

[33 IMP]

I am a "knuckle dragger" when it comes to Chevy, but was the sbc 400 really a 400? I ask because my coworker back in the day had a 1972 Chevelle SS 396, but it was actually a "402".

Yep, the 400 sbc was 400. Used a longer stroke crank, short 400 ONLY rods, and completely different b/s than the 396/402. The 402 was just a factory +.030 396. It WAS labeled a 400 on trucks, but the 396 mystique kept that designation for a couple years on camaro and chevelle.

 

[33 IMP]

The way I've understood it-

If you ordered a "400" in a 1972 truck- you got a 402 big block.

If you ordered a 400 in a 1972 car- you got a 400 small block.

Yep.

 

[33 IMP]

Yes it was..SBC 400 came with a bigger bore but shorter stroke than the 350. Like a Mopar 400, it had the biggest bore of that engine family (4.125 vs 4.0 for a 350).. the only reason GM kept calling the BB 402 a 396 in 70 was for marketing reasons because it was so popular, but they did eventually market it as 402 as my friends 71 Chevelle SS had it on the air cleaner. The change was to help offset the lower HP ratings. (He now travels the country authenticating SS's being sold).

Nope. 400 had a longer stroke and bigger bore than a 350. But some 400s were redone for racing (rpm) purposes with 327 or 350 cranks. (Steel cranks. 400s were cast, using spacer bearings, or just spacers).
The longer stroke 400 crank in a 350 block gets 383-388 inches.

 

[33 IMP]

Yes it was..SBC 400 came with a bigger bore but shorter stroke than the 350. Like a Mopar 400, it had the biggest bore of that engine family (4.125 vs 4.0 for a 350).. the only reason GM kept calling the BB 402 a 396 in 70 was for marketing reasons because it was so popular, but they did eventually market it as 402 as my friends 71 Chevelle SS had it on the air cleaner. The change was to help offset the lower HP ratings. (He now travels the country authenticating SS's being sold).

Agree, other than the 400 crank stroke.

 

[RemCharger]

Nope. 400 had a longer stroke and bigger bore than a 350. But some 400s were redone for racing (rpm) purposes with 327 or 350 cranks. (Steel cranks. 400s were cast, using spacer bearings, or just spacers).
The longer stroke 400 crank in a 350 block gets 383-388 inches.

The 400 crank was a 3.750 ?

 

[33 IMP]

The 400 crank was a 3.750 ?

Yep
.030 over 400 block with 327 crank? 353"
.030 over 400 block with 350 crank? 377".

 

[BearDodge67]

Nope. 400 had a longer stroke and bigger bore than a 350. But some 400s were redone for racing (rpm) purposes with 327 or 350 cranks. (Steel cranks. 400s were cast, using spacer bearings, or just spacers).
The longer stroke 400 crank in a 350 block gets 383-388 inches.

Yup.. my mistake, I put stroke instead of rod. I fixed it. Thanks for pointing it out for me.

 

[DanielSlocum]

YA i know about the sbc but you all are losing me here because chivvys aint my thing.

 

[Thunderdan]

...but there are verifiable reasons for a sbc 400 to be "second fiddled" that don't apply to a Mopar 400 or 360.

1- no 4 barrel version ever offered. Not true of the Mopar 400 and 360.
2- oddball heads that don't interchange. The Mopar 400 does have different heads, but they are no worse than 383 heads and do interchange.

I'm NOT a chevy scholar, but those are the two that I know.

While not initially offered with a 4 barrel, once the 400 SBC was introduced in the pickups by the mid-70's it used the q-jet like the 350's.

 

[kfbrueske]

My Uncle had a ‘73 400 Roadrunner in the early 80s…it was pretty much stock but man that car was a beast. No badging, interesting vinyl top. It must have been gone over with the golden screwdriver as I’ve owned a lot of cars over the years…up near the top. I don’t recall him losing a street race. RIP Uncle Jim.

 

[YY1]

Hmmm-

That actually looks like it could have "Satellite" badges on the quarter panel.

That's a normal "canopy" vinyl top.

The grill is not a Roadrunner grill, unless it's been painted and not masked like an RR.

That looks like a 1974 hood- no cowl vent.

Even of it is a Satellite, it still could have a 400 4 barrel.

 

[Randy Wilson]

Yes, awhile back the 400's were "discovered" and are recognized now to be a great building block (pun intended) for an excellent engine.

I have a 383 Road Runner. I took out the original, untouched numbers matching 383 to protect it and replaced it with a stroked 400 displacing 500 cubic inches, roller cam, . Back in the car, it still looks (mostly) like a stock 383 but it has torque galore. Awesome motor!

View attachment 1922381

HawkRod, is there any kind of valve train noise after you switched to the hydraulic roller set up?

 

[33 IMP]

HawkRod, is there any kind of valve train noise after you switched to the hydraulic roller set up?

I am NOT answering for Hawkrod, but....
I've definitely heard of flat tappet hydraulics with aggressive grinds making noise, but I haven't heard complaints of that nature from hydraulic rollers.
I would think the rollers would mitigate noise, even with a fairly aggressive ramp.
But what do I know. All my roller cams are solids.

 

[Virg464]

I'm running a hyd roller in my motor, 408, 10.5:1 CP, Comp Cam XR292HR-10, .549 Int / .544 Ext, 106 Center Line, 110 Lobe Sep. No valve train noise.

 

[JC Boatguy]

I am NOT answering for Hawkrod, but....
I've definitely heard of flat tappet hydraulics with aggressive grinds making noise, but I haven't heard complaints of that nature from hydraulic rollers.
I would think the rollers would mitigate noise, even with a fairly aggressive ramp.
But what do I know. All my roller cams are solids.

I switched to solids on my flat tappet 383, I'll probably never ever go back to hyd. Almost no noise. My buddies cant even tell I'm running solids. They are lighter and easier for the spring to control, and contrary to popular belief, don't need constant adjustment.

 

[HawkRod]

HawkRod, is there any kind of valve train noise after you switched to the hydraulic roller set up?

No, really nothing to speak of. My car does sound "aggressive" though!