421 Tri-power Redline Question

I've got a 1966 421 YJ Tri-power engine in my 64 GTO. Could somebody tell me what the redline is for this engine. I tried, but Google ain't my friend on this topic.



Thanks in advance.

 

I wouldn't spin it much faster than 5500, maybe 5800 rpm. Depends on what kind of shape it's in. It might make 6k a few times, but it's not making power up that high anyway and it's not worth hurting it IMO.

My stock 421/428's liked to shift @ 5100-5300 as power really drops off fast beyond that.

 

find a 66 full-size Poncho factory tach for that engine....on Ebray...pontiac forum...they'll usually mention the redline...or you can "enlarge" the photo.

dj

 

If it's like the tach in my '64, the redline is adjustable.

 

Not more 5200-5300 rpm's!
Pontiacs are not high rev motors.

 

I think mine is all green lined to 6000, but Ive never pushed mine over 4800

 

Ditto!!!!!!!!!!!!!

 

421's had the Armasteel crank and good rods. The HO was rated at 370hp(353hp)* @5200 rpm. They can safely go higher than that if they are in good shape. I would put the redline at 5500, but there is no need to spin them faster.

*depending on head casting

EDIT, found some literature that states max shift point of 5900 rpm for the HO. But again, there is no need to go that high.

 

YJ is the designation for the 353 HP 421 w/automatic HP rated at 5200 rpm's after that your just pushing your luck!

 

There's not too many of these 421's or 428 motors around like the belly button small block chevys... I'd keep the revs below 5000 that way it will live longer.. I'd hate to see one of those get destroyed..

 

I used to shift my tri power GTO at no more than 5200. Why spend lots of cash on a rebuild when you can avoid it.

 

Pontiacs are torque motors, not rpm motors.

 

Unless your 421 happens to be a rare and
valuable 'Super-Duty' version.....two words
for you to think about when you're winding it
up - "CAST RODS". With standard, 'non-SD"
cast rods' Pontiacs shouldn't be spun past
5500. And if you're running a stock Pontiac
cam - even one of the "good" 'O68' cams
- in a 421, you probably won't make any
more power spinning it beyond 5000-5200
rpm anyway. Low and mid-range torque
(massive gobs of it!) is your friend with this
motor...not high rpm horsepower.

Mart3406
======================

 

I always shifted my '64 389 tri power at 5500-5800 and I never had any problems with it. Two of my friends had '65 GTOs with tri power 389s and they shifted at
about 7000 but they were running open headers and I think they were running
310 degree Isky cams. Back in those days, the factory rated the horsepower of
muscle cars at about 5000 rpms in order to show a lower horsepower rating than
what the engine actually made; that was done to help the owners get lower insurance ratings and to place their cars in a lower class at the drag strips.