What is this 454HO rated at stock

I have an 1990 454HO engine bought straight from buick. It even came with the GM aluminum performance intake.
Casting is 10069286 which mortec says is 90-91...4-bolt, Mark IV, Short deck.
Few things I read about that say 330HP in the Mark vehicles BUT it was always with different heads.
When it was sold as the HO it came with then 14096188 heads. Mortec says.
70-71...rect...OPEN...454 service replacement, also used on later Mark IV LS-6, LS-7 and 454 HO crate motors, 116cc chamber

Obviously in this case the heads are the 454 HO crate versions and not the ones cast in 70-71. One message board had a post listing them as 425HP which i don't know if it was true or just some guy trying to sell them for more money?

I can not find what this combination was rated at. Any help is appreciated.

Also was the 90 454 a fuller roller block?
Thanks!

Pretty damn sure the 425HP is true,we have that motor in our 25' Checkmate and thats what its rated as.

Im pretty sure the 90 block has a roller setup.

There were no Mark IV engines in 1991. 91 was the start of the new GenV blocks. GM didn't produce production roller blocks until 96.

There are a lot of 454HO engines available through the years including the most modern Mark VI block. All are rated around 425 hp.

Thanks guys! So the 425hp/500tq is right. I can live with that since someone swapped in a bigger bump stick some aftermarket rockers and some long tubes. Should be a good little setup.
Right now it's fouling plugs and poping through the exhaust when started.

850DP with 78/80 jets.
Maybe it's not pulling enough vacum and the power valves are opening up at idle.
Seems to be ok when you get on it some though.

What kinda intake is on it?

Backfiring out the exhaust sounds like a timing issue.

It's got the aluminum GM intake they came with. Don't know if thats any good performance wise.

when you start it the plugs are fouled some of the gas gets down in the exhaust before it pop's.
Once you hold the rev's at like 2000 for a minute or two it stops it starts hitting on all 8 then it idles better. It's blew out the guts of the mufflers from doing this since they are right after the headers.

I have the carb all apart and I really don't see anything odd. Pretty stock 850DP with one accel pump being upgraded to 50cc.
Have a second 750DP I am going to take the plate out of to give it 4 corner idle. The PV's aren't labeled normal
They are stamped and numbers spaced around the PV.
L 6 5 6 or L 9 5 9

Problem is as you rotate it, the 6's could be 9's depending on which side you look at. As you rotate it, it's 9 below the L on the left and 6 above the 5 on the right side.
Do I assume it's a 6.5in vac PV?

It's got the aluminum GM intake they came with. Don't know if thats any good performance wise.

when you start it the plugs are fouled some of the gas gets down in the exhaust before it pop's.
Once you hold the rev's at like 2000 for a minute or two it stops it starts hitting on all 8 then it idles better. It's blew out the guts of the mufflers from doing this since they are right after the headers.

I have the carb all apart and I really don't see anything odd. Pretty stock 850DP with one accel pump being upgraded to 50cc.
Have a second 750DP I am going to take the plate out of to give it 4 corner idle. The PV's aren't labeled normal
They are stamped and numbers spaced around the PV.
L 6 5 6 or L 9 5 9

Problem is as you rotate it, the 6's could be 9's depending on which side you look at. As you rotate it, it's 9 below the L on the left and 6 above the 5 on the right side.
Do I assume it's a 6.5in vac PV?

yup 6.5 PV

if you have raw gas fouling the plugs and while running higher than idle that clears up - sounds like you have over full float bowls or fuel is leaking into the intake
A zillion times I've had a crapy idle/fouled plugs from the primary needle/seat not closing properly.

You should check eng. vac. since cam was changed PV may be too high 5.5 should cure the flooding, plus if it ever backfired the PV is gone anyway. I see floats set too high a lot of the time, most guys raise float till fuel spills out sight hole, (wrong), you should shake eng. lightly till fuel sloshes out, thats plenty high and will stop a lot of idle and driveabilty problems. Danny Mc