I have a fellow on here trying to work out a deal on a set of B&M 420 mega blowers. He says hes not sure if his intakes are for a tall deck or short deck. The measurement in the picture is what he has. all my short deck motors are the same 6.250.
My question is if his manifolds are 6.250 are they short deck? I would assume (which we don't do is to assume) the tall deck would be 1/2" wider would it not?


Holley could not give me the answer. I have a part # as well. The #8000130 is on the B&M manifold...Googled everything I could to solve this problem with no conclusion. Anybody have the answer? If you have a tall deck block or manifold could you please take this measurement?

You have 9.8 short deck number in you pic.
10.2 is a tall deck.

I'm aware that a tall deck is 10.2 that's not the question, the question is the manifold this guy has measures 6.250 across like the picture. Is there any possibility that it could be a tall deck manifold which I cant use.
I know that a short deck manifold is 6.250 across at the bottom. Is a tall deck wider or does he have the correct (short deck) manifolds for my engine.

take a short deck intake and add .375" to the port sides.that will tell you if he has for an intake.

I just measured my tall deck which is out in the garage and it measures 6 3/4 across at the measurement you show in the pic. Hopefully that helps.

6 3/4 for a tall deck casting numbers 8000425 and 8000450 underneath. 6 1/4 for short deck casting 8000425 only. Just measured both b&m manifolds i have. You can take it to the bank. Seems as if b&m had one mold and they would machine off the surface down to make one and another taking off a set of numbers in the process. If you put them side by side you would understand what i mean.

Also, i just checked and i dont see 8000130 anywhere on them. Maybe that pn is for oval port or sbc or maybe for 250 blowers? Feel free to pm me your numbers and i can send you any pics you might need of them

The 250 and 420 blowers use the same intake manifold,if you could post a pic of intake it’s easy to tell a tall deck manifold,the flange part that goes against the heads is very thick,all my tall deck intake the flange that goes against the heads is about 3/4 of an inch thick.Unfortuneatly my tall deck blower manifold is on my boat,hope that helps

That is all the info I need right there boys!!!!!
This forum is awesome, you guys are fantastic! Thank you for the info.
I was pretty sure they were short deck Manifolds, and I also had a sneaky suspicion that they were oval port as well. (surprised that Holley didn't know by the part # though)
If I make this purchase I know I'm going to have to hog the manifold intake ports to fit large square port heads. I always port match my manifolds anyway.