what,s a safe boost on a mid 90.s 454

In my 79, I have a mid 90,s 454 so something like 7.7 compresion ratio.
Have a new 6-71 left over from a project, It,s about time to put it in use,
Don,t want to do a lot of engine work, most likely just a mild blower cam.
I have the truck running on propane, that,s octane nr of 112
am thinking about 8 psi boost, Or is that verry conservative ?

Remco

I’ll take a stab at this. Running a 671 on a big block isn’t really the thing to do. Yes, it can and is being done, but not recommended. The blower has to spin a lot faster to make the same boost as an 871. Which puts off a lot more heat. The more boost you run and the added heat leads to detonation. So I’m guessing 7 lbs or less to be safe. Not sure if the bottom end is forged or not. I’ve heard of guys running 4lbs, which to me defeats the purpose of put one on. But this is just my opinion, of course. My little small block with 671, forged bottom end, and blower pistons is running 10 lbs and temps are 195 in our 100+ heat here. I drive her everyday and drive her hard. Only issue I’ve had in 12 years is blowing a head gasket in a burnout competition 3 years ago. If I were you, I would sell the blower, add a little money to that and get an 871. You and the engine would be much happier. Hope this makes sense. Sometimes I confuse myself.

I dont know anything about this but, sounded good to me Joe.

I too wanted to boost a low compression 454 for not a lot of money. But I agree with CoggedBelt75 that the 871 is the right choice if you really want to use the blower on the big block.

Devil’s advocate: Why not drop in a cheap low mile small block and put the 671 on that? Sell the big block to recoup some project costs.

But if it was me I’d go for the 871. I’ve just waiting for the right deal to come along lol.

My advice is you want to boost anything, make sure you use the right stuff or you are just throwing your money away. Stock components will hold up at a low boost. But where’s the fun in that. Guaranteed you will not have control of your right foot. So plan once. Spend once.

Remco, what was the project that you mentioned?

@ coggedbelt75 project was / is a build of a old 392 Hemi But that is on a long hold .
so better to put that 6-71 in use, Am in the netherlands where cars with a supercharger are not much seen.
a relative low boost is ok , its a 6000 pound truck , not a Lamborghini ,

Any pictures of what you have?

I would think one of the big questions is the pistons? Cast or Forged and the detonation which is directly tied to the heat. Since you don't see them over there I would stick it on. Back it the day as the saying goes everyone ran the 6 71s and it was good. Now days there are 8s, 10, 12's, 14s would be correct each produces more air than the smaller version.
I would start low still probably will be very cool to drive and make a good difference. I have been in underdriven stuff that makes good power, look at where your starting from 8 to 1 probably a real dog now.