Those heads are considered stock replacement heads. The cam is probably not a good match with those heads, even with porting. What will your compression ratio be?

 

sbc 408 build

i know they were stock replacements. but i was told if i did some work to them they would be a good set of street heads.. an comp-cams suggested the cam.it's a 11.5.1 motor. i would like to get a set of afr heads in the near future.

 

If its 11.5:1 you'll need to run e85 or racing fuel, around 100 octane. I'd change the cam and lower the compression, depending on how well the heads were done you could end up with 500hp.

 

i know they were stock replacements. but i was told if i did some work to them they would be a good set of street heads.. an comp-cams suggested the cam.it's a 11.5.1 motor. i would like to get a set of afr heads in the near future.

What pistons are you using? Dish, flat, Dome? AFR 227 heads are nice. The only thing you may have to do is drill steam holes.

 

With that much compression with the short 5.565 rod which puts the rod to stroke ratio at a horrible 1.48:1 is asking for it. To get it to keep from detonating itself to death in short order as mentioned you`ll need racing fuel.
If your using the stock 400 crank I would either get it balanced or get a scat cast steel crank. We used to run a 400 in mud racing and the power they can make is very impressive, but we found out by using the stock crank without it being balanced pounds the main journals so bad it knocks them out of round. The number 1 main cap on our block is so far out if you install a main bearing it just falls out. I also think the cam choice is not a good one, that cam is massive and it`s likely the vacuum will be so low vacuum related accessories won`t work. When your working with a 400 with a stock bottom end you have to go by it`s rules, the short rods don`t like revs and neither does the crank. That cam`s power band stretches to 7000 RPM and the stock bottom end doesn`t need to go over 5500, especially with the short rods. If your car has a free flowing exhaust system with headers you don`t need a split duration cam, a single pattern with around .236 duration@.050 is about as high as I`d go. 400`s can swallow big cams, but the cam we ran in our 400 for the last 2 mud races was near the size cam you have and the power brakes didn`t work anymore. Now if you look at the cam you have and the heads you`ll see a rather nice mismatch. The heads as you know are stock replacement, 400`s can breathe very deeply and for the cam to make any power it`s got to have heads that can handle the job. With your current combo if you plan to drive it on the street your not going to like it. What I`ve learned in my time is, techies at comp cams, summit racing, crane cams, most of them don`t have a clue. The only company I delt with who had the best tech support ever and I didn`t have to wait 30 minutes to talk to was Isky cams. The guy I spoke to had to stop in the middle of installing a test cam to talk to me which made it even better as it told me he had hands on experience. Just friendly warning, if you plan on street driving it, you`ll be driving a car that has the manners of a rodeo bull that`s a ticking time bomb.

 

sbc 408 build

thanks hotrodders for the advise. wish i would have found this site before i started building.... i will look at that cam cause i,m not looking for power additives. just old school power. an to answer your question the pistons are [Icon forged flat tops] an the rods are Eagle H-Beam's. an that's about what i was looking for was 500hp\430tq or in that ball park.

 

AFR227 64CC with 2.1" int. and 1.6" exh is the ticket you need to get 500HP.
You should get around 11.2 compression.

 

sbc 400 build

should i look at the AFR227 race ready heads or the AFR227 competition package.