i just bought a set of brownfield / afr heads....215 cc runners..2.05/ 1.6 valves....56cc combustions chambers......im goign to be putting them on my 355....its basically a 9.5 to one motor with a .555 lift.....will these heads be over kill....and if so what do i need to do to make my motor match with these heads

 

Stroking it to a 383 will help use up that airflow. Even then, thats a lot of head for a 383. Unless it'll be a higher revving 383

 

That is too much head for almost any 350. Unless its a really cammy engine that will need to rev to the moon, with at least 11:1 compression, you'd be MUCH better off with something in the 180-200cc range. It will run alot better at all RPMs and probably make more power too.

 

But since you already bought them run as much compression as you can for the octane you will be using. Look into a custom cam. It can help on the oversize runners.

 

ok if i decide to make it a 383 ...is that just getting new pistons , rods, and a 400 crank.....and what about machining the block?

 

well to make it a true 383 i think it is a .030 overbore and clearancing of the block for the 400 crank but if it doesnt need to be bored you dont have to
then you need to check for rod/cam clearance... the machine shop will need the entire rotating assy. and cam to do the clearancing and should be done before balancing

 

you could just get a rotating assembly for a 383.. the block will need to be clearanced for the larger stroke too.. trust me, its not gonna fit in there as is.. you might have to get a set of small dish pistons so you dont run the compression up toooo high.. 56cc chambers are tiny..

use this to calculate compression ratio

http://www.kb-silvolite.com/calc.php?action=comp


with a similar setup to mines, and those 56cc heads, i get around 11.5:1 compression.. doable with pump gas but pushing the limits.. my motor specs are in my vbgarage.. a 385 but essentially a 383 with a bigger bore

 

+1 on the 383. On a 350 those heads wont work at street RPMs they will do like 3500-8000. Hell im only going with 200cc heads for my 406 (I like torque). A 383 spinning to 7000 will use those heads a little better. If I were you I would just buy a rotating assembly balance it and plop it in (do the measurements of course lol). Finding this part and that part piece by piece is enough to drive you bonkers, you will find a great deal on rods but no pistons for them or vice versa. And make sure you get a good crank and studs! the difference between every 1000 rpm in your engine is DOUBLE the load! 7000 rpm is 4 times 5000 rpm on your engine!

 

well for money reasons if i was to do that ...that would have to be a winter project.....if i were to keep it a 355 but go out and buy a nice set of pistons , rods and a bigger cam how would this do.....i know what these heads are capable of but im really not trying to maximize their performance i just want the car to run in the low 12's high 11's.....i bought the heads cuz its a great deal and i know someday when i build a bigger motor and want to go ten seconds these will be perfect...but for now like i said low 12's high 11's is what im looking for......and when you mean by not run good do you actually mean the car will actually run like **** or that it just wont be able to maximize those heads ( basically put i know its a shitty setup , things dont match up too well , but if this will get me in the low 12's and actually run ok that is fine for me for now

 

I'm going with AFR 210's for my 383 and they are even a little big for my engine but once i get my 415 sbc ready I'm just going to sawp the top end with the AFR's onto it. But those are way too big for a 355.

 

ok i think i found a solution...i am currently co owner of a 406 and just talked the other person into letting me use it.......its a 406..with eagle rods and mahle 11:1 pistons....i believe these heads should work much better on this....but right now i only have a .535 cam...how big would you guys go?

 

Don't worry about the slight difference in lift so much. Think about the duration and LSA. You want to match the heads to the engine size and RPM range you plan on running it in (cam and properly matched compression for the fuel you are using). That being said- those heads will be a good match to a 400 in a street performance RPM range (6500-7000 max). 400s it's tough to go too big with the heads- they want just about as much as you can throw at them. 215 heads on a little 350 get a bit doggy below 3000-3500. In a 400 they'll pull good from about 2500-3000 up. Remember you're trying to feed big block amounts of air through a small block cylinder head.

At a certain point it's not just about flow bench numbers- bigger engines require physically larger ports to prevent restrictions at higher RPMs. Velocity is a good thing up to a point, but with big cubes at elevated RPMs too much velocity starts to choke flow. I believe that point happens when the intake velocity reaches about .5 Mach (half the speed of sound). That's math that's way above my pay grade, but I can tell you from my experience that 200-220cc intake runners on a strong street performance 400 are just about where you want to be.

 

so if i just left the .535 in there but then bought some 1.6 made it a .555 ...that sounds pretty good?

 

DAMON--you seem to definitely knjow what ur talkign about...ill go over this again...the motor is a 406...mahle 11.5:1 pistons..eagle rods...56 cc afr heads ..215 cc runners , 2.05 /1.6......victor jr intake....34-3800 stall ...basically my power band should be between 3-7000.....i have to get a completely new cam now...and plan on going mechanical solid.....does a 557/571 sound pretty good?.......one big problem i do have is that i still have the stock 7.5 rear end with 26 spline axles lol...with a 3.42..