BBC heads question

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BBC heads question

Post by prairiehotrodder »

So i used a set of AFR 335 CNC heads for a number of years on my 555 BBC. They worked good and i think the motor was making about 850 hp according to my math. I took the motor apart to fix a spun bearing this fall and i decided to sell / upgrade some of my parts. I sold the AFR heads for a really good price within 2 hours of advertising them. I was thinking of changing my rotating assembly to make a 572 or 582 if i can sell my old parts but that might not happen. I am content to re-use my old 555 parts if they don't sell. In the mean time I bought a new set of the AFR 385 heads. Now I know full well that everyone will say these heads are to big. I'm ok with that. The plan is to eventually go bigger on the cubic inches but maybe not right now. My question is if anyone has any dyno experience with this ? Is my car going to slow down alot ? What can i expect to happen ? The 555 has 12.9 CR, a tunnel ram with a pair of 750's and a custom solid roller 280 / 288 .760 / .730 112 LSA.
Right now the car runs 9.20's at 142 ish at 3250 pounds.
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Re: BBC heads question

Post by swampbuggy »

How many RPM's have you been turning it ? Mark H.
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Re: BBC heads question

Post by prairiehotrodder »

shift around 7100 - 7200
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Re: BBC heads question

Post by mt-engines »

That cam is in the ballpark, compression is a bit soft. but coupled with a 6500 stall converter should make some steam. Those heads are not waaaay too big like most non engine builders on this site will lead you to believe and try to change your entire combo.

in my opinion, if you are going to up the cubes, do it now. i have used those heads, and they are in the same ballpark as BB3 380s. I dont like the giant 122 cc combustion chambers.

I would use more lift. Howards has a decent cam that 285 295 .810" 112 that works great in that size and compression with similar sized heads
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Re: BBC heads question

Post by prairiehotrodder »

actually i usually use 1.8 rockers on the intake valves which puts me around .800 lift.
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Re: BBC heads question

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prairiehotrodder wrote: Mon Nov 09, 2020 9:24 pm So i used a set of AFR 335 CNC heads for a number of years on my 555 BBC. They worked good and i think the motor was making about 850 hp according to my math. I took the motor apart to fix a spun bearing this fall and i decided to sell / upgrade some of my parts. I sold the AFR heads for a really good price within 2 hours of advertising them. I was thinking of changing my rotating assembly to make a 572 or 582 if i can sell my old parts but that might not happen. I am content to re-use my old 555 parts if they don't sell. In the mean time I bought a new set of the AFR 385 heads. Now I know full well that everyone will say these heads are to big. I'm ok with that. The plan is to eventually go bigger on the cubic inches but maybe not right now. My question is if anyone has any dyno experience with this ? Is my car going to slow down alot ? What can i expect to happen ? The 555 has 12.9 CR, a tunnel ram with a pair of 750's and a custom solid roller 280 / 288 .760 / .730 112 LSA.
Right now the car runs 9.20's at 142 ish at 3250 pounds.
I have a question: Using your math how much HP is 142.2 @ 3600 pounds?
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Re: BBC heads question

Post by Orr89rocz »

vortecpro wrote: Tue Nov 10, 2020 8:33 am
prairiehotrodder wrote: Mon Nov 09, 2020 9:24 pm So i used a set of AFR 335 CNC heads for a number of years on my 555 BBC. They worked good and i think the motor was making about 850 hp according to my math. I took the motor apart to fix a spun bearing this fall and i decided to sell / upgrade some of my parts. I sold the AFR heads for a really good price within 2 hours of advertising them. I was thinking of changing my rotating assembly to make a 572 or 582 if i can sell my old parts but that might not happen. I am content to re-use my old 555 parts if they don't sell. In the mean time I bought a new set of the AFR 385 heads. Now I know full well that everyone will say these heads are to big. I'm ok with that. The plan is to eventually go bigger on the cubic inches but maybe not right now. My question is if anyone has any dyno experience with this ? Is my car going to slow down alot ? What can i expect to happen ? The 555 has 12.9 CR, a tunnel ram with a pair of 750's and a custom solid roller 280 / 288 .760 / .730 112 LSA.
Right now the car runs 9.20's at 142 ish at 3250 pounds.
I have a question: Using your math how much HP is 142.2 @ 3600 pounds?
800+ at 3600. Not 800+ at 3250
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Re: BBC heads question

Post by prairiehotrodder »

my best pass is 9.26 at 144 when the car was 3400 pounds. I use the calculator on the pro-systems website. I feel given the math that my motor is making a legit 850 hp. Obviously its going to fluctuate based on the air and my awesome tuning skills. I lightened the car up since that pass and went 9.24 with a few other variables and different air / traction / 60 foot. We could likely argue my 850 hp claim until the cows come home but my original question is kinda where i'm hoping to learn something.
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Re: BBC heads question

Post by PRH »

Coming at it from a different angle.......

If you had the car still up and running, and did nothing but unbolt the 335 heads and replace them with the 385’s....... I think the car would slow down(poorer ET).

I can easily see where 850hp, STP corrected on the dyno, could end up running 144mph@3400lbs at the track.
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Re: BBC heads question

Post by prairiehotrodder »

thought i would bring this thread back to life since i've made some progress. Last fall i damaged the motor (spun a main bearing). I've since ground the crank (.010rods. 020mains) and put it back together with a little smoothing on the pistons and a different moroso oil pump that has a built on small windage tray. I've also learned how to check the bearing clearance properly thanks to my friend "old school" and i bit the bullet and put on the AFR 385 heads. So basically other than a couple tiny mods (the oil pump and the piston edge beveling on the inner side) this is pretty much a back to back test of the AFR 335 vs the AFR 385 heads. I'm excited to see what happens. Common thought says these heads are way to big for a 12.9 CR 555 and that well may be true. Faster or slower i'll pass on the results and we will all learn something hopefully.
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Re: BBC heads question

Post by mt-engines »

prairiehotrodder wrote: Fri Feb 05, 2021 9:44 pm thought i would bring this thread back to life since i've made some progress. Last fall i damaged the motor (spun a main bearing). I've since ground the crank (.010rods. 020mains) and put it back together with a little smoothing on the pistons and a different moroso oil pump that has a built on small windage tray. I've also learned how to check the bearing clearance properly thanks to my friend "old school" and i bit the bullet and put on the AFR 385 heads. So basically other than a couple tiny mods (the oil pump and the piston edge beveling on the inner side) this is pretty much a back to back test of the AFR 335 vs the AFR 385 heads. I'm excited to see what happens. Common thought says these heads are way to big for a 12.9 CR 555 and that well may be true. Faster or slower i'll pass on the results and we will all learn something hopefully.
Brian

they are not too big... you will make a bunch of power and be happy
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Re: BBC heads question

Post by PRH »

No changes to the combo other than the heads?
No new cam or converter, different gearing?
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Re: BBC heads question

Post by prairiehotrodder »

nope all the same. although i plan to switch to pro gears it will be the same 4.10 ratio.
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Re: BBC heads question

Post by PRH »

Your TR intake may be enough to cover it up, but my prediction is the 60’ times will suffer with the new heads, and the car won’t overcome that deficit by the end of the 1/4.

I’ll def be watching to see just how it actually plays out.
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Re: BBC heads question

Post by prairiehotrodder »

with a 29 x 10 hoosier slick, this car was allready not super consistent on the 60 foot. I think my best is a 1.33. I'm also quite curious to see what happens. Hopefully i don't have any more oil / bearing problems.
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