Thread: Cylinder head advice

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I am new to the boards here and need some outside advice on building a 650 HP 468 BBC on pump gas.The pistons are SRP, will rework to 11.5-1 with a 122 CC head. The cam i have is a solid roller .691/.684 .262/.272 @.050 on a 112 LC I am going to run a 250 HP shot of nitrous on this combo too so thats why the 112 LC My biggest problem is picking a set of heads. I have it narrowed down to a set of trick flow 320 rec ports. My engine builder wants to see bigger flow numbers on the exhaust ports to help the motor RPM to where it needs to be. this is also to accomodate the nitrous too. It is a sea of numbers out there, and i am scared to buy a set of heads in fear of going to big, on the same token, i am looking to spin this motor to 7000 RPM. So what is a smart rec port head for a 3500 lb pro street car.

I have run a best of 11.72 @ 115 with a oval port 427 with RPM performer heads and a hydraulic roller cam. The car went 9.92 @ 130 with a 1.39 60 foot with a 250 HP shot. through the mufflers and tail pipes. this was done with all small port stuff, so thats why i am scared to go real big? i am getting all kinds of advice, but nobody can tell me what to expect?

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hmmmm well did a engine for a customer a 462 big block before i got to work on it they went from workover merlins o ports to dart 310 i do not think it did much but the dart were alum so he did get the front weight off the car. but if you engine builder saids that is the way to go you mite want to listen to him if you want big numbers on the ex side was the numbers flowed with a tube on the head and what size headers are you going to run on this car.

Yes the numbers were flowed with a tube, my engine builder explained that too me as well. I have 2" hooker race headers 35" long 3-1/2" collectors. i also run a 3" mandrel bent exhaust with flow master delta force mufflers. I called dart today too, and they said they have a set of 265 race series oval ports that flow 380/294, and made 720 Hp and 600 tq on a 468 with 12-1 compression? mind you those heads are $3500.00 canadian, $1000.00 more than the 320 R series rec ports i want o buy.

i can tell you that i would go to bigger tubes on the headers they are to small . i can get very good deals on dart and live in mich if that helps

Thanks, but after all the research i did and in talking to my engine builder yesterday, i will stick with the trick flow heads.Plus with the .300 raised exhaust port, it will be close getting the headers i have to fit in the car. i also lowered the motor into the frame 1-1/2" for hood clearance, everything barely fits now, a 2-1/8" header would be unreall to install.

Originally Posted by Grumpy 427

Thanks, but after all the research i did and in talking to my engine builder yesterday, i will stick with the trick flow heads.Plus with the .300 raised exhaust port, it will be close getting the headers i have to fit in the car. i also lowered the motor into the frame 1-1/2" for hood clearance, everything barely fits now, a 2-1/8" header would be unreall to install.

no not really i built a set of 2 3/8 for a 75 nova. with big m darts on it. i have done tall deck with hi ports to. if you want to run fast you need to get the ex out .i wound not run any thing smaller than 2 1/8

Hey pat. after some more thought, i bought a set of AFR 305 as cast heads with CNC chambers. I also swapped pistons with my engine builder and now have a compression ratio of 12.3-1. With the cam and a bit of dome smoothing i should be able to run this on pump gas and a bit of octain booster. From what i have read, the AFR heads move a good ammount of air while retaining big bottom end torque. What have you heard about these heads in a BBC 468 combo. You still like the 2-1/8 header for this motor?

not to much on that head. i have not used the AFR .but have heard good thing on there heads. it sounds like a good heads . l think you are going the right way .yes i still like them big tube headers

Right on, I will see when i go to the dyno if i can line up a set of 2-1/8 tube headers just to see what gain they give and where in the rpm range. I have a set of 2" Hooker race hearers now, but i do know a couple guys with big tubes, i just hope they have them off the car when i need them LOLOL

Originally Posted by Grumpy 427

Hey pat. after some more thought, i bought a set of AFR 305 as cast heads with CNC chambers. I also swapped pistons with my engine builder and now have a compression ratio of 12.3-1. With the cam and a bit of dome smoothing i should be able to run this on pump gas and a bit of octain booster. From what i have read, the AFR heads move a good ammount of air while retaining big bottom end torque. What have you heard about these heads in a BBC 468 combo. You still like the 2-1/8 header for this motor?

You are scaring me with that comp. ratio on pump gas and octain booster and then the n20 on top of it.
Even with all the dome prep. and CNC combustion chambers and the cam will bleed off some of the comp ratio.
I.M.O.,I would go all the way to 13.5 to 1 on race gas or go back to your other pistons for pump gas..
I have used the AFR 305's on a lot of 496's pro-street engines and for what you are doing there great.
The exhaust to intake ratio will really help whenever you use the n20.

Well for driving it around, i will use pump gas and octain booster, but for nitrous i will run C-12 race fuel.

Originally Posted by Grumpy 427

Well for driving it around, i will use pump gas and octain booster, but for nitrous i will run C-12 race fuel.

That's what I wanted to hear.

Yeah i have spent time on developing tune ups for nitrous, i have had help from a seasoned veteran. i have a Crane digital box with timing retard in he car, and a very good fuel system to keep up with the nitrous and the motor. It should never go lean??/ i hope. I only run the nitrous at the track as well, better track surface and a safe controlled enviorment.