Need help with head choice on a 496 BBC...details within
I am building a 496 as we speak...going into a 71 chevelle...Its going to be a strret/strip based car, but more so 85% high perf. street warrior and 15% track time here and there during spring and summer months...I know there will be some debate on some of my choices on different components due to personal experiences or use. I am open to advice and guidance, but I really want most of the info/guidance I recieve to be on cylinder head choice mainly.
I will list some of the components I will be using in the build that will help with your advice.
Cam 242/248 .566 on 112 LSA - Hydraulic Roller
Flat Top Pistons
Comp Cams hydraulic roller vertical link bar lifters
1.7 Ultra Gold Roller Rockers
Rectangle Intake ports
Round Exhaust Ports
Edelbrock Air Gap Dual Plane Intake
Hooker Super Comp Headers 2" Tube/3.5" Collectors
One of the questions I had what on what kind of chamber I should run, Heart, semi open, open???
Each of these heads run a different chamber type...Other than a few cc different on the intake runner and exhaust ports and Im sure maybe some quality and flow number differences they have alot of the same included parts. This is where I need the most help in choosing the right heads for my build.
If you need more info on engine parts I will be using let me know and Ill list more components...
The heads I couldnt get comparision chart for refererene to work so you may have to go to each link and compare from there...(Let me know what you think)
Place your choice and reason why in reply....thanks in advance for all help!
World Merlin -- Dart Pro 1 -- Edelbrock Vic Jr. -- Edelbrock RPM
The combustion chamber will control your compression so you should decide which one you need through calculations. If that merlin is iron I wouldn't do that because of the 80 extra pounds. I don't run 496's but on my 468's I run oval ports, so if you are gonna run rectangular ports in that heavy car with that smallish cam I would get the one with the smallest intake port. If it was mine I would probably get an oval port about 300cc on the intake and which ever chamber got me the compression I wanted. I'm SURE most people will tell you to get a much bigger head judging from what I see on here most of the time. Good luck!
With that small of a lift camshaft and such a wide lsa you need to pick the head that gives you the most CR and the best overall low-mid lift flow. AS JWstevens said an oval port would be better. BBC's need CR at least around 10.5:1 and a net quench area around .032-.037 inch to get the best HP and TQ. that calls for the piston to be at zero deck to about .005 above deck. Then the chamber size needs to be around 110cc. IMO opinion for the same money the dart pro 1 heads cost the afr 305cc cnc chamber heads flow better at low-mid lift (300cfm@ .400" lift and 344cfm@ .500" ) than all the ones you indicated. All the other BBC heads you listed flow at low-mid lift like SBC heads at low-mid lift. The afr heads are $100 cheaper than the dart pro 1. But I like AFR heads, they also have thick 3/4 inch thick decks so you can mill to get desired CR. The best bang for the buck IMO. But who the hell am i anyways. Hope this helps. Keep us posted
If it were my engine i would lean towards an oval port. The retangle ports may make a better peak horsepower number, but at the cost of lowend torque in the part of the RPM curve you will be using most. AFR makes 2 oval port heads, a 265cc and a 295cc. You may wanna take a look at the 295s. I think they would give you the best of both worlds on your 496.
Hands down, these are the best for street/strip performance. We run them on my wifes 489, with 10.5 to 1, 4000k stall, th400 and 3.90 gears runs mid 10's. We run a bigger cam than you have listed. I would think that your choice of cam is too small for that big of an engine.
GM aluminium oval port, the ones used on 502 crate motors. GM performance parts has a number listed. I used em on a 427 years ago. It was more a higher rpm motor. Should give you awsome torque/ response on this 496.
Hi Hill, looking at flow numbers at lift of the 4 choices you have listed, IMO the edelbrock Victor heads looks to be the best choice for the money spent. You can get them in 106cc combustion chamber size to keep your compression up with those flat top pistons. Then with the edelbrock air gap you'll need to port match and then you'll have a matched setup. Flow at .500-.600 lift is over 300 cfm where your camshaft is matched to. BBC's need compression and good flowing heads to perform well. The victor heads you listed are 118cc combustion chambers. Not knowing other specs of your engine like net quench, pistons at zero deck, volumn of gasket, etc. the 118cc heads can be milled to get your 10.5:1 compression and you'll be able to run pump gas without issues. Hope this helps
This is the 2nd pass right off the trailer for the 67 with a brand new combo.Monster cam and big compression?Not really.This same car ran low 10s with a stock crate ZZ502 with 9.5 compression and oval port heads.Over 480 passes and 1000s of street miles before a rebuild with mild upgrades.His wifes 70 Monte 454 runs low 11s.PM if you want his #.He will put you on the right combo.