You might like this write up, it answers almost everything
https://www.svtperformance.com/threads/difference-in-2001-cobra-heads.745711/
https://www.svtperformance.com/threads/difference-in-2001-cobra-heads.745711/
4V Intake Suggestions
- Thread starter CobraSwappedV6
- Start date
Ive decided I'm going with the 03+ 4v heads, I can get a set from an aviator for $154. Ive also decided to go carb for the moment with the Sullivan intake.
A sully with an n/a 4v will be absolutely miserable everywhere under 7k. Please don't do that to yourself. Run the 01 intake you already have with the 03 heads you're going to buy and enjoy your car until you can boost it. Even when you go boost, those 03 heads and 01 intake will still be good enough to use.
Dont go carb on a street car. Stick with the 01 intake it will do what you want.
03 Aviator heads for $154 is a great deal, just realize that they are probably gonna be another $500-$800 for a shop to go through everything unless you fancy lapping 32 valves yourself and have the tools to do the guides. I've never seen them that cheap myself, just make sure they are actually 03+ heads. Look up the correct serial numbers. I mean even if they are 99-02 heads that is still a screaming good deal for them in good shape. I personally love 99-02 style heads, they are dirt cheap and the price to performance difference between them and the 03+ heads is nil.
My local junkyard has three 03 aviators in the yard. I honestly don't mind lapping valves or replacing valve guides.
The flow data Ive found for all three heads actually shows a pretty big gap between the 03 and C heads. I graphed the data and found that the B head intake runners flow better than the C heads. The 03+ heads flow the best though.
- Joined
- Feb 28, 2007
- Messages
- 19,523
Skip the PSR, uneven air flow and other issues.. Holley ECU/Sullivan/ and power adder of choice with cams matched for that. Don't go throwing random ass parts on a engine or else you won't be happy with your out come. Plan your build out and built it accordingly. If you're looking for 7500+RPM go with a sullivan.
That is the plan.
Flow data and real world performance between 99-02 heads and 03+ heads is the key here. NA its like 5hp at most. Boost, you just add another lb or not even if you are running 99-02 heads. Ppl make a way bigger deal about it than it actually is. Unless you are going for a big power build the 99-02 heads are enough.
Power does drop off on the OEM 99-01 intakes at around 6200. Cams help a little, but cam choice and runner length have to be mated correctly to get power at the higher rpms.
More power at the higher rpms will mean loss of torque at the bottom end.
Area under the curve or distribution is just changing shape.
Adding cubes is what gives you more to play with.
More power at the higher rpms will mean loss of torque at the bottom end.
Area under the curve or distribution is just changing shape.
Adding cubes is what gives you more to play with.
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