northey

Can anyone answer this please?

How much horsepower do 2v o.c. and 2v c.c. heads flow?
Stock, unported.

Thanks Northey

4Vman

I find flow figures to be rather misleading.
A head can flow a gazillion HP on a flow bench but without a cam and set-up to match its irrelevant.
Id say the most you'll get from stock 2V heads with a big Hyd cam and 5.8l would be probably mid to high 300's?

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xdclevo

When i had some 2v open chambers ported 10 years ago, the porter told me he tested before and after.
Stock port was 420hp.
Ported it was 490hp.
Hope this helps.

russxr67

In astock situation you would find that on the bench the open heads can outrun the closed heads because the valves are unshrouded in comparison to the closed head which requires a bit of opening up to allow them to breathe adequately. Open head flow around 200 cfm @ 28 in stock form which theoretically is enough to support around 400 hp. closed heads flow significantly less. Make no mistake though,iron will get the job done if you are prepared to spend the money needed.

351ZAFairlane

Well that clears up a mystery for me. Many people who should be in the know are adamant that 2Vs flow ‘bout 400hp, but I’ve asked head specialists and they say that is way too high. So it’s all in the chamber eh?

The general consensus I’ve found is 360hp. That must be the closed chamber.

northey

The reason I'm asking this is to decide what heads to use in building a 2V 351 engine.

I did want to use 2V c.c. and a small hyd cam and hopefully end up with 330 - 350 hp approx. It seems to me that to use even the small cam some head work still needs to be done to get good flow through the whole rev range.

The fellow who will be doing my heads has suggested his best results even for a mild engine are with turned down 4V valves and relief/unshrouding, etc and minor port work. My friends tell me he is a very trustworthy person and I know he has good results so that's not the issue.

Haven't had a chance for further conversation to find out all port work.

The cost of completely rebuilding the heads is about $2500 total cost inc. good port job.

Problem is they're only worth around $ 500 - 1000 when completed.
If that last line is not correct please let me know; it's just what I've been told elsewhere.

I'm now wondering whether or not the money would be better spent on my 4V's. No port work just rebuild and plonk on. I would prefer not to put in tongues.

The whole plan is to have a mild streeter/cruiser but one that goes hard down low where it counts (1800 - 5500).

Any suggestions welcome.

CJR09

How much compression do you lose through the use of O.C heads?

I thought the whole point of using the C.C heads was to achieve the greater compression/quench in turn giving greater and more complete combustion - therefore creating more power/torque for less effort?

shaynet

I agree that you would be lucky to get a $1000 for them. I have a set of mildly ported 2V closed chambers with 4V valves, double springs and single groove collets. Have not been on the car since being reco'ed with new exhaust guides and hardened seats for unleaded.

Anytime I have mentioned anything like a grand (they owe me more than that) the enquirer has disappeared so fast they would leave Victor Bray for dead.

Do yourself a favour and put the $2500 towards a set of alloys. If you only want to rev to 5500 you only need the cheaper valves and springs combination. Would have to consider rockers on top of this though as I believe the alloys will only accept the bigger diameter studs

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xcgxl

What about closed chamber heads that have had had the chambers opened to prevent shrouding?

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northey

The heads I initially looked at getting done were 2V c.c. heads.
Yes, they do offer better performance than 2V o.c. heads.
The advantage I thought was to use c.c. heads and run less advance than with o.c. heads. They should still make more power and be more responsive and have better torque than o.c.'s.

I believe from posts here and conversation with head man that o.c. and zero deck flat tops offer APPROX. 9.0 - 9.3 : 1.
With zero deck and flat top, c.c. heads APPROX + 11.? : 1.

Two bothers I have are:
cost of building 2V head which are worth bugger all the minute I hand over the money.
And : I had heard the stock heads flow about 400 hp also. Why then do they need so much work to actually get anything out of them once on the engine?

Is using a big cam the only way to make 350 hp with stock 2V's?

I understand that flow figures don't mean a lot. But I don't really have anything else to use.