Valve Size?

If I run a stock cam with dual Weber ICT's and 1:4 ratio rockers and 4 into 1 exhaust.. What size valves should I be ordering in new cyl heads.

I have a choice of 40+35.5 or 42+37

Basically I want to do a to overhaul, plus new barrels and pistons 85.5, stock 1600. Dual port engine.

Ken

O dear....do you want stock or modified. 40x35.5 when ported properly to match will out perform your carbs and cam.

In answering your question, with what you have proposed, my recommendation would be stock heads 32x35.5 but mildly ported. But probably with 1.25 rockers, your stock springs wont take any more....IMO

X 2
Matt's advice will guide you right

Thanks Matt, hopefully you can see where I am going?

Trying to get the best solution when fixing my oil leak and wringing a little more performance out of the vehicle without too much mods. After torque and reliability, not acceleration and over the speed limit speed.

If I can sit on the speed limit comfortably when on rallies, I will be content.

If I can overhaul the heads I have, then this will save a bit, but I don't mind purchasing the 1444 044 special heads from CB.

Tried to take the spark plugs out of 1 & 2 cylinders, gave up. They feel like they have almost been loctited in or forced.

Ken

Wouldn't a set of 40 x 35.5 Los Banditos be a good bang for buck with future reserve

Ditch the ratio rockers in favour of a mild cam and use stock rockers with solid spacers

A lot less mucking round and easier on valve train

The big valve heads will work on a 1600, and work quite well, but they're a hefty overkill and depending on their cost may not be worth it to you.

Keeping in mind that 20-30% of all the flow improvements you will get in the heads are due to improvements in just the valve seat and valve shape alone with no porting at all, it may be very cost effective to buy new performance valves (GOOD ones, like SI Valves and CB Performance) and then get a reputable head shop to do some really nice seats for them and call it a day. When you buy your valves, you can also buy some "heavy duty Singles" performance springs/collets/retainers as a kit, then you can use your 1.4 rockers and not have to worry about any damage, as the cam flow will limit the motor to safe revs usually. An extra 20% flow will give you an extra 10% HP with no other change, and since you need to service the stock heads at least before re-assembly, why not use the better components for very little extra cost?
http://www.piersideparts.net/CB1476.html
http://www.piersideparts.net/CB1475.html
http://www.piersideparts.net/CB1503.html

I bought SI valves for my own little baby motor, quality and flow rates are outstanding, equal to anybody.......
http://www.sivalves.com/ocforeign_valvessp_vw.html

This is all of course assuming that you are just going to hone the cylinders, throw in a new set of rings, throw on your heads and call it a day without having to get into the motor at all. You'll be amazed at the improvement over stock.

Bizarre wrote:Wouldn't a set of 40 x 35.5 Los Banditos be a good bang for buck with future reserve

Ditch the ratio rockers in favour of a mild cam and use stock rockers with solid spacers

A lot less mucking round and easier on valve train

Agree to that, but presently unavailable and only with a cam upgrade which he doesn't want to do, ie. not splitting case, AND he only has ICT's, not IDF's.

Forgot the not splitting the case bit

I agree with Modrod that a performance valve job is necessary, I have them on all my builds, even 36hp engines. To me it's free horsepower/longevety, plus some heads have poor valve seating brand new/out-of-the-box, and the best way to check is to actually perform a valve job

Thanks to modrod, have talked to Matt and it seems we are all on the same page.

Now it will all depend on what I find when the engine is out.

Thanks once again, it has been a great help.

Ken

landfall wrote:Thanks to modrod, have talked to Matt and it seems we are all on the same page.

Now it will all depend on what I find when the engine is out.

Thanks once again, it has been a great help.

Ken

👍👍

Sorry to throw another spanner in the works but For a stock 1600 I would consider these to.... I put them on my 1699cc (74mm stroker crank with relatively stock 1600cc top end) and am really happy with the set up... Other guys know a lot more then me on here but just another option 👍

At this point in time I am very hopeful not to split the case. No oil leaks and end play in the crank is spot on. No real reason to go any further.

Time will tell, but the advice I have been given for the top end is gold.

Ken