Dart heads?

[88bluestar]

On a new set of Dart S/S 10024360 heads how much can they be milled down to?

[resurrectionjoe]

Darts recommendation

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[1980RS]

What are you looking to take them down to? I am sure Chad S could shed some light on how much can be milled on those heads.

[88bluestar]

68cc chambers.

[Walter R. Malik]

On a new set of Dart S/S 10024360 heads how much can they be milled down to?

If you're not following a rule for that particular part number ... the Dart s/s 180's are available in 49 cc's.

Of course I have heard that Dart is having foundry issues at the present time.

[ProPower engines]

These heads are made as a stock replacement head and the amount of material removal suggested on the spec sheet is the same as World products has on theirs.

Personally I have taken .020 off on an angle then flat milled 060 off with no issues for a local class that runs that head as a spec head with a comp. rule.
No issues to date with warping or cracks in 5 seasons.
I have heard they have had some issues with castings as well but have not seen any yet.

[88bluestar]

USRA HOBBY stock
I gather it's best to get bare heads with no valve jobs straight from the manufacture so valve seats are not sunken and it allows better volume in the runner and behind the intake valve. I plan to go with 1.94/1.50 valves but not sure on valve job to yet. I am needing to surface the heads to get to my ideal compression ratio but also per advice on here to unshroud the valve. Went to the brezenzki site and the darts are more desirable for these rules I gather.
NO PORTING IS ALLOWED. I assume this also means no blending allowed.

Cast iron stock production or aftermarket steel stock replacement heads are permitted. Porting and/or
polishing is not allowed. GM cars must utilize 76cc heads (approved head numbers are 336, 339, 388,
441, 454, 487, 624, 813, 882, 991 and 993). Aftermarket head numbers are: GM – EQ Part #CC167ES2
or #CH350I; Dart Part #10024267 or #10024360; World Products Part #043600 or #042670; Ford
– World Products Part #53030; Chrysler – EQ Part #CH138B; RHS/Indy Part #20300 or #20301. Heads
may be flat milled to reach the 9.5:1 compression rule. Valve size no larger than 2.02 intake and 1.60
exhaust. VORTEC heads are not allowed. Beehive valve springs are not allowed.
13.6.11 Screw-in studs, guide plates and poly-locks are permitted.
13.6.12 Roller cams and lifters are not allowed. Roller Rocker arms are not allowed (stock-type stamped steel
rocker arms or cast steel rocker arms only). Roller tip rocker arms are permitted. Chryslers may utilize
OEM steel shaft rockers but may not exceed one hundred twenty (120) pounds of valve spring seat
pressure and must maintain OEM valve spring dimensions. Under valve cover pressurized valve train
oiling systems are not allowed.
13.6.13 Mushroom lifters are not allowed (stock diameter only). Must match make and model.
13.6.14 Stud girdles are not allowed.

[steve cowan]

I have a set of 165cc wissota Dart cast iron heads that I first started porting on about 4 years ago.
They come with a valve job from dart,not sure if you can buy them without valve job ??Dart directly I spose you can.
Like most 23 deg heads they get noisy on the bench around 400- 500 thou lift on the intake and exhaust, this will limit you if you can not port as the SSR need work like most heads.i just recently put a 50 deg valve job on mine as machine shop flat milled the top cut away on the valve job and killed the head.
Had to sink valve job to bring in a 40 deg top cut.i asked to angle mill heads to 62cc but they didn't listen.
Those heads take a 50 deg very nicely in my opinion but there is chamber and SSR to bottom cut blending required.
The flow numbers advertised are pretty close but after 0.500" lift they turn to crap.

[Walter R. Malik]

I guess that I am not understanding the point of this milling ... IF the compression ratio allowed is merely 9.5/1 maximum as the rules above say.

[ProPower engines]

USRA HOBBY stock
I gather it's best to get bare heads with no valve jobs straight from the manufacture so valve seats are not sunken and it allows better volume in the runner and behind the intake valve. I plan to go with 1.94/1.50 valves but not sure on valve job to yet. I am needing to surface the heads to get to my ideal compression ratio but also per advice on here to unshroud the valve. Went to the brezenzki site and the darts are more desirable for these rules I gather.
NO PORTING IS ALLOWED. I assume this also means no blending allowed.

THE BEST THING TO DO IS ORDER THE HEADS BARE. THEN ORDER REPLACEMENT SEAT CUTTERS FOR INT.+EXH
The seat design is the best that they will get using the Dart cutters with no port work allowed.

You will need to do bronze liners at the very least and hone fit the stems to the guides.
We use them for several spec class engines and they do work well when you don't try to reinvent the valve job they come with.

[88bluestar]

I guess that I am not understanding the point of this milling ... IF the compression ratio allowed is merely 9.5/1 maximum as the rules above say.

"LOCAL TRACK" has .5 allowable difference in regards to compression ratio(max 10.0 or under) according to the Whistler box that measure ratio(Katech). I'm looking at just about 9.85:1.


Steve Cowan, Can a thinner stem valve help at all to calm that .400-.500+noise?.... like a 7-8mm valve

[steve cowan]

I guess that I am not understanding the point of this milling ... IF the compression ratio allowed is merely 9.5/1 maximum as the rules above say.

"LOCAL TRACK" has .5 allowable difference in regards to compression ratio(max 10.0 or under) according to the Whistler box that measure ratio(Katech). I'm looking at just about 9.85:1.


Steve Cowan, Can a thinner stem valve help at all to calm that .400-.500+noise?.... like a 7-8mm valve

I have never tested thinner stems on the bench,
Its all about the SSR and turning the air,add fuel to the mix then higher depression (RPM) and everything is out to lunch.
Of course it will run fine but your hands are tied with specifications.
I agree with Dave (pro power) on valve job deal.

[ProPower engines]

I guess that I am not understanding the point of this milling ... IF the compression ratio allowed is merely 9.5/1 maximum as the rules above say.

"LOCAL TRACK" has .5 allowable difference in regards to compression ratio(max 10.0 or under) according to the Whistler box that measure ratio(Katech). I'm looking at just about 9.85:1.


Steve Cowan, Can a thinner stem valve help at all to calm that .400-.500+noise?.... like a 7-8mm valve

I have done the 5/16' stem deal and in made no difference in flow numbers or how clean the air flow sound was.
The lighter valve weight was all the bonus I got from it which did not hurt.