Bret,

Thanks for the input. Is there an advantage to this?

 

Countless SBC setups are running with even more overlap and making big numbers, not to mention the afr 225's.

IMO not an advantage, but not something to panic over either.

 

Give me a call tomorrow and I can tell you.I have a set of AFR 205's, 5.7 MLS's and 6.0 MLS's at my house that I can measure out when you call.

 

Bret, thank you for all your help! I guess I need to start worrying about other things now...like how to pay for this latest round of mods!!!

Vettenuts, I agree with your opinion of their response...especially on a LS series engine where you can't just punch it out .030 for 20 bux per hole!

Galen

 

Hear Ye, Hear Ye
Let it be known that: When creating the Dart LS1 head a bone stock head was initially used to pattern everything (including the bore size) from. In response to the concern that some have voiced about bore sizes being big, six finished LS1 heads were randomly pulled from a pallet of out going parts. The result was that every one measured was 3.940". Vettenuts measured 3.960" which we can only explain as a difference in measurment technique (such as one person squeezing the caliper, then setting it to zero. Versus measuring "loose") or it could just be calibration or quality of the calipers - .020" is about the width of a lower case L on this screen. So it is a tiny width, Galen - you're correct about the molehill. To give an example, the big block chevy motors (396",427", and even 454") have a notch in the deck to provide clearance for the intake valve and the factory chambers overhang the bore quite a bit... yet the old big blocks are known for power. Not saying that a cross section of the head and block should look like a mushroom - but a little bit of overhang is not gonna harm you.
Refreshment break ...
... ok, As far as spring compressors go if it works with other aftermarket heads it'll probably work on ours. If it only works on a stock head, it'll probably not work on ours or will need to be modified.
RJW - Your heads look nice. It should really say something for the quality of the head / and that you did not go nuts with the hard rolls since you have removed about 1cc from the chamber. To have a as cast head with tolerances this tight is really something.
About guide plates fitting ... we honestly never thought anybody would go that direction. The factory system is based on a shaft type - so are most of the aftermarket upgrade rockers. There is a newer offering by a company called Curtis Built that really bears looking into - they are nice! Retail around $495.00 and are individually adjustable heightwise.
Vettenuts - Good lookin out on the 3.970" gaskets! We'll add that to our info!
Hope this helps clear up the confusion - sorry for the long post.

 

Dyno them with the same cams against a AFR and THEN say they dont work..These heads are 1300 not 2100 and if they come in 10RW light over a AFR I could care less...

 

Malihoochie,

Couple of quick questions. Is there a recommended gasket size/manufacturer? I have found Cometics in 3.97, 3.98 and 4.013 and then there is the GM option mentioned previously in this thread of the 6.0 gasket, but I don't know specifically what the diameter is but assume it is slightly bigger than 4.0.

Per the recommendation of rcw in another forum, the 4.013 or 6.0 GM gaskets might be the best due to tolerances of the block/heads/gasket just to ensure no overhang.

 

Mal

Echoing the above post, could you give us some specific gasket (stock and aftermarket) recommendations for the 205 heads?

 

After doing some searches, I have found that Patriot Performance distributes the 6.0 GM gasket with their heads. The bore seems good, but I am not sure of the thickness of the gasket. This appears to be the best option if you want to stay with the GM gasket rather than the Cometic. I haven't decided which way to go on this, as some guys have had problems with the Cometics leaking.

 

What'd you use? Sanding rolls, flap wheels, what? Looks good, the pics a little fuzzy tho.

 

Flap wheels and rubber wheels to get into the tight places...

spoke to patriot 6.0 mls is 4.035" hole they say pn is 12569365, but chevy says 12589227

Should be a better fit than 4.130"

 

12589227 is the correct part number. Its the same thickness as the 5.7 MLS (.054-.055) and the bore sounds about right. The 6.0 MLS gasket would overhang a bit on my old 414 (4.060 bore).

 

Hmmm... My 3.910 MLS OEM gaskets measured around .049"

I just ordered the 6.0 MLS's, so I'll know tomorrow

 

I know, my .045 (compressed) cometics measured at .040 after they were used. It depends how much you tighten the mic I guess i may be wrong on the GM MLS thickness, just going from what I remember but they are the same thickness as the 5.7.

 

OK this seems to be the subject of the week, so thought I might try to shed some light. After checking about 6 castings it seems to range from 3.940-3.960 across the widest part of the chambers. This is common among all of the aftermarket heads in the LS1 market. Also think of this if a stock chamber is 3.900 wide and you have it cnc ported is it still 3.900 wide? No because if you remove material is has to get wider. Chambers that have been wider than the bores of engine blocks has been around for over 40 years. When using bigger valve on the 4.250 bore Big Block Chevy you would notch the top of the bore to allow for this. Also the 396 engine had a bore of 4.095 bore and used the same head as the 454 with a 4.250 bore.

Now that said we did work with a stock LS casting when we did our design work, and epoxied the chamber with the goal of keeping the chamber small to allow to fit the 3.900 closer. Will the bore being .020-.030 larger per side cause any power lose or gain? No it wont hurt anything, chances are all the aftermarket heads that guys have been using already have the same issue.

Head gaskets: there are a lot to choose from, and we dont have any alliances with any brands. We have used Cometic MLS in the past, but have also had failures. We are now using Fel Pro MLS stuff and like it alot. Fel Pro made a huge investment in steel dies to do the stamping after spending time trying other alloys, the steel dies make for a consistent stamped part that will seal better. If you have a gasket on the engine with a inner diameter of 3.960 or larger the chamber issue just doesnt matter.

Ok after doing a little research while writing this, we have found the chamfer on the top of the sleeves to be about 4.030, and with a head gasket less than that in diameter would be bad, so it would be best to use a fel pro 1041 or equivalent. This has a inner diameter of 4.135 which would give a little more than .050 between the wire and and the chamfer which would be very wise to allow for a quality sealing area.

In our experience you never want to run a head gasket that is right to the bore edge, always run one that is back from the edge. The gasket can be more prone to failures, and can also be a potential hot spot.

Guide plates: I'll be honest nobody we spoke to out there ever mentioned anything about these things. We never even looked at them. It amazes me that someone makes a rocker and guide plate for these, isnt that going backwards anyways to go from shaft to rocker and guide plates?? When all of the first Gen small block guys go from rockers and guide plates to shafts for increased valvetrain stability, strength, and overall reliability. The harmonics on the rockers versus shaft systems are quite a bit different, and it is well worth the little extra for the shafts. If you could see the rocker deflection on the spin tron versus the shaft system you would sheet yourself.


I know that the title of this post is Dart Issues, believe me these things are not issues, guys have built engines for 40 years with these types of "issues" these are not issues but rather normal occurences, that have zero affect on what you are going to do with these parts.

Happy New Year!!

 

Good information. I hadn't considered the Fel Pro gaskets, but they seem to find favor over on the truck site. Worth looking into.

Actually, the guide plates are used with the Crane rockers, which are also shaft mounted. Guide plates provide further valve train stability than the single shaft rocker such as the stock setup. The ultimate would be something like the Jesel system. Crane is also introducing a shaft system in the near future that uses composite bearings. Supposed to be very quiet and stable.

Thanks for looking into these issues for us. I appreciate the feedback on the gaskets and the bore chamfer, since I don't have access to an open block at this time.

Happy New Year

 

Hmm? Unless Crane changed their LS1 rocker setups they are not shaft mounted, they have a roller fulcrum/trunion. The reason they need the guideplates is because without them they would turn side to side on the stud and it wont work without them - no 'extra' stability involved. True shaft mounted rockers dont need guideplates. Nothing wrong with the Crane design, same thing people have been using on SBCs for 50 years.

If you look at a set of comp cam pro mag LS1 rockers and you can see the guideplates are cut out in the back so they most likely fit the Dart heas fine.

 

Yes, those guideplates look like they will fit the head as is. Turns out I need to take off about 1/16" to 1/8" to get the Cranes to fit.

 

Yep they fit just fine.... I checked all the clearances on the Pro Mag stuff before I assembled the heads.

Let me add that the extra material around the rocker bosses is a GOOD THING! The guys who race GM OEM heads in road racing weld up around the rocker bosses or they end up failing the heads in this area, DART fixed this problem from the factory, even though they can probably change the CNC program to help with clearance around the Crane and stock rockers.

Hopefully I will button up the car here soon, and the customer can take it and get it dyno tuned. I'm thinking around 450rwhp or more.... with 230/236 cam, 11.2:1, headers, a LS6 intake and ported TB. Don't know how much the SLP lid is going to hurt though.

Bret

 

Can somone measure the length of the intake and exhaust ports? For the intake, measure from the intake surface down the centerline of the port to the valve seat. For the exhaust, measure from the exhaust manifold surface down the centerline of the port to valve seat. No need for a measurment to the .001, but the more accurate the better.

Anyone know the size, in cc's, of the exhaust runners?

Thanks in advance!