I'm finally back to working on my Dart Pro 1 230cc cylinder heads. I had a post a while back about finding a roller rocker that would clear the 1.550 OD valve springs. Needless to say I ordered up a shaft rocker system from Comp Cams.

I still ended up with some surprises or concernes setting up the shafts. The kit supplies you with 2 sets of shims (thick and thin) to optimize the height of the shaft and a little gage tool. Since this shaft system is supposed to be setup for my particular head, I would expect things to be reasonably close. I followed the instructions, and my roller tip is nearly coming off of the valve tip on the exhaust side.

I ended up having to shim the shaft up .2000" (WOW!) so that the roller tip is slightly off center on the intake side of the valve stem (base cirlce of the cam), and rolls slightly off center to the exhaust side at max lift. A +.150" pushrod will work just great, but I am surprised and concerned that I have to shim the shaft assembly up that high to produce the desired results.

I called Comp Cams, and they just told me to call T&D Shaft and see what they think. T&D makes Comp Cams shaft rockers. I haven't been able to get a hold of them once in the last two weeks.

I would think that the shaft base should have been made +.150" to +.200" taller rather than expecting people to shim the whole thing up. I'd have to get longer bolts to secure it to the heads. Weird.

Anyone have any similiar experience with their shaft setup from Comp Cams, or any other Jesel, Crane, T&D, etc....?

Thanks

 

I don't have shaft rockers on my Dart 227 cc heads. I should have went with shaft rockers and offset lifters. But costs were getting out of hand and I started cutting some corners.

I have worked on some shaft rocker motors. so I do understand them.

To get my rocker tip to valve stem right. I went with the .500 taller ARP 7/16th rocker studs. I also use .200 longer push rods. The taller studs is the same idea as you shimming up the shaft center point.

I have 1.56 springs and 1.7 rockers to get .685/.714 lift. I almost bought 1.75 or 1.8's, but my $$$$ springs are only lasting about a year as it is.

 

I have the 230 dart heads on my 383.I used a 7/16 stud and didnt have problems with the comp cams roller rockers that I used.Geometry is fine.

 

Taller studs are required when your locking nuts are just grabbing a few threads because the rocker is so high to clear the larger spring diameters and center on the valve tip

 

Thanks for the response. I finally got through to T & D shafts. They're swapping out the stands no charge. They make the mounting portion for the shafts +.100" and +.200" taller. I was hoping that's what they would say. The parts are on the way. I 'll check piston to valve clearance this weekend, and order my pushrods. Hopefully I can dyno the motor over Thanksgiving.

Later

 

Thats good that you found the different rocker stands. But one area that most seem to not think of is the height of the valve stem. This is part of the whole set up to work together. Most seem to just take what ever they have there to get seat and open presures and thats it. Them they use longer studs as a fix and shims when you really want the stud to be as short as possiable to limit flex even with a stud girdle. What you are doing will work for a street type engine but my not be the best way, of coruse it may be right but we do not know all your measurements to come up with the best and correct fix if this was a ***** out engine.

 

Because of a offset problem with my pushrods, i was considering going the shaft route, but reading this made it clear you just don't buy over the counter.

And gkull, you're right, they are expensive... costs on our engines easily get out of sight.

 

As the valves get bigger they are not placed like stock heads. My 227's are even the next level called 60/40 where they are rotated like a big block - kind of. the intake is closer the manifold and the exhaust is towards the headers.

I',m not sure about Dart 230 heads, but I would also guess that the exhaust port are .600 inches higher than stock exhaust. That is why the Dart Pro1 heads flow 230 CFM on the exhaust.

Very much higher than any of the other manufacturers

 

Interesting. The valves are +.100" longer. The Intake valves are offset .250", but nope they are not offset like a BBC. They also do not have raised port exhaust. (There not supposed to be raised.)

I suppose everyones definition of ***** out motor is different. I'm shooting for 730HP on the blower motor, and 900HP with the addition of NOS. Other than having the Dart heads cast so that there is no reason to raise (shim) the shaft assembly, I don't see any other viable alternatives that would be stronger than a non shimmed +.200" raised shaft base. What's better than a shaft system? i would bet that some people would just keep adding shims. I can only imagine how much the valve train stability would be compromised with the shims wiggling around. Ugh.

I didn't exactly order the the shaft system over the counter. I contacted Comp Cams found out all of the information, and then had the speed shop order the parts. You'd think that they would have known to send the raised shaft base. We supplied them with the Dart part number for the heads.

I checked the piston to valve clearance this weekend, and there was no issue. The JE piston dish measures -.250". The exhaust didn't even nick the clay the 2.08 intake valve made a .010" nick. FYI .633" of lift.

Thanks again your experiences, comments, and suggestions.

 

Both of my Pro1 heads had .600 raised exhaust ports. It did not make a difference to my hooker S/C pipes

I have always felt that 23 degree type heads were a limitation. Especially up in your power range. Because of the primary pipe size. You should have used spread port exhaust heads and use 2 or 2 1/8 inch pipes

 

Oh crud grrr.... I specifically asked the Dart tech if the ports were raised. I had a lot of money into my Hooker Super Comps, thermo coating, and 3" aluminized exhaust. I didn't want to change my headers, and exhaust I knew it was going to add another $1000. Ironically now I'll most likely be buying the 2 1/8" Stahls and adapters. The dyno shop has a few sets with larger tube primaries, I'll have to confirm the sizes hopefully I'll be able to test and optimize the primary size before ordering the Stahl headers.

My Pro 1's are supposed to be a newer casting. Maybe I'll get lucky and find out they aren't raised exhaust ports (doubtful). My dyno operator was all geeked up about the heads. He's only heard good things about them, but hasn't had any on his dyno yet.

I had a hard time deciding on the heads. I have always ran AFR, and really wanted the 227's. The cost, and the wait steered me towards the Darts. All in all, I'm sure most would agree that the power level I'm targeting is plenty fine for driving on the street and a few passes now and then at the strip for some legal fun. If I know me, I'll be making changes once it's all dialed in, I'm just playing and having fun learning the next level of performance.

 

I looked on the Dart sight and it just claims standard exhaust port.

I doubt if they changed their casting. People got scared when they said raise .600 My AFR 210's are raised .300 inches.

The reason why it is no big deal is you have to look at a V-8. raising the exhaust port also moves them outboard. So it doesn't cause the pipes to be that much higher

 

Are the dart pro 1's 215's raised on the exhaust ?