Quote:

---

Maybe someone knows how to link directly to a pdf document?

---

http://www.jeselonline.com/docs/instructions/INS-07238.pdf

what did you end up getting for a cam?

dont need all that much clearance for dyno work, especially if you have plenty of spring..

i had a 383 Chevy i was doing some cam testing with, and one of the cams i tried had about .035 intake/.050 exhaust clearance.
no issues.

i know some of the SS guys routinely run around .030 clearance on the intake side.

Comp sent me a 1722/1850 grind. The problem is that with the 1.70 rockers the valve accelerates faster than the piston down the hole. So I have lots of VP clearance at TDC but the valve catches up to the piston at about 10 degrees ATDC. If I dial the cam in at 4 degrees advanced the valve kisses the piston on the way down. If I put it in straight up I might have 0.035 clearance. If I retard the cam a bit then I have clearance.

I also have a Scott Brown cam which is a little smaller than the Comp and I have a Crower 300R which is another 10 degrees smaller yet. The SB cam also smacks the piston. I haven't tried the Crower yet.

LSA is 110 on that Comp roller. I'll need to double check the exhuast but it seemed to have more clearance.

I have a 6.800 long rod in the motor and the combination of long rod and big rocker ratio really eats up the VP. As I turn it over slowly you can see the valve accelerate off the seat while the piston basically just sits there. It takes almost 20 degrees of rotation to move the piston significantly. Meanwhile, those 1.70 arms just rocket the valve into the piston.

The Comp cam card calls for 0.026 lash so that is some more safety factor. I'm measuring everything now with zero lash. When you talk about running 0.030 VP clearance is that with the valves lashed, or with the rocker tight against the valve tip when the cam is on the base circle?

I also have a Crower 300R cam on hand so I put it in to see how it looks. It appears to have about 0.050 clearance on the intake when installed straight up. It is also a 0.026 lash cam. It is pretty agressive cam for being such an old design. 261/263 at 050 but .457/.464 lobe lift. It showed .792 lift on the dial indicator so the lobe I was checking was a little big. The Crower is ground on 105 LSA which seems a little tight.

Andy, I have an Ultradyne grind (R54) both I and E 316/283/201 .4765" lobe on a 110* lsa .026" lash. If you would like to try it let me know.

If I dial in the Comp 1722/1850 cam at a 108 installed centerline I get about 0.075 clearance on the intake and 0.100 on the exhaust. So that is fine IF the cam centerline doesn't change. The problem is that if the belt drive isn't rock steady then we could have problems. Probably be okay for a few dyno pulls.

I'm kind of curious about the power difference between the Comp cam and the Crower that I have. The Crower 300R cam is about 15 degrees smaller at 050 but has the same amount of lift. It is also on a 105 LCA and has to be installed around 100 or so to get everything to clear.

I also have a Scott Brown cam that I was going to run but it is a tight lash design with decent duration and I just don't think it clears.

Dont worry about the intake P/V clearance, impossible for the intake to catch the piston and any retarding effect will only improve the situation. Unfortunately, any retard effect will hurt exhaust clearance. I have .030 Intake and .110 Exhaust on my present project, (383 with 13.75/1 comp ratio) had me pulling my hair out to get everything to fit here. installed centerline at 102

Yeah I'm comfortable running it too now that I've found a sweet spot where it looks like it will fit. The margin for error is kind of small though since a few degrees each way and it runs out of clearance in a hurry. One nice thing about the belt drive is that it only takes me a few seconds to adjust the centerline and then I can double check the clearances. Doing it with a chain can take a bunch of time.

Any thoughts on the Crower 300R cam? I bet it will make some torque, just not sure it will hold on long enough to make much power in the 505. It is probably too aggressive to be a street cam although Crower doesn't really recommend super stiff springs for it. 261/263 at 050 and 460 lobe lift. The 105 LCA seems a little odd also. I called and asked them if it would work with 1.70 rocker arms and they said it would be fine up to 7000 rpm. Guy I talked to said it is a really old cam design that seems to work great. I bought it 20 years ago at a swap meet but never ran it.

the test i would do......is compare the new Comp with another cam that has very similar seat to seat, and .050 numbers, and if possible.....similar .200 numbers....but with noticably less lift, to see if the big lift is really going to buy you anything in that application.
and if it does....how much?
in other words....does it justify the added expense and wear and tear of the really big springs that are required to be able to use that type of cam for "X" amount of added power??.

as i had mentioned before, in that 383 SBC, going from .625 lift to .715 lift, while maintaining the seat to seat and .050 numbers of the 2 cams....showed no increase in power for the added lift.
that motor was making about 1.56hp/ci.

the test between the cams would be to try and determine which was more beneficial in that motor.....higher lift, or a higher discharge coefficient.

Quote:

---

Any thoughts on the Crower 300R cam?

---

i'd expect that with the short duration and tight lsa.....it would make a pretty big number in the middle somewhere.....but probably not provide the kind of overall power curve someone building that kind of motor is going to be looking for.

That is an interesting idea. Since I have the 1722/1850 110 at the moment I suppose I could order up a 4205/4032 110 to try.

The 4205 is 308/276/195 with .406 lobe lift as compared to the 1722 which is 308/275/195 and .488 lobe lift. So pretty darn close.

The 4032 is 318/282/195 and .420 lobe lift as compared to the 1850 which is 320/282/194 and .460 lobe lift. So not as dramatic a difference on the lift but still should be a decent test.

You find any lobes that look better than the 4205/4032?

I just got my "upgrade" kit from Jesel so I can run standard offset rocker arms on the intake. That means I won't need to grind a ton of pushrod clearance in the head. This is a slick kit since it allows a guy to run the Jesel setup on the EZ or SR heads. I'll post pictures as soon as I get some stuff bolted together.

One interesting tidbit is that in the box was some promo material for the new Jesel rocker arms that are made from steel. Evidently they are coming out with some new stuff, some of it is very trick looking. They have steel rocker arms with machined trusses and windows. They look like the old Mechart connecting rods. Kind of wild looking, like little bridge trusses. I don't see that stuff on their website yet but there was a flyer in the box.

Here is a shot of the conversion kit that Jesel sent me. The setup on the left is the 440-1 kit that you can buy from Indy. In the center is the std offset rocker arm with an inner and outer spacer that you replace the .800 offset arm with. Once you have it all put back together you get the std offset kit on the right.

Once the conversion to standard offset is done this is what it looks like mounted on the head. There is plenty of clearance on my EZ heads for a 3/8 pushrod and I think I can run a 7/16 pushrod without any grinding. I'll know for sure next week when my new pushrods show up.

Here is a picture from the valley side that shows the pushrods. With this standard offset rocker arm kit you don't need offset lifters or any grinding on the heads. So I think I'm about done with this project. I need to verify the clearance for the 7/16 pushrods and then install the valve springs and head back to the dyno.

I hit a bit of a snag but nothing that time and money won't solve. I ordered up 7/16 pushrods from Smith Bros. They showed up the next day and were exactly what I ordered, but they aren't exactly what I need. They rub the rocker arms pretty hard so I need to call them back to see if they make a special "Jesel" end for their 7/16 pushrod. The catalog doesn't show one but I'm guessing I'm not the first guy to run into this problem.