Team Chevelle banner
1 - 15 of 15 Posts

·
Premium Member
Joined
·
9,520 Posts
Discussion Starter · #1 · (Edited)
How dangerous is .055 total PV clearance on a solid roller cam steel rods iron heads. With 1.7 rockers 0 lash no gasket I had .040 pv clearance. .040+ .040 + lash .014 .094. If I change rocker ratio to 1.8 my lift increases 039 and I think I end up with .055 PV clearance.

I was in a rush to get out the door and neglected to say this is intake clearance
 

·
Premium Member
Joined
·
13,104 Posts
How dangerous is .055 total PV clearance on a solid roller cam steel rods iron heads. With 1.7 rockers 0 lash no gasket I had .040 pv clearance. .040+ .040 + lash .014 .094. If I change rocker ratio to 1.8 my lift increases 039 and I think I end up with .055 PV clearance.

I was in a rush to get out the door and neglected to say this is intake clearance
=
No problem what so ever on the intake ;)
 

·
Premium Member
Joined
·
9,520 Posts
Discussion Starter · #3 ·
Thanks Mike you can expect a call from me. I have Harland Sharps now so we can go from there, I'm not particular about color:D
 

·
Registered
Joined
·
13,351 Posts
Regardless of the total lift of the cam, you only pick up .005" lift at .050 (.085 valve lift w/ 1.7's vs .090 valve lift w/ 1.8's). The number is seven smaller. At .014 lash, the difference is only .0008" lift at the valve. By the time the effect of the higher ratio rocker occurs, that piston is well on it's way down the cylinder.
 

·
Premium Member
Joined
·
9,520 Posts
Discussion Starter · #5 ·
Hi Joe Thanks, I just need to figure out if changing ratios would translate to an improvement et and mph wise that would be worth the investment.
 

·
Premium Member
Joined
·
9,520 Posts
Discussion Starter · #7 ·
Hi Brian when I put this combination together it was for a mean street rice hunter. My first gear is 3.27 and 3.55 make a 11.61 multiplication which hurts the low end traction. I'm still trying shift points it seems like it likes 6400 need more track time to figure it out low end is awesome. Thanks
 

·
Premium Member
Joined
·
9,520 Posts
Discussion Starter · #9 ·
Joe I understand what you are saying .650 is lashed .018 .393 is lobe lift. I just wanted to run it up the flag pole and see the response. Thanks
 

·
Premium Member
Joined
·
3,250 Posts
Mike,

I'm running an Isky solid roller with 1.8's on the intake and 1.7's on the exhaust. This cam has fairly gentle ramps (for a roller) and have had no issues. The specs are 248/[email protected] .050, .638"/.646" lift. (with 1.8/1.7 rocker ratio). The rockers are the Crower Stainless Steel "Enduro" rockers.

I wanted abit more lift/aggressive profile on the intake side. The 1.8's not only add some lift but makes the cam "seem" a little bigger and more aggressive at the valve. Talked with Ron Iskendarian before the swap and he said with my lobe profile it would not only add aditional lift but 2-3 degrees more duration at .050" and about 4-5 at .200" lift. The engine in effect sees a more aggressive lobe profile that is a little bigger. Make sure the springs will work with additional lift, there was minimal piston to valve clearence change. One thing to watch is possible clearence issues with pushrods clearing the "pushrod holes" in the head. They get kinda close.

This cam is considered "old school" compared to alot of new cams, (like yours) but it still runs very strong. Makes great power in my 454 from 2500 to 6500+ rpms. After adding the new ratio rockers, going only by seat of the pants, it pulls a little more up top. They seem to have extended the rpm range a little maybe 200 rpm. It also is very easy on valve train parts. IMO, with the lobe profile that you are using, I don't think you need them, but that's just my opinion.
 

·
Premium Member
Joined
·
9,520 Posts
Discussion Starter · #11 ·
Thanks Darren, I have to decide how much farther I want to go new shocks and tires and I'm at the door for having to have a roll bar. I never intended to make a race car out of it. It is still a full dress street cruiser with AC and a 6 disc CD changer I don't know if I want to put in a roll bar......decisions decisions:rolleyes:
 

·
Registered
Joined
·
157 Posts
1.8's will take you from a net lift of .636 to a net of .674. JMHO, the Dart 308 heads won't benefit much from the added .040 lift. Also, I think you will make the valvetrain unstable for the duration. The valve acceleration rates are already very high on that cam.
The acceleration rates are NOT high on that cam. That's one of Harold's 31° ramp cams. The same ramps as just about all of our street cams.So far, these ramps have broken 2 driveshafts and 0 valve springs.

We ran those exact ramps in our truck engines to 9300 with .815" gross lift, 210LBS of seat pressure and a 1.85 rocker, before the gear rule came into effect. Dynamics are rock solid.:thumbsup:
 

·
Premium Member
Joined
·
9,520 Posts
Discussion Starter · #13 ·
Mike thanks for responding. Very interesting info what would be the net gain in the end and would changing just the intakes be enough. This cam is so mellow on the street that my wife can drive it. I'm just wondering if the gain would be worth the investment or just sell this cam and do it right. A full set of rockers is almost the same as a new cam.
 

·
Registered
Joined
·
157 Posts
Mike thanks for responding. Very interesting info what would be the net gain in the end and would changing just the intakes be enough. This cam is so mellow on the street that my wife can drive it. I'm just wondering if the gain would be worth the investment or just sell this cam and do it right. A full set of rockers is almost the same as a new cam.
I don't see a problem at all with putting 1.8 rockers on just the intake side. This will give you more lift around max piston velocity without increasing seat duration, which should show a gain.

Is the price worth the gain? You'll have to answer that one yourself. Each gain gets a little more expensive than the last. That last couple hundredths is always the most expensive.

Going to a larger cam or tightening the LSA up will just make you P-2-V that much tighter.
 

·
Premium Member
Joined
·
9,520 Posts
Discussion Starter · #15 ·
Thanks Mike this cam is great and Guy has the same cam and is going on the dyno soon I can't wait to see the numbers. Thanks again
 
1 - 15 of 15 Posts
Top