Big lobe & lower ratio rocker or smaller lobe & high ratio rocker? whcih will live and which makes more power?

Go down

Big lobe & lower ratio rocker or smaller lobe & high ratio rocker? whcih will live and which makes more power?

Post  CDMBill on December 14th 2017, 1:21 am

For my next post that mostly nobody will care about I'm curious about who has tried this both ways? I have gone the route with more rocker ratio, 1.8:1 then 1.85:1 then 1.9:1 to get more area under the curve. This being a 598" 12:1 pump gas Drag Week/True street deal. I have already gone to Isky Max bushed solid rollers at .904" diameter with bushed bores.

The alternative is a bigger lift cam with similar specs and effective flank rates with a lower rocker ratio. The issues I run into are how long wil the cam last with a combination of street miles and track passes? How long will the valve springs live (using T&D stainless shaft rockers with spring oilers)? And, how long will the lifters live? And, is there really any preference? A few lobe catalogs ago the higher ratio was the only choice, now there are higher lift and higher rocker ratio choices with similar lobe profiles. I am not yet addressing 60MM cam cores and such.

I am trying to make more power in the same rpm range with the same engine (short block, heads, intake, TB's) with more cam and still have it live for 1220 miles and 20 laps, or really two seasons, 4000 miles and 100 laps.

Any preferences from the experts here?

CDMBill

Posts : 168
Join date : 2010-08-09

View user profile

Back to top Go down

Re: Big lobe & lower ratio rocker or smaller lobe & high ratio rocker? whcih will live and which makes more power?

Post  JBR-3 on December 14th 2017, 3:56 am

Without going to a larger diameter journal, a lobe with more lift will have a smaller base circle.
A smaller base circle is never a step in the right direction for reliability. Lifters like large base circles.

JBR-3

Posts : 194
Join date : 2009-08-17

View user profile

Back to top Go down

Re: Big lobe & lower ratio rocker or smaller lobe & high ratio rocker? whcih will live and which makes more power?

Post  rmcomprandy on December 14th 2017, 10:26 am

Getting the correct valve action, (at the valve), for that particular engine's needs will make the most power no matter how you get there.

rmcomprandy

Posts : 5142
Join date : 2008-12-02
Location : Roseville, Michigan

View user profile http://www.rmcompetition.com

Back to top Go down

Re: Big lobe & lower ratio rocker or smaller lobe & high ratio rocker? whcih will live and which makes more power?

Post  dfree383 on December 14th 2017, 10:32 am

Big base circle (use biggest core you can fit in the block) and easy the intensity on the lobe, keep it sane it will live.

And use the biggest lifters you can get.

Higher the rocker ratio the more stress on the cam, lifters and pushrods.

What heads you use will have a big effect too.


It's all a balancing act.
avatar
dfree383
BBF CONTRIBUTOR
BBF CONTRIBUTOR

Posts : 14162
Join date : 2009-07-09
Location : Home Wif Da Wife.....

View user profile

Back to top Go down

Re: Big lobe & lower ratio rocker or smaller lobe & high ratio rocker? whcih will live and which makes more power?

Post  BOSS 429 on December 14th 2017, 1:28 pm

CDMBill wrote:For my next post that mostly nobody will care about I'm curious about who has tried this both ways? I have gone the route with more rocker ratio, 1.8:1 then 1.85:1 then 1.9:1 to get more area under the curve. This being a 598" 12:1 pump gas Drag Week/True street deal. I have already gone to Isky Max bushed solid rollers at .904" diameter with bushed bores.

The alternative is a bigger lift cam with similar specs and effective flank rates with a lower rocker ratio. The issues I run into are how long wil the cam last with a combination of street miles and track passes? How long will the valve springs live (using T&D stainless shaft rockers with spring oilers)? And, how long will the lifters live? And, is there really any preference? A few lobe catalogs ago the higher ratio was the only choice, now there are higher lift and higher rocker ratio choices with similar lobe profiles. I am not yet addressing 60MM cam cores and such.

I am trying to make more power in the same rpm range with the same engine (short block, heads, intake, TB's) with more cam and still have it live for 1220 miles and 20 laps, or really two seasons, 4000 miles and 100 laps.

Any preferences from the experts here?



what valve train parts are you tearing up?
avatar
BOSS 429

Posts : 2229
Join date : 2009-08-10
Location : Ill

View user profile

Back to top Go down

Re: Big lobe & lower ratio rocker or smaller lobe & high ratio rocker? whcih will live and which makes more power?

Post  Straubtech on December 16th 2017, 2:50 pm

CDMBill wrote:For my next post that mostly nobody will care about I'm curious about who has tried this both ways? I have gone the route with more rocker ratio, 1.8:1 then 1.85:1 then 1.9:1 to get more area under the curve. This being a 598" 12:1 pump gas Drag Week/True street deal. I have already gone to Isky Max bushed solid rollers at .904" diameter with bushed bores.

The alternative is a bigger lift cam with similar specs and effective flank rates with a lower rocker ratio. The issues I run into are how long wil the cam last with a combination of street miles and track passes? How long will the valve springs live (using T&D stainless shaft rockers with spring oilers)? And, how long will the lifters live? And, is there really any preference? A few lobe catalogs ago the higher ratio was the only choice, now there are higher lift and higher rocker ratio choices with similar lobe profiles. I am not yet addressing 60MM cam cores and such.

I am trying to make more power in the same rpm range with the same engine (short block, heads, intake, TB's) with more cam and still have it live for 1220 miles and 20 laps, or really two seasons, 4000 miles and 100 laps.

Any preferences from the experts here?

What are the heads and camshaft combination in this drag week combo? Is it in a NA class or a power adder class? I had 2 customers compete this year for the first time to finish 3 and 4 in each of their classes. Both true pump gas builds, both true street driven cars. Either one does not have a camshaft over .740" lift.

Straubtech

Posts : 292
Join date : 2015-03-31

View user profile

Back to top Go down

Re: Big lobe & lower ratio rocker or smaller lobe & high ratio rocker? whcih will live and which makes more power?

Post  CDMBill on December 20th 2017, 5:12 pm

At this point the valve train has been stable and healthy, no breakages since 2012, I replace valve springs every two years and have had the Isky bushed lifters rebuilt once and then bought a new set on the same two year cycle. Pushrods are Manton three piece and the rockers are T&D stainlesswith spring oilers.

The heads are TFS A460 gen3 with Lem's chamber and TFS's CNC ports circa 2012.

I'm looking to make more power without spending money for new short block, heads or manifold or machining the block for a 60mm cam.

So the question is more lobe or more rocker and I'm already at 1.85:1.

CDMBill

Posts : 168
Join date : 2010-08-09

View user profile

Back to top Go down

Re: Big lobe & lower ratio rocker or smaller lobe & high ratio rocker? whcih will live and which makes more power?

Post  BigBlockRanger on December 20th 2017, 7:11 pm

I would think rocker ratio might be better since any additional lobe lift moves the entire valve train more. That would seemingly make the spring work harder to maintain control of everything and possibly warrant higher spring rates. Higher rates is probably not the direction you want to go for good street reliability.

Then again, I'm not an engine builder. I'm just a guy that screws stuff together and hopes it does not self-disassemble at some point.

Laughing
avatar
BigBlockRanger

Posts : 705
Join date : 2008-12-02
Age : 47
Location : Amarillo

View user profile

Back to top Go down

Re: Big lobe & lower ratio rocker or smaller lobe & high ratio rocker? whcih will live and which makes more power?

Post  Straubtech on December 22nd 2017, 11:18 am

CDMBill wrote:At this point the valve train has been stable and healthy, no breakages since 2012, I replace valve springs every two years and have had the Isky bushed lifters rebuilt once and then bought a new set on the same two year cycle. Pushrods are Manton three piece and the rockers are T&D stainlesswith spring oilers.

The heads are TFS A460 gen3 with Lem's chamber and TFS's CNC ports circa 2012.

I'm looking to make more power without spending money for new short block, heads or manifold or machining the block for a 60mm cam.

So the question is more lobe or more rocker and I'm already at 1.85:1.

List the cylinder head flow and camshaft that is in it. From there we will have the info needed to see what if anything the engine needs.

Straubtech

Posts : 292
Join date : 2015-03-31

View user profile

Back to top Go down

Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum