Jarren_b

Ok guys I have a 97 corvette
Just installed the Brian Tooley Racing stage 2 NA cam

specs are 227/234 .614"/.576" 113+2

My valvetrain is super noisy and and my power flatlines at 5500 RPM when I expected this cam to make power up to 6000

Nothing else was changed.. I still have stock heads, intake and lifters.

Im previously had a texas speed 228R and used 7.400 pushrods with no issues. (.588 lift)

BTR recommended that I went with 7.400 on this cam as well so I did and It sounds like im driving around a herd of sewing machines.. Im aware that any cam will be noisier than stock but Ive had other cammed cars and this is excessive

Ive read about guys going with a 7.425 pushrod just to quiet things up and so im concerned that Since my intake lobe has so much more lift, I feel like thats what causing the noise

Is it a bad idea to run a different length pushrod on the intake valves vs the exhaust?

If I switch to a 7.425, is that a big enough difference that I would blow out my lifters or run into clearance issues?

I currently dont really have a way to measusre to get my dead on pushrod length.

What would you guys do in my situation??

Hopefully some vendors will chime in as well!

Jarren_b

Here is my dyno sheet from this saturday

Kip Fabre

If both cams were ground correct the lifter on the .614 lobe will drop .016 more than the .588 cam. Put in the 7.425 push rods that might fix it.

Jarren_b

thanks for the response kip.. Should I just put 7.425 on the intake side only? or all of them?

Kip Fabre

How much did you change the EX lift? 7.425 on the EX should work.

Jarren_b

lift on 228R was .588/.588

I now have .614"/.576"

So exhaust lift is actually less than previously..

Id love to run 7.425 all around if its safe to do so

Kip Fabre

Should not be a problem.

Jarren_b

awesome. Ill give it a shot!

Jarren_b

Any other opinions will be appreciated as well!

.boB

iTrader: (1)

This surprises me, that the base circle is different. I'v been working on Fords for the last couple of decades. The base circle is always the same for a hydraulic roller, regardless of the cam profile. Of course, .688 lift on a SBF is pretty rare.

So, is this a common practice? Will the base circle vary from cam to cam, depending on profile? When I replace the cam should I measure base circles?

Kip Fabre

LS1 cam have a 2.165 main cam bearings. If we make a .320 lobe lift and leave the top of the lobe .005 below the bearing we need to make the base circle 1.515 if we make a .360 lobe lift and have the tip of the lobe .005 below the bearing we need to make the base circle 1.435. On some OHC you can make the base circle the same size even with a higher lift.

Darkman

iTrader: (2)

I would measure the preloads - both intake and exhaust - and then choose pushrods.

.boB

iTrader: (1)

That makes sense. So, anything more than about .610-.615'ish of valve lift may have a smaller base circle. Good to know, thanx.

Hardcoresoldier

iTrader: (2)

get a push rod length tool and measure them to be on the safe side.

Goody_Seven

So, I realize this is a Comp cam and not yours, but in a situation like this, say you have a .360/.340 lobes and need the 1.435 core for your intake lobe. When you select the core do you:
1. Select a core with a 1.475 base and cut it down to 1.435 for intake only? (2 different base sizes)
2. Select a core with 1.435 and cut the .340 lobe on the smaller base? (1 base size)
3. Find a core with an intake and exhaust near what you need?

Kip Fabre

The base circle is dictated by the cam bearing size. If I put a 360 lobe on a LS1 it will have a 1.435 Base circle. If I put 360 lobe on a Small Block 350 the base circle will be 1.138 because the SBC 350 has a main bearing size of 1.868. On the LS1 core you can make the 360 lobe and the 340 lobe with the same base circle and that would max 1.435 but you could make the 340 lobe 1.475 if you did that the intake lifter would drop .020 more than the EX lifter.

BKsNHRA

iTrader: (4)

Call up a vendor and get a pushrod lenth tool. I think I got the trickflow one from summit for $12. Vendors have the comp tool for around $20 and go to harbor freight and get a 8" digital calipers for around $30. No more guessing for under $60. I used to guess to and $300 worth of pushrods later I found out all 3 set were to long. Wasted money .

Exidous

iTrader: (11)

My TSP 228R with .588" lift had a smaller base than stock. Had to run 7.425". You really have to measure, all else is a guess given Kip's is more of a hypothesis than a guess. :-)

The OHC motors do not have this smaller base circle restriction given that the cam does not slide in through the bearing to be installed. If you look at some of the aftermarket LSx blocks you will see that they have larger cam bearings allowing crazy solid roller lifts.

Jarren_b

I ran a 7.400 with my 228 also and it was kinda noisy but not anything like this..

Kip should I leave the 7.400 on the exhaust and run 7.425 on intake?

or 7.425 on both

redbird555

iTrader: (14)

like everyone else said man just measure. it will take all the guess work out. in reality a 7.425 will probably be good if the heads and deck are uncut but why take the chance. I would order the 7.425's and the checker tool. then you can measure and if it works then great if not then simply return them and get the correct length