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I am in need of some camshaft help.

General engine tech -- Drag Racing to Circle Track

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jet1
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I am in need of some camshaft help.

Post by jet1 » Mon Sep 09, 2019 12:36 pm

I have an odd ball combination and I have posted about it on here before but rather than everyone have to read through the whole post I will give a condensed version of here.
LS based 260 Ci twin turbo on e85
8.7: comp 3.89 bore x 2.725 stroke
mast ls1 heads
holley hi ram and holley fuel injection
cam right now is 244/248 .662/.662 115 lc+2 solid roller jhe x650 springs 185 on the seat and a 674 rate
The engine runs great but I feel the cam is big for what I need. it is in a jet boat and runs around 6600@16 lbs of boost for long periods. I have the scramble set up to go to 22 lbs for short stents and it pulls 7250 at that. The problem is that the engine has not even hit the tq peak by 7300. What I am hoping to achieve is a smaller cam for around 6700 tq peak and maybe even be able to go with a hyd roller. Thoughts?

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CamKing
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Re: I am in need of some camshaft help.

Post by CamKing » Mon Sep 09, 2019 1:14 pm

I recommend staying with a mechanical roller
Cam# LS1, R70360-114
230/230 @.050"
.360"/.360" Lobe Lift
114 LSA
Mike Jones
Jones Cam Designs

Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449

jet1
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Re: I am in need of some camshaft help.

Post by jet1 » Mon Sep 09, 2019 2:55 pm

I was afraid you were going to say to stay with the solid roller. We have just had a lot of problems with solid roller valve train not being forgiving enough. We see some times the valve job will start to go. Not enough to tulip a valve but enough that we start to notice. We run multiple leg marathons and not much time between them. I have had before when the hyd roller actually allowed me to keep racing where a solid roller would have held a valve open and burnt it ending my marathon.
Would short travel hyd lifter work any better?

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CamKing
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Re: I am in need of some camshaft help.

Post by CamKing » Mon Sep 09, 2019 3:09 pm

I'm not a fan of running a hydr lifter at 6,600 rpm, for long periods of time. Any aeration in the oil, and you will have big issues.
The profile I recommended is a very mild design, and should be really easy on the valvetrain. No need for an aggressive profile, with a turbo.
Mike Jones
Jones Cam Designs

Denver, NC
jonescams@bellsouth.net
http://www.jonescams.com
Jones Cam Designs' HotPass Vendors Forum: viewforum.php?f=44
(704)489-2449

F-BIRD'88
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Re: I am in need of some camshaft help.

Post by F-BIRD'88 » Tue Sep 10, 2019 12:27 am

On a hard running turbocharged motor the exhaust valves run hot(er) Especially if the spark timing is run retarded to avoid detonation under wot boost.
So this makes the hotter ex valves grow in stem length when run at wot under boost. May want to open up the ex valve lash setting a bit more to compensate for the net decrease in hot running lash @wot under continuious boost.
A bit wider valve job seat width will last longer.
Inconel ex valves. Be sure the ex valve guide clearance is not too tight to also acount for the hotter running valves.

If you are running the wot timing retarded to account for lack of fuel octane to avoid detonation, use a better fuel , add intercooling, or lower the boost a bit to allow for less boost retard.
The increased spark timing will allow cooler exhaust temps and valves.

gruntguru
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Re: I am in need of some camshaft help.

Post by gruntguru » Tue Sep 10, 2019 1:43 am

8.7:1 CR, 22 psi boost on E-85 should be able to run MBT timing without det.

jet1
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Re: I am in need of some camshaft help.

Post by jet1 » Tue Sep 10, 2019 11:10 am

F-BIRD'88 wrote:
Tue Sep 10, 2019 12:27 am
On a hard running turbocharged motor the exhaust valves run hot(er) Especially if the spark timing is run retarded to avoid detonation under wot boost.
So this makes the hotter ex valves grow in stem length when run at wot under boost. May want to open up the ex valve lash setting a bit more to compensate for the net decrease in hot running lash @wot under continuious boost.
A bit wider valve job seat width will last longer.
Inconel ex valves. Be sure the ex valve guide clearance is not too tight to also acount for the hotter running valves.

If you are running the wot timing retarded to account for lack of fuel octane to avoid detonation, use a better fuel , add intercooling, or lower the boost a bit to allow for less boost retard.
The increased spark timing will allow cooler exhaust temps and valves.
Good info and this engine is intercooled with intake temps at boost of 75 F, incconel valves, wider seats etc. my main issue for wanting to go Hyd is because of time restraints. We run multiple legs during the day and in different locations, plus we have to pre run the 40 -60 mile coarse for the next day that evening. We literally run out of time to do much engine maintenance. something as simple as a valve adjustment means removing the valve covers and some lines to do it. Unless we want to make another trip down to the river to check for leaks(more time we don not have) we are forced to put it together and hope for the best.

jet1
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Re: I am in need of some camshaft help.

Post by jet1 » Tue Sep 10, 2019 11:12 am

gruntguru wrote:
Tue Sep 10, 2019 1:43 am
8.7:1 CR, 22 psi boost on E-85 should be able to run MBT timing without det.
We dont see ANY det at all and it does concern me some. the timing is up at 32 deg even at the 22 lbs of boost. can a person not see any det but still be causing issues?

oldhead
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Re: I am in need of some camshaft help.

Post by oldhead » Tue Sep 10, 2019 2:53 pm

what about a SBC-400 vortech YSI with 22# 8,2 to 1 Comp, Same cam??????Oldhead Sorry to push my question in here
Quicker then most

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Re: I am in need of some camshaft help.

Post by F-BIRD'88 » Tue Sep 10, 2019 4:15 pm

When you do do this between round valve lash check- adjustment are the valves then found to be out of adjustment?

Which valves? Lash increases? Lash decreases, on check. A trend? Random?

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Re: I am in need of some camshaft help.

Post by F-BIRD'88 » Tue Sep 10, 2019 4:35 pm

If you get the initial lash right so that the hot running lash is correct on the ex valves when hot, the valve on seat time will no longer decrease (lash closing up when hot WOT.) The valves will have more cycle time on seat to transfer heat, thus stopping ex valve overheating, tuliping and seat pounding. The ex lash should then stay put and valves last ... No more burned ex valves.

The exhaust valves may simply need a bigger lash setting to start with.

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Re: I am in need of some camshaft help.

Post by F-BIRD'88 » Tue Sep 10, 2019 4:47 pm

Jones' milder cam may/should have more ex valve on seat time per cycle by nature of its shorter valve open time (duration). Once ex valve lash hot- cold lash compensation is found for your specific running conditions.
More ex valve on seat time per cycle means more ex valve cooling time when running.
Last edited by F-BIRD'88 on Tue Sep 10, 2019 5:02 pm, edited 1 time in total.

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Re: I am in need of some camshaft help.

Post by F-BIRD'88 » Tue Sep 10, 2019 4:59 pm

One way to lessen-minimize the performance loss effect of oil areation on hyd roller lifter function is to change the oil between rounds. You need not discard the oil. Save it, let it sit 1 -2 days till the air gets out and you can reuse that expensive racing motor oil again.

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