Good day, 300 plus miles on fresh 454 with retro roller lunati cam lifter setup and fast efi...Valves set at half turn preload from 0. Runs starts perfectly hot or cold...Issue is when she gets hot hour into drive she starts to spit n pops at cruise and bottom end acceleration thru throttle body. Lunati states .035 preload for Aluminum heads on cast block. Initially told .050 but that figures for Aluminum on Aluminum. Bud informed me we did set at half turn from 0 ♂️
What does cam card say for lash ? .050 seems alot ?! .020-.030ish ,,, also may need to run a little richer , try 13.0-13.5 afr see if there a difference also you might want to move this to the new part of site off-topic Hot Rod and custom because of the EFI ,, thread will be deleted ,,maybe somebody will move the thread
If you’re thinking that the lash closes up when the engine warms up, you’re wrong. As the engine gets hot the gap opens up. Hot lash is more than cold lash.
so...is the .050 number, the preload? "lash" means clearance, "preload" means the opposite of clearance. Using the correct terms keeps us all from getting confused. I doubt it's a valve lash issue, there should be no problems at all with .050 preload if everything is working as it should. Might be a fuel starvation or percolation problem, or an ignition problem. Pretty hard to tell from here, unfortunately.
On a hydraulic you preloaded typically a 1/2 a turn to 3/4 of a turn(pre load) from zero lash cold, rocker arm tip to tip of vavle
yes, sorry, meaning preload from zero. She runs perfectly first hour then pop pop. All new electrics,street fire etc.
Some 454 engines in especially commercial application were very prone to valves sticking in valve guides under higher heat conditions. Valve stems start galling and picking up material from valve guide bores and problem gets worse. What if any work or modifications were done to the valve guides or valve stems ? Was there any "specing" , measuring and trial fitting done on valve installation. Also......is sufficient oil getting to valve guides ?
Whats the timing 15-20 initial, total 35 to 40 , Sounds Lean ,,, Plug heat range , May be a miss fire , Plug , cap , wire , May be lifter bleeding down hot
My self if running a single O2 , I run it on #6 bank , Test has shown 6 on gen1 sbc/bbc is the leanest of the cylinders
Have a heat dissipation base gasket coming, no issues or overheating whatsoever but once motor shut off and temp rises above 180 sitting for 10 min and then started up and driven acts up.
Is this a New combo that has never been run with a Carb , If so just because New parts , there will be alot of testing ,,, Like all thats been mentioned above needs to be tested,,, You state it pops 1 hr or so after Hot,
Me personally I never could get a champion plug to live anything besides a Mopar and a lawnmower even black Champions I usually use shiny Ngk or old stock 35 ish year old Ac Motorcraft ,Auto lights
When you say spits and pops, do you mean out the exhaust, or up through the throttle body? Is there a noticeable miss when this happens?
Before you adjust the Hydraulic roller lifter preload you really should know what the plunger travel in the lifter is. Different lifters can have different travel. You can then calculate how many turns to make on the adjuster nuts based on the rocker stud thread count. For example a full turn on a 7/16-20 thread is .050". If you have .100" plunger travel, 1 turn from zero lash/zero preload will put the plunger in the center of it's travel. An example could be if you have short travel lifters and you adjust say 1 turn then when parts get hot and grow you could be holding the valves off of the seats. That would make it pop! If timing curve and everything else is working properly, maybe your EFI is not tuned correctly for the conditions.
Buddy says they were adjusted half turn from 0 Says The .050 figure is for aluminum block and heads as per Lunati. My Spec is .035. Thanks for all the help. Movin frwrd with everyone’s advice.
The fact that it is spitting back out the intake does sound like a valve is sticking or the intake valve is being held off of the seat - just back off the preload a little bit and see if things change. My guess is that it is too lean and once it gets hot . . . it gets leaner. I'd be checking my AFRs and the tune. Fatten up the tune a bit and see how the engine responds. In most EFI systems you can monitor it with a laptop while going down the road - make changes and test it again and see what the AFR map shows.
Will do, of course I installed the cheaper self tune instead of the sportsman, but can change the three basic parameters from 12-14.5. On the monitor.
The EZ works decent, I used for over 10,000 miles on a large cid sbc , mild .600 solid roller , there more there thin eye can see on purpose, 283 ? If I recall correct , the down fall on the Ez you can not do a data log ( I was using a stand alone logger ) Holley snipper in more Advance then the Ez from 8ish years ago ,
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