Help me diagnose noisy valve train on new stroker.

[Bender]

I just finished a stroke motor but have noticed the valve train is quite a bit louder than stock.

Background...

4.6L Low budget stroker..
68-231-4 Comp Cam
Moper Performance valve springs.
Stock rockers
Stock pushrods
Head Milled .010"
Block left alone.

When I first fire up the motor on a cool day the noise is barely audible...sounds good. As it warms up the valve train noise begins to get louder. The shop that assembled my motor seems to think the lifters are bleeding down to quickly with the increased cam lift and spring pressure, however they lifters are the ones recommended by Comp Cams so I figured they would be the correct ones.

Does anyone have any experience with this cam/spring setup?

Cheers!

 

[Dr. Dyno]

I hope that's just a normal function of having a higher lift cam and stronger springs because I'm going to be in the same boat as you when I finish my own stroker (Crane cam & lifters, Mopar springs/retainers/locks).
What viscosity oil are you using? Perhaps a thicker oil might help to reduce valvetrain noise?

 

[Bender]

Dino,

I'm working right now trying to determine what the problem is. My break in oil was a non-syn 30 weight. I ran this for the first 600 miles changing it twice...the noise has been consistent from the beginning. Since I only took .010" off the head and didn't machine the block I think I can safely rule out pushrod length issues due to machining. The only thing I can think of right now is a high bleed down rate on my current lifters...however, I'm running the lifters recommended by Comp Cams for their cam.

Unfortunatley the noise seems too loud to be normal. With my stock engine I used to be able to hear my injectors firing....now that noise is drowned out.

I've currently added some oil thickeners to see if it lessens the noise. I'm trying to determine if the problem is in the lifters or elsewhere.

 

[strokedwoody]

Mine has lifter noise on start up but then quickly goes away, it drives me crazy b/c my stock motor was wooped out and it never had lift noise....My guess would be the lifters, but who knows what to do to fix it....

 

[MudDawg]

Is the base circle of the new cam smaller than the stock cam? If so, there may not be enough lifter preload.

 

[rsalemi]

I have 12000 miles on the stroker with the 235 cam and there is some lifter noise which is normal. same setup as you have comp lifters and cam Mopar performance springs and retainers - cam one step hotter. Block and head not milled - are you sure you have lifter noise - at idle, not under load - that could be pinging due to higher compression or not indexing the distributor properly.

 

[Bender]

rsalemi,

Is your valve train noise louder than a stock 4.0L?

I have the distributor indexed so the rotor is "just" past the #1 post at TDC. I used an old cap and cut the side out to set it up. The noise occurs at idle but increases with engine speed.

I'm not sure on the cam's diameter so perhaps that may be an issue. I'm going to pull the valve cover in the next couple days and try to determine whether it is insufficient pre-load.

Thanks for the suggestions so far.

 

[Dr. Dyno]

I have a slight ticking noise from the valvetrain on my stroker but it doesn't really bother me. There's none at all when the engine's cold but once it warms up it starts to appear. I've noticed that it's related to the oil viscosity.
When the engine's cold, the oil's thicker and the noise is muffled. As the engine warms up, the oil thins and the muffling effect is reduced. It's also more noticeable since I switched from 20W-50 dino oil to 0W-40 Mobil 1 at 3000 miles. Nevertheless my stroker's still quieter than my 4.0 was when cold and it's about the same when hot. There's no piston slap at all.
Since I switched to Mobil 1 I've noticed that the lifters tick very slightly upon start up for about a second until they pump up under oil pressure, but only after the engine's been switched off for a long time. It's possible that the thinner oil bleeds out of the lifters at a faster rate so there isn't enough in them at the next start up. I wonder if this is normal for the Crane anti-pump up lifters that I have.

PS: Now have 3800 miles on my stroker and it's so far, so good (knock on wood).
_______________________________________
Dino's "Mean Green Machine"
1992 XJ Laredo 4-dr - 4.6L I6 HO Stroker - 178k miles - AX15, NP231, D35c, D30

258hp@4800/320lbft@3200, 1/4 mile = [email protected], 0-60 = 5.9secs
Websites - Jeep 4.0 Performance, 4.6L Stroker Build-Up, Dino's Jeep Tricks

 

[old_man]

My valvetrain is definately louder than stock on my stroker with the crane low rpm cam. I think the increased lift is the source of the noise. I've got 15k miles and it still sounds the same, works fine.

 

[Dr. Dyno]

What are your oil pressures when the engine's hot, and what grade of oil are you using?
Mine are 20-25psi at idle, 40psi at speed with Mobil 0W-40.
When the engiine's cold, the pressure's a constant 50psi.

 

[Eagle]

Is the base circle of the new cam smaller than the stock cam? If so, there may not be enough lifter preload.

My thought as well. With a hotter cam, the pushrods may not be long enough.

Remember, the cam lobes have to fit through the same bearing holes regardless of how mild or wild the grind. So a cam with a higher lift doesn't have taller lobes, it has a smaller base circle ... which means when the valves are closed the lifters drop farther away from the head.

 

[CW]

My engine is noisy at idle but smooths out when over 1500rpm. I have 3k on it and it's always done it. It doesn't bother me. I run a comp 250h and comp lifters.

 

[Dr. Dyno]

My thought as well. With a hotter cam, the pushrods may not be long enough.
Remember, the cam lobes have to fit through the same bearing holes regardless of how mild or wild the grind. So a cam with a higher lift doesn't have taller lobes, it has a smaller base circle ... which means when the valves are closed the lifters drop farther away from the head.

If we applied your hypothesis to the Crane 753905 cam (0.302" exhaust lobe lift) and the stock cam (0.265" lobe lift), the difference in lobe lift is 0.037". There's definitely a lot more clearance than that in the cam bearing holes so there seems no reason to grind that particular Crane cam on a smaller base circle. If the lobe lift was much greater than that, a smaller base circle would then of course be necessary.
With the cams that we're using on our strokers, I don't think the base circle is an issue so the likelihood of the stock pushrods being too short is remote.

 

[BajaXJ92]

What are your oil pressures when the engine's hot, and what grade of oil are you using?
Mine are 20-25psi at idle, 40psi at speed with Mobil 0W-40.
When the engiine's cold, the pressure's a constant 50psi.

I'm running 10w40 and have about the same oil pressure as you. Actually closer to 50psi at speed.

I've "heard" a good rule of thumb is that good oil pressure is 10psi per 1k rpm. *shrug*

I've got similar valvetrain noise in my stroker w/ about 3500miles.

 

[wascobi]

I'm about to use the same cam (68-231-4) in my '90, but still unsure about the stroker part. I have been giving pushrod lengths a lot of thought lately. if my lift difference is .034, and the head is milled .010, thats still .024 of extra slack for the lifter to pick up. according to comp cams, non-adjustable rockers require .030 of lifter preload.that should be accounted for in the original lift. so a pushrod .020 longer would be a safe starting point? am I on the right track?

 

[MudDawg]

When I built my 2.5...for all practical purposes the valvetrains are identical...I ran into the situation of needing longer pushrods...my machinist and I went through a catalog and found pushrods of the required lenght without breaking the bank on a custom set....I used a set from a 70's model 455 buick....Sadly they won't work in a 4.0 based motor due to the taller deck height of the 4.0 block compared to the deck height of my 2.5 block.

Another problem I ran into was wear on the rocker arm pivots...I run a pretty aggresive cam and valvespring combination...I sent a set of rockers and pivots out for cryo treatment...so far so good...If they wear...it will be a set of shaft mounted roller rockers next.

 

[Dr. Dyno]

Another problem I ran into was wear on the rocker arm pivots...I run a pretty aggresive cam and valvespring combination...I sent a set of rockers and pivots out for cryo treatment...so far so good...If they wear...it will be a set of shaft mounted roller rockers next.

Yeah, I've got my eye on a set of Yella Terra YT6627A shaft-mounted roller rockers if my existing stock rockers wear out prematurely.
Quadratec.com sell them for $440 but I can get them directly from Yella Terra in Australia for about $360.