Camshafts and Compression
- Thread starter Valman
- Start date
-
You can't give him that information because you wont have it until the engine is run and tuned correctly.
22 degrees at idle.
BSB67
Well-Known Member
Has the OP given us a detailed description of when and what conditions there is auditable detonation other than 30 degrees is okay and 32 is not?
mderoy340
Well-Known Member
A seperate on/off switch for the ignition box will cure the hot start issue.
VM,
Idle ill be a LOT smoother with more idle timing, probably wth 35-40*. You can simulate this by using an adj vac adv unit hooked to manifold vacuum [ MVA]. 5 min to test the benefit: simply turn the dist [ advancing ] with engine idling, in gear if auto. Advance until rpm stops increasing, THEN check the timing. RPM increases because engine is making more hp. Result is cooler running, better tip in response, smoother idle, more vacuum. I could give plenty of examples, here are just three:
Idle ill be a LOT smoother with more idle timing, probably wth 35-40*. You can simulate this by using an adj vac adv unit hooked to manifold vacuum [ MVA]. 5 min to test the benefit: simply turn the dist [ advancing ] with engine idling, in gear if auto. Advance until rpm stops increasing, THEN check the timing. RPM increases because engine is making more hp. Result is cooler running, better tip in response, smoother idle, more vacuum. I could give plenty of examples, here are just three:
Legend Bewy, thanks heaps mate. Idle is pretty good with 22-24, no rpm drop when pulling it into gear. I have adjustable vac advance on the dizzy, so I’ll give MVA a go, got it on ported vac right now, also tried no vac advance.
I have the vac canister set for 6 degrees only ATM. (crank degrees).
Should get more control of idle mixture screws if all goes well with MVA instead of ported. - cheers for that info!
I’ve got some info from Rhodes about the lifters. Have to check my notes, I think the ppl I bought them off may have given me the wrong install instructions….. I’m seeing a glimmer of light now.
Another thing I have noticed on TQs.....
The nipple in the base for the AV dashpot. Occasionally, it will be a brass tube with a very small hole in it. I drill the hole to 3/32" so that the hole in the dashpot nipple is the restriction. I believe a hole that is too small on a high hp engine might restrict AV movement too much, lose hp.
The nipple in the base for the AV dashpot. Occasionally, it will be a brass tube with a very small hole in it. I drill the hole to 3/32" so that the hole in the dashpot nipple is the restriction. I believe a hole that is too small on a high hp engine might restrict AV movement too much, lose hp.
True. I’ve seen them without the restrictor orifice in both the AV dashpot and the baseplate as well. Maybe some mixing and matching going on.
Do any of you guys have a technique or trick to bleed down hydraulic lifters still installed?
I’ve always taken them out in the past and done it by hand. Don’t have a spare set of intake gaskets ATM…
I’ve always taken them out in the past and done it by hand. Don’t have a spare set of intake gaskets ATM…
Just askin, but to what end?Do any of you guys have a technique or trick to bleed down hydraulic lifters still installed?
I’ve always taken them out in the past and done it by hand. Don’t have a spare set of intake gaskets ATM…
Need to bleed down the lifters to readjust / check the Rhodes lifters. They need to be bottomed out initially to adjust them properly
They must be V-Max.
Newbomb Turk
Well-Known Member
I would V-Max them right into the trash but that’s me.
So that would be a no then. Cheers.
If you have the V-Max lifters, then you also must have adjustable rockers. Just get each one on the base circle of the lobe and adjust tighten the rocker down to force the oil out of the lifter. Then make your adjustment and move to the next.
What Valman is saying is that spring pressure alone might not be enough to collapse the lifter. What else can be done?
Remove the rockers & refit the shafts. Fabricate a bar that goes under the shaft & locates on the prod. Lean on that slowly to bleed the lifer down, careful not to bend the prod.
Remove the rockers & refit the shafts. Fabricate a bar that goes under the shaft & locates on the prod. Lean on that slowly to bleed the lifer down, careful not to bend the prod.
I ran a set of Rhodes long ago but not sure if they made a difference.
Now that I understand more about engines I wonder how do they know what the individual engines oil pressure curve is ? And some engines will run low idle pressure but high pressure further up in the rpms. Then you have high volume vs low volume pumps to consider . Then there is oil viscosity. I don’t think you should select viscosity based on what Rhodes lifters want .
And after reading this post I wonder what the point of them is at all …. If your running a big cam you probably have high compression and will run into exactly the issue OP has . If your running a small cam you don’t need them .
Now that I understand more about engines I wonder how do they know what the individual engines oil pressure curve is ? And some engines will run low idle pressure but high pressure further up in the rpms. Then you have high volume vs low volume pumps to consider . Then there is oil viscosity. I don’t think you should select viscosity based on what Rhodes lifters want .
And after reading this post I wonder what the point of them is at all …. If your running a big cam you probably have high compression and will run into exactly the issue OP has . If your running a small cam you don’t need them .
They work on time, above 3,000 rpm they don't have time to bleed down.
Or run the compression that will work with rhoads lifters and or run more cam.
To me they seem like a good idea, instead of running a medium sized cam as a compromise between power and street manners, run the bigger cam instead. eg. a 245-255 instead of 230-244.
Last edited:
The operation of Rhoads lifters isn't controlled by oil pressure, but RPM. From the Rhoads site:
"Q. Is it oil pressure or rpm that restores duration?
A. Rpm. Quite simply, at lower rpm Rhoads Lifters have more time to leak down. As the rpm increases they have less time to leak down and at approximately 3500-4000 rpm virtually full lift and duration are restored."
And see that little word up there, ^^^^^ "virtually"? That means "almost". Herein is why I DETEST hydraulic lifters of any kind. Because essentially, no one knows exactly how much plunger movement there is. Even with standard hydraulic lifters, the plunger "floats" a certain amount and that amount reduces total lift and duration. The Rhoads lifters just do it more. How much more? Even the Rhoads company itself doesn't know, so they use the word "virtually". Hydraulic lifters were NEVER meant to be a performance lifter, I don't give a DAMN who or what article or forum guru say they are. They're not. They were invented for two reasons and two only. To get rid of the solid lifter noise and to eliminate the need for adjustment. PERIOD. There's really only ONE hydraulic lifter that'd I'd agree kinda goes "toward" performance and those are the "short travel" lifters. Even those still vary the amount of lift and duration. By how much? Who the hell knows? When you have solid lifters, you know EXACTLY how much play is in the valve train. It is EXACTLY the amount of valve lash.
Last edited:
So they act like a shim stack in a motocross bike ?
You read what I copied. Not bein a smartass, but they don't go into any more detail than what I posted. Again, more ambiguity about hydraulic lifters.
-
