A998 & TF-1 - Harsh 2-3 shift

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I guess I could shim the rocker arm shafts if needed. It sounds good though.
 
Comments in the quote
olei said:
Wow, thanks for your detailed reply, again!
I haven't heard about shorty headers might being a issue with tight LSA before, thanks for bringing it up. It has always been to my impression that tight LSA cams make low vacuum, and need more RPM to stay alive at idle.
Tight LSAs are usually found on big cams., cuz they have to steal the duration from somewhere.It is not the tight LSA that causes the poor vacuum, but rather the very late closing intake. Your cam does not have a very late closing intake. By my guesswork, it might be around 52* ABDC. And your overlap, I'm guessing is also around 52*.
So It should idle around the same as a "normal cam" with similar .050 specs, except for a slightly raunchier idle.
Hughes doesn't mention anything about header changes on their website.
I noticed that too, but if you go to the technical section,they do talk about headers. I think long-tubes are kindof the norm, and may be assumed.
This is the camshaft I run; Hyup, that is the one I referenced in my calcs
Hughes Engines
On the flat tappet Whiplash cam though, they do mention vacuum to be in the 9"-11" range; Imagine that,lol
Hughes Engines
I emailed Hughes yesterday asking about what idle quality/speed I should be able to get. I will see what they have to say about this first. OK,I'm very interested
My calculations gave me 9.64 SCR.
I have not been having issues with detonation, as far as I know (but we haven't been using equipment for listening to knock). I run a fuel that equals your 91 Octane.

I posted my dyno results here; I checked 'em out
My 318 dyno results
Based on these results I feel the engine looks healthy, even though Hughes meant I should have made even more power. Being the short duration cam it is, I believe it seems about right from my power figures?
Yes and no. Typically the tight LSA will increase specific horsepower, while exaggerating the peak,at the expense of average power.
The way this is done is with the headers "supercharging" the cylinders during the overlap period. Your graph shows no such effect, so that seems to support my theory in as much as the shortys are not working the overlap cycle.
The graph does show an early climb in torque, and that supports the early-closing intake theory. But the curve is nearly dead-flat, and exceptionally long. Unfortunately, in the typical fashion, the test was terminated too early. My guess is with the right springs and lifter preload, this engine could still be making power at above 6500 rpm, which is unusual for this size of cam. I have to think that the shorties are suppressing the peak.
And speaking of preload, you have an excessive amount.
I would not try to rev it very high, cuz there is a good chance that unless you have well-matched springs,the lifters could get pumped up, and the valves crashed into the pistons.
IMO, I would fix that ASAP or put a rev-limiter on it.
IMO, with that curve, and the A998,and the 2.94s and the 31s, I would like more revs. Currently, at 5300 rpm, you are probably getting about 58 mph. That dyno curve shows such a gradual top end drop-off, that I am sure the engine has the potential for more rpm. 65 would be just under 6000. But again, springs are paramount. and a much reduced lifter preload. I run .020 and Hughes 1110 springs and this is good for well into the 7000s, with 2.02/1.60s . more rpm would get you all the way to the speed limit in one gear. With the A998, this is important, cuz the shift into second drops the Rs waaaay down from 5300 to 2980. If you look on your graph, I estimate this to be about 50% power or 167 hp, so pretty much the race is over. But again; on the graph,6000 might have still 90% power or about 300 hp. That is the fast way!
I'm very happy with how the camshaft drives, with the exeption of the idle quality. I wouldn't mind high idle RPM, but I hate that harsh engagement.
The only thing that I believe was out of spec doing the engine build, is that I run quite some lifter preload, about .110"-.120". Hughes recommends .090"-.095" using their 5006 lifters with aluminum heads, so I'm not that far off either. They told me I should be fine running the higher preload.Fine yes,so long as you stay within the confines of zero lifter pump up. If you exceed the capabilities of the springs to control the valves, and if the lifters pumped up 100%, then the valves would end up .110 to .120 times the rocker ratio, less angularity issues, say .175 closer to the pistons. If your piston to valve clearance is less than this, when pump-up occurs, this could be instant disaster, as in you need a new engine. I say "could be", cuz if the valve breaks and falls into the cylinder, there is usually nothing left over except the crank and rods.
But if they just kiss and the valves bend even a little bit, then it just won't idle anymore, and be very difficult to start. An LD test will instantly reveal the pressure loss.
So, fine,yes; but not nearly optimum.
With adjustable arms, IMO, optimum is .020,and you can adjust them back to that every couple of years,or as they may get noisy,if it bothers you,lol.
With non-adjustable arms, no more than about .030 to .040 to allow for wear during the life of the parts.
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But yeah, that's a crazy-flat torque curve!
 
No, you should not shim the shafts to correct a too-long pushrod.
The shafts can be shimmed to correct for rocker geometry,using job- specific shims.
If the pushrods are too long, there are only two options; shorter ones or adjustable ones.
No; adjustable rocker arms are not an option. Not until the geometry says so.

And that does still not solve the spring issue. You must keep the valves from floating, in conjunction with the correct minimum preload,; then you can sell your rev-limiter, or at least crank it up some.
I am not suggesting that if your engine can rev to 7200, that you should do it. Not at all.
Without oiling system mods, she won't last long up there.But the occasional romp to 6500 is not likely to kill her either. And regular runs to 65mph in first gear,(6000 in your combo), should be no problem.Just don't run her low on oil! and don't pump it all into the valve covers,lol.Cuz then the driverside rod bearings have a nasty habit of complaining, especially #1; I have spun that one twice in 340s.
 
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I will get some 6.700" length pushrods (6.780" OEM length) to reduce my lifter preload then. I have looked into adjustable rocker arms, but I just think the cost is too high compared to the gains.

I bought the Edelbrock Performer cylinder heads assembled and I'm using the valve springs they came with (120# at seat, 310# at .580").

I do also have 3.55 gear ratios to replace the 2.94s, this should suit my driving better.

How much will plenum volume affect idle quality?
 
Comments inside
olei said:
I will get some 6.700" length pushrods (6.780" OEM length) to reduce my lifter preload then. I have looked into adjustable rocker arms, but I just think the cost is too high compared to the gains.For most,I almost agree.

I bought the Edelbrock Performer cylinder heads assembled and I'm using the valve springs they came with (120# at seat, 310# at .580").I used those on my 270/280/110 @.020 preload and saw no valve float at 6500. With hundreds and hundreds of trys,lol

I do also have 3.55 gear ratios to replace the 2.94s, this should suit my driving better. You won't sell me on that decision, unless you are happy to short shift.
Your current starter gear is 2.94 x 2.74= 8.06, and according to the dyno chart, you probably have tons of low-end torque, so I imagine you have no problem spinning those 31s, and so 3.55s will not be any significant improvement. Also, at 35mph, your current rpms should be 1650 in 2nd and 3210 in 1st. Looking on your graph, at 3210 you are already making peak torque, and making 87% of peak power.
But if you cannot spin those big 31s from a stop, then 3.55s will make it happen;
3.55s will increase your starter gear by nearly 21%; to 9.73;Which is tire-boiling territory. And 3.55s will also increase your Rs at 35mph by that same 21%, or to 2074 and 3691. Again, looking on the chart;by 3691 your engine is making 90ish% of peak-power, so it will quicken the pace, by a few percents.
The problem I see with 3.55s and having to shift at about 6000, is 54mph . When the shift occurs the Rs may drop to 3372, and.... Ohhhhhhh............

You know what? Your curves are so flat, it just doesn't matter much at all. If you can live with 3.55s on the hiway, they will certainly get you off the line a little quicker.
Go for it!
How much will plenum volume affect idle quality?
In your case, as good as nothing.
If you had long tubes and idled at 700, then a too large plenum could be a tiny bit of a problem.But by 1000 rpm, you are out of the troublesome area. Also, with as flat as your curves are, I doubt you would have an issue with any plenum size. Your ICA, I'm pretty sure, is very early, and so plenum volume matters not a bit at idle.
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The reason for me to try 3.55s is that I don't do a lot of highway driving, and when I do the speed limits are 60 MPH. We do have a lot of steep hills, so I still believe 3.55s are gonna suit me better. :)
 
olei said:
The reason for me to try 3.55s is that I don't do a lot of highway driving, and when I do the speed limits are 60 MPH. We do have a lot of steep hills, so I still believe 3.55s are gonna suit me better. :)
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I have 3.55s, and they're staying! They are an excellent choice, for almost any application,short of drag-racing.
 
Hughes says idle is usually between 850 and 1000rpm using this camshaft.
 
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