chinese 1.6 steel roller rockers & RHoads lifters

[nm9stheham]

Except on the intake side,at low-rpm, the piston is coming up on compression perhaps half way, up or beyond, and that stinking intake is still not sealed. So the piston is pumping A/F charge back into the intake. That makes for lousy fuel efficiency. Between that and the early opening exhaust, you just cannot cruise at low-rpms and expect fuel economy.

That misses the point, IMHO, AJ... if the flow is essentially 0 at some opening level, then the valve is acting as if it is closed. How much of that reversion is going to flow back through a valve that is .002" or .003" or .005" from closed, even under the start of compression? I don't have a flow bench to test or I'd know the answer.

@greymouser7 John, is any of this BS doin you any good?

What the heck? Being responsive to the OP? That's not the 'internet way' LOL

 

[AJ/FormS]

yep long intake close is a Dynamic compression killer
problem at overlap is not so severe
but slow exhaust opening bleeds power (especially on low compression motor) and torches exhaust valves and seats
at high pressure even a small opening has flow
Aj nails it

I used to think that overlap was the fuel-mileage killer, but if you think about it, at steady-state it ain't all that bad.... unless you have a really deep hiway gear.
But lotsa overlap in city-mode will kill mileage too, but if you have a cam with lotsa overlap, you shouldn't be thinking about that anyway, cuz at the other end, lotsa overlap comes with the penalty of late closing intake and early opening exhaust anyway; so which are you gonna blame for your rotten fuel-economy.
I'd rather have the overlap cycle working for me, especially with a smaller engine.....

 

[nm9stheham]

but slow exhaust opening bleeds power (especially on low compression motor) and torches exhaust valves and seats

Hey wyrm, I'm being slow today.... Do you mean a slow lift speed on the exhaust valve?

 

[RustyRatRod]

That misses the point, IMHO, AJ... if the flow is essentially 0 at some opening level, then the valve is acting as if it is closed. How much of that reversion is going to flow back through a valve that is .002" or .003" or .005" from closed, even under the start of compression? I don't have a flow bench to test or I'd know the answer.
What the heck? Being responsive to the OP? That's not the 'internet way' LOL

LMAO.

 

[greymouser7]

@greymouser7 John, is any of this BS doin you any good?

I think after your input, that if I want to go in the opposite direction of everybody else (high HP builds) -on an economy/daily driver, that a smaller camshaft is better to get the engine into the power band like what you told me.

I am not wise enough to understand the fine details of valve timing in relation to overlap in relation to LSA, etcetera. -dialing in the perfect cam (& then following yellowrose’s advice with cam grinder consultation)

IQ52 did this on this on a truck build here a while back. He put a 318 cam into a 360.

The question becomes how small is just small enough.
. 318willrun put the crane cams 693901 in his 2.45 geared duster?dart?
-it is at least 500 pounds lighter, but with only a 904 or 727 (or does it have that modified 904?{a999?}?? Which has a different gear set. 204 intake and then 216 exhaust which seems like it was designed for the choking exhaust of a 302 head?

The a833 turns a 2.45 first gear into a 2.846 rear axle ratio compared to the 904,727,regular 833. Maybe that could make up for some weight?

One thing you pointed out Rob that got me thinking:
The Honda does something with the fuel injection where the engine does not lug when high gear yet coasting too slow for the gear.

My road runner doesn’t like THAT (type of driving) with a carb and it took an experienced mopar man with me driving to point out my mistake lugging the RR at low speed.

Which is an effect of exactly what you were talking about (besides driving out of/below the torque band of the cam/weight/gear/engine displacement.

(Again thank you!! I’ve learned so much on FABO)

Another problem I am experiencing here without marine gas is what I believe to be vapor lock. I pull up to gas station, car is running GREAT! Turn it off, fill it up, & crank the starter forever to start it again. (Could be the carb)

Rob I think your efforts have convinced me to start with a higher gear with the 8 1/4’s : 2.71

Which would make the car more fun
Effective 3.148 rear gear, but much better 2nd and 3rd

 

[AJ/FormS]

As to fine-spline A833 ratios;

The T/A box has ... 2.47-1.77-1.34-1.00.
The standard has ... 2.66-1.91-1.39-1.00.
The Commando has 3.09-1.92-1.40-1.00

The regular TFs are 2.45-1.45-1.00..
but the TCs have a built in torque multiplier, at zero mph, that can nearly double the output for just long enough to get moving. This is why from the factory, autos nearly always came with the next smaller rear gear. And after the initial launch, the TC may decay to in the range of; 1.10 to as little as 1.05. So when you nail it, those TF ratios could act like 2.70-1.55-1.05 with a starter in the TC of possibly as high as 1.8, that would make taking off like it had a 4.41 low in it, albeit ever so briefly. So if you arrange that properly, it looks like
4.41 decaying to 2.70-1.55-1.05-and cruising could be less than 1.00, depending on the combo. If you gear the back to put second gear where you want it, the automatic can do a great job, in a streeter easily behaving like a pseudo-4speed; Perhaps 4.5 with a loc-up clutch in the TC.