427R Drive Ability

[Anthony]

I’d leave the motor and rear gears alone, just run it at higher rpms, keep from shifting to a higher gear until rpms are up, and when cruising, if it is bucking or running rough, just drop it to a lower gear.

[14vision]

Originally Posted by Anthony

I’d leave the motor and rear gears alone, just run it at higher rpms, keep from shifting to a higher gear until rpms are up, and when cruising, if it is bucking or running rough, just drop it to a lower gear.

Thanks Anthony that’s how I have been driving it. Higher rpm’s upper gears no problem, 1st gear from red light or just starting needs some Ron’s for sure to smooth it out ...

[ha_pe_1968]

Hi Dough!
I have a 427R too, with more or less the same experience, even with a dual plane intake.(RPM Performer)
Changed to a smaller carburator (Quick Fuel 750) modified timing curve, idle at 1.000-1.100rpm and now it is ok. Fore sure it is not a cruiser Motor but driveable above 1.400 and the fun Begins at 2.000.

Peter

[eschaider]

Doug,

Adjusting the idle, going to a shorter R&P, changing carbs etc are all superficial changes that might but probably will not mask the drivability problem you are having. The issue is, as John (Grubby) had already noted, the camshaft and in particular the overlap and possibly also the duration.

If you use a cam with significant overlap it will, with a very high level of fidelity, reproduce the 60's lumpy muscle car idle everyone so lusts after. It will also produce the poor driving manners you so dislike. CompCams actually makes an entire line of cams they call the Mother Thumpers which will also produce the raggedy idle that some find so desirable (until you own it).

When you increase overlap (tightening the lobe separation angle or increasing duration or both) you play havoc with idle and low speed cylinder filling. That havoc will give the engine the 60's muscle car idle. It will also destroy the low speed driving manners of the engine. A swap to the Roush 427sr cam will help but you will still have some residual bad low speed driving manners.

Shortening the duration, even a little, and spreading the lobe separation angle will produce a high vacuum idle and very smooth low speed power for a pleasant low speed driving experience — anywhere. If you use contact Roush and ask for one of their milder cams you might (I sort of doubt it but might) be able to keep your original Roush warranty. An aftermarket cam selection would likely be better, less expensive and of course void your Roush warranty.

I think the warranty is very likely going to be a casualty if you fix the bad low speed driving manners. In the FWIW bucket EFI is not going to fix the cylinder filling problem at low speeds and the conversion is anything but inexpensive. A tight lobe separation angle camshaft will still turn a sunny side up cylinder filling event into a Denver Omelette, to use a breakfast analog.


Ed

[KDubU]

I agree the cam swap would help but not something I personally would do. I had a custom cam with a lobe of 114 and it was sometimes a challenge at idle based on what the engine builder set it to. I increased the idle slightly and it was manageable although some thought it was about to choke sitting at a red light sometimes but it never did. I do like the lumpy sound.

[ha_pe_1968]

It depends what you want...if you would like to have a Mercedes feeling around idle then it is the wrong Motor...but with the cam swap it can be very smooth. I have a 427R and was in the same boat. My target was to have a driveable car and it was working without a cam swap. I would start with small and cheap Things...check timing and timing curve...carburator adjustment, checking power valve, idle up to 1.000rpm and then try if it is ok for you. If not ...next step...cam swap and fighting with warranty.

Peter

[CHANMADD]

I mean ..one does not buy a race car and expect it to drive like a Rolls.

[FredG]

Originally Posted by CHANMADD

I mean ..one does not buy a race car and expect it to drive like a Rolls.

When I purchased my car, I wanted the Roush 427r based upon all of the characteristics it has and the value it added. I had already gone the big block route in my 66 Vette. I didn't want another big engine that ran hot, needed valve adjusting and put extra weight in the front of the car. If I wanted something tamer, I would have got a car with one of those Iconic engines. I love the thrill that engine gives you when you give it a foot full of pedal and the RPM's sprint over 6k in an eyelash. INMHO.

Fred

[FredG]

Originally Posted by CHANMADD

I mean ..one does not buy a race car and expect it to drive like a Rolls.

When I purchased my car, I wanted the Roush 427r based upon all of the characteristics it has. I had already gone the big block route in my 66 Vette. I didn't want another big engine that ran hot, needed valve adjusting and put extra weight in the front of the car. If I wanted something tamer, I would have got a car with one of those Iconic engines. INMHO.

Fred

[t walgamuth]

I agree, set up the idle and practice driving smoothly.

[genolan]

I have the 427r and all’s I can say is rpm’s are your friend. Keep it in a lower gear for slow driving or she’ll buck like a bronco.

[KDubU]

Or hand over the keys and I will gladly tame her.

[olddog]

My guess is that opening up the engine will void what ever warranty it has. Based on some stories over the years, I'm not convinced the warranty is all that is suggest before the sale.

Going to a dual plane intake (assuming it has a single plane now) helps low rpm torque, but depending on the heads and cam you may end up with a combo that give the worst of all worlds.

A reduction in rocker arm ratio would calm a cam down.

I would talk to Roush. Tell them what you do not like. You might be able to tweak the timing curve to make it a little more civil.

[eschaider]

Originally Posted by eschaider

,,, Adjusting the idle, going to a shorter R&P, changing carbs etc are all superficial changes that might but probably will not mask the drivability problem you are having. The issue is, as John (Grubby) had already noted, the camshaft and in particular the overlap and possibly also the duration ...

Grubby nailed it out of the gate in post #2. The cam is one of two problems you have. The second problem is deciding what to believe and what you intend to do.

You can spend a lot of time and potentially a lot of money chasing ghosts that always disappear as you reach out to grab them. In the end you wallet will be lighter, you'll be frustrated and likely worn out while the engine will still have all the same bad low speed driving manners.

The flip side of that coin is the highly probable loss of warranty when you do the swap. Real world, as olddog has already pointed out (and many have experienced), the Roush warranty sounds good until you have to use it. When you use it, you need to remove the engine from the car and ship it back to Roush before they tell you your problem is not covered by their warranty. Then you get to pay shipping one more time back to you. Nothing has changed at this point yet except you have less money than you had before you shipped the engine to Roush.

Cam installs are a walk in the park, even for those with limited mechanical skills. BTW Cobra's are not good car selections for owners with less than limited mechanical skills. Sooner or later it will get painfully expensive to pay others to do the work you should be capable of.

The character of an engine is attributable almost exclusively to the camshaft installed. Pick a better cam — get better low speed manners. It is that simple!


Ed

[Ozzie Goat]

One more thing I have not seen mentioned.
Because our engines tend to not have warm preheat for the carb, my car runs very poorly until fully heated. Therefore, my car won't ever idle well until fully warmed.

Are the concerns you site as the vehicle warms up, or during normal operation ?

[olddog]

It occurred to me that the OP has never actually explained the bad manors. We have all assumed that he just doesn't like the low rpm tendency to want to buck and hop if you try to make a quick blip on the throttle or open the throttle too much at very low rpm.

An engine running too lean can hesitate, even pop up the carb and backfire. It can also cause surging. Not all engine builders take the time to tune anything other than WOT on the dyno. In fact most do not. Especially if they are a large shop that builds cookie cutter engines (100s of the exact same engine). They may tune one or two and just set all the rest the same.

Then there is the timing. The big three engineers spend hundreds of hours finding the ideal timing to make maximum break torque at every rpm and every % load combination. Then they change the commanded fuel ratio and do it all over again. All this while measuring emissions. This is how they maximize mpg, minimize emissions, and get good manors and good Hp.

Most engine builders will not even make a low rpm dyno pull. This is the danger zone where engines self destruct from detonation. They will argue that you should never operate a performance engine in that range anyway. Fair enough, but this is the proof that nobody has spent the time getting a good tune down in the low rpm range. This can be done with EFI, but there are not many tools to work with on a carb and mechanical distributor.

Does your engine have vacuum advance? If not, one less tool, and a terrible way to run a street engine. It's fine for a race only engine, because it will spend little time at low rpm.

I have digressed. My point to all this is: Take your car to a good tuner with a chassis dyno. The best dyno for this is the type that can hold a set load or a set speed and can change this on the fly. I forget the name for this. The dyno that just spins a heavy wheel is better suited for WOT pulls. You can do some tuning, but not everything. Then they have to take the car out on the street to finish up.

With the engine well tuned, it may resolve most of your issues. Then it is a matter of training the driver not to try to run the engine where it does not want to run. At some point in time you just have to realize this is not your fathers station wagon. It's a fricking race car, and you need to treat it as such.

[fastd]

olddog,
Excellent points.

My experience is that most engine tuners don't have the patience to do it right; a couple of WOT pulls, add power valves and they are done.

I think an adding air/fuel gauge is never a bad idea, it looks cool and can make you your own best tuner - the only downside is that you have a tendency to stare at that thing when you eyes should be on the road.

Changing the jets, power valves, etc. is not very difficult and kinda fun if you can move your ratios in the right direction.

[olddog]

I wasted 20 minutes of my life that I will never get back on the Roush website. The engine has aluminum heads, a single plane intake, and a hydraulic roller cam. That gave me all the specific details I will ever need. Now I have a lower opinion. Kind of like Phuckem.

[patrickt]

Originally Posted by olddog

I wasted 20 minutes of my life that I will never get back on the Roush website. The engine has aluminum heads, a single plane intake, and a hydraulic roller cam. That gave me all the specific details I will ever need. Now I have a lower opinion. Kind of like Phuckem.

Well I had to see if you were right. Here's the page: https://www.roushperformance.com/engines/427-r.html They do tell you that the stroke is 4.0", so I guess the bore has to be about 4.12" -- you'd think they'd at least give you the cam specs, but I couldn't find them.

[twobjshelbys]

Originally Posted by patrickt

Well I had to see if you were right. Here's the page: https://www.roushperformance.com/engines/427-r.html They do tell you that the stroke is 4.0", so I guess the bore has to be about 4.12" -- you'd think they'd at least give you the cam specs, but I couldn't find them.

Here is the cam spec I was given for the 427IR (which is supposed to be the same as 427R inside the box).