427R Drive Ability

[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

[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