Why would this happen?

[billoddie]

Hi gents.
With the exception of a 402 big block 1966 Galaxie that I once had, v8's from the past have all had irritating tappet noise to some extent.
Recently, I discerned the same in the Rove whilst sitting inside it. :x
Standing next to the car, it was largely absent (drowned out by the chattering of the fuel pump), but made its presence known from the drivers seat.
Upon closer listening, I hoped it may be a leaking manifold gasket (please please).
Upon tightening the bolts from where it seemed to originate, the ticking disappeared...sigh of relief
When I next drove the car, apart from the improved engine smoothness and silence, I noted the trans changed significantly smoother and with greater "precision".
Still not totally perfect, but a marked and welcome improvement for 5 minutes work.
My question is, why would this be so?

 

[chrisyork]

A good result, Bill!

As to the cause? Well, this is highly speculative. The exhaust manifolds on the P6 auto are highly restrictive, even after late '73 ('74 model year with the low compression engine) when the slightly larger "S" manifolds are fitted. A good rule of thumb would be that a decent set of tubular manifolds should liberate an extra 10 bhp with no other engine work. So if they are that restrictive, presumeably your small blow was allowing just one cylinder to run rather better. Now that you have restored equal badness across the engine, perhaps the engine will run more smoothly? A smooth engine should certainly lead to smoother auto changes as there are no longer any hesitations or surges caused by the unequal power from each cylinder. If you like, the opposite of eliminating a misfire.

How about that for a tenuous set of linkges!

Chris

 

[a15htn]

How about that for a tenuous set of linkges!

Chris

Chris, isn't that what is fitted to the tc & v8 anyway? Tenuous linkages? ....... Sorry, I'll get my coat

 

[billoddie]

Being an auto vehicle, will tubular headers affect low rpm torque?

 

[chrisyork]

I can only report what happened with Lucky. In theory, 4 into 2 into 1 headers can be arranged to boost the torque at a particular rpm, chosen by the exact lengths of plain tube between the two junctions. This is usually a lowish rpm. In theory, 4 into 1 headers lose low rpm torque and deliver at high rpm.

Because of the space constraints on the starter motor side of the engine between the block, starter motor, engine mount and chassis rail, our judgement was that a choice of pipe diameter small enough to get two pipes through this gap to make the 2 into 1 join roughly under the starter motor was so small as to make the whole event not worth the effort. So we made a 4 into 1 with the join far enough up to release a single pipe to go through the gap and with a decent pipe diameter off the heads. BUT the artist who made this all up did a truly wonderful job on the actual 4 into 1 joint. I'm going to have to try to describe this as I don't have a photo. First of all the four pipes are brought together in a bundle. Clearly there is a gap in the middle of the four pipes. This was filled with a prominent peak, to give the appearance of a spike at the centre of the bundle. Next up the bundle is wrapped in a piece of pipe of a diameter equal to the whole bundle. This was then rapidly swaged down to the final single outlet pipe diameter. The whole effect is to give an impression of each pulse of gas from each tube being smoothly guided into the single outlet whilst being separated by the spike from neighbouring outlets. By far the best arrangement I've ever seen of a 4 to 1 junction and, to this engineer's eyes at least, positively beautiful!

And the effect? A delightful rasp from the exhaust at about 1,800 rpm and another much louder rasp at 2,200 rpm. Since the rasp usually is a good indicator of when gas entraining is occouring, I'd say that indicates some good low speed characteristics. That's certainly born out in driving, the car remains extremely punchy at low rpm. Spinning 205 tyres from a straight take off from rest (with an auto!) is definitely possible. And performance further up the rev range definitely supports a gain of around 10 bhp. I haven't had it on a rolling road yet - the needles fitted at the last session were a tad rich at the top end with the orginal exhaust, so the extra freedom seems to have brought everything to a state of perfection! So if I'm right that implies around 125 bhp at the rear wheels - which students of power loss in a Borg Warner will tell you is really outstanding!

These manifolds were made up by a sub-contractor to RPi and RPi now sell copies. But note that with the later engine mountings, as opposed to the early P5 type mounts for which the set up was designed, some fairly worrying trimming of the drivers side engine mount is required.

Chris

 

[billoddie]

Hi Chris.
Thanks for your detailed reply.
Sounds like a few $$$ and skills there.
I'm probably not at that level yet!
I even baulk when I see "off the shelf" Pacemaker headers for $695.
I'd imagine the work you had done to be a bit more expensive than that. :roll:
There is a gent wrecking a 3500 in South Aust that has a full stainless system, but he wont separate it, and I cant figure a cheap way to transport it, so i will just keep looking.
Add it to the want/to do list...
I can see now that you actually never "finish" these cars...that they make you revert to a boy so you can tinker and play with them, and dream up all sorts of imaginings in your head of how to improve/modify them!
What rich pickings if one happened to win the lotto!!
Which reminds me...it's a 50 MILLION jackpot tonight...so I will get that ticket in.
If I happen to win it, or more than 10 mill, I'll stump up a couple hundred grand and we can all build the perfect P6 as a collective project.