Dave Robsons Challenger R/T

Dave-R · Post by **Dave-R** » Sat Dec 03, 05 5:53 pm

Bit of paint on now. Thanks Matty.

Dave-R · Post by **Dave-R** » Sat Dec 03, 05 5:58 pm

Nice and straight panels.

Dave-R · Post by **Dave-R** » Sat Feb 04, 06 5:38 pm

Mainly for the curious and the guys still learning I thought I would post some photos of our cylinder heads. I have just cleaned up this one.

The heads are the most important part for making power. If they flow too little they limit the power you make. However if they flow too much than you need for your application then they do not work as well and you can actually loose some power. In particular at low rpms.

These are stock type 1968-1970 "906" cylinder heads. They have been fitted with slightly bigger than stock valves and hardened valve seats for unleaded fuel. the ports have then been "ported" by Dave Hughes to his "Stage 1" spec.

This entails opening out the port bowls to the size of the new valves and enlarging the stock port runners slightly. Anything in the stock casting that gets in the airflow (like the valve stem guide) is smoothed. He leaves them with a smooth surface finish on the exhausts and a slightly rougher finish on the intakes. He also cuts valve reliefs into the sides of the chambers to give some airflow around the back edge of the valves.

I have then taken them a little further by polishing the exhaust runners even more and smoothing the combustion chambers to get rid of the rough cast finish. I also blend the floor of the chamber into the valve seat and blend the valve reliefs in a bit better. These reliefs are matched with notches cut into the top of each cylinder just above where the top piston ring comes to.

There are two reasons for smoothing and polishing. One reason is flow. the better the airflow the more fuel and air gets in each cylinder so you make more power.

The second reason is to reflect heat.
The more heat is contained in the engine cylinder during combustion the higher the gas pressure and the more torque you make. Also less heat gets into the water jacket.

The same with the exhaust. The more heat is kept in the exhaust the cooler the water in the engine and the faster the exhaust moves down the exhaust pipe. This draws more spent gas from the cylinder making more room for fresh air and fuel.

These are small things but all these small things add up.

Dave-R · Post by **Dave-R** » Thu Jun 08, 06 9:55 am

Progress still very very slow. But at least the engine is starting to look more like an engine instead of a bunch of random parts.

Dave-R · Post by **Dave-R** » Sat Jun 10, 06 5:55 pm

Here are some shots of the manual six pack set-up. It is not quite finished. This is just a mock-up to get the rather complicated linkage working as it should.

Dave-R · Post by **Dave-R** » Sat Jun 10, 06 6:02 pm

Forgot to say.
I made a little cover for the choke well the other day.

It was just a bit of scrap ally plate I had kicking about and a couple of bolts out of the parts bin that I ground and polished on the heads.

Dave-R · Post by **Dave-R** » Sat Jun 10, 06 6:14 pm

You see what I mean about not being able to see the carbs?
Looking at that photo i will have to do something with the front of the carb plate. maybe just paint it black?

Dave-R · Post by **Dave-R** » Mon Jul 10, 06 6:24 pm

Found some old photos. May as well post them here.

Dave-R · Post by **Dave-R** » Tue Oct 10, 06 10:09 am

This looks a mess.

I am trying to run -8AN right up to the six pack and then branch off on -6AN into each carb.

I have managed it but I think it looks ugly. It does not help that I have found one of the carb adaptors is a bit thicker than the rest (center carb) so it kinks the "fuel rail" slightly. I will move thet one to the far end I think.

And yes Duncan. I am going to take the gold paint off the carbs and give them a bit of a polish instead.

Dave-R · Post by **Dave-R** » Thu Nov 16, 06 12:05 pm

It looks as if I will have to shelve the Challenger for a while.

On top of other finacial pressures we just found out there is a good chance my wife Diana will be laid off work and as she earns more than me that is a bit worrying.

Her employer, the Inland Revenue, has about 100,000 workers. They want rid of 25,000 in total (1 in 4) in stages up to sometime in 2011. But initially they want rid of 300 staff in Newcastle alone by 2008. More after that if initial National quotas are not met.

This is double the figures they were told before today. Those that are not laid off will be re-trained and some will be re-graded (up or down they don't know) to suit the new working practises.

So we had better get our house in order just in case.
That means I doubt very much the Challenger will be on the road next year. Not something I am very happy about.

Dave-R · Post by **Dave-R** » Fri Nov 24, 06 11:01 am

Only that my wife has now heard that 800 jobs at her place have to go in Newcastle now. 500 over the next year or two.

The only progress is that I might have sold the Jeep. If the guy turns up on Sunday then the cash will go towards paying off some debt but most of all we need to get away for a week on holiday. Diana is still upset about the dog and I don't know when we will be able to afford a holiday again. So fingers crossed the guy turns up.

However!

Through seling some other stuff and doing jobs for people I am in a position to buy a pair of ceramic headers for myself as my Christmas present.

Once I have those I will be installing the engine, trans and K-frame all as one unit with the headers in place.

So look out for a few photos after Christmas.

Dave-R · Post by **Dave-R** » Fri Nov 24, 06 1:54 pm

AllKiller wrote:Fingers crossed, Good luck to ya Dave and Diana .

Ceramic headers they sound nice, what make ??

Thanks mate. I still have not made up my mind but probably Dougs as they are a few hundred dollars less that TTIs and I have not heard of any fitment issues. Bit of a gamble. But time will tell.

I'm still wondering if 2" primaries are too much for my engine or not.

Dave-R · Post by **Dave-R** » Fri Nov 24, 06 2:27 pm

Blue wrote:I'd go for the 2" Dave, if you don't you"ll be wishing you had in a couple of years time when the wicks been turned up a bit more, do you see aftermarket heads in your future?

This is why I am wondering what to do. I do not intend to change the heads in the future. I don't want more power than it has now. I just want more efficiency and refinement from the engine. So what I want is something to work with the current combo. And last a long time.

I may re-build the short block one day with lighter pistons and rods but that is about it.

My understanding (from memory) is that larger primaries will give less low end torque but more top end horsepower?

The new cam however should give more low end torque and slightly less peak horsepower than before. But the loss of horsepower is at the rpms above my shift limit anyway and average HP over my shift rpm will be higher.

So I am wondering how the 2" headers (3.5" collectors going into a 3" system) will effect the power curve??

AllKiller · Post by **AllKiller** » Fri Nov 24, 06 2:44 pm

Dave so the one on there now or were..... 1.7/8" s or 1 3/4 ?

Low to mid grunt is smaller and longer tubes
High end bigger and shorter tubes
or
Heavy street car smaller tubes,
light race car big tubes

Street 1 3/4 to 1 7/8 383 to 440
street strip 1 7/8 to 2" 383 to 440
strip only 2 to 2 1/8 440 to 500

hope that helps

Dave-R · Post by **Dave-R** » Fri Nov 24, 06 3:41 pm

AllKiller wrote:hope that helps

Not really.

Yeah the existing ones are 1-7/8ths So only 1/8th smaller than the ones I am thinking of.

I don't know the length of the tubes but they look something like the photo below.

With well over 500hp at the crank I am probably boarderline between the current size and the 2".