Low compression 505

[oldkimmer]

Actually I think I made a mistake the compression was calculated with only the 7.100 rod both times by 2 different ppl. Not the 6.8 rod. Maybe someone can calculate this for me. 4.25 crank, 7.100 rod. 1.340 cd piston .060 over with a 26.7 dish. 75cc head and a .040 gasket. Thanks. Kim

 

[33 IMP]

Now I feel dumb. The stroker kit I have is 4.25 crank, 6.8 rod and 1.770 cd pistons. .030 4.350 bore. 75cc head and a .040 gasket. 13-1. So then using the .060 over 1.34 cd pistons it comes to 8.0-1. So if I use a 7.100 rod it is 10.2-1. The. It will be a 512. Which is a win. Kim

There you go! 10.2 for pump gas, or 13 for E85.
(Honestly, for a track only car, here in socal or az desert, I'd chose the E85. Its available, and runs SO much cooler in a drag application. Maybe not a great choice in Canada tho......)

 

[33 IMP]

The 1.34 ch is a killer. And that dish is gigantic!! Unless I did something wrong, even with the 7.1 rod, I get it .155 in the hole, and 8 to 1.
7.1 rod, plus 1.34ch, plus 2.125 (half stroke)=10.565. Blueprint deck 10.720.

You need a 4.5 crank for those pistons. 542 inches. (I could Calc the cr with a 4.5 crank, if you're curious.) (I got 10.3, with a 4.5 crank)

 

[RemCharger]

What exactly is not fall out of a tree?

It was extremely and disgusting slow
to the point of embarrassment!

Common slang if you are 75+.

I'm not 75, but I do understand racing terminology

What I meant was, did it run 3 /100s too slow for index?
6 seconds slow?
Disgustingly slow and embarrassed can mean a lot of different things!
What did it run!

 

[PROSTOCKTOM]

Actually I think I made a mistake the compression was calculated with only the 7.100 rod both times by 2 different ppl. Not the 6.8 rod. Maybe someone can calculate this for me. 4.25 crank, 7.100 rod. 1.340 cd piston .060 over with a 26.7 dish. 75cc head and a .040 gasket. Thanks. Kim

Bore: (diameter)	4.38 in.
Stroke:	4.25 in.
Cylinder Head Volume:	75 cc
Effective Dome Volume: Use (-) for Dome and (+) for Dish.	26.7 cc
Deck Clearance:	.160 in.
Compressed Gasket Thickness:	.040 in.
Number of Cylinders:	8
Compression Ratio :	7.94 : 1
Total Displacement (in.3) :	512.29
Total Displacement cc's :	8398.2

Either way I wouldn't build an engine with the pistons .160" in the hole, even though a have a factory motorhome engine that's .156" in the hole. Just not ideal for performance.

Tom

 

[RemCharger]

There you go! 10.2 for pump gas, or 13 for E85.
(Honestly, for a track only car, here in socal or az desert, I'd chose the E85. Its available, and runs SO much cooler in a drag application. Maybe not a great choice in Canada tho......)

Our choices are; race gas, 91 pump gas, or alcohol.

 

[padam]

Now I feel dumb. The stroker kit I have is 4.25 crank, 6.8 rod and 1.770 cd pistons. .030 4.350 bore. 75cc head and a .040 gasket. 13-1. So then using the .060 over 1.34 cd pistons it comes to 8.0-1. So if I use a 7.100 rod it is 10.2-1. The. It will be a 512. Which is a win. Kim

Uhhhhhh…

 

[GTX JOHN]

I'm not 75, but I do understand racing terminology

What I meant was, did it run 3 /100s too slow for index?
6 seconds slow?
Disgustingly slow and embarrassed can mean a lot of different things!
What did it run!

In our 73 Roadrunner Stocker the 400 runs 1.20 under the index.

The 340 Low Comp. runs a bit faster than that
in same car (People will find out at Indy this year Hopefully).

With a optimized gearing and convertor combination the 440 (Pistons .125 down)
well tuned was .3 to .5 under the index bring up the very bottom of the qualifying
ladder and embarrassed the crap out of us. The engine had all the "technology"
that the other engines incorporated. In G/SA @ 3750 at Sea Level it would run
11.60 to 11.70 in normal tune and was the slowest car in the Class in our part of the
world. The 400 in I/SA at the same weight in the same car was actually faster
(ET was better not just against index).

These figures are with the motor chilled and light oil. They were all very well tuned
for optimal performance.

In Division 7 the mid point of the field is around .80 to .83 and most folks
are holding a tenth or two for when they needed it!

 

[oldkimmer]

I do have a 4.5 crank which would make 543 or so cubes. It takes a lot of grinding to make it work.

 

[fullmetaljacket]

I do have a 4.5 crank which would make 543 or so cubes. It takes a lot of grinding to make it work.

That cam which is very similar to mine except it is a solid roller will work spectacular with 12.1 and aluminum SR's.
Mine is 271-276 @50 640 lift, but it is a solid stick in a smaller combo. Very street mannered with good fuel.

 

[33 IMP]

Our choices are; race gas, 91 pump gas, or alcohol.

With only those choices, and only the choice of a sub 8 to 1, or a 13 to 1, and considering the price difference of methanol and race gas. For a track only car, 13 to one on methanol is a no-brainer. Imo. (Might have to start it on ether in cold weather).

 

[33 IMP]

In our 73 Roadrunner Stocker the 400 runs 1.20 under the index.

The 340 Low Comp. runs a bit faster than that
in same car (People will find out at Indy this year Hopefully).

With a optimized gearing and convertor combination the 440 (Pistons .125 down)
well tuned was .3 to .5 under the index bring up the very bottom of the qualifying
ladder and embarrassed the crap out of us. The engine had all the "technology"
that the other engines incorporated. In G/SA @ 3750 at Sea Level it would run
11.60 to 11.70 in normal tune and was the slowest car in the Class in our part of the
world. The 400 in I/SA at the same weight in the same car was actually faster
(ET was better not just against index).

These figures are with the motor chilled and light oil. They were all very well tuned
for optimal performance.

In Division 7 the mid point of the field is around .80 to .83 and most folks
are holding a tenth or two for when they needed it!

Frankly, I'm surprised that a low-comp 400 is faster (not only against the index) than a low-comp 440, at the same weight in the same car.

 

[33 IMP]

I drove a friend's GTX for a while in socal, a few years ago, that was running on E85. You could tell exactly who was running E85. Mine, and the others, were idling in the staging lanes on a 85 degree day.... trying to get engine temperature high enough to make a pass.
I think the E85 was about $1.45 at the time. FJB.

 

[RemCharger]

With only those choices, and only the choice of a sub 8 to 1, or a 13 to 1, and considering the price difference of methanol and race gas. For a track only car, 13 to one on methanol is a no-brainer. Imo. (Might have to start it on ether in cold weather).

Lots of alcohol guys around here run on a gas primer until they hit the burnout box. Then back to gas ont the return road.
There's extra baggage to go along with running methanol though.

 

[GTX JOHN]

Frankly, I'm surprised that a low-comp 400 is faster (not only against the index) than a low-comp 440, at the same weight in the same car.

400 is .75 down in the hole
440 is .123 down in the hole
Both are really awful.
Possibly the extra .50 affected flame
propagation/squelch or some other damn thing?

I do not have a clue and I was surprised
and did not expect those results or I would not
have spent the large pile of money and the work to build the 440.
Both engines shared the very same heads and camshaft.

They both leaked down extremely well and the 400 is the fastest
of its kind in stock eliminator (Our old 1973 400 Roadrunner that our friend
Steve now runs is very close to our current car).

 

[malex]

Hey Kim, my 526 that I started out with was 8.0 CR. I did what I could to get the compression up with head gaskets and head resurfacing. It just completely lacked any sort of frisky. It was built to cruise and take a big shot of nitrous which wasn’t in my plan. The seller maintained that it was a pump gas motor, which he wasn’t kidding on. That’s when I built the 505.

 

[oldkimmer]

Hey Kim, my 526 that I started out with was 8.0 CR. I did what I could to get the compression up with head gaskets and head resurfacing. It just completely lacked any sort of frisky. It was built to cruise and take a big shot of nitrous which wasn’t in my plan. The seller maintained that it was a pump gas motor, which he wasn’t kidding on. That’s when I built the 505.

Mike, did u run it at the track? If so what did it run? Thanks. Kim

 

[oldkimmer]

I’m gonna have to check into running alcohol to see what’s all involved. I hear it can be a pita. Kim

 

[malex]

Mike, did u run it at the track? If so what did it run? Thanks. Kim

Nope. Didn’t pass the seat test so it went into the corner and I put together the 505. Years earlier I ran a smog 440 with a decent cam and nitrous shot and that worked great. Come to think of it now I think I sold you the cam from that package.

 

[qkcuda]

Kim, do you have 400 block available? I think the 1.34 compression height piston is for a 400 stroker combo.