technicalities of my motor design (long)

[primal1]

i have finally gotten my motor broke down. everything inside looks good. the oil pan had an indent from the inside that looks like the chain broke once, but that was it. as i'm getting ready to pick the component for the motor, i'm getting more confused with the more stuff i'm finding. like "optimal rod to stroke ratio". is this something that can be achieved on a budget. where can i read about this. i've searched here and have found people mentioning it, but no explanation on how to figure what mine would be. my block and head is a '77. i'm still working out a deal for an aussie head. if i can't get it i'm going with the 3x1 like patricks. i want low end power. i thinking of getting the dual pattern cam with a 110 lobe center. 302 valve springs. beefed up retainers. port & polished head. going to run the ds2 ignition w/ msd. i want to get d.u.i., but not in the budget now. maybe for x-mas in 2010. i want to get my compression to 9.5 to 1 because i want to run e85 but be able to run regular with an octane boost in a pinch. maybe even 10 to 1. i have already planned for the e85 and have learned (thanks to all here) about making sure my fuel pump, lines, carbs, ect can handle e85. the block will be honed, i'll use flat top pistons, and deck the block. i have been planing this together for almost a year. as far as what hp and torq numbers am i looking for? i have know real idea, i have never owned a fast vehicle. all i have is reference to my '99 chevy tahoe 2wd 2 door. i comes with 200hp at the wheels. so thats about 1 hp per 20 pounds. so that means the equivilent in my 62 comet would only need about 125hp right.

 

[Eric Rose]

Is your '77 motor a 200 or a 250?

As for everything else, there are dynos of some different setups posted on the Classic Inlines site. 125hp at the wheels with the log head shouldn't be too hard of a goal but you will have to do something to open the log head up. Porting, direct mount 2v, 3x1v carbs, etc.

 

[Patrick66]

a 3x1 on an aussie head? sounds like a fun project!

rod to stroke ratio is just what it sounds like. generally a longer rod to shorter stroke ratio is preferred, but unless your planning on making a race car you shouldnt be concerned. doing it on a budget is probably not going to happen, the only way to change it is to:

1) destroke the engine. you'll lose displacement, and you'll likely need a set of rods custom made, but you may be able to find rods from another engine that will fit.

2) have a set of pistons and rods custom made. shorter compression height on the pistons to allow for a longer rod. $$$$$



imo 9.5:1 isn't enough compression for E85, and you won't need octane booster to run pump gas with that CR. definitely go higher if you want to run E85.

 

[fast64ranchero]

Rod ratio, you can figure that by deviding, take your rod lenth and devide that by you cranks stroke, lets say you have a crank with a stroke of 3" and a rod lenth of 5", 3 goes in to 5 1.667 times that would be a 1.67 or so rod ratio, don't worry to much about that as it is not as big of a factor in an inline as it is in a V engine

next if you want to run E85 as the main fuel but would like to run 91 octane as a back up, depending on your elevation sea level 11-1 max with a cast iron head, here in Boise we are at 2900ft we can run 12-1 on 91 octane and 13.5-1 on E85 with that said I am not sold on E85 ya it has 100+ octane but you ever seen what it does to steel and rubber?
for a standard driver motor I would shoot for 10-1, and clean up the head's Chambers to prevent detination and run pump gas, get to 10-1 by decking the head, that way if you don't like it all you have to do is change the head rather then pull the whole motor apart.

 

[primal1]

Is your '77 motor a 200 or a 250?

As for everything else, there are dynos of some different setups posted on the Classic Inlines site. 125hp at the wheels with the log head shouldn't be too hard of a goal but you will have to do something to open the log head up. Porting, direct mount 2v, 3x1v carbs, etc.

sorry about how this sounds i've been living on theraflu for the last 3 days. i can't complete a thought. it is a 200. i don't have the welding abilities to put in a 250. since nobody manufactures a kit for the 250 in a roundbody i'm going from a 170 to a 200.

 

[primal1]

a 3x1 on an aussie head? sounds like a fun project!

rod to stroke ratio is just what it sounds like. generally a longer rod to shorter stroke ratio is preferred, but unless your planning on making a race car you shouldnt be concerned. doing it on a budget is probably not going to happen, the only way to change it is to:

1) destroke the engine. you'll lose displacement, and you'll likely need a set of rods custom made, but you may be able to find rods from another engine that will fit.

2) have a set of pistons and rods custom made. shorter compression height on the pistons to allow for a longer rod. $$$$$



imo 9.5:1 isn't enough compression for E85, and you won't need octane booster to run pump gas with that CR. definitely go higher if you want to run E85.

the 3x1 is what i'll do if i can't get the aussie head. i found this today
http://cgi.ebay.com/ws/eBayISAPI.dl...ay to expensive for me. but it would be cool.

 

[CZLN6]

Howdy back All:
THe rod to stroke ratio is 1.5:1 on stock 200s and 250s. 170 has a 1.6:1 ratio.
Stroke, Rod length
170- 2.94" 4.715" = 1.6:1
200- 3.126" 4.715" = 1.5:1
250- 3.91" 5.88" = 1.5:1

4.712 / 3.126" + 1.5:1.

In a perfect word, for optimum performance, a R to S ratio of 1.75 or 1.8:1 is considered ideal. For Engines, about the only realistic option for a slight increase in stroke is to have the crank journals offset ground. The difference in ratio is so slight that it is not likely to be noticeable in your situation. You would be better off spending your time and money optimizing the combustion chambers.

I will run some numbers on the Compression Ratio Calculator on our website and get back to you. The calculator will also give me some hp estimates as well.

Adios, David

 

[falcon fanatic]

Woah, don't get too carried away re-engineering the whole thing with rod ratios and whatnot. Just have it really nicely balanced and lighten as many reciprocating componenets as you can, get the right cam, headwork, exhaust and ignition, and you will have more than your target goal. Especially if you can eke out a few hundred more rpm. Right now it probably runs out of steam at what, 4200 rpm? If you can tune it to make power (and breath) all the way to 5000, for instance, then you will be making quite good horsepower, and the torque won't suck, either.

What kind of tranny are you running? If manual, then taking a few pounds off the flywheel will help it rev better, too.

 

[primal1]

Woah, don't get too carried away re-engineering the whole thing with rod ratios and whatnot. Just have it really nicely balanced and lighten as many reciprocating componenets as you can, get the right cam, headwork, exhaust and ignition, and you will have more than your target goal. Especially if you can eke out a few hundred more rpm. Right now it probably runs out of steam at what, 4200 rpm? If you can tune it to make power (and breath) all the way to 5000, for instance, then you will be making quite good horsepower, and the torque won't suck, either.

What kind of tranny are you running? If manual, then taking a few pounds off the flywheel will help it rev better, too.

the car it is going into has been parked for quite sometime. i don't really remember were it fell off at, but that seems to be the area everyone has said. what about skirting the pistons. i was not going to hop right on to re-designing the engine. i just found a term that some people around here have debated about and did not know what it was. if it was something easily taken care to allow a couple more hp's, i was going to. it does not seam to be the case on this.

 

[grocery getter]

I fixed the link .
http://cgi.ebay.com/ws/eBayISAPI.dl...1355&_trksid=p3907.m32&_trkparms=tab=Watching



I also have an aussie head for sale. let me know if you're interested.

 

[CZLN6]

Howdy Back primal and All:

These won't be too exact but will give you an idea.

200-
52 cc chambers, zero deck height, .050" head gasket, stock type dished pistons @ 5,000 rpm and 85% VE = 141hp. This combo yeilds a CR of 9:1.

Same as above, but with flat-top pistons CR increases to 9.9:1. HP to 155.
This combo calls for 245 cfm to achieve.

Adios, David.

 

[primal1]

Howdy Back primal and All:

These won't be too exact but will give you an idea.

200-
52 cc chambers, zero deck height, .050" head gasket, stock type dished pistons @ 5,000 rpm and 85% VE = 141hp. This combo yeilds a CR of 9:1.

Same as above, but with flat-top pistons CR increases to 9.9:1. HP to 155.
This combo calls for 245 cfm to achieve.

Adios, David.

that was going to be another question. what is "Volumetric Efficiency" and how can i make it better in mine.

 

[Patrick66]

that was going to be another question. what is "Volumetric Efficiency" and how can i make it better in mine.

google = your friend.

basically its how much of the volume in your cylinder(s) is filled by the air/fuel mixture. ie. 100% = 200ci of air/fuel every 2 revolutions, 80% = 180ci of air/fuel every 2 revolutions. peak power occurs at peak VE.

 

[Bort62]

peak power occurs at peak VE.

Incorrect. Peak torque occurs at peak VE.

Peak power occurs at the point where the balance of RPM and VE is optimum.

100% VE @ 1000 RPM makes less power than 75% VE @ 5000 rpm, for example.

 

[Patrick66]

oops

 

[Lazy JW]

Woah, don't get too carried away re-engineering the whole thing with rod ratios and whatnot.....

Yup. There is very little to be gained and somewhat to lose. A longer rod will slow down the piston speed that is needed to keep your low-end torque up. If this is a dedicated racer then go for it but if it is a daily driver I would be loathe to do anything that hurts low speed torque.

The Ford 300 has a terrible rod/stroke ratio by most standards but that short rod/long stroke certainly gives the piston a good quick yank downward that helps fill that big bore at slow speed: hence the excellent low speed performance.
Joe