quote Originally posted by lou_dias:Let's make this easy for you and Will. Just show me a naturally aspirated motor making 1 HP per cubic inch with a ratio of 1.6:1 or lower that isn't using racing heads and isn't a race-prepped motor.

Factory stock GM LT5. 1.57:1 ratio. >1HP/cu.in.

Ah yes, the motor with 32 valves...which goes back to what I said about high flowing heads... Not exactly a common motor...

who really cares about the crank-train geometry?! unless its a max effort engine in which every last bit of horsepower needs to be extracted, theres no real reason to debate. theres more gains in a properly built and matched topend. and in this case, the engine needs to be durable.

quote Originally posted by 34blazer660: who really cares about the crank-train geometry?! unless its a max effort engine in which every last bit of horsepower needs to be extracted, theres no real reason to debate. theres more gains in a properly built and matched topend. and in this case, the engine needs to be durable.

or a good balance job.

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there's a Group on 60degreeV6.com for us 660 Fiero owners!

Fiero Owner's group on 60degreeV6.com

I know these lines Look crooked on paper, but I swear I've got them straight in my head.

quote Originally posted by lou_dias: Just show me a naturally aspirated motor making 1 HP per cubic inch with a ratio of 1.6:1 or lower that isn't using racing heads and isn't a race-prepped motor.

What does that have to do with anything?

There was another article on the Reher-Morrison site (can't find it now; they may have reorganized) in which he said that of the top 10 things that are important to and engine's ability to make power, rod ratio is about 50th.

I've read the long rod 350 article before... They used top shelf heads that should allow any built 350 to duplicate that output...

Cylinder heads = horsepower
A long rod engine and a short rod engine will both make crappy power with crappy heads and will both make good power with good heads.

[This message has been edited by Will (edited 12-19-2012).]

quote Originally posted by lou_dias: Just show me a naturally aspirated motor making 1 HP per cubic inch with a ratio of 1.6:1 or lower that isn't using racing heads and isn't a race-prepped motor.

Almost any 383 or 400 SBC crate? Or any 383+ LS stroker motor?

6" rod or 5.7" rod, 1.6 or 1.52 raito for a 3.75" stroke. Ratio doesnt make a measureable power difference for street cams and heads. Look at all the stroker gen III/IV motors out ther producing well over 1hp per in^3. Design goals are to place the largest rod you can in an engine to lower stresses on the rotating assembly. There is no ideal ratio for power production. Torque lost to moment arms in one area of crankshaft rotation can be made up for in other areas. Street engines are so mild, that it doesnt matter. 1hp per in^3 is hardly a measure for high output anymore, just proper engine design.

[This message has been edited by FieroWannaBe (edited 12-19-2012).]

Any 427+ inch circle track or dirt track small block will be at 1.5:1 with 6" rods and 4" stroke.... They make 600+ HP pretty easily

quote Originally posted by FieroWannaBe: Almost any 383 or 400 SBC crate? Or any 383+ LS stroker motor? 6" rod or 5.7" rod, 1.6 or 1.52 raito for a 3.75" stroke. Ratio doesnt make a measureable power difference for street cams and heads. Look at all the stroker gen III/IV motors out ther producing well over 1hp per in^3. Design goals are to place the largest rod you can in an engine to lower stresses on the rotating assembly. There is no ideal ratio for power production. Torque lost to moment arms in one area of crankshaft rotation can be made up for in other areas. Street engines are so mild, that it doesnt matter. 1hp per in^3 is hardly a measure for high output anymore, just proper engine design.

I think the point is being lost on how/why the discussion started. The discussion began on why the 4.9 will never win any horsepower wars. It doesn't have heads that allow for big top end power based on its ratio. The golden 1.75 ratio is the perfect STREET ratio because you don't need fancy components to make power across a BROAD range and still get good fuel economy. It's ratio is designed to produce low end torque. Even looking at the LT5, you see it has less torque below 2500RPM than an L98 and needs to spin much higher to make the extra HP...as I said, it loses it's low end torque to do this.

The rule of thumb is you destroke for hp and your stroke for torque. However, ANOTHER way to play with your power band is to change the length of your rods and the height of your pistons. The assumption here is that you are going to use the same heads and keeping the same displacement. The longer dwell time near TDC allows for higher compression ratios which will allow such a motor to maintain that bottom end torque. The 3.1/3.4/4.5 and many other GM motors use 1.72. You'll find those motors rev to 6000 rpm and have broad power bands, unlike the 4.9. That's all I'm saying.

quote Originally posted by lou_dias: I think the point is being lost on how/why the discussion started. The discussion began on why the 4.9 will never win any horsepower wars. It doesn't have heads that allow for big top end power

Totall agree with this as-quoted. But... rod ratio does not enter the equation.

quote Originally posted by lou_dias: The rule of thumb is you destroke for hp and your stroke for torque. However, ANOTHER way to play with your power band is to change the length of your rods and the height of your pistons. The assumption here is that you are going to use the same heads and keeping the same displacement. The longer dwell time near TDC allows for higher compression ratios which will allow such a motor to maintain that bottom end torque. The 3.1/3.4/4.5 and many other GM motors use 1.72. You'll find those motors rev to 6000 rpm and have broad power bands, unlike the 4.9. That's all I'm saying.

Can't destroke and keep displacement without increasing bore, which allows bigger valves and improves breathing. The top-end biased powerband comes from the improvement in breathing... NOT the rod ratio.
Can't stroke and keep displacement without decreasing bore, which requires smaller valves and reduces breathing. The torque-biased powerband comes from reduced breathing... NOT the rod ratio.

Destroking and reduction in displacement reduces torque. The cylinder pulls LESS air per rev, which means it can rev to a higher RPM before saturating the ports, which results in a top-end biased powerband. Rod ratio is not relevant here.
Stroking and increasing displacement increases torque. The cylinder pulls MORE air per rev, whcih means it saturates the ports at a lower RPM, resulting in a torque-biased powerband. Rod ratio is not relevant here.

I defy you to find a comparison test in which ONLY the rod ratio was tested and found to be distinctly superior. A 5.565" rod 400 will make the same power as a 6" rod 400, built equivalently, with the same heads.
A 5.565 rod 400 makes a GREAT street engine.
There is *NO* "IDEAL" rod ratio, street engine or otherwise. The dwell is not significant when considering equivalently prepped chambers.

LT5 Dyno: http://web.archive.org/web/...000LS1vs%2090LT5.PDF

More than 300 ftlbs from 1200 RPM to 6400 RPM.
Power is in the HEADS, not the RODS.

[This message has been edited by Will (edited 12-19-2012).]

quote Originally posted by lou_dias: I think the point is being lost on how/why the discussion started. The discussion began on why the 4.9 will never win any horsepower wars. It doesn't have heads that allow for big top end power based on its ratio. The golden 1.75 ratio is the perfect STREET ratio because you don't need fancy components to make power across a BROAD range and still get good fuel economy. It's ratio is designed to produce low end torque. Even looking at the LT5, you see it has less torque below 2500RPM than an L98 and needs to spin much higher to make the extra HP...as I said, it loses it's low end torque to do this. The rule of thumb is you destroke for hp and your stroke for torque. However, ANOTHER way to play with your power band is to change the length of your rods and the height of your pistons. The assumption here is that you are going to use the same heads and keeping the same displacement. The longer dwell time near TDC allows for higher compression ratios which will allow such a motor to maintain that bottom end torque. The 3.1/3.4/4.5 and many other GM motors use 1.72. You'll find those motors rev to 6000 rpm and have broad power bands, unlike the 4.9. That's all I'm saying.

No, I get the point. I disagree. The best rod/stroke ratio for a street motor will always be the biggest rod that fits between the piston rings and the crank. A longer rod/stroke ratio that produces the best dwell time at TDC, the greater the chance for spark knock, flow reversion, and more heat transfer can occur lowering the isentropic efficiency of combustion. Again, this alludes to the basic fact that the package would need to be designed around induction and the mechanical framework. So this so called perfect ratio is a product of the sum of the engines parts and design. The perfect ratio 327 is what happened when GM engineers got lucky on parts application and induction design. It doesn’t apply to all engine systems.
As all this applies to the Cadillac FWD OHV V8's:
In 1990, the PFI 4.5L produced:
180@4300 rpm
240 lb.-ft.@3000 rpm
Rod Length: 5.512"
Stroke: 3.307"
In 1991 the PFI 4.9L produced:
200@4100 rpm
275 lb.-ft.©3000 rpm
Rod length: 5.709"
Stroke: 3.622"
Which motor makes more power at 4100 RPM?
Which motor makes more torque at 3000RPM?
Note the peak torque didn’t change location. This is because induction tuning is the primary performance factor in engine performance BEHIND displacement.
Rod length has little to do with performance potential. Net work remains nearly the same. We are talking small inertial effects in factors less than 1/2% to 2% percent difference. If anyone knows anything about a slider crank mechanism, such as a reciprocating engine, the connecting link can only transmit the total force seen at the nodes, if the stroke remains the same, how is the net work done on the piston different from one rod length to another? The time seen at dwell is fractionally different from one available length to another. The ultimate rod choice when building a street engine should be minimizing shaking and inertial forces on the reciprocating assembly. A longer rod does this, reducing the side loading on a piston, also lowering piston mass, which is the primary contributor to harmonic resonance; allowing a high rpm limit of the lower end. Quench and charge motion all contribute to performance, heat transfer detracts more. Picking all your components solely off the basis of an "ideal ratio" is making a big deal of about a 1/2 percent of the entire 4 stroke Otto cycle. There are many complex kinematic and thermodynamic processes that define the ICE engine, and what has been seen through its history, the whole process is incredibly forgiving to poor or suboptimal design choices. Airflow wins, the camshafts job is to distribute the flow based on the shape of the combustion chamber at any given time in the induction/exhaust cycle. The more displacement an engine has the more potential there is for power. Using airflow tuning allows that potential to be fulfilled. Select internal components to minimize stresses created by the production of power for the given displacement. Picking an "ideal" rod/stroke ratio limits design choices and corrupts the pursuit of ideal power production and stress management, there are much bigger fish to fry elsewhere in street motors.

quote Originally posted by FieroWannaBe: In 1990, the PFI 4.5L produced: 180@4300 rpm 240 lb.-ft.@3000 rpm Rod Length: 5.512" Stroke: 3.307" In 1991 the PFI 4.9L produced: 200@4100 rpm 275 lb.-ft.©3000 rpm Rod length: 5.709" Stroke: 3.622" Which motor makes more power at 4100 RPM? Which motor makes more torque at 3000RPM? Note the peak torque didn’t change location. This is because induction tuning is the primary performance factor in engine performance BEHIND displacement. Rod length has little to do with performance potential.

Agree... the changes in the motion of the piston from short rod to long rod are tiny.

I think you're quoting the wrong rod length, though. The '89 and older TBI 4.5 used short rods. I think this is the number you quote. The '90 PFI 4.5 used the same piston compression height as the 4.9 and had longer rods... I think it had essentially the same geometry as the Northstar. I don't have the info in front of me, but there was an Engine Rebuilder Magazine article that detailed the changes through the years.

Edit: Reference citing different conrod lengths: http://www.standardcranksha...atalog.html?sid=4271
TBI (=<'89) 4.5 is 5.512
PFI (1990) 4.5 is 5.905
4.9 is 5.709

[This message has been edited by Will (edited 12-19-2012).]

quote Originally posted by Will: Agree... the changes in the motion of the piston from short rod to long rod are tiny. I think you're quoting the wrong rod length, though. The '89 and older TBI 4.5 used short rods. I think this is the number you quote. The '90 PFI 4.5 used the same piston compression height as the 4.9 and had longer rods... I think it had essentially the same geometry as the Northstar. I don't have the info in front of me, but there was an Engine Rebuilder Magazine article that detailed the changes through the years.

I think you're right. 4100 and early 4.5s shared rods, the switch to PFI changed the rods and pistons. Replacement pistons are compatible for 4.9L and 4.5L engines. 4.5L rods have to be longer if the block remains the same.

@Will,

I never said I would de-stroke. I said that typically that was the rule of thumb and that instead, considering heads and cranks for the motors that come in STOCK GM cars are extremely limited, what can be changed is rod length and piston heights. THIS DOES NOT CHANGE DISPLACEMENT!

If you want, please continue this discussion here: https://www.fiero.nl/forum/F...L/075502-6.html#p227

Interesting discussion, but this is a discussion for another thread, dontcha think?

Lou: You were speaking about principles... so am I.

Go somewhere else with this discussion unless it is about Capt 's car engine please and ruin his thread.

quote Originally posted by Will: I thought the 4.9 had a deeper dish than the 4.5.

Federal Mogul 573P

Funny... I thought this was a build thread. Did I click on the wrong link?

quote Originally posted by Blacktree: Funny... I thought this was a build thread. Did I click on the wrong link?

agreed. the pissing match took over.

Any news from FOY? A running Fiero sure would be a great Christmas present.

Going in for the last time. I think I may kill myself if something goes wrong this time

Mind what you wish for literally speaking, stranger things do happen.

The light at the end of the tunnel..........

Edited because my smart phone isn't very smart sometimes........

[This message has been edited by olejoedad (edited 12-20-2012).]

I have gotten all giddy the last few times you have posted that we are close, and look what has happened the last few times, so this time, I am just going to say Thank You for the update, I was starting to worry. Please keep the updates coming. I will be happy to have it back.

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857GT Part 85GT Part 87GT Part Caddy, 93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Now with Nitrous. Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

nice to see this coming together

again


I hope you get a nice christmas present.

Any updates?

I got a PM on Christmas eve stating the engine was in just needed final hook ups. I was hoping to hear back on the 26th or evening of the 27th and am waiting to hear if th engine fired up or not.

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857GT Part 85GT Part 87GT Part Caddy, 93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Now with Nitrous. Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

Finishing up today

So whats the word? Did we fire up, or end in fire?

Took it for a drive this afternoon. I forgot to put the plates back on the struts so I need to pull them out and put them back in and then take a long drive.

Trying to maintain my cool here, but if you forgot the strut plates there are only 2 ways to put those back on, drop the entire cradle / suspension, or remove the 2 lower strut bolts and totally screw the alignment that you said was already done to the car. So long as the car comes to me with a straight alignment as promised, I will be happy, but this does concern me. Your post on this was just short of 24hrs ago, how did it go.

I guess whats bothering me, is that you said the car was done, and I paid nearly $430 for insurance that will expire now a month from today. Feb 1st. So me being able to take this car to Oregon is out of the question until I get it back here to Canada get it to pass emissions then extend the insurance for the remainder of the year, (which I can't do until it passes emissions testing).

I use the term frustrated because I don't like to get mad or angry, but I am really starting to get overly frustrated at this. I know its the Holiday season and its important for you to spend time with your family. Its your first Christmas with your new baby, but I as well have obligations to deal with my fathers estate in Oregon that I have been putting off and delaying over this entire fiasco. Please keep my updated on what is going on. Even if you can spend a couple mins to drop me an email at night just so I know where we are at.

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857GT Part 85GT Part 87GT Part Caddy, 93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Now with Nitrous. Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

FoY regrets this job so much.

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I had showed the pictures to my father and he had me second guessing about the plates. I pulled the top nuts and checked, they were there lol

I can drive the car up this weekend

Hang in there, both of you. Breaking new ground is not easy, nor is it quick. At least you didn't have to cut down the forest and pull out the stumps........

Any Intention to still dyno test? Just wondering how the new intake affects power.

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Powerlog manifold, Northstar TB, LS1 MAF, 3" Flotech Afterburner Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

I have a lot of frustrating things going on right now, and I'm sorry to vent it to publicly on the forum.

Dennis I don't know if a Dyno session is still in the works or not, that's up to FOY. So long as I get my car back this weekend, I am going to be happy with it Dyno or Not. However I will not delay delivery for a Dyno as I really want my car back. I want to drive it around for a couple weeks to make sure that everything is fine and if need be get anything dealt with that needs to be done then I am taking it and installing my trailer hitch on it and making a 6 week run with it to Oregon and back. My wife may be following me down with our kids in our Grand Prix a week or so after I head down. Trying to liquidate my fathers estate is tearing me up a bit more than I was expecting. Now the house I grew up in and would love to keep has to be sold because the stupid F'ing USA Government says that they won't let our family immigrate to the US. Even though we would be coming down with money, house, cars and even speaking English as a first language because I FREAKING GREW UP IN THE USA. (yes I am a Canadian, we immigrated to the US when I was 2, however because I moved back to Canada for longer than 5 years, my US Status was deactivated) So I can't move back. We went through all the paperwork and were denied.

The funny side is I read every day, how the US is helping illegal immigrants get free health care, free housing, drivers licenses and everything. Almost makes me want to come down for a month and just stay. However I want to work above board, in a decent job and you can't do that as an illegal immigrant. So I am screwed, selling off all the stuff my father loved.


I am tempted to delete this post, but I feel it is relevant so you all know why I am letting myself get more upset over this car than I probably should be.
P.S. My wife's Father is an American, and we tried that route, but they still denied us because she did not ask for her US Citizen ship before she was 18. I always thought that if one of your parents was an American, it gave you automatic skip to the front of the line. However I guess that has changed.

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857GT Part 85GT Part 87GT Part Caddy, 93 Eldorado 4.9, 5spd Dual O2 Custom Chip, Custom Exhaust. MSD Everything Now with Nitrous. Capt Fiero --- My Over View Cadero Pics Yellow 88GT 5spd Full Poly Suspension, Lowered 1/2" in front, Corner Carver.

You guys are ENTIRELY too desirable for us to want you here in the US.

Good luck with everything, man.