Drivetrain dreaming/ ideas :)

[Smokintire70]

What's up guys! I'm dreaming kinda right now but I've got a '70 LWB OG yellow and white, ET IVs and the truck looks beat up and has seen better days but that's ok cuz it original paint and panels. It's got a ramjet 350 (two bolt main, OE roller gen, vortex heads and a ramjet FI system) that makes 351 horse and 403 TQ. It's pretty slow. I wanna ditch the FI, since it's non tuneable ( am I crazy for this) and ruins the 70s truck look... I would swap that with a team G single plane that's sitting around the shop, or a air gap that's cheap, from CL. It would be one of those two intakes. Dart iron Eagle heads, and a extreme energy XR294HR. (294, 300 dur.), and some chromeoly pushrods. I don't know what carburetor to get but I was thinking a Holley. I wouldn't go past a 650 otherwise I figure I'd drown it. Anyway this all started because I drove it too hard one too many times and the 700R4 is goin out on me. Since that I figured I could replace the torque converter since I torque braked it a lot doing burnouts and for a bigger cam eventually and since the the inner grill is broken, I would need to take part of the front end apart. Then I could pull the radiator and throw a cam in it. Maybe a set of heads, an intake and a carb... I don't know. I just want it a little more peppy.
I just want it in this order, 1. Adjustable/ tuneability, 2. Performance 3. Looks/ more period correct
I don't think I'm going to do this but it would be cool to know if I'm insane.
Thanks! Have a good one.

[hugger6933]

Leave the vortec heads on and get an intake for that. I would love to have a ramjet i know that they are not adjustable, what about going to a different control like mega squirt or something like that. I know there is some ramjet guys out there that have taken on this problem

[James the III]

Love how you think you can tune it better than the g.m.engineering dept..
Good luck..
Also good luck on an honest.. mild running 350+hp 400+ ftlb 350..

What rear gears this have. and tire height? if a 350cid with a fat torque curve and 350hp is slow..

i'll gladly take the efi off your hands

[Overdriven]

There are scan and tuning tools available for the MEFI ecu used on the RamJet engines, they're just not the big names like HP Tuners. So it is possible to adjust the tune for a new camshaft or other mods with the stock RamJet ecu. Then there's always the option of switching to another ecu, Mega/microsquirt, Holley, etc while utilizing the stock sensors and injectors. Cost wise you're probably better off switching to a Megasquirt and you'll have a bigger knowledge base and more efi tuning shops familiar with the software if you're farming out the tuning.

I think you should do a whole lot of google searching before changing anything. There are MEFI forums out there, research some mods others have done to the engine and the results. You may find the perfect cam to swap in, that the RamJet intake is better than you think or even a way to make a cheap LS ecu work. Personally I'd keep it efi but I'm not a carb genius and know I couldn't get it running anywhere near as good as the efi. Plus I doubt it would offer much power gains.

[Smokintire70]

Originally Posted by James the III

Love how you think you can tune it better than the g.m.engineering dept..
Good luck..
Also good luck on an honest.. mild running 350+hp 400+ ftlb 350..

What rear gears this have. and tire height? if a 350cid with a fat torque curve and 350hp is slow..

i'll gladly take the efi off your hands

Like I said I'm 99.999% sure this won't happen. It's got 33x10s KO2s for the rear and 31x8.5 for fronts. It's got the 3.08 open diff. I'm just thinking. It's also a LWB. I've heard they come tuned a little on the rich side. I'm goin off what I've heard. Now that I think of it I should just start with a posi....

[Smokintire70]

Originally Posted by Overdriven

There are scan and tuning tools available for the MEFI ecu used on the RamJet engines, they're just not the big names like HP Tuners. So it is possible to adjust the tune for a new camshaft or other mods with the stock RamJet ecu. Then there's always the option of switching to another ecu, Mega/microsquirt, Holley, etc while utilizing the stock sensors and injectors. Cost wise you're probably better off switching to a Megasquirt and you'll have a bigger knowledge base and more efi tuning shops familiar with the software if you're farming out the tuning.

I think you should do a whole lot of google searching before changing anything. There are MEFI forums out there, research some mods others have done to the engine and the results. You may find the perfect cam to swap in, that the RamJet intake is better than you think or even a way to make a cheap LS ecu work. Personally I'd keep it efi but I'm not a carb genius and know I couldn't get it running anywhere near as good as the efi. Plus I doubt it would offer much power gains.

Thanks good to know.

[HO455]

Originally Posted by Smokintire70

Like I said I'm 99.999% sure this won't happen. It's got 33x10s KO2s for the rear and 31x8.5 for fronts. It's got the 3.08 open diff. I'm just thinking. It's also a LWB. I've heard they come tuned a little on the rich side. I'm goin off what I've heard. Now that I think of it I should just start with a posi....

YES a posi with a different carrier. 33's with 3:08 gears! No wonder it seems slow. You need to look into some lower gears. Unless your looking for MPG record or a land speed record. Find a gear ratio calculator and start playing around with your tire sizes and your new ratio. I run 31's on my truck with 4:11 gears. Your poor combination has a lot to do with your transmissions issues. There is too much load on the tranny and then power braking it to boot, not many automatics would survive under those conditions. The ratio change will really wake up your truck. Plus if you do decide to change it up your already set up correctly.


https://tiresize.com/gear-ratio-calculator/

[Overdriven]

When op said it was slow with 350hp I wondered about the gearing but then focused on the questions asked. Definitely change the rear gearing to at least 3.73 if not 4.11 and you'll see a big improvement in acceleration. You'll also be able to actually accelerate when in overdrive instead of forcing the trans to downshift on the highway.

Btw, since this sounds like a toy you beat on, put the trans in D3 when you do. These trans don't like shifting from OD to 2nd gear and the fluid paths and line pressure are better in D3.

I like these gearing calculators a little better. The Spicer calc assumes the 700r4's .70 overdrive ratio for "auto in OD".
http://spicerparts.com/calculators/e...pm-calculator#
This one has a bunch of different calcs on the page, scroll down.
http://www.rocky-road.com/calculator.html

[Smokintire70]

Originally Posted by Overdriven

When op said it was slow with 350hp I wondered about the gearing but then focused on the questions asked. Definitely change the rear gearing to at least 3.73 if not 4.11 and you'll see a big improvement in acceleration. You'll also be able to actually accelerate when in overdrive instead of forcing the trans to downshift on the highway.

Btw, since this sounds like a toy you beat on, put the trans in D3 when you do. These trans don't like shifting from OD to 2nd gear and the fluid paths and line pressure are better in D3.

I like these gearing calculators a little better. The Spicer calc assumes the 700r4's .70 overdrive ratio for "auto in OD".
http://spicerparts.com/calculators/e...pm-calculator#
This one has a bunch of different calcs on the page, scroll down.
http://www.rocky-road.com/calculator.html

How do I decide what it shifts down to of its in auto? If it's in the manual valve body, then I get it but without actually shifting then I don't get it. I appreciate the advice! Also what do you think I would run RPM wise on the freeway. Right now it's liek 2,300-2,500 at probably 65 (speedometer does not work...)

[HO455]

With the 3:08 gears you have and 33 inch tall tires you should be turning 2030 RPM at 65 mph. You are closer to 75 mph at 2400 RPM. The link to the gear ratio calculator I sent isn't the best calculator, but it also has the gear/tire chart at the bottom to show where you are compared to how most manufacturers set up vehicles. Take a look at it and see where you fall on the chart.

With a 700r4 the transmission decides what gear to shift to based on speed your moving and the amount of throttle you have applied. The throttle communicates (mechanically by cable or electronically) with the transmission and then the logic path decides which gear is the most appropriate for conditions. The tranny will also disengage the lockup in the convertor. The tranny can also not shift down but adjust pressure to the convertor to allow it to slip and it may seem like it has shifted down. But this is quickly getting far to technical. If you want to delve deeper there are great threads in the drivetrain section.

[67 chevelle]

Originally Posted by HO455

YES a posi with a different carrier. 33's with 3:08 gears! No wonder it seems slow. You need to look into some lower gears. Unless your looking for MPG record or a land speed record. Find a gear ratio calculator and start playing around with your tire sizes and your new ratio. I run 31's on my truck with 4:11 gears. Your poor combination has a lot to do with your transmissions issues. There is too much load on the tranny and then power braking it to boot, not many automatics would survive under those conditions. The ratio change will really wake up your truck. Plus if you do decide to change it up your already set up correctly.


https://tiresize.com/gear-ratio-calculator/

100% dead on , ramjet is an awesome engine

[67ChevyRedneck]

The 700R burned up because your RPM range is way too low. Driving it hard probably didn't help, but your truck is a "dog" because your gearing is absolutely terrible.

http://www.accuautoparts.com/calculator.php

A 700R has 30% OD, with 33" tires and a 3.08 you're only turning 1200 RPM (will a 700R even shift into OD at an RPM that low???) at 55 mph and at 70MPH you're only turning 1700 RPM. Not good for a heavy ass truck. It looks like you would want a minimum of a 4.11 gear, unless you go to a smaller tire. A 700R4's "happy place" in overdrive is somewhere between 1700-2400 RPMs for cruising (between about 50-75 MPH).

I run a 28" tall tire and a 3.73 rear with my 700R.

I also do what overdriven suggests. I drive my truck in 3rd (drive) when I'm running any speeds below 45 mph as the OD will just toggle back and forth between 3rd and 4th (D vs OD). When I get to where i can cruise at 50+ mph I bump it up into 4th gear. It helps "save" the trans. I put my 700R in about 11 years and 50-60K miles ago, still shifts like the day in Installed it.

[clay68c10]

Just put that Ramjet intake and ECU in a box and send it to me, I'll be happy to dispose of it for you.

Seriously, 4.11 and a limited slip of some sort will make the truck a lot more fun.

[HO455]

I would like to reinforce the thought about not using OD around town. Leave it in D unless your going to be driving at least a mile at 45 mph without slow downs. On my S10 if I drive between 35 and 40 in OD the tranny will constantly shift in and out of overdrive with every change of throttle position. It's even worse if I have the cruise on. I am sure the reason my 700r4 has 174k on it is that I limit my use of OD.

[Smokintire70]

Originally Posted by HO455

I would like to reinforce the thought about not using OD around town. Leave it in D unless your going to be driving at least a mile at 45 mph without slow downs. On my S10 if I drive between 35 and 40 in OD the tranny will constantly shift in and out of overdrive with every change of throttle position. It's even worse if I have the cruise on. I am sure the reason my 700r4 has 174k on it is that I limit my use of OD.

90% of the time it's in Drive. It's only my if I'm driving around and feel like shifting, this is when I shift easily and pretty close to when the trans would do it on its own. Or if I'm really gettin down and I decide to shift at like 5 grand.
I'm thinking about getting a TCi street Fighter. It's rated to 725 horse. I figure as long as I don't brake/gas at the same time then I'm good for a while since the tranny is so over built for the motor.