727 first gear ratio versus reverse ratio

[shadango]

I have a 727 in my fish and I think Terry, back in 2009, told me it was a 78 based on the numbers I gave him...not positive...but he did say it is a van tranny....has the hole at the top of the "bellhousing".

Anyways, I have found that my low end isnt all that stellar when I get on it.....can barely chirp.  I know I have a cam that is made for the top end, and j heads that kill my compression....but when she revs high she goes really good.  I swapped from a 2.76 single leg to 3.55 tru trac and that woke her up, but still not abel to light them up.  I have just figured the "weak" low end is due to the cam and heads...that the motor was built for top end.....was thinking new cam or maybe a stroker motor for xmas.  LOL

Then I just happened to get on it in reverse the other day.....lit them up without hardly trying.  I was kind of surprised. 

Got me to thinking.....what is the usual ratio in the tranny gears for 1st and reverse?  I have heard of folks swapping in different gears, but that wasnt done on my tranny when she was rebuilt.  Its too late now I know, but could it be that the gears in the van tranny are just not right for the car?

Or is this a really really dumb question?

Dont worry, I can take it.....fire at will.  LOL

[Cooter]

I wouldn't be looking for the trans ratios to be what's causing the "Spinning" in Reverse as much as I would the reverse action itself. Whole lotta difference in going foward which causes the axles to "Wind up" as designed, and going backwards causing obviously the opposite to happen...


Sounds like you didn't install a Higher enough stall speed converter at the time of the cam install as most do. Alot of mismatched parts will cause what you describe. "Noballitis" when you step on it.

[GoodysGotaCuda]

No mention of a torque converter, what torque converter are you running? Engine, cam, rear axle ratio and the torque converter need to all be combined correctly to get the most out of it. A quality custom tweaked torque converter can really wake up a driveline.

[shadango]

No mention of a torque converter, what torque converter are you running? Engine, cam, rear axle ratio and the torque converter need to all be combined correctly to get the most out of it. A quality custom tweaked torque converter can really wake up a driveline.

Its a TCI breakaway.

No ideas what cam is in it right now....its a purple "something" and the only way I know that is I see the purple paint on it....so I went with the Breakaway since it said it was about 2400 stall speed.

Wanted something that was going to be ok cruising.

I still dont get why I have loads of wheel spin in reverse and not in drive...the convertor would be hooking up the same in either gear, wouldnt it?

Axle wrap up makes sense, but with the add aleafs making everything much stuffer and the snubber...well, just seems like they are two different levels of power/torque.

Maybe I should start driving everywhere in reverse...LOL 

[shadango]

"Noballitis" when you step on it.

LOL.....love that term.

Dont get me wrong.  She doesnt fall on her face when I take off....and if I preload the convertor it is much better...takes off with authority.

But breaking them loose in Drive...well, just not likely.

[Strawdawg]

I am from the school that equates, "You spin, you lose", but...

Low gear ratio is normally 2.45 and gear sets are available to lower it to 2.74.  These are normally suggested for heavy cars.

Reverse is 2.20 so it is slightly higher than low gear.

When you hit it in reverse, the rear end of the car tends to unload which provides less traction as opposed to going forward where weight transfer is shifted onto the rear of the car necessitating more power to break the tires loose.

Seems to me that you need to know what is in your engine in order to determine a suitable matching combo before you start picking solutions out of the haystack    It might save you a lot of money.

[shadango]

I am from the school that equates, "You spin, you lose", but...

Low gear ratio is normally 2.45 and gear sets are available to lower it to 2.74.  These are normally suggested for heavy cars.

Reverse is 2.20 so it is slightly higher than low gear.

When you hit it in reverse, the rear end of the car tends to unload which provides less traction as opposed to going forward where weight transfer is shifted onto the rear of the car necessitating more power to break the tires loose.

Seems to me that you need to know what is in your engine in order to determine a suitable matching combo before you start picking solutions out of the haystack    It might save you a lot of money.

Oh dont get me wrong.....wasnt planning on changing the tranny at this point....just trying to figure out what is going on....your explanation of weight transfer makes sense......

It does hook up nice.....with the single leg 2.76s I could chirp the back tire a little.......with the tru trac that is gone and I can feel it hook up better.

The motor I have was a pig in a poke when I got it....didnt even know if it ran.  I know it has J heads and a purple cam, etc....but no specs.  SO I figured I would use it and work my way forward.  I now have 3.55s and a 2400 stall convertor.   

If /when the time comes that the motor needs redone I am thinking crate stroker small block where I know the internals.

In the meantime, was considering a cam, but that top end is SO awesome, I would hate to lose it...I mean, I can drop it into 1st at 45 or so mph and she goes like a bat out of hell....pulls hard till I back off.

Just the low end that leaves me a little limp.  AS I get past 3500-4k rpms she really turns on.

So just playing with random thoughts in the ongoing quest for "more"...LOL

[Strawdawg]

I had a similar problem with an unknown purple stripe cam.  When I pulled the engine to do some rust repair, I swapped a Lunati 303 into it...much happier now.  Also added a PTC converter that stalls around 2400-2500 rpm which matches the cam well.  When I pulled the front cover, I found a well worn timing chain as well.

[tactransman]

Your camshaft and compression ratio are not working together.(compression is too low for the cam specs) I would pull the purple shaft and go with a Lunati Voodoo that is milder.

[shadango]

Your camshaft and compression ratio are not working together.(compression is too low for the cam specs) I would pull the purple shaft and go with a Lunati Voodoo that is milder.

Yeah, you and a few other experienced folks here have said that...and I am sure thats right.

My issue (I have so many of them...LOL) is I dont want to throw good money after bad trying to patch something together with unknows in the mix, though I am now in a place with fewer unknowns than I had before at least.

Here is a picture when I had the intake off for my rag disaster......



At the bottom of the pic, look at the cam...clearly purple paint on two or three sections between the lobes....that is why I say I have a purple cam....but truth be told who knows what it is.

I dont know WHAT compression I have either....I just know I have really low vaccuum.  I did a compression check and had posted those numbers somewhere a long time back....at the time folks told me they were OK but not wonderful.

I was considering a cam for a late fall/winter project....But I have no idea what valves etc are in the heads......I was told the engine itself (short block) was rebuilt to stock specs, just added things like a double roller chain and milodon pan.  The J heads I have no idea what was done.

It has stock looking non adjusting rockers and what look to be doubled-up springs --- springs inside the springs -- but no idea what specs etc.  So then I thought maybe I should go to Indy hheads too and scrap the J heads.

If I can just swap the cam, lifters and pushrods, thats one thing.  A few hundrd bucks, right? But if I have to get into rockers, springs, heads...well, maybe its better to just shoot the wad and go crate. LOL



So given all this and knowing what I know:

318 (76?? block, assuming stock pistons etc)
3.55s,
727 auto,
2400-2600 stall Breakway convertor
J heads (unknown valve sizes)
Edie performer intake
Dougs headers
What have I forgotten to list??

I dont want to lose the top end, cause its a blast to wind up that high and still be pullin'....but want low end.

What Lunati would you guys go with?  What about Hughes cams? 

Think its safe to just swap the cam/rods/lifters out and leave the heads as is?

I dont want to spend tons of $$$ playing with this motor cause one day I do want a stroker......but I really cant justify spending the $7-8k on the one i want right now.....the damn 318 I have runs good for the average person my wife says...LOL

Looking back at this thread I realize it is now offtopic for the tranny section....and doing a search lots of folks have threads going for "help me soup up my 318"....Guess I will go off and do some reading....But any help you guys want to volunteer, I am all ears.

If nothing else, posting this here helps me collect my thoughts...LOL

Thanks guys

[tactransman]

This is what I would put in it. CP or someone else that deals in engines more might have a better choice.
http://www.summitracing.com/parts/LUN-60401LK/

[shadango]

This is what I would put in it. CP or someone else that deals in engines more might have a better choice.
http://www.summitracing.com/parts/LUN-60401LK/

Think I could go with whatever springs and rods I have ?

I guess I could measure my rods, right, to see what length they are and compare to stock and confirm they are stock....but how can I tell what springs I have?

I noticed in Huges cam's ads that they guarantee the cam not to go flat, but you have to buy their springs as well as the lifters and cam....

Changing out the cam is tempting....for $209 for the Lunati cam/lifters, some new gaskets, coolant, oil and my time.

The other thing that scares me a little is "degreeing in" a cam.  From what I see you are supposed to pull the right head off so you can verify TDC to do the degreeing.....

[Strawdawg]

On a relatively stock engine, you should be able to get by without degreeing the cam, but, it is preferable to do so just in case you have a timing gear set that was not cut correctly.

You do not need to remove the head.  You can use a piston stop that screws into the sparkplug hole.

I suspect that your current springs and pushrods will be fine.  You can always check the preload when you are finished on the pushrods and/or check the springs later if you think they are too weak.

I used Joe Gibbs Break In oil when I swapped cams recently.

[tactransman]

If you use a good Cloyes double roller style timing chain, you do not HAVE to degree in a cam. It is gonna be close to where it is designed to be. I think you would be fine with the springs you have. It is when you go with bigger cams that you MUST have springs at the right spring rate so the lifter will follow the lobe correctly. You would not want high rate springs on a cam that did not need them either though.

[shadango]

If you use a good Cloyes double roller style timing chain, you do not HAVE to degree in a cam. It is gonna be close to where it is designed to be. I think you would be fine with the springs you have. It is when you go with bigger cams that you MUST have springs at the right spring rate so the lifter will follow the lobe correctly. You would not want high rate springs on a cam that did not need them either though.

See that is where I get worried....I dont know what springs I have.

So that could get into changing the springs.  I have done a head before, but never springs while the head is on the engine.  Maybe I should just spend a little money and swap the heads out while I am at it...LOL   Those Indy LA-X heads look good.

Still not spending HUGE money.....that assumes I can use my current eddie manfold with them.

What kind of HP/TQ you think I would be at with the Indy LA-X heads and the lunati cam you suggested?

Wish I knew what I have now....both in equipment and HP/TQ.  I guess thats the problem with a pig-in-a-poke engine.