No Bottom End

Mopar-Charger · Aug 21, 2015

I just rebuilt/built my 360. The original I had in the car was all nearly all stock:

Stock bottom end
Stock heads
Points
Performer intake
750 Holley Vacuum secondaries
727 TF

The engine I replaced it with has:

2.02, 1.60 Heads
RPM Airgap Intake
Holley 750 DP
Stock crank
Stock piston
Mp .458 Cam

Car:

1973 charger - 4000lbs with driver
727 tq - Stall UNKNOWN (probably stock)
3.55 Sure Grip

My problem is, prior to the rebuild. I could burn rubber like it was nothing. Now, with the built engine, I can barely get the tires to turn.

Burned rubber at 2300 RPMS with old engine - Reved up like a mad dog
Burned rubber at 1400 RPMS with new engine - Barely turns till about 2800 RPMS

What I'm thinking the problem is the stall converter? The new engine performs 10x than the old engine from 3000-6500 RPMS

TIming is set high for initial, about 15-17 Degrees. (doesn't kick the starter back) I've put it between 10-17 Initial and it performs the same on the bottom end.

You guys are racee car guys, this is my setup. How do I get the bottom end better?

THanks,

Jake

Hemi Rebel · Aug 21, 2015

Yup, you need a converter to match the cam.2800 to 3000

Mopar-Charger · Aug 21, 2015

That easy huh? What brands do you recommend? What size I see 11" 10" 8"?

And what is flash, Trap? Don't want to sound noobie but...

Also, I drive this car everyday. However, I'm a kid and I'd rather have fun then driveability

Belle66 · Aug 21, 2015

Hi, not an expert and generally the camshaft manufacturer will recommend a stall range for different grinds. I'd contact the cam company, that's the easiest and cheapest start. How's timing at bottom end and how's the whole curve?

Mopar-Charger · Aug 21, 2015

Belle66 said:
Hi, not an expert and generally the camshaft manufacturer will recommend a stall range for different grinds. I'd contact the cam company, that's the easiest and cheapest start. How's timing at bottom end and how's the whole curve?

Curve sucks, waiting for MSD igntion to come in.

The cam I installed is said to be a .458, guy who gave it to me said it was that? So I'm not sure.

Hemi Rebel · Aug 21, 2015

Flash is the rpm at which the converter stalls to when launching from idle speed. Maybe 100 or so depending of the car. Heavy car with a high rear end gear and sticky tire will give it more rpm.

440roadrunner · Aug 21, 2015

"cam degree"

Mopar-Charger · Aug 21, 2015

440roadrunner said:
"cam degree"

Is that where i can adjust it at the cam. If I can remember I had
+4 - 0 - (-4) options?

Hemi Rebel said:
Flash is the rpm at which the converter stalls to when launching from idle speed. Maybe 100 or so depending of the car. Heavy car with a high rear end gear and sticky tire will give it more rpm.

Alright, cool. I was looking, TCI transmissions, B&M? what do you guys recommend. I'm on a budget, and don't plan on drag racing it more than once or twice year. So I don't necessarily need the top notch name brand.

Also, my 360 is externally balanced. Do i need to buy one prebalanced or is there a way to do that myself?

Hemi Rebel · Aug 21, 2015

I know you are on a budget, but this is one area where I consider it necessary to bite the bullet and get quality. You get a cheap loose converter it will just waste gas and build up heat when cruising. A good one will have better manners when cruising, and flash to the rpm you need, when you need it to.

- - - Updated - - -

The converter will come balanced for the motor. Frank Lupo seems to be popular. Dynamics converters

Mopar-Charger · Aug 21, 2015

Hemi Rebel said:
I know you are on a budget, but this is one area where I consider it necessary to bite the bullet and get quality. You get a cheap loose converter it will just waste gas and build up heat when cruising. A good one will have better manners when cruising, and flash to the rpm you need, when you need it to.

- - - Updated - - -

Alright, thank you for that information. I'll start taking a look at those.
The converter will come balanced for the motor. Frank Lupo seems to be popular. Dynamics converters

What size converter should I look for?

Hemi Rebel · Aug 22, 2015

I would say something like the 11 inch street converter here

http://www.dynamicconverters.com/converters.htm#11" Street

Budnicks · Aug 22, 2015

Some decent suggestions already
{just the converter shouldn't cause that necessarily}

Just spit-balling here

Maybe possibly also;
Try a little more initial ignition timing, especially with low compression,
it gives you a little more bottom end too

I like to shoot for about 38* total
when all the mech. advance is in, on low compression engines
less initial & total timing on engines with more compression...

It might help to wake it up some on the bottom end...

Just for shits & giggles
& it won't cost much, but a little fuel & some time & test drive
Possibly;
Old school stuff, try setting you idle up to about 2500-2800rpms,
loosen & turn/adjust the distributor tell you get the highest RPM,
tighten down the dist. & reset the idle,
then put a light n it, check to see where the timing actually is,
then test drive it, back it off/retard the timing {or retard it a little if it pings like crazy}
a degree at a time until it starts to fall off, loose bottom end...

20*'s timing needed on a low comp. engine is very common
especially with a performance based cam,
that's designed to use with a higher compression ratio,
headers & free flowing exhaust, a hotter ignition, with better low ohm resistance wires
& hotter coil {to help actually burn the now more extra fuel properly},
with a better intake & better/bigger carb, etc. etc. etc....

or possibly maybe tear apart the front of the engine,
properly degree & probably advance the cam

it's all still a Band-Aid for other tuning & overall combo issues thou

are you running a vacuum advance ?
what other changes did you do ?
did you re-jett the carb ?
have you checked out the plugs ?
have you checked the fuel/float level in the bowls ?
is it lean ? is it fat ? have you even checked ?
those things probably will need changing/tuning with the parts you added too

{it could be another fuel or ignition related problems still too}

good luck & happy Moparing

Mopar-Charger · Aug 22, 2015

Budnicks said:
Some decent suggestions already
{just the converter shouldn't cause that necessarily}

Just spit-balling here

Maybe possibly also;
Try a little more initial ignition timing, especially with low compression,
it gives you a little more bottom end too

I like to shoot for about 38* total
when all the mech. advance is in, on low compression engines
less initial & total timing on engines with more compression...

It might help to wake it up some on the bottom end...

Just for shits & giggles
& it won't cost much, but a little fuel & some time & test drive
Possibly;
Old school stuff, try setting you idle up to about 2500-2800rpms,
loosen & turn/adjust the distributor tell you get the highest RPM,
tighten down the dist. & reset the idle,
then put a light n it, check to see where the timing actually is,
then test drive it, back it off/retard the timing {or retard it a little if it pings like crazy}
a degree at a time until it starts to fall off, loose bottom end...

20*'s timing needed on a low comp. engine is very common
especially with a performance based cam,
that's designed to use with a higher compression ratio,
headers & free flowing exhaust, a hotter ignition, with better low ohm resistance wires
& hotter coil {to help actually burn the now more extra fuel properly},
with a better intake & better/bigger carb, etc. etc. etc....

or possibly maybe tear apart the front of the engine,
properly degree & probably advance the cam

it's all still a Band-Aid for other tuning & overall combo issues thou

are you running a vacuum advance ?
what other changes did you do ?
did you re-jett the carb ?
have you checked out the plugs ?
have you checked the fuel/float level in the bowls ?
is it lean ? is it fat ? have you even checked ?
those things probably will need changing/tuning with the parts you added too

{it could be another fuel or ignition related problems still too}

good luck & happy Moparing

I have been fighting ignition since day one. I have an MSD dist and box coming it. I'm not about just pull the trigger on the torque converter because of that.

THanks for the info, once I get home and on my computer I will give you the specs to everything I did.

Thanks again,

Jake

dvw · Aug 23, 2015

I'll bet you didn't figure out your compression ratio? Maybe 8-1 if your lucky, probably 7x-1. Now stock converter, bigger cam, bigger intake, DP carb=dog. Quicker advance curve,looser converter, more gear,Thermoquad carb would all help. But it truly needs more squeeze.
Doug

Mopar-Charger · Aug 23, 2015

dvw said:
I'll bet you didn't figure out your compression ratio? Maybe 8-1 if your lucky, probably 7x-1. Now stock converter, bigger cam, bigger intake, DP carb=dog. Quicker advance curve,looser converter, more gear,Thermoquad carb would all help. But it truly needs more squeeze.
Doug

I want to make a correction to my earlier post. I do not know the cam size. Car lopes a quite a bit for a small block. I hadn't swapped the cam during the rebuild.

When I checked compression with the stock heads, I did have 8.5 to 1.

Car is significantly faster with the DP.

For Budnicks:

20*'s timing needed on a low comp. engine is very common
especially with a performance based cam,
that's designed to use with a higher compression ratio,
headers & free flowing exhaust, a hotter ignition, with better low ohm resistance wires
& hotter coil {to help actually burn the now more extra fuel properly},
with a better intake & better/bigger carb, etc. etc. etc....

I have headers - 1 5/8 - 3 inch collector - 2.5 inch reducer - 3 inch exhaust with H pipe - 2.5 inlet flow master - 2' outlet. (I purchased 3 inch reducers, saving money for new system that's 3 inch.)

I have an MSD Probillet DIst with super conductor wires, and a better coil coming in. This Friday I will receive the distributor, then purchase the box.

are you running a vacuum advance ?

Yes (not sure how much advanced it provides, I always set idle without it.)

what other changes did you do ?

I didn't change ignition. Only changed intake, heads, highflow oil pump, new pan, timing chain, and water pump. The cam had been set to +4 degrees, when I swapped the chain I put it back to 0.

did you re-jett the carb ?

either the primaries or are secondaries are 76, and the other is much smaller.

have you checked out the plugs ?

Haven't pulled the plugs (it's a b*tch to get #5 and #7 out)

have you checked the fuel/float level in the bowls ?

Floats are set correctly.

is it lean ? is it fat ? have you even checked ?

I have it about 3 turns out on idle screws, still smell gas in the exhaust. Runs at about 170 degrees

{it could be another fuel or ignition related problems still too}

I'm aiming more towards the ignition. I've been having problems with it since I swapped from points. It's the generic Proform distributor. It eats through coils, caps, and rotors.

niteshift70 · Aug 27, 2015

Are the heads ported, etc, or just heads with big valves installed? Pardon the other brand reference, but back before vortec and ls motors, a popular mod for the small chebbie was installing double bump heads (300 hp) and quite a few guys I knew totally lost the bottom end because the huge ports drastically reduced port velocity. Couple that with lost cylinder pressure from too much cam overlap on a low compression short block and you've got a real dog off the line. Not knowing the cam specs makes it hard to diagnose. Since you said the engine has a severe idle lope, i would lean toward that direction.

Longroof · Aug 27, 2015

niteshift70 said:
Are the heads ported, etc, or just heads with big valves installed? Pardon the other brand reference, but back before vortec and ls motors, a popular mod for the small chebbie was installing double bump heads (300 hp) and quite a few guys I knew totally lost the bottom end because the huge ports drastically reduced port velocity. Couple that with lost cylinder pressure from too much cam overlap on a low compression short block and you've got a real dog off the line. Not knowing the cam specs makes it hard to diagnose. Since you said the engine has a severe idle lope, i would lean toward that direction.

Haha yeah that was a few years back when camel hump heads were huge. ... not so much in reality but those were the days...

furyus · Aug 27, 2015

Sounds like the one change you made that would affect bottom end is taking the cam back to "0". Might want to put it back to 4+ , even though it's a lot of work.

Hemirunner · Aug 27, 2015

Everything you changed led to moving the torque up in the RPM range. If you increased power substantially, it could be driving through the converter and you may need to tighten it up. Most likely you just need to add some deeper gears and have at it.

Mopar-Charger · Aug 27, 2015

Hemirunner said:
Everything you changed led to moving the torque up in the RPM range. If you increased power substantially, it could be driving through the converter and you may need to tighten it up. Most likely you just need to add some deeper gears and have at it.

So if deeper gears aren't an option, torque converter is the only thing to help that? I don't think compression is the problem. I had good compression prior to the new heads, they do have some porting, but notthing insane. Bigger valves mainly.

I'm going to put in the MSD ignition probably next weekend. I have a Pro billet Distributor. What curve should I use? I can swap out the springs.

No Bottom End

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