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sb72elcamino350 09-04-2005 12:38 AM

No low end torque
 
Hello i'm just seeing what you guys think.
I have a 11.3:1 sbc 406, with a 235/245 camshaft at .488/.510 lift
1.6 roller rockers
holley contender intake manifold
sbc 882 heads 2.02/1.6 valves ported too
and right now a 825 race demon carburetor(Borrowing it and way to big i think)
HEI with proform tuneup kit 36 degree total advance

The problem i have is that it is gutless on the low end till about 3500 then it starts to go, not like it should but it goes better.

It is running rich i know that but you would think that it would go alittle bit better on low end, or maybe not.

Its in a 1969 chevy Kingswood wagon that weighs around 5000 pounds, with 4.56 gears and 12x26 tires. you would think that it would beable to do a burnout at least? I have a stock stall converter in it( I have a 4000 stall in the garage) But that tranny has had a hard life so i don't want to fill up my good one with shavings.

I am going to be using a quadrajet if i can get it to hold any fuel pressure. Does it sound like i'm just way to rich and that is why I have no power? What do you think?

Thanks

Trent

NorthStar 09-04-2005 01:20 AM

I think your carb is way too big.
Even though your heads are ported theyre not going to flow a whole lot.
How does it idle?

club327 09-04-2005 05:11 AM

Like Greg, I'd be giving that big carb the flick to make way for a 750vac secondary unit. With that gearing, cubic capacity, comp ratio and cam you'd expect the thing the be quite eager from low RPM.

shine 09-04-2005 05:22 AM

you have a bracket motor. your power range is going to be 3k to 6500. getting a tune for the street is going to be tuff. big cam, big valves big carb = rpm. your best bet will be a small carb with a lean tune for street use. from there you will have to decide how much of one to give up for the other. street or strip. take your time and you'll get there. it's just really tuff to tune this type of set up for the street. see if you can borrow a 650 to start with and work up to what you want. most of your driving will be from idle to 4k. tune for that. you can always carry a big carb set up for play in the trunk :) good luck

TooSlow 09-04-2005 05:58 AM

Those cam specs look suspiciously like the Edelbrock Performer RPM cam. This cam is notorious for being soggy on the low end. Replace it with a smaller modern grind, something like a Comp Cams XE262 or XE268 and feel the difference.

Hippie 09-04-2005 07:19 AM

Well, let's see.............

Quote:

Originally Posted by sb72elcamino350

A. a 235/245 camshaft at .488/.510 lift

B. a 825 race demon carburetor(Borrowing it and way to big i think)

C. Its in a 1969 chevy Kingswood wagon that weighs around 5000 pounds,

D. I have a stock stall converter in it

Do you see anything wrong with this picture?

A. Too much cam for the vehicle weight.
B. Too much carb for the vehicle weight.
C. Too much vehicle weight for the cam, carb and possibly motor. This is big block territory. The '69 Chevy wagons were killers in Super Stock but with a 427/390HP Rat motor.
D. Not enough converter for any of it.

ap72 09-04-2005 08:22 AM

The cam is a little big for the weight, however if you go smaller you'll run into detonation on pump gas, especially with ported iron heads. I think its a good engine, but you're utilizing it poorly. Adjust your timing curve so full advance scomes in sooner, get a better carb- perhaps one with a vacuum secondary around 700 cfm. And get a higher stall- you have to gears and the engine matched, but the stall converter is way out of line- go for around a 2800- 3200. That will allow you to take advantage of the rest of your setup. You built a braket engine and put on a braket rear end- don't try to make it streetable by using a smaller stall- use a midrange stall and setup your shift points to make it more street friendly (make them about 600 rpm after your stall speed).

larryblack 09-04-2005 08:26 AM

Quote:

Originally Posted by Hippie
Well, let's see.............



Do you see anything wrong with this picture?

A. Too much cam for the vehicle weight.
B. Too much carb for the vehicle weight.
C. Too much vehicle weight for the cam, carb and possibly motor. This is big block territory. The '69 Chevy wagons were killers in Super Stock but with a 427/390HP Rat motor.
D. Not enough converter for any of it.

The 406 cubes and 4.56 gears should make TONS of low end. Since he is saying things don't do so good until 3500, a loose converter would do wonders. A 2400-2600 should wake up the wagon.

I think the carb tune is OTL. Check your vacuum, size the primary power valve so the valve number is 2 less than idle vacuum. You probably can drop the jets down 2 sizes around. If you have sceondary power valve, use a 2.5 or plug it. You show total timing, the initial should be 12 to 16 depending on gas quality.

sb72elcamino350 09-04-2005 11:39 AM

1 Attachment(s)
Yeah i'm just using the stock converter till I rebuild the orginal tranny, because the tranny in it now has had a hard life, and I really don't see the point in filling up my better converter with crap when that tranny goes. I just barrowed the carb for the heck of it, and hated it its a 825 race demon. I just figured that it would have alittle more bottom end with even a stock converter, totally gutless. I have a remanufactered qjet that i am going to try with hopefully better results, i am much better at tuning quadrajets too. I had one other on there before but it would not even hold 3 psi of fuel pressure came out the top like a mad man. I built that thing to make alot of torque and hopefully I can get it out of it what I want. I tried to match the best I could with a very limited budget(18 years old student and a lube tech lol).

Thats me and the land bardge

xntrik 09-04-2005 11:44 AM

Quote:

Originally Posted by TooSlow
Those cam specs look suspiciously like the Edelbrock Performer RPM cam. This cam is notorious for being soggy on the low end. Replace it with a smaller modern grind, something like a Comp Cams XE262 or XE268 and feel the difference.

************
Those cams will put the dynamic compression ratio so high that 93 octane fuel will probably not be near enough...... IMHO

sb72elcamino350 09-04-2005 12:00 PM

1 Attachment(s)
Its a summit camshaft too. I got it to run on pump gas somehow, it stays super cool, does not get past 150-160 range. I would think it would beable to run in the 14's even here at IMSP in Montana, with a adjusted altitude of like 7000-8000 feet.

Bumpstick 09-04-2005 03:09 PM

Just a looser converter 2800-3000 and a 650cfm possibly 700cfm carb will make it come alive...


But one other question where is the 11.3 to 1 compression coming from...? What pistons...? Those 882 heads with the large valves work good together but they are large chamber (76cc)...

BTW if that is a Summit cam with those spec`s its the 1107 part number and with a stock converter it must be hell...? :evil:

xntrik 09-04-2005 03:39 PM

Quote:

Originally Posted by sb72elcamino350
Its a summit camshaft too. I got it to run on pump gas somehow, it stays super cool, does not get past 150-160 range. I would think it would beable to run in the 14's even here at IMSP in Montana, with a adjusted altitude of like 7000-8000 feet.

That explains pump gas/compression. At 8000 ft density altitude you only have 75 % sea level power available. (I am a pilot, check the density charts) That's about 8.5 compression at your altitude. That low of effective static compression and that hot of cam, your dynamic compression is so low......you probably will never have any low speed power..... If you can run 14s, that is pretty good at 75 % power. Consider Nitrous.

sb72elcamino350 09-06-2005 11:54 AM

I was hoping for 14's because there is a guy at the track with a vortec headed 350, with a 3500 stall and 4.10 gears that will run a 14.0000 anytime he wants. He has a 69 Impala Car. So i was thinking that I would run as fast or faster then him. We have about the same size camshaft and everything! I need some super tuning!!

454C10 09-06-2005 12:36 PM

Those old heads need more timing. Try 40 degrees total.

Converter needs more stall

carb too big and running rich. richness kills torque. Install smaller jets. Get a holley 750 3310. Cheap and good running carb.

Really need better heads.


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