When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hello All,
First post newb here, 3ed vert.
Purchased my new baby out of South Texas a few months back and after fixing all the leaks from her sitting up, Im on the quest for some personal touches. Vin shows a L48 but the motor is modded excluding the 3 speed, block and heads (assuming these are the original L48 heads).
She has a decent kick form 3500-6000 RPM but sluggish off the line. Im thinking the mild cam and L48 heads are the culprit. Put a tune on the carb and timing, balancer replaced, new plugs, less restrictive breather and still like a turtle off the line.
Now coming for a '73 big block hitting 11 to 1 on the comp ratio, you can imagine my
Any input on getting a better line shot????
I'd do a dyno run first. Then you can determine if you're having engine issues or perhaps need a better diff ratio, a higher (or lower) rpm stall convertor or perhaps have transmission issues.
I recommend a stall converter and gears, but with out knowing what cam, i can only guess and my guess is a 2600 rpm stall. Any cam that has any duration at all ran with the stock L48 heads and compression is most likely going to have a low dynamic compression ratio, which would cause a lazy bottom end. If you really want performance out of her, a good set of heads and a roller cam with intake, rear gears and stall to match the cam plus headers and dual exhaust would put you in the performance zone your looking for. The stock L48 compression is low as advertised, but the pistons set low enough in the hole that the advertised is off by .25 to .5, so the advertised is 8.5 to 1 but in reality it's more like 8 to 1. A set of 64cc heads with a .015" shim for a head gasket would net you around 9 to 1 that coupled with a stall and gears would get you the bottom end.
Last edited by bluedawg; Feb 10, 2016 at 04:07 PM.
Make sure your ignition advance is dialed in for performance. Easy 50hp improvement for the price of an adjustable advance can, weights and springs. Once you have it right, throttle should be VERY snappy. I went with Accel Perf Replacement HEI on my C3 as it came with the adjustable advance can so a tuner could do a dyno session of several pulls as he dialed in the distributor weights and springs. Worth the $200 dyno session and the parts.
Once you have that, decide if still sluggish off the line. Unless the motor is set up with high rpm valvetrain, I would not push it over 5,000rpm. Also, with a stock L48, you have used up your power by 5K (time to shift).
See sig... My L48 is quite warmed over and plenty healthy.
Make sure your ignition advance is dialed in for performance. Easy 50hp improvement for the price of an
Ted I don't usually disagree with you and while i agree that properly curved distributor makes a difference I don't agree that you'll pull 50 horse. Bringing the timing in at the correct rpm and to the proper total might add a little to peak hp, but what it dose is add to the mid and low rpms, making it have a better torque curve. I totally agree that it's the best performance you'll buy for $23 and will double if not triple the fun factor.
Last edited by bluedawg; Feb 11, 2016 at 03:38 AM.
Ok, so is the transmission kickdown cable attached to the carb linkage? I cant see it in the provided pic.
No kickdown cable, I get to down shift her and Im ok with that for now. Ive started playing with the timing on the existing can but Im thinking she needs a new distributor, heads, cam, converter, and gears. I guess paint may have to wait. New paint for spring would rawk tho.
No kickdown cable, I get to down shift her and Im ok with that for now. Ive started playing with the timing on the existing can but Im thinking she needs a new distributor, heads, cam, converter, and gears. I guess paint may have to wait. New paint for spring would rawk tho.
Well seeing as how I had a carb fart start a fire yesterday, She gonna need a lot. LS1 swap keeps getting googled here. Bubbled paint on the hood just isnt an option when shes painted.
Newbee with a tech question/ '79 L48
