pj_corvette

Hi

I'm following up on an earlier post by me. My wife just had our firstborn, who decided he was too bored in her tummy and wanted to come out ahead of time. That is why I dropped the thread at the time, but we are all happy and fine now.

Now, I'd like to continue planning my L48 upgrade.

My '78 L48 has a full exhaust upgrade already, from headers to dual exhaust.
I want to upgrade the top end with a heads/intake/cam combo.

Following up on posts in the previous thread, I narrowed down my choices to the following:
http://store.summitracing.com/partde...8&autoview=sku
http://store.summitracing.com/partde...9&autoview=sku
http://store.summitracing.com/partde...1&autoview=sku
http://store.summitracing.com/partde...0&autoview=sku
http://store.summitracing.com/partde...5&autoview=sku

A couple of questions now:

1. Any experience with these combos?

2. Some of the kits advertise up to 445 HP. How much power/torque should I expect my stock bottom end and drivetrain to handle?

3. Should I be concerned with streetability with these combos? My '78 is not my daily driver, so I don't need it to be super smooth. But I would also not like to have bad idling problems.

4. My car has the stock automatic 3-speed tranny. Could these be an issue with these combos (or the cams in them). I've seen a couple of posts about needing higher stalls in auto trannies depending on the cam, but I don't know/understand what problem they are referring to, or what to watch out for.

Thanks a bunch

lincoln9

I just built my 76' L48 a couple of months ago and did it without losing the stock appearance at all. I installed dart 180cc irons 64cc chambers with .015 thick Felpro gasket for around 9.5 or 9.6:1 compression and edelbrock performer intake and Lunati 60102 cam with the stock exhaust manifolds and 2 1/2" dual exhaust. TH350 got a 2000B&M stall and transgo reprogram kit. This car runs great on the street lots of vacuum. Way more power than before very happy with it.

I would have done things different if I wasn't worried about keeping it looking stock. I would have used aluminum heads and had 10.5:1comp, a different intake something like an edelbrock airgap and I would have used Lunati 60103 cam and put in a 2400stall.

The other reason I built the top end the way I did was. Because these L48's have a cast crank, cheap dished pistons I decided it wouldn't be a good idea to put a cam in that needs say 6300 rpm to max out. With the Lunati 60102 it needs about 5800rpm to max out I thought that was a good level for this engine. I think if you use my combo, it is about as good as it gets without over revving your stock bottom end. Even the changes I listed as would have done may not have been in favor of the bottom end. I don't think you'll get it up over 400hp without changing the crank and pistons then your also getting away from streetable when you cam it for 6500rpm. Unless you change to a roller cam. See how easy a simple build can start getting away.

If you build a similar engine to mine you don't need to change the bottom end and it is very powerful, streetable and it gets better mileage with the timing upgrades. The stock airbreather fits under the hood and it sounds great with a touch of lope at idle. It will roast the tires on command and it will chirp into second and third. It is probably around 350hp and 400 torque.

dgruenke

I did not see the cam specs on the Edelbrock top end kits. If I remember correctly, they use the standard Performer RPM cam. I believe that this cam is too large for your CR, as well as your stock torque converter. The Holley and the 2nd Trick Flow kit are also too large for your setup. The 1st Trick Flow kit is not bad, but the cam is too small in that one. It is listed at 210/216 duration, while the larger ones are in the 230 range.

You will probably want a cam that is in the low 220 range, or high 210's/mid 220's with a dual pattern cam. The L82 cam was 222/222.

Glensgages

..... quoted-for-truth.....


Build as-much power as you can by 5500 RPM, choose rear-gears that'll let you use that power (3.55s minimum, 3.73s for better-scoot, or 4.11s for all-out acceleration ), and you'll have a streetable combination that'll run rings-around other stock C3s of your era on readily-available pump-gas, yet be very reliable & long-lasting.

73C3

Pj
I'm considering the same choices.

The one thing you need to do is make sure you're engine's bottom end is healthy and worthy of a complete top end rebuild. If you have a worn out bottom end you might as well rebuild it also which will add to the $1700+ cost of the kit. By the time you rebuild it and purchase the top end kit you can purchase a long block crate engine with a warranty for the pretty much the same price.

I did a compression test on mine and the results where debatable and I am still up in the air about it. I am leaning toward a crate 383 long block for about $3K.

Also take a good look at the power spectrum graphs on these kits. yeah they offer up to 445 hp but look at where in the RPM range that is, usually around 6K. I dont know about you but my car has a TH400 with 3:55 gears and I never pull over 4K RPM doing 75-80 and would be afraid to get my car going fast enough to peak horsepower at 6K on the street.
I can just see it now, 140MPH and the front end is getting light and the tach reads 6K, I'm at max HP, and a rear wheel bearing decides to lock up since it's 34 yrs old

Little Mouse

lincoln9 looks to have a good combo of parts. but if you don't just
want a dead stock look I believe you should consider the
aluminum IK180 brodix there $1050.00 the 180 darts at least in
summits catalog are now up to $1007.90.

pj_corvette

I do want to do a compression test and what not to make sure the bottom end is OK before installing the new top-end.
Hey,73C3, how did you measure your compression test? Is there a write-up I can follow somewhere, or did you just take it to a shop/dealer?

That said, maybe in the future (maybe) I'll do more things to the engine (383? who knows), tranny, & drivetrain. So I'm trying to pick a kit that wont be obsolete if I decide to keep upgrading later. But who knows, maybe I'll just do this upgrade and be satisfied with it.

What kind of HP percentage is lost on these cars? Like, if a combo says it makes "X" horsepower, how much of "X" should I expect to see at the wheels?

Regarding the Cams, yes, I don't want to over-rev the engine. I don't want a setup where all the power comes in at 6000 rpm. The problem is that I dont know how to read cam specs and tell what rpm ranges the cam will be good for, and so on. How do I select a cam so that the powerband is in the low to mid rpms? Do any of the cams in these kits hit that target? Here's the info I dug up on the cams in the combos I'm looking at:

Edelbrock 2098 Combo (Hydraulic Cam & Lifters #7102)
ENGINE: CHEVY 283-400 V8
RPM RANGE: 1500-6500
Duration at 0.006" Lift: Intake: 308° Exhaust: 318°
Duration at 0.050" Lift: Intake: 234° Exhaust: 244°
Lift at Cam: Intake: 0.325" Exhaust: 0.340"
Lift at Valve: Intake: 0.488" Exhaust: 0.510"
Timing at 0.050" lift: Open Close
Intake: 10° BTDC 44° ABDC
Exhaust: 59° BBDC 5° ATDC
Centerlines: Lobe Separation - 112° Intake Centerline - 107°


Edelbrock 2099 Combo (Hydraulic Roller Cam #2201)
ENGINE: CHEVY 283-400 V8 (1957-1986)
RPM RANGE: 1500-6500
Duration at 0.006" Lift: Intake: 296° Exhaust: 300°
Duration at 0.050" Lift: Intake: 234° Exhaust: 238°
Lift at Cam: Intake: 0.359" Exhaust: 0.365"
Lift at Valve: Intake: 0.539" Exhaust: 0.548"
Timing at 0.050" lift: Open Close
Intake: 10° BTDC 44° ABDC
Exhaust: 56° BBDC 2° ATDC
Centerlines: Lobe Separation - 112° Intake Centerline - 107°

Holley Systemax-II Combo
Intake Valve Gross Lift: .488"
Exhaust Valve Gross Lift: .510"
Intake Valve Duration: @0.050": 234°
Exhaust Valve Duration @ 0.050": 244°
Rocker Arm Ratio: 1.5
Intake Valve Lobe Centerline: 107°
Lobe Separation: 112°

Trickflow K314-350-400 Combo
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 1,900-4,900
Intake Duration at 050 inch Lift: 210
Exhaust Duration at 050 inch Lift: 216
Duration at 050 inch Lift: 210 int./216 exh.
Advertised Intake Duration: 266
Advertised Exhaust Duration: 272
Advertised Duration: 266 int./272 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.440 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.454 in.
Valve Lift with Factory Rocker Arm Ratio: 0.440 int./0.454 exh. lift
Lobe Separation (degrees): 110

Trickflow K314-420-395 Combo
Cam Style: Hydraulic flat tappet
Basic Operating RPM Range: 2,700-5,700
Intake Duration at 050 inch Lift: 228
Exhaust Duration at 050 inch Lift: 234
Duration at 050 inch Lift: 228 int./234 exh.
Advertised Intake Duration: 284
Advertised Exhaust Duration: 290
Advertised Duration: 284 int./290 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.480 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.494 in.
Valve Lift with Factory Rocker Arm Ratio: 0.480 int./0.494 exh. lift
Lobe Separation (degrees): 110

Glensgages

Note how duration @ .050"-lift effects where the RPM range is:
the longer (duration ) the valve is open beyond .050"-lift, the higher the RPM is where the power-band will be.

Based-on the few camshafts you've shown, the Trickflow K314-420-395 would be best for your application:
'generally-speaking', something in the .460"-.480"-lift range, with 224*-230* duration will suite your needs.

firefighter

What is the stock compression ratio on the L48? And the L82? Late 70's vintage.

Glassbowtie77

8.5:1 for the L48 and 9:1 for the L82.

Little Mouse

The 350-400 trick flow is the only one you could use on your 350
the rest have way to much cam not even close to what you need.
the other trick flow would be barley usable its really to much.

dgruenke

I also think that the second trick flow setup has too much cam for a 350, especially with the stock torque converter.

firefighter

Thanks I was looking for the info the other day but the specs are kinda hard to come by, what with the late 70's emissions the specs being kind of embarrasing.

When I told my wife that my '03 Blazer (180hp/260ftlbs) came stock with almost as much power as a late 70's Vette she got this look of absolute horror and said well you are gonna have to fix that for me I can't get shown up in a Vette. lol


I loved her so much more after she said that, it made me all warm inside. lol

I'm gonna try and look for an L82 car and throw some rings/bearing/pistons and get the block/crank/rods reconditioned and then throw an Vortec RPM airgap topend on it with a different cam probably (maybe not) and call it a day.

pj_corvette

Check this page out
http://64.233.167.104/search?q=cache...ient=firefox-a

I dont know why, but Trickflow does not have this page active anymore. I can only see it through the Google cache.

Anyway, they do list the 420-395 combo as being tested on a 350 block. That's why I was looking at that kit. They do have other kits for 383's further down on that page.

As for my auto tranny, well, that would be another issue. I was planning on changing it down the road to at least a 4-speed auto, but I want to do one thing at a time...

If a kit says it produces "X" Horseposer, how much of hat "X" can I expect to see at the wheels on these cars?

firefighter

I don't know if there is anything special about power loss on the C3 but tradionally it's 15%-20% mote for auto less for manual.

So a total *SWAG say a 450hp combo figure 90hp loss (20%) say 360rwhp with an Auto Trans.

*SWAG acronym

Scientific
Wild
***
Guess

pj_corvette

Hmm, how does this look to you?

http://www.prestigehighperformance.com/408/chevy408.htm
Then I would not have to worry about my bottom end.

One of the options for cams does not require a stall converter change:
The following Cams are available for this package: (The package price is the same for all cams)
* 275I/277E Duration .462I/.482E Lift Choppy Idle No Stall Converted Needed
* 292I/292E Duration .501I/.501E Lift Rough Idle 3000+ Stall Converter Needed
* 305I/305E Duration .525I/.525E Lift Rough Idle 3500+ Stall Converter Needed ***

How much could I sell my current motor for, assuming I went this route?

dgruenke

That's quite a jump in price from the kits that you were looking at. The engine is probably not a forged assembly, so it would not be much of an upgrade over what you have now.

firefighter

Yeah I glanced over the parts list and there was NO mention of the rotating assy. So to me that means stock cast which means same as you got. At the very least you need to get maybe an Eagle set up. I got one in my dads 383ci it was about $1600 unbalanced but was very nice stuff and the price was great.

But this brings you to a completely diff level of project.

pj_corvette

BTW. Nevermind about prestige high performance. I searched for them here in corvette forum. Very negative reviews.

I guess I'm back to considering the top-end combos.
PJ

Little Mouse

Brodix IK180, 64cc chambers, aluminum heads one pair,
BRO-1021004 cost $1013.95

Lunati Voodo cam and lifters. part # LUN-60102LK cost $189.95
.050 duration 219/227
valve lift 468/489
LSA 112

Performer intake EDL-2101 cost $119.95

www.summitracing.com
www.brodix.com
www.edelbrock.com