billla

Making sure I'm clear - my suggestion is that you NOT stroke it unless you significantly increase your budget.

Bigger valves on the stock heads is a waste of money; by the time you get bigger seats cut and the chambers swept you'll have spent a fair bit of cash...for some mediocre heads. Doing a straight rebuild of the heads for a 355 was good economy - but the expense of significant machining in heads that won't flow enough to make the valve size matter isn't.

As for the radiator, a properly functioning 2-row is fine - unless your budget is going way up an aluminum is out of scope.

In the end, you gotta put a hard budget down to drive some of these decisions. You can get caught up in a virtually infinite loop of options until you put a hard number on it.

billla

FYI, running a DD advanced with stock heads and shorties the 383 produced about 15TQ more from 2000 - 4500. Bigger valves were worth about 3HP, 1 TQ. This is all pretty consistent with my experience - mild 383 builds show a better torque curve but IMHO not worth the investment.

Step up on the intake, heads and exhaust and it's a totally different story - 425+ HP with the right cam.

I always tell people to build the engine they can build NOW vs. saying "well, I'm going to put all these mismatched pieces together now, but when I swap out the <intake, cam, heads, etc.> later it's going to be a screamer." It just very rarely works out that way.

To make sure we're comparing apples and apples - these are 3927186 or 3991492 castings? I've been saying 882's as I didn't have my references in front of me, but this is what I have for 350/300s' in 1970.

73, Dark Blue 454

Stroke it. Today's kits make it a no-brainer. Or, for budget purposes you can use your 5.7" original rods. That would leave block prep, pistons, crank, and misc,..about $2000-$2500 for the shortblock. Scat's 9000 series stroker cranks are about $275 plus ship and are said to be much stronger than cast. Probe makes a good forged piston for 5.7" rods that run about $400.

Agree with the above, eventually some bigger heads will take full advantage of the increased displacement,..maybe something in the 205cc range. I'd forget Vortecs or any other stock castings. Aftermarket heads can add 50+ HP over any stockers.

Instead of the Performer, the RPM Performer would be a better choice. Your Q-Jet and air cleaner are fine.

What rear and tranny? We'll pick you a cam.

yel76low

on all points. Pouring money into bad heads is just going to result in wasting money...

And isn't that the truth about the infinite loop of options.

You've got a point there, Billa. I guess I was thinking of for the future the 383 would be nice... but if you aren't planning on doing anything later, then whats the point? That money could probably go to better use elsewhere.

But, 15 lb-ft across most of the operating range of the engine seems like a pretty fair improvement if it is only $300 more. No?

billla

No easy decisions here - the shortblock cost isn't all that different (as noted) - the cost comes in feeding those extra cubes. I just don't think those heads are up for the job unless too much money is spent on them...but they'd feed a 355 just fine.

Like I said right up front, I'm pretty conservative. Most of the engines I build are <= 1.2 HP/CID and they're for guys that have very limited budgets and no opportunity to "back up" if something goes sideways. That needs to be factored into my recommendations...my focus is always ensuring the engine can get back in and running for the budget articulated. My designs are EXCLUSIVELY budget-driven, and I always build "matched" as those "I'm gonna" changes rarely ever happen once the engine is in and running.

stingr69

My Opinion - If the bores are worn too far to be reused and need to be rebored and money is tight, you need to stroke it on the cheap. The heads are fine if they do not need much work but have them looked at before you buy any other parts. The cost to recondition them may end up close to the cost of a nice set of Dart heads and I would rather have all new better flowing heads at that point. The head choice dictates the piston specs so buy them after the head selection is nailed down. You have to match the compression to the cam timing.

As for the shortie headers, who cares? They don't add much in this combination and the cast iron manifolds flow well enough that they do not hurt you enough to matter here. It's a toss up. If you already have them and want to run them then do it. You aren't running enough RPM's/overlap/open exhaust for shortie headers to do anything so there isn't much HP left on the table either way.

The Edelbrock 2101 is a power reducer on a 350 so it will hurt you even more with a 383. I did back to back swaps between that one and a Holley manifold and it was clearly obvious on my "seat of the pants" dyno. A stock aluminum L-82 manifold is a better piece and costs less too if you are on a tight budget.

Keep the stock rods and reuse them. You do not have money to burn and with the low RPMs they will be fine.

This should go without saying - the biggest HP robber on the stock late model C3 is the original catalytic converter. Remove it and replace it with a better flowing new design if you have not done so already. A true dual exhaust without any cats is even better but there are legal concerns here so use your own judgement.

That's my "within the budget" opinion.

-Mark.

sxr6

Here's what I did way back in the day.
I started with a low mile 1974 L-48.
I swapped on a set of 1970 1.94 heads, a set of header-sidepipes, a GM 370hp solid lifter cam & springs, an aluminum GM manifold from a LT-1?, & a quadrojet.

Ran couple time at the track & got a best 14.99 @ 107mph
Note the 107mph!! that was with a stock 400 tranny & 2.73 gears I believe or possibly 3.08s?? That was done with stick pulled into low & left there, letting the overide shift at 6,500rpm. That old bottom end ran 40,000 miles like that & was working fine when I sold it. What would that combo have run with a nice rear gear??

Since your not after max power & you have them I'd use those heads, stroke it for more torque, run a nice mild cam (max 5,500rpm), & like above poster said look for a GM aluminum intake & quadjet. One thing you didn't mention was what rear gear your running?? I recommend a nice 3.36 or 3.55s for decent cruise & acceleration. You have a very nice alaround combo for great street manners & enough umph to please.

billla

I wanted to make a quick comment regarding reusing existing stock rods since it's been mentioned here a couple of times. Machine shop prices vary drastically across the US, but generally by the time a set of rods is cleaned, 'fluxed and resized with new ARP bolts you'll spend at least as much and likely more than a set of Scat I-beam rods (P/N 35700P) at around $175 a set. Far better rods, less money.

Make sure you ask your shop for the price on reconditioning rods before making the decision.

Little Mouse

One of the rags built a 496 using a scat rotating kit like flatlander racing sells they checked it thinking maybe it needed balancing did not need it, by the time you buy a crank, rods, pistons, rings, bearings that come in the rotating kit seperatly then pay a machine shop to balance it you will come out the looser on cost. Buy an internal balanced rotating kit with flat top pistons for your 76cc heads run them if need be or if your bucks up now buy aftermarket heads. The very best over the assembly line fuelie heads from the 60s with 202/160 valves flow a miserable 185 cfm at .500 lift don't waste any money on your heads, if they need money spent on them S..T can them there not even a good head for a 350 much less a 383.
www.flatlanderracing.com
1-90150BI= (BI balanced internally)
3.750 crank
6.00 4340 I/beam rod
4.030 forged flat top piston
moly rings
bearings
$859.00

la80vette

You already have the aluminum intake if that's an 80'.

billla

Must be a mistake on their website - Scat rotating ***'y 1-90150-BI is a 3.48 stroke with 6" rods and hypereutectic pistons...not a 383 and not forged.

Scat 1-90500-BI would be for a 3.75/6"/hypereutectic kit.

Little Mouse

Yep they made a mistake up top I should have looked at the crank.
9-350-3750-6000 in kit 1-90450BI same price $859.00.1-90500BI kit $889.00 shows a forged dished piston would probably be just right for a 64cc aftermarket head.

firefighter C-3

So, the '80 L-48 and L-82 use the same intake???
Try this on for size guys...I sat down with a very expeienced man who is a corvette engine builder/mechanic/customizer with lots of experience with the older vettes. With keeping OEM air cleaner/carb/ 370 heads w 194/150 valves, shorty headers, true duals (2.25" w/o cats, and mainly cruising and out of state travel with a little fun here and there, gas prices/quality being what they are.....He suggested rebuild the bottom end (bored 30 over), mild cam w 110-112 degreee sep.,cast hyper pistons, polish my crank( if OK), & have balanced, have stock 2 row radiator redone, new water pump, hoses, motor mounts,.
The BIG change is to put the $ i saved from the engine and use 700 or 200 tranny with my stock 3.07 rear. The 700/200 1st gear is taller so with my 3.07 rear i'll get better get up-n-go than the TH-350 and with overdrive i'll get better cruising on those longer trips. Motor build $2K, tranny $1.5 K.
Hows that for a curve ball?? Any comments??

billla

So, basically a performance overhaul with a balance and a performance cam...gee, that sounds familiar

The devil is in the details on the build; if you head that direction I have a few specific suggestions. 2K is probably about right depending on the condition of the heads and assuming you're reusing everything possible.

The trans swap is a great idea - but the price looks a little low for an all-up; make sure that's a "drive away" price and not just the cost for the trans itself. I'm sure there are also some threads on that swap, so do your homework.

stingr69

If that crank needs more than a polish I would still think hard about putting the longer stroke in there. As Motorhead said - nobody ever said they would have rather left it a 350 after they tried a stroker. That said, the 350 will be a little better on gas.

Sounds like a good sensible plan to me either way.

-Mark.

la80vette

you're stock aluminum intake is a dual plane, very nice flowing intake.
Maybe better than the 2101. Same as the L-82. It was put on the 80' L-48 to reduce weight.