I’ve been reading a lot of threads on here, and still don’t see a real good answer...so I thought I’d post and see what kind of feedback I get.
Ive got an 81 that’s completely stock and unmolested with a 4 speed. About 80k miles, and runs great with no problems. I’m wanting to get a little more power and a better sound, and was wondering about just upgrading the top end. I’ve seen people talk about it on here and have great luck with it, and others saying don’t do it. I’m not wanting to spend a ton of money, and not trying to build a street racer. Just something to cruise around in and it sounds good.
Ive seen a few videos of a guy that did just that...nothing done to the bottom end (had good compression all the way around) and added new heads, thumper cam, intake and carb and said it runs and sounds great.
I was thinking of going this route and wondered what problems I might run into. Or will it just be a waste of time and money.
Like I said, not trying to build a race car...just something to cruise in with a little more power.
Thanks for any help or input you guys may have.

 

Why would it be a waste of money? Doing this exact think on my 82 right now. Hoping to make a respectable street car, mid to high 13s and I’ll be very happy with the build. You will always find people in this forum that want to give their negative opinion on others builds and how you should spend your money. However you also find those who understand and are extremely helpful!

Go for the top end rebuild and have fun!

 

Thanks for the positive words. So this is what you’re actually doing to yours right now? What are you doing to yours?

i know some guys on here might be wanting to build a 500 hp car that’ll smoke anything it pulls up beside and that’s completely fine, but I’m not. I just want something that runs a little better and sounds good. Mines just going to be for cruising around anyway.

 

Yes I have the top end off as we speak. Since I have the 82 crossfire I am more limited than you. So I am installing a mild comp cam, brodix ik 180 heads and the renegade intake. Last year per suggestions on this forum I deleted the cats and installed Hedman long tube headers. That alone made a big difference

 

Yep build it the way YOU want it to be! Everyone is going to have an opinion. I am building an 81 too and will build it the way I want it to be built. I am going for the street cruiser that I can drive cross country if I want. Am I over building it, probably but it will support what ever I want to do in the future. Going with a custom built 4L60E, Mike Dyer built Dana 44 with David Ogden billet u-joint caps and a old school 350 with AFR heads, Chris Straub custom cam and forged lower end. Thing is, I could build something with more horsepower but what is the point in building an engine with crazy torque and horsepower if you can't put it to the ground or if everything behind the engine cannot support it? So build it the way you want and go enjoy it!

 

Since you say its completely stock, unless you are planning to change the carb and distributor for a non computer controlled versions then you would need to be careful about which cam you select. Pick the wrong one and the computer will get confused about what is gong on.

 

Antz81...
my plan if I change just the top end was going to be heads, cam, intake, carb, and distributor.
I know people would probably say if you’re going to do all that why not do the whole thing. I could do what I’m thinking about without removing the motor itself and hopefully have a better running and sounding car. Plus put headers and new exhaust too.

Thanks for the the positive comments btw.
I figured I’d be getting bashed by now. Lol

 

Don't worry about getting bashed! There are definitely people here that have a lot of money to throw at their cars but not everyone and you have to start somewhere. Having said that you will get some expert advice also, some real knowledgeable people here. If you have a real STOCK 81, then there are a lot of things to consider as Antz81 was alluding to. If you have the original exhaust, then you have a catalytic converter and a single exhaust. Improving the exhaust is usually one of the first things people recommend doing to free up some HP. Also if you have the smog system (air pump, etc) these eat up power. You don't say where you are so not sure of your pollution requirements. Here in Ohio cars over 25 yrs you can do whatever - no smog check, which is good. That said, a top end kit could be a good improvement to your car as long as the bottom end is in good shape. Even with those goals there are a ton of options, not knowing how informed you are about engines. There are a lot of heads for sure! What's your budget? That will determine a lot. My recommendation:

Low budget: Iron vortec heads, Comp XE268 cam, Edel intake, Edel 650 carb, MSD street fire distr. (I had this)
High budget: change out to retro roller, or just get new engine. (I did this lol)

Jim

 

Jim...
yes the car is stock with stock exhaust. I live in a part of Texas that doesn’t require any kind of smog checking.
Im a little familiar with engines. I’ve never rebuilt one or replaced one, but have swapped out intakes and carbs before. Swapped dist before on a 69 truck from points to elec ignition. I know a little but not an expert by any means.
My budget is up in the air really. I first thought about buying a crate motor. And I know that would be the best way probably, as to have new with a warranty. But thought maybe it would be another avenue to go by just replacing the top end.

 

OP 66ca

I get it. All this is Low-Buck. And this is my opinion; not an edict. Not a street race motor. Want some performance upgrade & nice sound. Want No more than top end and cam.

Here goes:

As said, you need true dual exhausts; BOTH OE exhaust & intake manifolds are adequate for mild performance upgrades. Need true dual exhaust pipes & mufflers. For this mild combo, Headers aren't going to add significantly except to cost & maintenance.

You desperately need more compression. The most effective way to get there is to use a pair of heads from either a ZZ4 crate … OR … cars that came with L98 motor. They’re most effective because they are Aluminum & have small 58cc combustion chambers. The iron Vortec heads are GREAT and flow better but they have larger 64cc chambers which (when coupled with your low-compression dished pistons) won’t make as much compression as the L98 heads. And, you won’t need or use the Vortec’s superior flow with your mild goals. Also, the Vortec head requires an entirely different intake manifold whereas L98 heads can use OE 81 vette manifolds. If you chose a head which can use your OE intake, it will perform more than adequately for this mild combo. Both Vortec & L98/ZZ4 require center-bolt valve covers.

Those L98 / ZZ4 heads have GM casting number 10088113

and their (discontinued) GM part number is 12556463

L98 engines were OE in:

1985-1991 Chevrolet Corvette (standard)

1987-1992 Chevrolet Camaro (optional)

1987-1992 Pontiac Firebird (optional)

The 64cc Vortec heads and a shim gasket will yield about 9.4:1 CR

The 58cc L98 heads and 0.026” composite gasket about 9.8:1 CR

A GREAT alternative head to the above is the Engine Quest iron hybrid which has the superior chamber like a Vortec but uses a conventional intake manifold like your OE 81 has. The EQ part number for one Assembled head is CH350HA. EQ heads have a great reputation. You can use your existing valve covers with EQ CH350HA.
https://2u7bve3d8yjttiswb3gnx3uo-wpe...atalog-web.pdf

You need a larger camshaft along with new lifters.

The cam already suggested above is OK. Also Summit has their own house-brand line of cam & lifter kits for under $101; at least three which will match well with either above head choices.

When you change the cam, you should install a New timing chain set; you shouldn't spend more than $30 for this application / mild combo.

You also need a different distributor having Both centrifugal (mechanical) and vacuum advances. The one suggested above is OK, but most any HEI is fine. You can spend from $50 to $400.

Your OE Rochester carb is fine; it’ll benefit from a freshening and tuning.

 

I'm also thinking of doing the same thing eventually to my L-81. I bought some take off ZZ4 heads about 5 years ago and was planning on doing a mild roller cam that will work with the stock CCC but now I'm just thinking screw it and go with a spreadbore Holley or a Sniper EFI system and Distributor.

I just don't know what cam to use, doesn't have to be roller either, i'll do hydraulic flat tappet if there's one that work well with the heads. I think the ZZ409 cam might work well? and there's a flat tappet version too.

 

With an 81, the CCC will limit some of what you can do but should be able to support your goals as stated without any problems.

First thing to do is advance your base timing. It’s free and you’ll be amazed at the boost it’ll give you. It won’t take a ton of advance, but as I recall, my initial was somewhere between 10 and 14 degrees BTDC, set with the distributor to computer harness unplugged. Too much more than this and you’ll experience surging at cruise speed.

The next big bottleneck is the exhaust. The stock catalytic converter is a killer. Just replacing that with a modern, high flow cat will make a big difference. True dual exhaust will be that much better.

Next is heads. As others have stated, there are lots of better heads out there. Truth be told, you’d be hard pressed to find worse than the L81 stock heads. I had great luck with Summit heads. Very inexpensive and a very noticeable improvement over stock.

Notice that I didn’t mention cams. The stock computer system just isn’t clever enough to deal with much more cam, especially, one with lots of overlap. Unless you’re after significant HP, I just wouldn’t bother.

 

Even though you are looking for a mild performance build there are a few things to keep in mind as you are planning.
Start with your rear end gearing and the rpm's you are turning cruising down the highway.
Build your engine to make the most power in the areas where you want an increase.
Different cam grinds build power at different rpm's throughout the power curve.
Think about if you want a little more bottom end, mid range or more power in the upper end of the rpm range you use your car.
Purchase a cam that builds power where you need it.
Same thing with intakes, heads and different exhaust designs.
Certain brands and designs work better and produce power at different rpms.
Find the components that work best together for the best results.
Send your carb to Lars who is a forum member.
He is know as the best anywhere for rebuilding and tuning your OEM carb, which will be the best for you performance package.
As stated above, long tube headers won't help much, but if you want better scavenging of the exhaust and improved torque, look at a set of Sanderson short tube headers.
They offer equal performance to long tube headers under 3500 rpm and for a build like your's they would be worth the expense with a nice 2 1/2" dual exhaust system with an X pipe.
If you purchase a set of new heads complete and assembled, have someone check them before you install them.
Even the pro's who produce the big buck components make a mistake every now and then.
Don't forget about hood clearance either.
Good luck and keep us posted while you complete your build.

 

Wow I didn’t realize there would be so many options and things to consider.
When I saw this video...
this is what made me want to work on mine. I loved the way this car sounded. And after reading the description in the video, it seemed like all he did was the top end. That’s why I started going in that direction. Maybe mine would never sound like that since it’s an 81.
I have a few friends that are actually mechanics and have their own shop and do this for a living, and I was going to have them do the work for me because I really don’t trust myself to make it right.

After reading all all the inputs and suggestions, it almost seems as easy to just buy a crate motor and add a nice intake and carb. I know it’ll be way more money.
Like I said, after seeing that video and how he just did his top end, I thought I’d be able to go that same route to get the same results.

 

Here is a top end kit that would work with your 4 speed.
https://www.jegs.com/i/JEGS/555/5141...791+4294828856

 

FWIW ... OE ZZ4 cam has .474" lift intake and .510" exhaust ... so, your heads should safely handle that much lift ... you must measure yours to verify/determine if they'll handle even more.

pn SUM-K1103 214/224
https://www.summitracing.com/parts/sum-k1103?rrec=true

pn SUM-K1105 224/234
https://www.summitracing.com/parts/s...make/chevrolet

and here's a fleshed-out list of about 10 summit hydraulic FLAT tappet cam & lifter kits for sbc ... ALL under $115 ... the largest 5 or 6 probably won't work with 1981-1982 C3 computer/CCC. So, change the distributor and don't use computer. List ranges from tiny to probably WAY too much for you.You can probably find one that's similar to what you're seeking. Someone else could advise you about acceptable cam duration guidelines for those OE CCC/computer systems. With just a decent carb & decent distributor, you have huge range of choices that'll work with OE ZZ4 heads. Just remember, they don't flow as well as others and start falling down above about .500" lift. Also, ZZ4 heads require either self-guided/self-align rockers (like OE) ... or aftermarket guideplates. Also, regardless of cam or head, larger lifts require a stiffer spring.
https://www.summitracing.com/search/...rder=Ascending

 

Jackson....
so by using a better aftermarket distributor you pretty much bypass/do away with the computer that controls engine functions?

im definitely going to start making a list. You guys are all giving me great ideas to work with. Thank you very much

 

Before you go too far down this path, what state are you in and do you have to pass smog checks? If so, eliminating the CCC will almost certainly cause you to fail.

 

Ca-legal-Vette
im in Texas, but where I’m at they don’t do smog tests.
I think maybe they do in Dallas but not where I live

 

perfect example of why everyone here seeking info on project mods/repairs should include in their public profile an approximate geographic location of project (minimum County/Parish) ... someone here may be familiar with regulations in that government jurisdiction ... owner builder should be familiar with those regs BEFORE guessing /planningspending. How/if they are enforced varies wildly across USA.