Question: Go LS or build what I've got?

[damoroso]

Okay, looking for opinions out there.....
I've got a nice clean 81, that's currently stock. I'll be adding true dual exhaust in the next month or so. It used to be that when you went from stock exhaust manifolds to headers, there was a good hp boost (making sure you completed the job with the rest of the exhaust system). My 81 has factory "header" style manifolds on it now. Is there really a gain to be had in changing those to a set of the "hugger" style of header? My guess is to get the most benifit, I should go with long tubes (using koolmat under the carpet). Thoughts?

And now for the big one. I've really wanted to swap an LS2 into the car, possibly stroking it, changing the cam, heads and intake looking for about 450 - 500 hp. I plan on using a 700r4 trans (I'll at least do the dual exhasut and put the trans in the car before the swap so I can still drive it while gathering the rest of the parts) or possibly a 2004r. The rear gearing may have to change down the road.

The big question is, should I spend the money on the LS2 (assuming I build it from a short block up) or put the money into a traditional small block? So far, I think I'm looking at around 6-7K to do the engine work and swap (I can do all the work). I've not tried to get that kind of hp out of a small block before, I'm looking at stroking it, bringing the compresion up to about 9.5:1 (does anyone know if the 81 block is a 4 bolt?), the right cam, having the heads worked, (flow, matching ports, vavles, three angle cut, all the normal stuff) or changing them all together, matching the intake,(maybe fuel injection) and carb. I'm looking for drivability (including decent fuel mileage, with the LS and trans I'm expecting 25-30) and to smoke those annoying little metric cars that sound like model airplanes, and of course to BBQ Mustangs....

 

[bossvette]

looking for about 450 - 500 hp....................................................................................I'm looking for drivability (including decent fuel mileage, with the LS and trans I'm expecting 25-30)

it won't happen with the money you have to spend to get a @400 CI small block in that HP range it will have to be on the wild side unless you consider power adders like nitrous, turbos or a blower

 

[KANE]

....So far, I think I'm looking at around 6-7K to do the engine work and swap (I can do all the work). I've not tried to get that kind of hp out of a small block before, I'm looking at stroking it, bringing the compresion up to about 9.5:1 (does anyone know if the 81 block is a 4 bolt?), the right cam, having the heads worked, (flow, matching ports, vavles, three angle cut, all the normal stuff) or changing them all together, matching the intake,(maybe fuel injection) and carb. I'm looking for drivability (including decent fuel mileage, with the LS and trans I'm expecting 25-30) and to smoke those annoying little metric cars that sound like model airplanes, and of course to BBQ Mustangs....

I agree with Bossvette. For that amount of money... an LS swap isn't cost effective. I'd sell the L81 block and TH350 for around $400 and apply that towards a crate 350.

For around $2k, you can get a nice EFI kit. For around $4K, you can get a nice crate motor. You can also get a nice 700R4 for around $1,500. Total: $7,500. If you sell the L81 block and tranny for $400... you'll only be $100 over budget.

I've built my engine for driving. I don't intend to race it or anything like that. It is a lightly modified GMPP motor. I have 8.5 comprsion, around 300hp, and it's dead-on reliable. I also average 20mpg between city and highway with the TH350.

 

[Rodney Gold]

Problem could be the diff in the 81 , which is a pretty weakish version of a dana (think its a dana 44) You will need a higher ratio than the 3.0:1 , a 3.75 or so
700r4 would have to be reworked to get durability with a high hp application.
I worked with what I got , with a 3.55 gear and a TH350 box (I would prefer a 700r4 or a 4l80e) and my car is driveable and does a 13.4 in drive on lousy 265 tyres. Keeps blowing up TQ's however, TCI sat night specials.

 

[damoroso]

There certainly are issues with the diff in our 80-82's they weren't built for much hp. I'm sure no matter which way I go, that'll have to be addressed in the future. Just for clairity, I'm thinking the 6-7K for the engine, engine work and stuffing the engine in the car (either the LS2 or the built small block). The trans and rear are a separate budget. Mostly because I believe I can install the new trans with the stock engine and get the benifits of better gearing an a OD. What's really great though, is everything works well now, so I can keep driving the car as I gather the parts!!

Still looking for that hp though, and I'm afraid like Bossvette said, ya can't get there from here on a standard 400CI engine... That LS2 starts at 400 hp....

 

[minifridge1138]

Just a reminder, the 700R4 is not a direct fit for pre-1982 corvettes. You need a drive shaft from a 1982.

www.bowtieoverdrives.com sells different versions of the 700R4's. Each rated for a different amount of hp and tq.

Just my opinion, you'll have a much easier time fitting a standard small block in your engine compartment than you will an LS2.

Good Luck!

 

[mrvette]

I would think you can find a decent truck 4 bolt block and do a 383 to it, and aluminum heads, and even a LT1 modified induction for that kind of money, and like me, get 22.22222 mpg at 90 mph cruise....336 rear and 200 4r....

IF you can do your own wiring, DPFI is really not all that hard to install....

 

[upinsmoke]

I would go with the LS2. They are plentiful in the 4000.00 range with wiring harness and transmission included. Yes it would take some work but the mileage issue with 4/gallon fuel prices would be better and it would pass any emission test now or in the future. It would be a sweet package and a car you could live with everyday. It might end up a little over your budget by the time it is finished but in the long run I believe you will be better off.

 

[6880 Mike]

...Okay, looking for opinions out there.....
I've got a nice clean 81, that's currently stock...

Keep her that way and rebuild what you have. There are less and less unmolested, original cars around and getting fewer all the time.

Give her a break. She's managed to survive unharmed all this time.

 

[Tom Bryant]

Since you asked for opinions I'll give you my 2 cents worth. First off, your stock tube manifolds are 2" outlet and 1.5" primaries. These are just about right on for the stock engine or a mild build. The '82s are 2.5" outlet. I'm not sure if the primaries increased or not. If you are going to do a serious build long tubes would be the way to go if you are willing to put up with the usual flange leaks associated with headers.

As for block huggers you need to understand what they were designed for in the first place. I keep hearing guys say they are putting on block huggers as if block huggers equal horsepower when, in fact, it is more than likely the opposite as compared to your stock tube manifolds. Block huggers were designed for the street rod market where there is very little room between the engine block and the frame rails for exhaust. In these applications conventional headers or stock manifolds just don't work and usually end up requiring the same space that is now occupied by the frame rail. Block hugger headers tuck the pipes in close to the block to get them down past the frame rails. That's their whole purpose.

In exhaust system design a tighter radius or more bends equals a loss of power. Block huggers start off right from the flange with a tighter radius to tuck in tight then they have an additional bend to get them pointed down again. Two strikes already. With the outlet moved towards the engine you will also pull the rest of your exhaust system in narrower and you may not have the clearance for that. If you are installing an engine in a tight chassis then these can be a great thing. If you have exhaust room, like in the Corvette, they are of no use at all.

As for the LS block conversion be prepared for some serious fabrication. They don't mount the same and frame mounts will have to be made. Also if you plan to use your stock power steering pump and A/C compressor you will have to make mounts and come up with an accessory drive system that spins everything in the right direction. The LS equiped cars use entirely different pumps and accessories than the old cars. Pick up the October 08 issue of Car Craft for a primer on accessory drive components to put an LS in an older car. You will probably end up switching A/C and P/S parts to newer stuff. Buying a used LS2or LS3 with auto trans and all of it's components will put you money ahead.

If you don't want to mess around reworking the stock engine control harness GMPP (GM Performance Parts) has a plug and play engine controller kit for the Gen III small block that works with LS2, LS3, and LS7 engines. The kit comes with an electronic throttle control, (remember, these engines are drive by wire), 2 oxygen sensors, and a mass airflow sensor. It lists for $1150.00 but I see Scoggins-Dickey has them for $950.

Then there is the exhaust system. Look to spend up to $1500. for custom built stainless headers (your stockers are stainless so why go less with your new stuff) if the stock manifolds won't clear. It's looking like you could buy a used LS3 and hit your horsepower goal cheaper than building one since we haven't even started talking about the engine build itself yet.

If you keep your Gen I small block lots of guys have converted their '81s to auto overdrives. Search in the L81 Registry Forum for this topic. Several companies make complete kits built and dynoed to your engine specs so that is not a problem. Just be sure that if you change your rear gear that you don't go too low (higher numerically) and render your first gear useless. First gear in a 4 pseed auto overdrive is lower than your THM350. Somewhere around a 3.55 rear gear will be just about right.

If I was looking to upgrade performance in my '81 I'd do the exhaust, use flat top pistons and iron Vortec heads from GMPP that are drilled for old style intake manifolds. Hood clearance is a problem with tall intakes. Some fit but most don't. A search here on the forum for that topic will get you informed. You might want to take a look at aftermarket EFI conversions to gain torque and mileage too. I'd match a cam to the overall package and put on GMPP valve cover adapters to keep the original valve covers in place.

With the proper selection of components and gearing I think that you will be amazed at what you can gain without breaking the bank and stay bolt in for the most part. As for the 2 bolt block, unless you are going to a big hit of nitros or a blower your block is just fine for a spirited street build.

Tom

 

[damoroso]

Tom,

Thanks for the info, the header discussion is particularly helpful and as expected. I'll go ahead with putting true dual exhaust on now, bolted up to the stock manifolds. That way, when I do the engine work (regardless of which way I go) the exhaust sytem minus headers will be in place, and I can enjoy it now. As I see it, I'm looking at approx. $2500 for the trans for either the 700r4 or the 2004r. That's has to be done regardless of the direction I take with the engine. I have to do a bit more research (a call to Bowtie Overdrives will likley answer the question) to see if the trans selected will bolt up to the current engine and the LS2-3. If they won't bolt up, I'll wait and as suggested look for a used engine trans combination. If the trans will bolt up to both, I'll do that in the next couple of months, and look for a used LS2 or 3. I do know that since this has been done before, as you pointed out, there are wiring harness options, motor mount options and help with the accessory drives available. Thanks again, I'm looking forward to the entire process!!! (so far...ask me again when I'm at the install phase!!)

 

[Tom Bryant]

I'll be looking forward to your progress on this project. You're right that this has been done before many times so there should be a lot of good info out there. I was looking at a very nice LS1/700R4 install in a 1965 Corvette at Pro-Team during CruiseFest. I should have payed closer attention to the details. It looked like a nice fit though.

Tom