Help! About to rebuild an 81 motor

[Tstorm]

Hi All,

I now have the engine out of the car and I am trying to research the best way to get a bit more performance from this motor. I would like to keep the A.I.R. system online as it does not seem to matter too much if it is removed. I am not trying to set the world on fire, just tryint to keep my nuts warm here. I would like to keep the q-jet as well, maybe a tune from one of our members who has become an expert on the jet! I would like to get near the 300 hp range w/o buying a crate. Please, as much detail as possible.

Many thanks in advance,
Tim

 

[Granpooba]

Buy a Crate Motor !

 

[Tstorm]

"I would like to get near the 300 hp range w/o buying a crate."

 

[killain]

Hi All,

I now have the engine out of the car and I am trying to research the best way to get a bit more performance from this motor. I would like to keep the A.I.R. system online as it does not seem to matter too much if it is removed. I am not trying to set the world on fire, just tryint to keep my nuts warm here. I would like to keep the q-jet as well, maybe a tune from one of our members who has become an expert on the jet! I would like to get near the 300 hp range w/o buying a crate. Please, as much detail as possible.

Many thanks in advance,
Tim

Tim,
The first thing is to disassemble the engine of the emissions and starter/alternator and such. I would then recommend you bring it to 'Mahler Engine Service in business here just south on Mcdade blvd. of Southwest Philly 610-522-9344 @ 99 Clifton Ave. & PuseyAvenue. They are a excellant Engine rebuilder, In business rebuilding engines for 30 years now. and they can sit down ( Pardon the great dane) and they can tell you exactly what you can expect and what they can do to put it Stock, slightly modified, major modified or anything in between. You'll need a pickup truck to bring the engine to them, or they I believe can have someone come and pick it up.

I live in Essington, just past the runways of Phila.International Airport and they have done a number of things for me over the years. Most people pull their engines and bring them to Mahler. If you caall, they could most likely discribe what to bring and what to leave at home. Good luck, This is an exciting process.

 

[Peer81]

First disassemble the engine to see what you can use and what to replace. The heads are known to be bad so take a look at Dart or World Products heads, change the camshaft and maybe the pistons. Of course first to some calculations on all this before buying stuff.

Greetings Peter

 

[GT6Steve@aol.com]

First disassemble the engine to see what you can use and what to replace. The heads are known to be bad so take a look at Dart or World Products heads, change the camshaft and maybe the pistons. Of course first to some calculations on all this before buying stuff.

Greetings Peter

How much can we do before emission testing becomes an issue. I know hotter cams cause problems, how about the heads. Will aftermarket heads with a similar chamber size but larger valves be beneficial without penalty?

Is it principally the heads making the 81 the lowest HP Vette ever?

 

[Tstorm]

Hey,
I started to dissassemble the motor, intake and one head, all look pretty good, but I wont know the real story until I get to the bottem end. Thanks Killain, Peer and Steve for the posts!! I did some investigation and here is what I am thinking, Vortec heads Vortec intake, cam, I dont have the numbers in this computer but the comp cam program with the flow numbers from the Vortecs with a pretty mild cam will get me to about 280hp. I did notice after removing one of the stock heads that they are VERY restrictive, good call Steve!!!! The Vortecs seem like the best bang for the buck, but I may have to have them machined to get a bit more lift tolerance since they are only good to about .470" and the cam I am looknig at is near .460". I still want to use the Qjet and the stock exhaust.....We will see!!! Thanks, Tim
P.S. Please throw rocks if I am heading in the wrong direction!!!Much appreciated!!

 

[GT6Steve@aol.com]

I just got back from the machine shop so I asked about it while I was there.

I asked about the heads and he said there would be NO problem getting 330HP and still pass Smog testing. He's an old time Chebie racer from the Trans-Am days so he's built some horsepower in his time.

If my engine has to come out we'll talk further about it.

HTH, Steve

 

[Tstorm]

Thanks!!!

I just got back from the machine shop so I asked about it while I was there.

I asked about the heads and he said there would be NO problem getting 330HP and still pass Smog testing. He's an old time Chebie racer from the Trans-Am days so he's built some horsepower in his time.

If my engine has to come out we'll talk further about it.

HTH, Steve

Thanks Steve,
I am unfortunately an old time chebby guy as well!! I think the vortecs might be the best way to go for the low cost, I do realize I need the intake, I am just hoping for the high 200's on hp...but as I said, after looking at that head, I can see why the 81 is a dog!!!!! Pa does not test, they just do a visual, so as long as everything is there, they are fine with it. I am a bit worried about the ccm though!!!!

 

[navy2kcoupe]

Send "sensei" a PM. He seems to know QUITE a bit about the carbs on those '81's
Andy

 

[Tstorm]

Thanks Andy,,,,Sensei is the member I spoke of in the first post. I have read about his accomplishments and after reading a story about some heads that was posted, he is a stand up guy!! I have read alot about the qjet but experience is worth more than all the books, that's for sure!!!

Thanks Andy, and thank you for your service to our country!!!!!!!

 

[ducvw2004]

Hey,
I started to dissassemble the motor, intake and one head, all look pretty good, but I wont know the real story until I get to the bottem end. Thanks Killain, Peer and Steve for the posts!! I did some investigation and here is what I am thinking, Vortec heads Vortec intake, cam, I dont have the numbers in this computer but the comp cam program with the flow numbers from the Vortecs with a pretty mild cam will get me to about 280hp. I did notice after removing one of the stock heads that they are VERY restrictive, good call Steve!!!! The Vortecs seem like the best bang for the buck, but I may have to have them machined to get a bit more lift tolerance since they are only good to about .470" and the cam I am looknig at is near .460". I still want to use the Qjet and the stock exhaust.....We will see!!! Thanks, Tim
P.S. Please throw rocks if I am heading in the wrong direction!!!Much appreciated!!

Will Vortec heads directly bolt on an older small block?

 

[JohnZ]

Will Vortec heads directly bolt on an older small block?

Yes, but you need a Vortec-compatible intake to go with them; the intake bolt hole angles are different on the Vortec heads.

 

[black_81_vette]

Another way to go about doing it is find a place that sells rebuilt 305 ho heads casting number that ends with 416 being the best ones. most places that sell them offer them with either 2.02 intake and 1.60 valve sizes or they can do a set with 1.94 - 1.50 sizes. most of those heads have a 55 to 58 cc chamber vs the stock 76 cc chamber of your heads. Even with dished stock pistions you should be close to 9.5 to 1 compression if not just a bit more.I did this on a stock late model 350 with just a mild cam swap and the car went from mid 15s to high mid 14s. a good intake and other items will help if you can get away with it,but the heads look stock and with a mild cam you should pass easly.

 

[tyly]

I know you are already into the process of your motor work, but I figured I'd say to check out the edelbrock top end kits. We just got one for our 350 in our 72 when we were rebuilding and its a great kit. Just a suggestion.