tehjrow

I'm in the early stages of planning to replace my 1981 L81 350 with a Blueprint 383cid 430hp long block shown here.
https://www.summitracing.com/ga/part...3ct1/overview/

I'm wondering what I can reuse and what I will need to get rebuilt. I know I'll need new exhaust since i'm getting rid of the AIR pump and tubes at the same time. I'm assuming i'll need to rebuild the TH350 trans since it's at 100k miles? What about the stock rearend, will it be ok?
Can I also use my stock intake manifold? I've removed the ECU from this car so i'm assuming I can use the HEI SpeedWay distributor and QJet non CCC carb.

71VetteLover

You'll need lower rear end gears like 3.55's or 3.73's. I recommend a set of 3.73's and then install a beefed TH700R4.

Dennis Tapp

I am in the same project so I ask the question why would you put a lower rear end in the car? Unles you are racing. Wouldn't the increased torque be perfect for the 3.07 rear end? Would definitely want the transmission beefed up. Not saying I am right but that is my plans at this time. I do have an open mind.

CheezMoe

If you build it with the right Cam your are correct. And if sticking with the TH350, is the better plan imo. Lots of BB's came with 3.08!

M. Young

So I'm in the process of choosing an engine for my 81 build. I installed a TKO-600 kit from SST and did an iron rear end (3.55s) swap with a heavy dose of Van Steele and VBP front and rear. I've looked at LS3s, 406s, local builders and I still can't decide.

Les

The builder of the 396 SB stroker for my avatar car isn't real happy that the car has 4.10 rear gears, and it's going to have a pretty decent cam in it. He says these strokers like higher rear gears. I assume it's because the extra torque creates traction issues, but I also think it's a better match because they don't typically rev as high as an angry non-stroker SB does.

Khibbs

I'm doing a swap now and a 700R4 was part of the package but I considered a BP 383 and I wouldn't change the rear end ratio until you've had a chance to drive it. More power and torque could be perfect for the gears that are in it. Last thing you want to do is raise the ratio, find out your spinning the engine higher than you want with the TH350, and then go looking for a new trans.

Buccaneer

What is the cam spec for that motor?

cv67

dont choke it down with a stock intake

Knerf

spend the extra and get this,
well worth IMHO

Dennis Tapp

If you are considering Blue Print you should take a look at West Coast Engines. The shop I am working with has bought both and they say the West Coast Engine is a lot better deal. I plan on buying the Chevy SP383 and he was telling me to look at the West Coast deal to save money. For some reason I want to have one that went down the Chevrolet assembly line. My car does not have matching numbers but I would like to have a Chevy built engine. We are all a little funny on how we want to waist our money.

jim-81

If your gears are 2.87, then you would probably want a lower set back there as stated above. I went with 3.54 and they are nice.

As far as the manifold, just be a new one. You're getting a whole new engine.

And you will want a true dual exhaust for the 383. The dual system from corvette central is a good start except that it has block hugger headers.

jim-81

sorry - GET a new one. and for some reason I can't edit my posts

lars

The stock intake, as well as the aftermarket version of the stock intake (Edelbrock Performer) will choke down the intake side of the engine enough that you'll never see anywhere close to the advertised 430 hp. You'll also need a good set of headers to achieve that rated number.

Lars

NewbVetteGuy

For $280 more (or $205 more if you go with the dressed engine), you can get a BluePrint 383 with a ROLLER CAM. That's a no-brainer, IMHO. Get the roller version.


Save some $$ for exhaust; there's SOOO much streetability and low to mid range torque to be had with a properly matched exhaust system.

If those cams are on a 110 LSA (BP specs don't say), you'll have a decent amount of overlap and for the $220, a set of anti-reversion chambers right after long-tube headers is a great way to cut down on reversion and get a good mid-RPM boost in torque and cruising fuel economy. https://crateinsider.com/anti-revers...iced-per-pair/

Just get them welded onto a flange to bolt to a header with a 3" collector, then on the output side have them welded to a 3" to 2 1/2" reducer and Bob's your uncle!


I've been looking at custom circle track racing and road racing exhausts lately and all the super high-end stuff seems designed with anti-reversion in mind and see huge bumps in mid RPM torque and HP. The custom built exhausts are in the $4k-$5k range but if you go with full-length headers (particularly tri-y/4:2:1 headers) with the right diameter for your power levels, an anti-reversion chamber at the collectors, and the secondary/collector length being a tuned length (34.8" from the merge point) and the mid-range torque and throttle response should crush it and I think can get you 80% of the results for 1/4 - 1/5 the cost.


Adam

jb78L-82

I would not worry too much about the intake: the choices for intakes is VERY limited due to height restrictions. The performer RPM basically offers the same power as the standard performer up to 5,500-6,000 rpm with a modest bump above those rpms...who revs their engines consistently above those levels on the street? I certainly don't with my built 355 L-82 and kept the aluminum L-82 intake slightly ported on the advice of my expert builder who has built 100's of race and street motors with MUCH more HP than my engine...He told me unless you spend lots of time above 6,000 RPM, don't bother changing intakes...the numbers consistently support that advice when you look at intake comparisons.

Short Manifolds (Less Than 5.00 Inch Carb Pad Height)

Manifold PN Price Peak TQ Peak HP Avg. TQ Carb Ht. TQ at 3,000
Edelbrock EPS 2701 $139.95 506 461 466.2 4.80 476
Edelbrock Air Gap 2601 $225.95 504 458 464.7 4.92 478
Chevrolet ZZ4 10185063 $239.95 500 471 464.5 4.95 467
Weiand Street Warrior 8125 $151.95 501 463 463.5 3.65 470
Weiand Street Warrior 8120 $134.95 502 459 462.8 4.62 471
Summit Stage 1 226012 $131.95 498 459 461.0 4.65 468
Edelbrock Performer 2101 $157.95 494 456 459.1 4.60 470
Prof. Prod.
Cyclone 52001 $143.95 487 436 449.3 4.72 471

Hot rod test:

http://www.hotrod.com/articles/dual-...d-comparisons/

The chevy ZZ4 intake was within 5 hp of the others and had the highest avg torque as well..........Power is in the exhaust and long tube headers....

mobird

Why would he need lower rear end gears? That's pretty misleading...


Could he get more acceleration from some 3.73s? Yes of course.


Will he still have a ton of power to play with if he keeps his stock gear ratio? Yes.


OP, by NO MEANS do you NEED to change your rear end gears. Install the engine, THEN decide if you want to sacrifice some cruising RPM for better acceleration. That will all depend on the intended use for the car.

jb78L-82

Gears are most important in low hp/tq 4 cylinder engines, NOT 400+ HP/TQ V8...Can they help acceleration? Certainly but by no means crucial....

Dennis Tapp

I would also like to know why he even needs the TH700 R4 transmission. It is my understanding that opens a whole lot of hook up problems to fix. To drive it every day I might understand but for a play car I would like to know what it will do for you.

worship79

I did a 383 build not too long ago. I see you chose a roller which is what I should have done and also you went for 1.6 rockers.

So my 2cts;

- You need a higher stall convertor if yours is still stock to match the new cam curve
- With the new flywheel (and balancer) you may need different bolts to hook it up to the stall convertor,
- I run the stock 3.55 rear end and it's holding up fine so far (5 years now)
- I would go for a new aluminum intake. They are not very expensive, weigh less, stay cooler and flow better. Mine is a EDL-2701 EPS. Perhaps a RPM model would be even better.