348 Tri-Power Build

[Carlos Torres]

T=Tonowanda
F 1958-61 Pass. Car 250HP 348 V8 4Bbl. Manual trans.

Block# 3755011
Year used: 1959
Model: Passenger car
Engine: 348
Horsepower: 250,280,315
Bore: 4.125
Stroke: 3.25
Main Journal: 2.50
Rod Journal: 2.20
Notes: Second design released for the 1959 model year. Re-designed to provide water cooling to the new cylinder heads. Used for 1958 trucks after 3/31/58. Used for 315hp cars after 5/21/58. This block was used for all 1959-61 348 engines including service replacement blocks

Head# 3758379
Year used: 1959
Model: Passenger car
Engine: 348
Horsepower: 250,280
Intake Valve Size: 1.94
Exhaust Valve Size: 1.66
Notes: This cylinder head is the second design. Major design differences from the first design 1958 head #3732791. Water cooling passages have been added around the spark plugs. This head is distinctive as there are cored cooling slots visible at the spark plug relief area.

Intake# 3749948
Carb used: 3 x 2 Rochester
Year used: 1959
Model: Passenger car
Engine: 348
Horsepower: 280,315,335
Notes: Used on all 1958-61 3 x 2 348 engines. Originally designed to be made from aluminum, Chevrolet switched to cast iron before production

Exhaust# 3732793
Year used: 1959
Model: Passenger car
Engine: 348
Horsepower: 250,280
Side: left

Exhaust# 3732794
Year used: 1959
Model: Passenger car
Engine: 348
Horsepower: 250,280
Side: right

With the specifications shown above, the only discrepancy I see see is that it isn't an original Tri-Power engine. Good day fine people, its been a little while since i've last updated you folks on the build. Well the engine has made its way to the machine shop so im gathering information and insight on any performance parts recommended and or going with a factory build. I'm yet to get an update on how the block looks but during disassembly it looked solid. I'm not going with super performance but want an engine to have some pull, no intentions on racing or anything but i am planning on taking a few road trips with it. What direction did you folks go with when building your 348? As a reminder of where this block will be installed, '59 Impala Sport Coupe factory 4 speed. Im also still on the hunt for a BW-T10 as the transmission that came with it,if im not mistaken by the stamps is a '56 3-speed. Looking forward for your input ladies and gents.

 

[poison ivy]

consider a close to stock build, avoid probs with cooling in az, 2 1/2 stock cast exhaust. want pull gear it.

 

[Iowa 409 Guy]

Looks like a sweet program.

 

[Don Jacks]

I agree,close to stock,say 10.5-1 forged pistons,bigger valves,an 0950 cam[all from Show Cars],2 1/2 manifolds minimum,and a rear end geared at 3.36-1 ,will give you outstanding "pep " and decent mileage.Factory replacement cast pistons are weak,heavy,and have wide,friction laden rings.More friction,more heat,and less available power and mileage.

 

[models916]

409 crank and rods will add 50hp.

 

[Carlos Torres]

I agree,close to stock,say 10.5-1 forged pistons,bigger valves,an 0950 cam[all from Show Cars],2 1/2 manifolds minimum,and a rear end geared at 3.36-1 ,will give you outstanding "pep " and decent mileage.Factory replacement cast pistons are weak,heavy,and have wide,friction laden rings.More friction,more heat,and less available power and mileage.

I rebuilt the rear which at one point i was told it was swapped from original Posi. I believe they are 3:08, anyone have this set up? @models916, i'm sure finding the guts of a 409 are almost as difficult as finding the block itself. Aftermarket option possible?

 

[Don Jacks]

Carlos,409 cranks can be found for around 300.00 or so.I wouldn't want the stock 409 rods anyway.If you're intreasted,get a 409 crank,a set of 6.385 length big block rods[a little over 300 per set],and the K-B Icon piston[7815p30-600.],and you'll have 380 inches.There are stroker kits that you can get new to go up to 440 plus cubic inches,but then you need better heads.3.08's would be okay for a cruiser behind a mild 380,and you only need a posi for racing,or laying rubber .

 

[Carlos Torres]

Anywhere on the vehicle I can look at that may tell me info on the rear? Also, do you guys happen to have a helpful link to learn on the gear ratios?

 

[models916]

On a budget my friend just used the 409 crank and rods from from another friends stroker. Pulled out the 348 crank and rods and put it back together is what he told me. Little cost and some new gaskets. 409 rods are ok for a street cruiser.

 

[Rickys61]

Anywhere on the vehicle I can look at that may tell me info on the rear? Also, do you guys happen to have a helpful link to learn on the gear ratios?

If the inside of the rear decklid is original, there may be evidence of the post sticker there...

 

[Carlos Torres]

So it looks like i'll be going with a 380ci Stroker build. Getting prices now referencing parts mentioned and researched. Just heard back from the machine shop, all looks good, block, heads. Factory crank looks to be a bit worn at the connection but since i'll be replacing with a 409 crank it should be good. @Ricky's61, thanks for the reply on that posi. Any specifics on communicating with the machine shop regarding "decking" with this build?

 

[Don Jacks]

Carlos,The best prices on the pistons is from Show Cars,and their prices on the Scat rods are competetive,if not a few bucks lower.As to the decking,take off 020 then mock up.The main issue here is that you want to build a quench area of between .034 and .045 for pump gas.You are limited with head gaskets to .022 for the steel shim,.030 or .040 for Cometics,and about .052 for everything else.With about .010-012 off the deck on my 380,I wound up at .014 down.At this point,I got with Show Cars and got the steel shim .022 gaskets.

 

[Carlos Torres]

Don, will this setup work with factory valve covers? assuming so. Looks like the only thing i'll be needing is a 409 oil pan. I've seen some full Stroker kits avaialbel online. I'll go through Show Cars as it seems to be reputable from all that I've read. Now would the only reason to build a Stroker be because the block someone is building has some defects that will requiring these boring and/or decking already or because someone wants to add a bit more power? I assume the latter. Apologize in advance, still learning on the mechanics of it.

 

[Don Jacks]

You really don't need a 409 pan although Show cars has them.All you need to do is massage the area in the pan to clear the front crank/rod throw.Yes,the stock valve cover will be fine.The reasons for a stroker is 1-more torque/power,2-if you're gonna carry the weight,you might as well carry the inches.

 

[Carlos Torres]

Much appreciated guys!

 

[models916]

You can stack the 22 gasket and get 44 on a zero deck. JFYI