Hot Rod Forum : Hotrodders Bulletin Board

Hot Rod Forum : Hotrodders Bulletin Board (http://www.hotrodders.com/forum/)
-   Engine (http://www.hotrodders.com/forum/engine/)
-   -   Building a Mild SB 350 (http://www.hotrodders.com/forum/building-mild-sb-350-a-181150.html)

bigredk5 07-16-2010 10:53 AM

Building a Mild SB 350
 
Hello! I have a 1985 GMC K5 Jimmy that needs some engine work, so I'm planning a mild build. I'm an Aircraft mechanic, so the mechanical know how is there, I just need a starting point. Its equipped with a sb 350 and a 700R4 automatic transmission. I'm looking for good torque output, without any machining. I'd like to get away with just changing intake/carb and exhaust, and possibly the cam? Thats where you all come in. What would you recommend for and intake manifold, a carburetor, and a camshaft (if at all)? The exhaust I'm not worried about (my dad manages an Exhaust Pros).

Cunferferth 07-16-2010 11:03 AM

For the intake I'd get an edelbrock performer or something of the like. And either an edelbrock 600 cfm for a little more performace or a rebuilt Q-jet to keep good gas mileage. If you do end up changing the cam id go for some type of RV cam, they are good for low rpm torque. Id also suggest some headers and new exhaust since you can get it for free possibly. But number one for a huge difference depending on what you currently have and how much you drive it for the biggest improvement as far as feeling it would be to swap gears!

bigredk5 07-16-2010 11:11 AM

yeah, I forgot to mention - I'd like to save as much gas mileage as I can. I know its never going to be super, but it has to be live-able too.

Cunferferth 07-16-2010 11:17 AM

Well if you can get your hands on a good Q-jet then id go that route. If not id look into this.

http://www.jegs.com/i/Edelbrock/350/...oductId=757412

techinspector1 07-16-2010 11:37 AM

No matter what you do internally, you have to free-up the motor on the intake and exhaust sides to create a high-perf runner.
Change intake manifold to Edelbrock 7104 and mount a Quadrajet, then 1 5/8" long tube headers with an X or H pipe right after the collectors.
http://www.summitracing.com/parts/EDL-7104/
If you have a Quadrajet, send it to Cliff Ruggles for a rebuild and custom calibration. If you don't have one, have Cliff build one for you, specifically tailored to what you want the motor to do.
http://www.cliffshighperformance.com/

I'm sure you're aware that the power is in the heads, so don't expect a world-beater with the heads you have on the motor now. Personally, I wouldn't change the cam until I changed the heads.

bigredk5 07-16-2010 11:42 AM

What would you recommend if I choose to replace the heads?

techinspector1 07-16-2010 12:23 PM

Wow, here is where you will get a multitude of different opinions.

No doubt all on this forum will agree that GM L31 Vortec heads are probably the best production cast iron heads ever produced by Chevrolet, but they require some work and will not accept the intake I linked. They are thin castings, so finding a valid used set may present some difficulty. If purchased new, they need an upgrade on the valve springs/retainers for valve lift over 0.430". There are no guide plates, rocker alignment being effected by rail rockers which need to be replaced with conventional rockers if you are going to use a cam with any appreciable lift.

If I were charged with securing heads for you, I might opt for cast iron Pro-Torker Vortecs from Racing Head Service. This is an aftermarket head and has many improvements over the GM production head, including the proper springs/retainers for additional lift, thicker material to prevent cracking and can be purchased assembled with guide plates to facilitate conventional rockers. #12410-01 is assembled with flat tappet springs (0.560" lift), #12410-02 is assembled with roller tappet springs (0.600" lift).
http://www.racingheadservice.com/Cyl...st%20Iron.aspx
http://www.flatlanderracing.com/rhs-...rotorkerv.html

Whatever you decide to do, I can put all the components into my software DynoSim and run it up to find the best cam for your application. I already have the Pro-Torker Vortec flow figures in the software, but can add any other figures necessary from other heads.

bigredk5 07-16-2010 12:54 PM

Ok, so from the feedback, I can narrow it down to a couple different builds.

#1. http://www.jegs.com/i/Edelbrock/350...roductId=757412 Go this route plus ceramic headers. Sorry - it won't be true dual exh. b/c of emission regulations my dad won't remove the converter. I will, however dual it out behind the converter.

#2. I do the same build as above, except I install the #12410-02 heads.


Solid? Or does it need tweaking?

The stock 350 from 1985 in that Jimmy had 160 hp. Pretty anemic. I'm just using the current state of the engine (blown head gasket) as an excuse to get a little more oomph out of it.

techinspector1 07-16-2010 01:50 PM

Your link leads to a page with many items on it that mean nothing to me in the context of what we are discussing here.

If you intend to install a retro roller cam, then the -02 heads would be the correct choice. If you intend to use a flat tappet hydraulic cam, the -01 heads would be a better choice and less money.

I put a build together using 9.0:1 static compression ratio, the -01 heads, RPM, Quadrajet, 1 5/8" long tube headers and a mild CompCams flat tappet hydraulic cam, XE256H advanced 2 degrees and used with 1.5 rockers. If you have an extra $225, Scorpion makes a pretty nice roller rocker. The roller trunnion is where the value is, not the roller tip. So, don't be sidetracked by those cheezy rockers with a conventional ball and socket trunnion and roller tip.

This makes a really nice little torque motor for a truck, using the stock torque converter. It does make considerable cylinder pressure though, so a builder would have to pay attention to squish to help prevent detonation on pump gas. I don't know what the piston crown looks like, but if there is no squish pad, then beware. Ideally, a fellow would install these 18cc hypereutictic pistons to reach 9.0:1 with the 64cc heads. See the generous flat crown on the piston on the right side of the photo that mates up with the underside of the cylinder head to create a good squish over to the spark plug.
http://www.kb-silvolite.com/test/kb_...tails&P_id=154
The stack of parts with the KB pistons would be 9.001". The stock nominal block deck height would be ~9.025", so you would need to use either a very thin head gasket or cut the decks to 9.001" and use a conventional 0.040" gasket.

RPM HP TQ
2000 146 382
2500 186 391
3000 237 416
3500 294 441
4000 344 452
4500 385 450
5000 419 440
5500 431 412
6000 416 364
Peak volumetric efficiency 95.6% @5000
Peak BMEP 194.6 @4000

454C10 07-16-2010 02:25 PM

I recommend that you start with a 96+ vortec 350 engine with a factory roller cam. these engines came stock with 275hp and 330 ftlb.

you can find a used 350 vortec engine for $500 then just rebuild it to stock specs with a little bigger cam and a set of headers and make well over 300hp and get better low speed torque.

check craig's list in your local area for a complete 350 vortec engine

plus the roller cam will do much better than a flat tappet cam with todays crappy engine oil.

454C10 07-16-2010 02:28 PM

here you go.

http://desmoines.craigslist.org/pts/1789193393.html

bigredk5 07-16-2010 02:38 PM

Quote:

Originally Posted by techinspector1
Your link leads to a page with many items on it that mean nothing to me in the context of what we are discussing here.

woops sorry about that. My copy and paste got goofed up. Here you go.

http://www.jegs.com/i/Edelbrock/350/...oductId=757412

bigredk5 07-16-2010 02:40 PM

Quote:

Originally Posted by 454C10
I recommend that you start with a 96+ vortec 350 engine with a factory roller cam. these engines came stock with 275hp and 330 ftlb.

you can find a used 350 vortec engine for $500 then just rebuild it to stock specs with a little bigger cam and a set of headers and make well over 300hp and get better low speed torque.

check craig's list in your local area for a complete 350 vortec engine

plus the roller cam will do much better than a flat tappet cam with todays crappy engine oil.

How difficult is it to graft in the wiring harness and necessary fuel delivery lines? 96 and newer 350 is fuel injected right?

gofastz 07-16-2010 03:22 PM

on the intake, dont get the performer, bc its no better than the stock...the techinspector is very knowlegable all the ifo u need he can give u!!!!!!

bigredk5 07-16-2010 03:32 PM

Quote:

Originally Posted by gofastz
on the intake, dont get the performer, bc its no better than the stock...the techinspector is very knowlegable all the ifo u need he can give u!!!!!!

I appreciate the heads up. This is why I posted my thread. Performance tuning in general aviation is non-existent not to mention totally different engine configurations, so I'm not real up to speed with tuning in the auto industry. Thanks for the feedback. Any more info is much appreciated.


All times are GMT -6. The time now is 03:53 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.