383 for towing a travel trailer

[jbright300]

Anyone built a 383 SBC for towing? Anyone have any recomendations? It is going in a 74 Chevy 1/2 ton pickup with a TH400.
What I am going to do is pull out the 2 barrell 145 HP 350 and Th350 tranny and install a 383 with a TH400 for towing my 25' 4500 lb.travel trailer. I want to build the ultimate tow machine without having to buy a new truck for 25-40K. I already bought a used 90 3/4 ton pickup, and 2 O/D trannies later, I want to start with and older truck without a catalytic converter and build something for around $10,000. I bought a 1974 C10 with 54,000 original miles that is great shape. I am looking for torque more than HP at the 3000 RPM range, and on a VERY lean budget.

What I have so far is:
74 350 4 bolt main bored .030 over
Enginekits.com 383 balanced kit flat top pistons
Weiand 8150 intake
Holley 750 vac secondaries
Comp cams 12-262-4 cam
Heads are 882 casting numbers(Most likely 1.94, I know not the best) 76cc

[techinspector1]

Yep, got 'er right here.

KB135 hyper D-cup pistons, 18cc dish, hung on 5.7 rods. Pay close attention to KB recommendations for top ring end gap.
L31 Vortec heads, 1.94/1.50 valves. Stock except Comp springs and retainers. See spring requirements on cam card.......
http://www.compcams.com/Cam_Specs/Ca...x?csid=85&sb=0
Talk with Comp about using springs that have these specs, but are the same diameter as the spring seats in the stock heads to prevent having to spend money cutting new spring seats. There are some super-keen Beehives available for this application.
1.750" long-tube, equal-length headers with "X" pipe right after the collectors and 2 1/2" pipe to the rear through mufflers of your choice.
Edelbrock Performer RPM dual-plane, high-rise intake manifold mounting a 600 cfm carb of your choice. Cam advanced 2 degrees. 9.700:1 static compression ratio, 8.384:1 dynamic compression ratio. Set squish between 0.035" and 0.040". Stack will measure 9.008". If you need a little thinner gasket than normal to set your squish, a Victor Reinz #5746 compresses to 0.025". This combination makes a nice torque motor......
RPM HP TQ
1000 62 328
1500 113 397
2000 164 430
2500 206 432
3000 256 448
3500 308 461
4000 348 457
4500 379 443
5000 392 412
5500 365 349

Now, I just happen to like the L31 heads, but you could certainly do it close to these results with the GM 882 heads. You would have to use different pistons though, because the 882 heads are 76cc's. Use KB134 flat-tops to achieve the same 9.700:1 static compression ratio we had with the L31 heads.
RPM HP TQ
1000 62 325
1500 112 393
2000 163 427
2500 205 431
3000 256 448
3500 308 462
4000 348 457
4500 377 440
5000 387 407
5500 344 329

Changed to 750 carb and CompCams 12-262-4 because the OP already has this cam. This cam is for a computer controlled engine, but will work with a carbed unit like we are using here. The timing opening and closing points are a little different, but it's basically the same cam used on the other two sims.
http://www.compcams.com/Cam_Specs/Ca...x?csid=92&sb=0
Cam installed straight up on the marks.
RPM HP TQ
1000 63 330
1500 111 389
2000 160 420
2500 201 422
3000 253 444
3500 309 463
4000 354 465
4500 386 451
5000 400 420
5500 359 343

Dropping down to 1 5/8" on the header tube size drops 5 hp and 3 ft/lbs of torque, so if it's easier to fit the smaller tubes, I'd do it. DO NOT GO ANY SMALLER THAN 1 5/8". Using those cheezy "shortie" headers however, will drop 36 hp and 32 ft/lbs of torque, so I wouldn't do that. Stock cast iron manifolds drop 54 hp and 50 ft/lbs of torque down low where you need it.

The key to making this whole mess work on pump gas with a 9.7:1 static compression ratio and iron heads is the squish. In order to have a good, strong squish of fuel/air mixture jetted across the chamber, you need to have a nice, flat area on the piston crown to mate up with the underside of the cylinder head. This type of piston crown WILL NOT WORK.....
http://store.summitracing.com/largei...=stl-423np.jpg

This type of piston crown WILL WORK....
http://store.summitracing.com/largei...l2256f60_w.jpg

And if you need a dish piston to reach your target static compression ratio, use a D-cup piston such as this. Notice the nice flat crown area on the right side of the photo. This is the part of the piston that will mate up with the underside of the head to create squish.....
http://kb-silvolite.com/performance....etails&P_id=92

[jbright300]

I updated my original question with more info. But what about using the 882 cylinder heads that are on the motor? I know that they are the later ones that are prone to cracking, but since I am not looking for HP, but torque, couldn't these heads be massaged to work? If I have to buy a set of wrecking yard L31 heads, and then have them rebuilt, wouldn't it be better to buy some new heads from Summit or jegs?

[jbright300]

The kit comes with these pistons: They are cast, but since this engine will never see even 4500 RPM, I am hoping they will work okay.

http://store.summitracing.com/partde...0&autoview=sku

Also, I called the comp cam hotline and they recomended this cam: It is a little more agressive than the one you recomended. What do you think?

http://www.compcams.com/Cam_Specs/Ca...x?csid=92&sb=2

[jbright300]

This is the kit for the 383: It comes with speed pro cast flat top pistons.

https://shop.enginekits.com/osb/itemdetails.cfm?ID=81

Also, the comp cam tech line recomended this cam:

http://www.compcams.com/Cam_Specs/Ca...x?csid=92&sb=2

This one is a little more agressive than the one you recomended. Do you think that this cam is to much?

[DA34GUY]

Built basically the same as you've outlined and yes it was a TORQUE MONSTER. pulled a 32 ft trailer all over the western U S., also had a Gear Vendor in it.

[techinspector1]

Added some stuff to post 2, so will push it back to the top for all to read....

[jbright300]

Well, call it my first mistake. I ordered the 1 1/2" Summit "Budget" full length headers for the C 10 pickup...be here tomorrow.

Summit SUM-G9006

Believe it or not I have the "Cheezy" shorty headers on my 63 Nova so I could keep my stock column shift and they actually work pretty good.

[techinspector1]

"they actually work pretty good."

No they don't, you just don't know the difference.

[jbright300]

So everything on the Sanderson website is a lie? Or for a medium motor in a tight engine compartment, they would tons better than using exhaust manifolds.
I have a 350 with flat-top pistons, 76cc, 1.94/150 heads, roller rockers, Edelbrock performer intake with an Edlebrock 750 using a comp cams 12-242-2(XE268H). How much horsepower difference would long tube headers make as opposed to the Sanderson headers below 5500 RPM? My guess would be not enough to have to cut a hole in the floor in all original Nova to accomodate a floor shifter.

http://www.sandersonheaders.com/tech_get_technical.php

[jbright300]

How much HP and torque drop will 1 1/2" long tube headers have.....at 3500 RPM?

"Dropping down to 1 5/8" on the header tube size drops 5 hp and 3 ft/lbs of torque, so if it's easier to fit the smaller tubes, I'd do it. DO NOT GO ANY SMALLER THAN 1 5/8".

[techinspector1]

How much HP and torque drop will 1 1/2" long tube headers have.....at 3500 RPM?

"Dropping down to 1 5/8" on the header tube size drops 5 hp and 3 ft/lbs of torque, so if it's easier to fit the smaller tubes, I'd do it. DO NOT GO ANY SMALLER THAN 1 5/8".

1 3/4" headers 463 ft/lbs @3500
1 1/2" headers 433 ft/lbs @3500

You choose.

[jbright300]

Since I have already purchased the 1 1/2" headers, how can I make up the 30lbs of torque?

[techinspector1]

Ummmm, have you thought about selling the small headers and buying the correct ones?

[viking]

Since I have already purchased the 1 1/2" headers, how can I make up the 30lbs of torque?

Small huffer would be nice.