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post #1 of (permalink) Old 08-23-2000, 12:34 PM
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Rebuilding a 350 - part recommendations needed...

Well, I decided not to go with a crate motor for my `84 3/4 ton, as I just parted out another truck with a 4-bolt 350 that had not been previously rebuilt. I am going to take the block into the machine shop in the next few days to have it bored +.030" and honed (that's the easy part). I'm also going to have them turn the crank (needs it) and re-do a set of heads.

Next, I will need a rebuild kit. I have rebuilt a couple of engines in the past, but I never really used any performance parts - just stock rebuild kits. I want to make this engine sing, so it's going to get a mild cam and some other hi-performance internals. Here's some questions that I have...

The heads that came off the engine are 350 heads with a combustion chamber size of 76cc. Can I safely boost my compression ratio by running 305 heads with a smaller chamber? I have the set of 76 cc 350 heads and a set of 305 heads (don't know chamber size yet - checking tonight) on a 305 I've been keeping around for spare parts. I think the 350 was running somewhere around 8.5:1 compression before I took it apart, but it didn't have much power. Just a side note - are the intake / exhaust valves typically smaller on 305 heads???

What kind of +.030 pistons should I look for in a rebuild kit, dish type, flat top, or dome? I want to get around 300 HP out of the engine, yet I would like to keep the compression ratio low enough to be able to run 89 octane fuel - is this possible?

What kind of piston rings would be a better choice for durability and longevity of the engine? I know of at least 3 different types - steel, chrome-moly, and another kind I can't recall the name of right now.

What kind of cam, in terms of lift and duration, should I look for? I will be running a 650 CFM carb on the engine along with headers and 2.5" dual exhaust. I don't think that I want to go with a roller cam, but I might upgrade to roller rockers on the heads.

One last thing, who offers a good master rebuild kit with the parts I'll need at a reasonable price? There are some speed shops around town where I live - I'd just like to get some prices to compare.

Thanks again for your help!
Dan


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post #2 of (permalink) Old 08-23-2000, 02:13 PM
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Re: Rebuilding a 350 - part recommendations needed...

Try Performance Automotive Wharehouse (PAW) they offer a wide selection of kits and options, or you can pick your own crank, pistons, rods etc. http://www.pawengineparts.com Hope this helps [img]/wwwthreads_images/icons/wink.gif[/img]

post #3 of (permalink) Old 08-23-2000, 04:58 PM
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Re: Rebuilding a 350 - part recommendations needed...

I'd shoot for a flat-top, or maybe a small dome. The best thing would be flat-top with older 64cc heads. Don't use the cheezy 305 heads. If you can, put hardened exhaust seats in, and maybe 1.6" valves while you're in there. A bigger 2.02 vs the 1.94 intake valve won't help as much, but you can do that too. I wouldn't push the compression idea very far with factory iron heads, hot spots are inevitable. I'd stay between 9 & 10 to 1. A bigger cam helps reduce detonation. Summit Racing has some good "cheapie" cams. I'd go for the 224/234 minimum, or the 234/244 or 244/254. The latter one is kinda big. These will run smoother with Rhoads lifters, plus you can run a little lash up to .010" to run even better down low. (Only run lash with a lifter that has a retaining clip like Rhoads, the factory wire retainer will break!).
Pistons are cheap for a 350, I'd run Keith Black/Ohio Forge in plain or "hyperutectic".
The plain ones are actually very strong. I like gapless rings but they are an extra $100. Otherwise I'd just use the regular old iron jobs. I'd recommend the Edelbrock Performer RPM manifold.
I'd check-out a Circle Track magazine for all the parts suppliers like Speedway and Midwest. Most will send free catalogs and they have screamin' deals on 350 parts, rebuild kits, etc. Plus the magazine is an excellent source of info on the 350. Here's an ad from Storm Speed 515-961-7292: Fel-Pro gasket set, Sealed-Power rings, Clevite "77" rod/main bearings, $80. Keith Black flat-top pistons $79. Not bad for $159!
Good luck, Corey


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post #4 of (permalink) Old 08-23-2000, 05:09 PM
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Re: Rebuilding a 350 - part recommendations needed...

You want an engine that has a fat torque curve between 1500 and 4500rpm.

Use your 350 heads. 305 heads have smaller valves, can't be ported very much and still don't flow worth beans. Yes they will increase compression, but that is the wrong way to do it. Use higher compression Flat Top pistons. Shoot for 9.5:1.

Use a performer rpm intake, small tube headers (1-5/8" primaries maximum, they're good up to 425hp and provide lots of low end torque). 650cfm is plenty of carb. Pick a cam with around 214 deg duration at 0.050 tappet lift, 220 max.. As much lift as possible. Have a look at comp cams extreme 4x4 series. A tight lobe separation angle will improve power throughout the rpm range, stay around 111-112 to maintain vacuum. Don't use 1.6 ratio rockers, they don't make that much more power but do shorten valve spring life.

Have the rotating assembly balanced - best money you'll ever spend for reliability/longevity.

A good MSD or Jacobs ignition will go along way to helping power.

My humble opinions anyway. Be a nice strong running reliable motor. Won't get much better without a big block or turbo-diesel.

post #5 of (permalink) Old 08-23-2000, 06:14 PM
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Re: Rebuilding a 350 - part recommendations needed...

Ditto what the others said. You might have to fix a little bit with the HEI. A bigger shot of fuel and air, provided by a "bigger" cam, takes longer time to burn. To advance it a couple of degrees while ideling is fine, but you might get some new springs for the HEI when revving up there in the mid/high area. Then again, you might not need to do anything with it. Hereīs a good url, given to me by Dave (this forums engine wizard)
http://members.aol.com/DVAndrews/timing.htm
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post #6 of (permalink) Old 08-23-2000, 08:10 PM
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Re: Rebuilding a 350 - part recommendations needed...

I will answer the questions first.

Yes, 305 heads that are between 57cc - 60cc will increase the compression of a stock type 17cc 350 dish piston to about 9:1. A flat top piston with 76cc heads will be about 9:1 compression. The common intake valve sizes for the 305 are either 1.72" or 1.84". The common intake valve sizes for the 350 are 1.72", 1.94" and 2.02".

The new school on compression ratios and gas octane are different. The new school recommends multiply the compression ratio by ten to figure the octane needed. So the example would be 8.9 compression multiplied by ten would equal 89 octane gas. Another example would be 10.1 compression multiplied by ten would equal 101 octane gas. Kinda simple school.

Now onto the piston / ring option. I've built several dozen 300 H.P. 350 engines using plain cast pistons. I've used both plain cast rings and moly rings. I would recommend the plain cast rings for a 300 H.P. 350.

I would recommend using a Competition Cam 260 cam (.446 intake / .446 exhaust) for a 300 H.P. 350. There is no need for roller rocker arms for 300 H.P. 350. I strongly recommend the roller tip rocker arms for a 300 H.P. 350 engine!

I get my engine parts for a Wholesale Parts Supplier. I really can not say who has a good kit. I do know that there are several Mail Order Parts Suppliers that offer very competitive prices. There are some master rebuild kits that have all the parts you need for a stock type performance rebuild.

My personal recommendation to build a 300 H.P. 350 would be to use the stock type master engine rebuild kit with 17cc dish pistons, 76cc heads 1.94" intake, ( compression will be about 8:1) ask to get a mild RV cam upgrade of about .420 intake / .443 exhaust. The RV cam might not get quite as much performance as the Competition Cam 260 but the RV cam upgrade in a master rebuild kit is a very affordable option! Either the RV cam upgrade, or Competition Cam 260 will make a 300 H.P. 350 engine.
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post #7 of (permalink) Old 08-23-2000, 10:27 PM
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Re: Rebuilding a 350 - part recommendations needed...

I'd be interested to know if the combination Dave suggests could be topped by a factory Throttle body set up on maybe an aftermarket manifold...I can get a complete 96 LT1 (7000 mi) for about $3500...am I just goin' 'round looking for headaches?...I have an 89 K5 ...Thanks......JD

post #8 of (permalink) Old 08-24-2000, 12:18 AM
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Re: Rebuilding a 350 - part recommendations needed...

I would like to say that $3500 buys a very nice crate engine, with no miles! Check this engine out,http://www.sallee-chevrolet.com/Chev...8s/HT_383.html There are adapter plates that will bolt to the Vortec intake manifold to allow the use of the TBI. Just a thought.

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post #9 of (permalink) Old 08-24-2000, 08:13 AM
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Re: Rebuilding a 350 - part recommendations needed...

I got the parts for my rebuild from Northern Auto parts. www.naparts.com
They were real friendly, shiped it quick, and had very good prices. You may want to try to bargin with your machiene shop. The one I went to wasnt happy at all when they found out I was using someone elses parts. Even though I saved $150 from their prices I really lost out. A friend built a simmiler 350 and used that shops parts so they cut alot of prices on the machiene word and treated him like gold. Hope it helps.

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post #10 of (permalink) Old 08-24-2000, 11:34 AM
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Re: Rebuilding a 350 - part recommendations needed...

I took the engine block, crank, pistons / connecting rods, and heads into the machine shop this morning. They are going to redo the 76cc heads, grind the crank (needs it) and bore/hone the block. I checked the 305 heads that I have last night and it turns out that they are the same exact heads (same casting #) as the heads I took of the 350. No wonder that engine always ran like crap - compression must have been somewhere around 7-8:1 [probably could have ran beer in it if I ever needed to].

Here's the plan -
The machine shop is going to bore the block .030 over. I am getting the rebuild kit through them (figured they could give me a deal on the whole package that way), and using flat-top pistons. They are going to check the valve springs, regrind the valves and install new seats (if necessary). I am getting a Torquer cam setup through them, which I was told doesn't have much 'lope' to it, but it makes better power and torque down below 3500 or so RPM. As I'm not going to run the engine at WOT very often, I thought this would be a good compromise (not sure what the lift/duration is though). They'll also install the new pistons on the rods. My brother and I will do the final assembly of the engine.

So far, I was quoted approximately $600 for machine work and labor, but was told that the final damage will likely be a little less than that. The master rebuild kit and cam setup will be about another $400 or so. These figures are not assuming any discounts that they might throw in later on. Am I on the right track? [img]/wwwthreads_images/icons/smile.gif[/img]

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