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350///357 build

38K views 156 replies 15 participants last post by  0trbo4myCHEVUICK 
#1 ·
Hello! I have started numerous threads in the past and have always been helped. Im hoping to return the favor to someone like me, in the future. (Even though you can find this build type countless times on countless sites all the frick over the place)

Going to try and post the best pictures as well as price throughout the whole thing.

First step is buying different pistons for my 1986 STOCK rebuilt short block.
Then looking for a roller cam, spider, bones, etc roller train components.

Probably going to use H345CP spreed pro pistons. Im shooting for 9:1 compression. I dont have them yet but I have 400 set back for a set of 64cc vortec heads.

I spent 425$ on the short block and 50$ on a gasket set.
 

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#2 · (Edited)
I don't understand why you would buy a completed short block and then want to begin changing parts, but hey, whatever.

Pay attention to the compression height of the pistons you plan to buy. Stock CH for a 350 Chevy is 1.560", but rebuilder pistons have a shorter CH (1.540") to compensate for shortening the deck height of the block. The shorter CH will make it more difficult to achieve a tight squish. Hang just the tip of one jaw of a dial caliper into the top of the pin bore and the other jaw at the crown just above the top ring. A 1.560" CH piston will measure 1.096"/1.097".
 
#5 · (Edited)
I don't understand why you would buy a completed short block and then want to begin changing parts, but hey, whatever.

As this is my first build... I'm sure this wont be the first inefficient move I make.
I screwed up and jumped the gun on this deal. Now im hoping I will beable to install the new pistons myself? I assume I need to take the old piston/rod combo and have a shop switch the pistons?

Also I believe the H345CP speed pro hyper piston is a standard compression height piston.
 
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#9 ·
From the pictues it looks like your block has new pistons in it. What is the purpose for the change? With 64 cc heads looks to me like your going to be close to 9.5 to 1 and use larger gasket if need be. Correct me if im wrong but arent the 4 valve flat pistons +5 cc right?


I wish those were 4valve relief flat tops but they are stock style dish...
 
#11 ·
The pistons have 423Np stamped on them. Probably a rebuilder piston. Like i said i jumped the gun on this deal and bought the thing before i did research on the pistons.

Looks like I would be lucky to have 8:1 compression with these pistons and probably wouldnt even have that.

I dont want to build a dog of an engine i want good quench and strong compression. I have been looking at H345CP speed pro hyper pistons, they state 9:25 compression with a 64cc head.

Now I am wondering about my rods, I know they have been "resized". Does that mean I should NOT be looking for a piston designed for a 5.7 rod?

I cant seem to find a weight spec on either one of these pistons and I know about balancing issues....
 
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#15 ·
If your only looking for 350 reliable HP, and are on a beer budget.....find some 416 heads, spend some time, not money,time, porting them at home.....add 1094 felpro headgaskets, a used performer rpm or knock off equivilant, Holley 750, small 268 cam, long tube headers.....and a recurved Hei. This can be easily accomplished with the current short block you have. And likely for under 750$ on top of what you have already invested. It will be dead reliable, make the number your looking for, and give you a great feeling of accomplishment. And its fun when your buddies laugh at your budget build until they ride in it......there.,,,,,,I waited as long as I could.....sorry.
 
#19 ·
Yep, before you get to stressed out about your pistons, search 416 heads, try and wade through the garbage from people who hate them, and have yet never used them, or used them wrong.....the more time you put in, the more you will get out. Find F-bird 88 posts, he knows what he is talking about.....yes, they are 58cc, yes, they CAN flow more then enough to meet your goals....and then some.....and people almost give them away.....mine were given to me free, my neighbour has a set for sale, 40$.....they are out there...with 1094 shim style gasket your compression will be there. I have a stone stock short block, my pistons look just like yours, I have a porting kit I bought, a small compressor, and a die grinder....assorted length carbide cutters.....and about 40hrs into them. Small lunati barebones cam, under 100$, I had a perfomre Intake, and a stock qjet card....it pulls....hard...very....on a gtech dashboard dyno it traps 112mph, factor in 5mph optimism....and I'm still around 107mph in the quarter......the math says 367hp......yah yah, its not a track.......I get that.....trust me...the math is close.....the motor works.....800$, from top to bottom....sees 6000rpm daily....gets decent mileage, sounds good, and has been reliable as hell.....look into it.......you will enjoy it.
 
#18 ·
The 423np pistons are Speed Pro cast dished pistons. According to the Speed Pro electronic catalog they are 1.54 compression height "rebuilder pistons", with a .100" dish, 10cc dish/valve reliefs.

I don't see a H345CP piston listed.

The H345ACP is a hypereutectic flat top 4 valve relief piston with 1.548" compression height, so it's still .012" shorter compression height than the standard 1.560", but not as bad as most of the rebuilder pistons. The piston dome volume is 6.88cc, and the weight is 545 grams.

The H345NCP is a hypereutectic flat top 4 valve relief piston, full 1.56" compression height, 5cc dome volume, weight 546 grams.

You already have the short block with basically the factory piston style except for the shorter compression height. Either use it as is, or as suggested, disassemble it and have the block decked. Figuring you now have about .045" "in the hole", use a Fel Pro #1094 shim head gasket .015" thick, that will give you a .060" quench. With vortec 64cc heads you will still be about 9.4:1 static compression ratio, the same as the '96 thru 2000 vortec truck engines, and the same as the GM Performance Parts 350HO 350 cubic inch 330 HP crate engine and the CT350 350 cubic inch 350 HP circle track crate engine. These engines both use a very mild hydraulic flat tappet cam with .435"/.460" lift, 212*/222* duration at .050" lift, 112* lobe spacing angle. Even a very mild roller cam will improve these figures so you can reach your 350 HP goal.
 
#20 · (Edited)
Here is a website with the pistons that you have in your block. Federal Mogul Pistons 423NP - SummitRacing.com. Like was said the compression height is 1.540. 9.025-1.740-5.700-1.540=8.960. The piston would be .065 down in the block if the deck height is 9.025". Here is a website with the pistons H345CP that you want to buy. Sealed Power Hypereutectic Flat Top 4 Valve Reliefs Piston Std Size | Northern Auto Parts. The comp ht. is 1.548. 9.025-1.740-5.700-1.548=8.988 The piston would be .037 down in the block. With the new pistons in the block and a .015 compressed thickness head gasket with 64cc heads would have a static compression ratio of 9.669 and a quench of .052. If I had to make a decision like this I would get my measurement from the center line of the crank to the top of the deck. Then you can figure what comp. ht pistons you need. You can figure the compressed head gasket thickness and quench.
 
#21 ·
cdminter59, with the 1.54" CH pistons + 5.70" rods + 1.74" (half of stroke) I get 8.98", which would leave the pistons .045" in the hole with a nominal 9.025" deck height instead of .065" in the hole.

The GMPP 350HO and CT350 both use a .028" thick head gasket, with a "standard" .025" deck height would give a .053" quench distance. With .045" piston deck height with a .015" shim gasket would give a .060" quench distance, not ideal, but workable. It would make your CR just slightly lower than the stock spec of 9.4:1.
 
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#25 ·
No need to apologize I should be thanking you for the long post! Looks like ill be putting this thing together and calling it good for now. hope its not a dog. Moving on to find vortec heads.. I would go the 416s route but finding 40 extra hours for porting would probably take me a quarter year.
 
#31 ·
Sorry looks like ive answered my own question and it does.. The price is def right but ill keep looking at similar priced cams. The hunt continues for vortecs around 400... There is plenty of stock rebuilt vortecs for that price but none with the upgrades i would need. The hunt continues!
 
#35 ·
The only 12 bolt intakes that even come close to matching the Vortec ports are called raised port (RP) intakes. RP intakes are a single plane design w/large runners and are made primarily just for racing. Using such an intake on a street engine- unless it was a carefully built semi or full race deal- will not be a good idea.

Other 12 bolt intakes lack enough material above the ports to enlarge them to match a Vortec head and still have enough material to reliably seal to an intake gasket unless the intake is welded first. The port sides may also be mismatched.

For a strong performance build I would recommend the Edelbrock RPM intake made for the Vortec heads, p/n 7116.

Too late now, but for not much more you could have bought the Bow Tie Vortecs.
 
#36 ·
thought the bowtie vortecs were over 1200 for the pair?
I know the heads are drilled for early intake patterns but i DO plan on using a VORTEC STYLE intake.
I was wondering if the milling of the heads down to 59cc will effect how the intake botls up? Ive read that if done properly It should not.
 
#37 ·
It will change the port alignment and how close the intake ends are to the block. Look them over when you get them to see if the intake flange has been milled to correct for the deck milling.

A guess is that about 0.035"-0.040" was removed to get that volume. But the amount removed also depends on what the volume was when they were original- often the volume is larger than what's published. You might even ask the seller how much was removed and if the intake flange was corrected.

For more info, see: Milling cylinder heads

EDIT- Bow Ties are more, my mistake.
Good luck
 
#41 ·
Yes something in that area, I do have a OE roller block though. Im sorting through some now.. Really dont want to spend 300 on it.

Does the milling of the heads effect what pushrod length I require?
I plan on shifting this thing around 5200 on weekends. Is that a problem? friends say no, just wondering if I should install arp rod bolts while the oil pan is off.
 
#43 ·
Okay I am leaning towards this howards cam..
181145-10

Basic Operating RPM Range:1,500-5,600

Intake Duration at 050 inch Lift:219

Exhaust Duration at 050 inch Lift:225

Duration at 050 inch Lift:219 int./225 exh.

Advertised Intake Duration:272

Advertised Exhaust Duration:278

Advertised Duration:272 int./278 exh.

Intake Valve Lift with Factory Rocker Arm Ratio:0.510 in.

Exhaust Valve Lift with Factory Rocker Arm Ratio:0.525 in.

Valve Lift with Factory Rocker Arm Ratio:0.510 int./0.525 exh.

Lobe Separation (degrees):110


Im looking for some imput hopefully I know cam selection has been beatin to death. :embarrass

80's STOCK rebuilt short block. 4valve relief dish cast pistons.
906 vortec heads milled to 59cc ready for .600 lift. ( I know i need to change the .600 springs)
Im not sure what intake but probably a edelbrock 650 carb. havent bought intake stuff yet. No computer stuff for sure. vacuum brakes.

Its going in my 1982 chevy c10 long bed daily beatin truck.
I mud in it, I tow with it, I sit in traffic in it, I putt around downtown fort worth in it, I cruise long distance in it, and yes, I drag race in it. not very effectively but none the less I am always trying to beat up on rice zingers :thumbup:

It should be mentioned I have a RMVB TH400 I will be using.

stock gears :mad: 33x12 50 R15 rear tires.

I do not want to choose a cam based on my stock gears. I will be changing them. You guys rock
 
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