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355 sbc min/max quench

  
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355 sbc min/max quench

 
grr_sanpete grr_sanpete
New User | Posts: 14 | Joined: 12/12
Posted: 12/24/12
12:56 PM

Working on a 350 build for a '96 Sierra 4x4 p.u. Reliability a concern but some fun allowed. Used for street and some towing of 5000# trailer on rare occasion. Mostly working above 4500 foot elevation. A spun rod bearing created this project. Engine is a '99 VIN R with port injection which needs to be retained. Trans is a 5 speed , rear ratio is 3.73:1 with 32" tires. Mostly driven 60-70 mph at 1300-1500 RPM. Looking for wide power band to 5500 RPM. My ideas so far...

Bore 4.030
Deck .010 above piston top
Scat 9000 series crank w/3.48 stroke
Stock rods w/ARP bolts
Stock Vortec heads. (Measure 60-62 cc ???)
Speed Pro H669ACP30 flat top 4 valve relief pistons (-7cc)
Felpro PN 1094 .015 head gasket
Stock rockers/pushrods if possible
Replacement valve springs to match roller cam chosen.
Melling oil pump (Standard volume)
Cloyes single roller cam gear set.
I'd like to reuse roller lifters. They seem to be in good shape.

My cam consultant(?)says he can design a cam that will work within these parameters. I calculate the SCR to be about 10.53 with on-line calculator. I am not able to determine DCR. So far actual cam numbers have not been disclosed.

I am in early stages of build with teardown done but parts yet to be taken to machine shop. Engine shows a lot of pitting of cam bearings probably from infrequent oil changes/high mileage. I bought the truck with supposedly low mileage engine installed. So much for that.

What I am asking for on this forum are suggestions and some insight into minimum/maximum quench distance and suitable roller cam. It goes without saying money is a serious consideration. Any and all suggestions will be welcome.  

68scott385 68scott385
Guru | Posts: 1990 | Joined: 10/09
Posted: 12/24/12
09:36 PM

JMO but if you have to buy pistons and crank anyway, why not go with a stroker crank and make it a 383? The added inches will add to the fun without adding much to the cost. You CAN get internally balanced cranks easily these days. JMO

To the question, about .040 for a quench distance between piston and head. Anything over .055-.060 starts killing power quick. Anything under .040 and you get into a danger zone of two objects occupying the same space at the same time.  
68scott385 68scott385 68scott385

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 12/25/12
12:20 AM

grr_sanpete

Until you have all the parts you are going to use any compression figures will not be correct.

I agree with Scott if you need to purchase all those rotating pieces why not go to a 383. Get more torque from that engine. its in a truck.

I have to ask your your talking about trying to save money. Custom Cams cost money. If your wrong in choosing the correct roller cam your in the neighorhood of about $450 dollars. I am not going to make recommendations for cams anymore. The last 2 builds I helped on the engine builder did what he wanted.
  My suggestion to you is get all your parts then have your engine builder figure out the cam specs you'll need.Its will be very hard to give you figures for compression.
  You also don't have a rear gear gear ratio, and tire size. All the needs to be figured into the equation to pick a cam out. You really need to know at what RPM your engine is at 60 MPH.  Cool  Grin
Bob  

pepsi1 pepsi1
Guru | Posts: 1718 | Joined: 09/11
Posted: 12/25/12
12:31 AM

I just thought of something you should be concerned about. Your engine controller is OBD-2. That ECM and PCM will not tollerate many performance changes. So again if you are willing to recalibrate the controller you can't go very far with engine modifacations.
Bob  

grr_sanpete grr_sanpete
New User | Posts: 14 | Joined: 12/12
Posted: 12/25/12
08:40 PM

Wow.. I am impressed! Here it is Christmas day and you guys are answering questions and helping out. That is quite commendable and I am grateful.

OK...355 or 383? I like the mileage I was able to squeeze out of the stock engine. 17-19+ mpg on level roads. I think the mileage would decrease proportionally with the 383 would it not? Like a 9.4% reduction if my math is correct? My thinking is the more volume of air/fuel pumped for the same number of revolutions for the same distance would be proportional to the engine size increase given the same efficiency. Please correct me if I am wrong and that could very well be the case.

Based on the info given out on this site and the nature of the responses I am sure there are real experts with real world experience here dishing out advice. I have lived long enough to never take those kinds of people for granted. That is why I have chosen to register here and post my questions and concerns. I have spent considerable time lurking on various forums before choosing this one.

Must I determine the amount of time/money to devote to the PCM/ECU issue before choosing the parts I will use? How many mods can one do to the engine before requiring new programming or modules/controllers with '96 OBDII? How limiting is the stock Powertrain Control Module (PCM) when making mods? That was also a reason to think I would be better off with the 355c.i. engine. My gut feeling was that may be more conducive to the computer to compensate for changes.

So what do y'all think?

***
Christmas for me is over.... the grandkids are gone and the wife is sleeping...  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 12/25/12
11:39 PM

i would stick with a 355.. instead of a 383... as i have done other fuel injected motor swaps that had issues and required larger injectors to make up for differences in the displacement during OPEN LOOP OPERATION...

even with Throttle body injected  small blocks.. it requires larger injectors from a police special 350 to make up the difference in the displacement needs..

i don't know if there are increased rating injectors for vortec powered police specials..

let me explain...  during closed loop.. the system adjusts the air fuel ratio by looking at the exhaust content.   this is closed loop.. where the system controls the mixture from the feedback from the oxygen sensors and is fine tuned by the secondary oxygen sensors..

during heavy loads.. TOWING up hills.. hard acceleration and warm up. the system runs in open loop..   where the system reverts to PREPROGRAMMED Fuel control calculations..  it does not know that you have increased the displacement.. so it will run your motor lean..

i don't know how much of the time your motor is going to operate in open loop..   as it does have oxygen sensors and i have not ridden around in chevy trucks with the scan tool hooked up to see how often they come out of closed loop operation..

since you have the engine apart.. please examine the fuel injector tubes.. are the current injector spider assembly equipped with pairs of wires to each of the nozzles..  this later injector set up is better than the earlier version ..

i also worry about increasing compression over the stock level if you are planing on towing.. as you will require the more expensive fuels or the electronic spark timing will crank back the ignition timing to avoid the pinging.. it may do so anyway. but it might take away too much power...  i am all for forged pistons.. tri metal rod and main bearings..

you are also going to want to inspect the crank reluctor on both motors.. i don't know if there is a difference in the tooth count.. there might be..  the 96 motor probably has 4 teeth on the crank snout mounted reluctor.. i seem to recall that GM changed to additional tooth count on later vortec chevy motors.. not counting the rear of the crank reluctors on LS Motors..  i could be wrong..

there are about 40 car and truck magazines on this site..  let me take a look around over the next few days..  see if i can find any articles on cams or other power improvements on vortec motors in the other magazines.. or even here on CHP..

since you have the engine apart.. and are doing some improvements..  you might want to spend some time doing things like porting the rear main cap and passage corners.. to improve oil flow.  

your truck might also have a remote oil cooler.. please also replace the check valve in the adaptor housing where the cooler lines hook up..  its only a few bucks...   examine your vortec distributer gear.. the upper distributer shaft for play or squeaks when you spin the shaft..  the gear teeth have worn to a paper thickness.. the upper bushings in the housing have gone dry and squeak.. just before they fail..

i am NOT trying to talk you out of a stroker.. or out of a custom cam...

there are a LOT of other forum members who probably know more about what vortec power improvements work and what cause problems..  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 12/25/12
11:51 PM

here is one article on just swapping to the newer style fuel injectors.. with the individually operated electric controlled injectors at the ends of the tubes..


http://www.off-roadweb.com/tech/1012or_csfi_to_mpfi_vortec_engine_fueling_fix/

more to come over the next few days.. need to finish off this eggnog now..  

waynep71222 waynep71222
Enthusiast | Posts: 448 | Joined: 03/12
Posted: 12/26/12
12:09 AM

here is another one where they installed new exhaust and a increased flow air cleaner and throttle body... but it pushed the system leaner..

one really has to look at the short term and the long term fuel trims with a scan tool to know if the engine is running too lean...   watching the actual oxygen sensor waveforms live in graph mode..


http://www.sporttruck.com/techarticles/0406st_first_generation_vortec_350_power_upgrades/

i really am going to finish off that eggnog now.. good night..  

grr_sanpete grr_sanpete
New User | Posts: 14 | Joined: 12/12
Posted: 12/26/12
12:21 AM

Thanks for the link.... it will not work for me though. Maybe one needs to be a subscriber to be allowed access to the article.. I went to the site even and tried to bring it up there with no luck...  

grr_sanpete grr_sanpete
New User | Posts: 14 | Joined: 12/12
Posted: 12/26/12
10:40 PM

In answer to the tire size... 32" high, LT265/75R M/S radials.  
Rear gears... dunno. Can this info be found on a GM database with the VIN # or is there a sticker someplace with the info??

I seem to recall the RPM @ 60 mph was around 1350 (??) I was going to write it down but never did. Crazy  Right now the snow is piled up around the truck up to the bumpers with more coming down. So counting gear teeth is probably not going to happen anytime soon.  

BuzzLOL BuzzLOL
Enthusiast | Posts: 380 | Joined: 12/10
Posted: 12/27/12
12:56 AM

.. You may have to turn off your popup blocker or reduce your security settings a bit for the links to work... they worked fine for me with I.E.10 browser Windows8 OS Norton Anti-virus.

.. Your .010" deck and .015" head gasket gives only .025" quench distance, I would aim for .035" minimum... OK if it slides out to .040" or so max... not much more... as others above mentioned...

.. If your cam is smaller than the one in the Ram Jet 350 / HT383 crate engines, then that amazing little 196/206 duration .431"/.451" lift one is prolly the one you want. It works over your desired RPM range in a 350/355... including your need for strong 1350-1500 RPM cruising torque. GM dyno chart for stock Ram Jet 350HP 400 lb.-ft. 350" stock Vortec head crate engine:

Dc 12499120
.. Your stock crank is prolly vastly better quality than the Scat or Eagle cast in China ones... I would get it re-ground and re-use it... or swap it for another already reground one of the same GM kind... or get a crank/bearings kit with the same GM crank... or buy a new GM crank...

.. You may have to use an ounce or two of kerosene or other octane booster per tank of gas if it pings with your flat top pistons... it may not with good quench, high elevation, the Vortec's fast burn chambers, and a high lift fat lobe roller cam...

.. If you decide to fiddle with the EFI and go 383", consider the GM HT383 forged '383' crank and pistons as well... which would basically give you a complete HT383 engine... well, OK, that crank and a .030" overbore gets you a 389" !!

http://www.hotrod.com/techarticles/engine/gm_ht383_crate_small_block_tune_up

.. Your rear end may have a tag on it with the gear ratio... or you can jack up both rear wheels on safety jack stands and count the driveshaft turns...  

grr_sanpete grr_sanpete
New User | Posts: 14 | Joined: 12/12
Posted: 12/27/12
09:38 PM

Went to the site for the injector upgrade.... very good info and probably something I will include in my build. Definitely worth doing since the old injectors are showing their age for sure.
The Advance Auto part was $700 and eBay had one for $309. What a difference! The part was AC Delco #217-3029 for anyone looking. (BarmacAutomotive) Wink

Update: Rear axle ratio is 3.73:1.  Tires are LT265/75R16 M+S and 32" high.  

grr_sanpete grr_sanpete
New User | Posts: 14 | Joined: 12/12
Posted: 12/31/12
07:14 PM

I'm such a nu-bee I don't know quite how these replies work exactly.... but I would like opinions on cast hyper eutectic vs forged pistons for this build based on the propensity of lean running and subsequent damage. In searching for possible parts to include I have read some opinions that forged pistons are an absolute necessity when using high compression numbers (~10.5:1+)and a real tight quench (~.025-.030") I am at 5900' elevation (thin air) and using CPFI and stock PCM.
The marketing hype from the Skip White website would suggest that using anything but forged pistons (Probe) would be inviting certain disaster. I have read on other forums that the hyper pistons (~$200-$300)would be fine. Is it money well spent or not? The forged pistons can be 2-4X (~400-$800+) the cost of the hyper pistons.

Also, the same vendor raves about the SCAT (Series 9000) crank being 25% stronger than the stock cast nodular iron.... is this also just hype or??

And lastly.... the rear axle is a 3.73:1 Posi. Tires 32" dia.  

76Skylark 76Skylark
Guru | Posts: 854 | Joined: 12/11
Posted: 01/01/13
01:00 PM

the Gas avail. is barely able to sustain a 10.5 comp engine today,hyper's are fine for a streetable engine,Factory cranks have proven themselves to 500 hp so hopefully you are good. good rear gear.  

BuzzLOL BuzzLOL
Enthusiast | Posts: 380 | Joined: 12/10
Posted: 01/01/13
08:30 PM

.. Some websites have to please their sponsors like Probe, so take some of their advice with a grain of salt...

.. I have a Ford 351"W with 10.5:1 hypereutectic pistons (KBs) that makes around 425HP in a boat, I sometimes hold it WOT for several minutes at a time out on Lake Erie or in the Maumee River... engine hasn't broken in over 10 years yet... but some outdrives have... It has iron World Windsor Sr. heads, so I do run 4 ounces of kerosene to each 40 gallon tank of premium gas to control detonation...  

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