355 SBC, Bad Combo?

Lmus10

Member
Trying to help a friend with 355 SBC. He thinks he has a bad combination of parts.
Wanted to see what you think.
Has a stock bottom end. Stock heads with no port work. Has a Herbert Cam, 510I/535E solid flat tappet.
260/270 Duration @ .050. Lobe Center 112. With a Holley single plane intake and 750 dp mech.
secondaries. In reading your posts it would seem to me the duration would need to be 240ish with
a 106 lobe center. Maybe with an RPM Air Gap intake and a 600-650 CFM Carb???.
 
some idea on the engine's true current compression ratio,
rockers, and their ratio,valve springs,load rates and clearances,
what head casting numbers, the car/truck weight , rear gear ratio,
the transmission used, the stall on the converter if its an auto transmission,
tire diameter , fuel octane, and a dozen other bits of info would be..
VERY VERY HELPFUL HERE!
in getting a good idea as to what the few parts listed are likely to do.
 
I can answer some of the above.
1.5 ratio roller tip rockers, 3200# car, 4.10 rear gear,
350 turbo trans, 3500 stall, 26" tire diameter, 91 octane.
True compression, valve springs/load rates, clearances unknown.
Want be able to gget head casting numbers till the weekend.
I know, not alot to go on.
 
the choice of cylinder head, and compression ratio , would make or break the combo here
the cam YOU SELECTED
http://www.herbertcams.com/260-270-dur-050-510-535-112lc-3500-7500-9734/
4.10 rear gear, a Holley single plane intake and 750 dp mech.
350 turbo trans, 3500 stall, 26" tire diameter
are well enough matched to work,
but you'll need cylinder heads that can breath in the 6500-7500 rpm range
and near 10.7:1-11:1 compression to get it to breath well,run the math and it should be obvious that no stock clinder head can flow the required air flow to match the cam and intakes flow potential thus power will suffere with any stock cylinder head,
YES EVEN STOCK 170cc VORTEC HEADS< OR OLD FUELIE HEADS
http://www.wallaceracing.com/runnertorquecalc.php
http://www.wallaceracing.com/ca-calc.php
http://www.wallaceracing.com/area-under-curve.php
http://www.wallaceracing.com/chokepoint.php
http://www.wallaceracing.com/header_length.php
http://www.circletrack.com/enginetech/1 ... ch_engine/
porting+valve_area.jpg

RELATED THREADS WORTH READING IF YOU WANT IT TO RUN CORRECTLY
keep in mind theres no real replacement for added displacement
the increase from 350-383 in a sbc generally benefits you in two ways, it obviously adds the 33 extra cubic inches of displacement
and youll generally find your N/A engine makes about 1-1.3 hp and ft lb of torque per cubic inch, it also tends to effectively increase compression if the similar piston design is used simply because you compressing an increased volume per cylinder into the same size combustion chamber.
one other factor often over looked is the longer stroke of the 383 increase's mid and lower rpm port speeds this generally increases cylinder fill efficiency, in the lower and mid rpm ranges.
obviously if your going to supercharge or use turbos the piston and rods and crank assembly should be made to withstand the stress levels so a 4340 forged steel crank, forged pistons and after market forged connecting rods with the significantly stronger 7/16" ARP rod bolts are strongly suggested as is dropping the static compression to the 8:1 range to increase the potential volume of compressed fuel/air mix to be stuffed into and burnt above the piston,
Id point out that most transmissions are designed to shift at well under 6000 rpm and most hydraulic valve trains won,t retain best stability above about 6300 rpm, so going the 383 or the 406 SBC stroker route tends to maximize the SBC potential on a mild or mid range performance build
http://garage.grumpysperformance.co...gine-to-match-the-cam-specs.11764/#post-55651

http://garage.grumpysperformance.co...-calculators-and-basic-math.10705/#post-50173

http://garage.grumpysperformance.com/index.php?threads/calculating-ideal-port-size.624/#post-8692

http://garage.grumpysperformance.com/index.php?threads/sellecting-cylinder-heads.796/#post-49711

http://garage.grumpysperformance.co...rpm-350-for-street-strip-use.9583/#post-35406

http://garage.grumpysperformance.com/index.php?threads/port-and-runner-math.148/#post-34936

http://garage.grumpysperformance.co...lve-seat-angles-and-air-flow.8460/#post-31961

http://garage.grumpysperformance.com/index.php?threads/shopping-for-heads.10602/#post-45479

http://garage.grumpysperformance.co...ldylocks-and-the-three-ports.5537/#post-16744

http://garage.grumpysperformance.com/index.php?threads/port-speeds-and-area.333/#post-37693
 
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theres dozens of decent cylinder heads out there for sale,
but with a 4.10:1 rear gear, a Holley single plane intake and 750 dp mech.
350 turbo trans, 3500 stall, 26" tire diameter, and that solid lifter cam,
http://www.herbertcams.com/260-270-dur-050-510-535-112lc-3500-7500-9734/
your obviously more concerned with the engines performance as a week end toy,
than its low rpm driveability in traffic on the daily commute to work

something like these might be a decent match

https://www.summitracing.com/parts/bro-1001001

https://www.summitracing.com/parts/edl-5085

http://www.jegs.com/p/Blueprint-Eng...20cc-Aluminum-Cylinder-Heads/2461162/10002/-1

http://www.jegs.com/i/ProMaxx-Performance/723/2120/10002/-1

yes I'M fully aware some people will tell you the port size is too larger for a 350,
but with that cam, compression ratio gearing and tire size and a 3500 rpm stall converter .
its going to REQUIRE a decent flowing cylinder head to maximize the engines power potential.
and you can basically forget about, off idle torque.
your engine will produce decent power in the 3700-rpm-7500-rpm power band.
IF you get the compression up to at least 10.7:1 ,
with the listed components and a decent set of heads, and yes that assumes youll use good long tube headers,
of at least 1.75" primary tube size and about 30" length.
with a fairly long collector, and NO RESTRICTIVE EXHAUST
(open headers would be ideal)
(and before anyone suggests a set of VORTEC heads be aware that stock or similar aftermarket 170cc-180cc vortec heads run out of port air flow at about 5700rpm on a 350

http://garage.grumpysperformance.com/index.php?threads/calculating-header-design.185/

http://garage.grumpysperformance.com/index.php?threads/calculating-required-exhaust-pipe-size.11552/

http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/

http://garage.grumpysperformance.co...-between-shorty-and-full-length-headers.1303/

btw if you intend for the engine to last a decent time frame.
Id suggest rocker stud girdles and a 7-8 quart baffled oil pan with a decent windage tray installed.

http://garage.grumpysperformance.com/index.php?threads/oil-system-mods-that-help.2187/

http://garage.grumpysperformance.com/index.php?threads/whats-a-windage-tray-do.64/

http://garage.grumpysperformance.com/index.php?threads/rocker-push-rod-wear-issues.9815/#post-37266

http://garage.grumpysperformance.co...ich-is-best-steel-or-aluminum.3124/#post-9141

http://garage.grumpysperformance.co...and-setting-up-the-valve-train.181/#post-7156

http://garage.grumpysperformance.co...-rockers-vs-rocker-stud-girdles.663/#post-911
 
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I personally would not use that cam, if it's a OEM block it will blow before gets to effective RPM range. If its a DART SHP block I would go with 240-50 dur @ 050, 200cc heads at least, anything smaller would run out of airflow. You'll need stronger valve springs also. Unless its for strip only, I'd go with a hyd roller cam like these 2:
http://www.herbertcams.com/cc6j-500-500-lift-240-250dur-050-110lc-2000-6200-cam-lifter-kit/
http://www.herbertcams.com/535-535-lift-240-250-dur-050-110-lobe-center/
Maybe not that brand but similar, for street either AirGap or AirStrike intake.
The 750 cfm carb is okay for up in RPMs. Personally, I like first cam for street, peak HP is 6500. Just better curves on the dyno est software also! TQ is great at stall 3500!
 
I based my post on what he gave and the engine being at SCR of 10.7:1. I think 6500 should max rpm for street. With the first cam advanced bout 2degrees, with open long tube headers I have about 548 hp @ 6500/473tq @ 5000. That's RHS 200 cc heads and the single plane manifold.
 
just for discussion sake here.....
lets discuss why you factor in piston speeds

Ill point out that the probable strength limitations,
in the 355 block and rotating assembly
(assuming good forged components and ARP main studs are used)
yes as pointed out earlier, both engines below would be pushing well past the limitations imposed by a STOCK, O.E.M. production block
but assuming that the O.E.M block will hold up at least for a hundred 1/4 mile passes,before it comes violently apart at peak rpm, that stress limitation,
will be imposed by both common valve spring limitations and piston speed on the rotating assembly and block,
on a 355 chevy with its 3.48" stroke , (assuming a 4200 fpm max reasonable piston speed)
has a peak rpm near 6700-7200 engine rpm, selecting a cam that peaks below about 6700 rpm-7000 rpm,)
leaves the potential advantage of that shorter stroke the 355 sbc on the table.
this is one reason that the 383 with its longer 3.75" stroke is currently the most popular combo with a 4.30 bore block.
if your going to build a 355, then you may as well take full advantage of the engines potential strong points.
a similar longer stroke 383 would be limited to about 6300 rpm-6700 rpm but the trade off is about 40 ft lbs more torque over most of the potential power band
the formula for hp is
torque x rpm/5252= hp
if both engines make about 1.2 hp per cubic inch
the 383 will peak about 400 rpm lower than the 355 if both are built to maximize the engines potential strong points
just for giggles and to point out
why you maximize a RACE ENGINE potential RPM LIMITS

lets assume the 355 power peak is at about 6800 rpm and,
the similar 383 would be peaking nearer 6400 rpm
if you have 1.2 x 355=426 ft lbs x 6800 rpm /5252=551 hp
if you have 1.2 x 383=460 ft lbs x 6400 rpm /5252=560 hp
why would the 383 generally be faster with the power so close?
its simply the extra 40 ft lbs of torque over most of the power band not just similar peak HP

" you can PAY NOW for good parts or PAY MORE AGAIN LATER , FOR BETTER PARTS WHEN YOU REBUILD AFTER IT FAILS, YOUR CHOICE"
 
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I was suggesting a DART block, I would not push an OEM block that far, just to make that clear.
I agree, with all I have learned the last 10 yrs I don't think I would build anything smaller than a 383. The cost is almost the same!
 
yes Id agree with that fully, and have stated that many times!
yet from experience,
I know most guys only learn the flaws of using an O.E.M. block,
after having one catastrophically fail under loads
" you can PAY NOW for good parts or PAY MORE AGAIN LATER ,
FOR BETTER PARTS WHEN YOU REBUILD AFTER IT FAILS, YOUR CHOICE"
keep in mind valve train control and rod bolts failures,
and keeping the cooling and lube systems fully functional,
and selecting components that will exceed the stress limitations,
and verifying clearances ARE key factors to maintaining long term durability
bcvs1.jpg

blockcrackl.jpg


http://garage.grumpysperformance.com/index.php?threads/block-choice.10472/

http://garage.grumpysperformance.com/index.php?threads/types-of-crankshaft-steel.204/

http://garage.grumpysperformance.com/index.php?threads/engine-block-cylinder-wall-thickness.976/

http://garage.grumpysperformance.com/index.php?threads/valve-springs.9613/#post-50601

http://garage.grumpysperformance.com/index.php?threads/main-cap-fit-in-block.5945/#post-18302

http://garage.grumpysperformance.com/index.php?threads/rod-bolts-rpm-vs-stress.341/

http://garage.grumpysperformance.com/index.php?threads/why-build-a-383-vs-a-350.715/

http://garage.grumpysperformance.com/index.php?threads/block-prep.125/

http://garage.grumpysperformance.com/index.php?threads/which-dart-shp-4-0-or-4-125.3219/

http://garage.grumpysperformance.com/index.php?threads/what-con-rods-would-you-buy.942/

http://garage.grumpysperformance.com/index.php?threads/redline.343/

http://garage.grumpysperformance.com/index.php?threads/valve-train-clearances-and-problems.528/

http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/

http://garage.grumpysperformance.com/index.php?threads/checking-piston-to-valve-clearances.399/
 
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Just for shits and giggles I ran my 400 with the same heads and single plane intake with the same roller cam and mine would be close to 615 hp @ 6500/525 tq @ 5000. With my setup I am 504hp @6k/514tq @4.5, good for me.
 
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Just for shits and giggles I ran my 400 with the same heads and single plane intake with the same roller cam and mine would be close to 615 hp @ 6500/550 tq @ 5000.



please clear that up, you ran the same cam as WHICH CAM?
and compared to what cam?
 
Well, I goofed on the heads! Mine has RHS 200cc ! The comparison was with the 355 I looked up some pistons that would get the SCR up to 10.70:1, and the DCR down to 8:1 with that cam(CC6J). The heads I used were AFR 195cc comp heads and I used the Herbert CC6J hyd roller with 1.6 rockers in both, mine already has them. I used the same pistons, same AFR 195cc comp heads in my calc for my 400, I had to do couple thinks to make mine streetable, the same pistons pushed my dcr up too high, so I retarded the cam 4 degrees to get it into range for pump gas. I figured both at 7000 rpm for carb size, 355 was 102.6 VE 400 was 102.4 VE so I used a 750 for the 355 and 800 for the 400. Both were run with long large tube open exhaust. I compared the cam from his 355 solid flat tappet in both engines I did not write down the tq like a dummy, peak hp 470(355) and about 525(400) Then I put the hyd roller(1.6 rr) in both DD simulations and and got 548 hp @ 6500/473tq @ 5000(355) and misread it earlier 620hp @ 6500/525tq @ 5000(400)
I realize its not that even cuz the CR was higher in my 400 but with bigger bore and stroke the CR is going to go up and that shows the benefit of the larger engine. Still it surprised me that mine went that high in HP.
 
Just shows that a longer stroke and mores cubes is the easiest way to build tq and hp! To be honest I used a small dome piston for the 355 and I backed off to a lot smaller dome on the 400 to get it down where I could get it into pump gas range after retarding the cam 4 degrees. 355 was a 125 dome and I used 50 on the 400.
 
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