Author Topic: bottom end question  (Read 12255 times)

Offline 305chevy c-10

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bottom end question
« on: April 17, 2011, 08:45:42 PM »
i have a 2 bolt main (#638) block 350.with the following specs ...
vortec heads
750 dbl pumper holley
268 cam (roller)
.030 block
hei distr(procomp)
1.5 roller rockers 3/8 stud
electric fuel pump 130gpm
2500 stall on 350 trans auto
 2.73 gear but will upgrade to 3.42
stock crank and rods 5.7
dished pistions
now my question is is this gonna make too much power for a 2 bolt main....i seen an upgrade kit to convert a 2blt to a 4 blt main .....just wondering what u guys think..........i hate to get this thing built and let it have it one .....and bottom end cant handle it ....i was told 2 bolts are no good ....
.now my question
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Offline VileZambonie

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Re: bottom end question
« Reply #1 on: April 17, 2011, 08:51:51 PM »
You'll be just fine since this doesn't sound like it's going to be anything radical. In fact it sounds like you are building a gas pig. Have you really thought out your whole powertrain combo?
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Offline 305chevy c-10

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Re: bottom end question
« Reply #2 on: April 17, 2011, 08:58:40 PM »
well tell me where im going wrong .........some things are already purchased someare not ...dont have fuel pump stall, or gears in yet
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Offline VileZambonie

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Re: bottom end question
« Reply #3 on: April 17, 2011, 09:10:40 PM »
Well I've actually had better luck with two bolt blocks over 4 bolts blocks. If you are building a small block that you plan on punishing, splayed caps are recommended. As far as where you went wrong, I'm not suggesting you did anything "wrong" but How about some more details about your ride, What is it, what are you trying to accomplish, why dished pistons, what made you pick that converter?, what size tires are you running?
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Offline 305chevy c-10

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Re: bottom end question
« Reply #4 on: April 17, 2011, 09:22:34 PM »
ok its a 85 c-10 chevy shrt bed 2wd .stock no body mods ....tire size will be 31-32 .i was told that dished work well with vortec s and it would not make my compression to high ..............want to run well on 87 oct ..........well on the converter i was told that with the cam i got i needed a bigger than stock conv.i kinda guessed on that info .......2500......yes i will punish it some time not racing just ......showing out a little ...i know the carb is big but the guytold me he can tune it to work on my app
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Offline Psycho71

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Re: bottom end question
« Reply #5 on: April 18, 2011, 09:29:23 PM »
My 2cents; and some will say that's about all it's worth.

86 the dish pistons and run some flat tops. Just watch the quench and you can still run 87 octane fuel. While you're doing that, since you wanna show off a bit, go ahead and get some forged piston and ss valves so you can squeeze it a bit too.

Call the cam manufacturer, tell them about your set-up, and see what stall converter they recommend with that cam, carb, gears, tire size, etc...

Loose the double pumper carb and get a vacuum secondary 650 or so. It won't require nearly as much tuning, and will be a much more street friendly carb.

Unless you need it to fix other issues, or just want electric, you don't need a 130gph pump. A stock pump will feed that engine just fine.

Get a re-curve kit and adjustable vacuum advance for that dist. Timing tape too if your timing light doesn't have the advance feature. Set up the timing right and it'll make a world of difference over that pro comp dist out of the box.

Make sure the valve springs match the cam too. 

the 2bolt block will work just fine for that build. If you want a little added strength, you could always stud the mains. Many a builder has told me a studded 2 bolt block is stronger than a bolted 4bolt factory block. Mine is a 4bolt, but it just happened that way. I certainly didn't seek it out. A 2 bolt would have been just as good for me.



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Offline 1980c10

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Re: bottom end question
« Reply #6 on: April 18, 2011, 11:25:46 PM »
-Flat tops will give you a 9.7ish to 1 compression ratio on a 64cc head. (87 octane will work)
-Heavier valve springs will also be needed with that cam.
-A large carb will decrease your vacuum. (650 will work good and keep your vacuum up). Althought he 750 can be made to work just not as well.
-A stock fuel pump is good for your set up and will be much more dependable than the electric.
-2 bolt main is fine.
Just my opinion...

Offline 305chevy c-10

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Re: bottom end question
« Reply #7 on: April 19, 2011, 03:00:42 PM »
nice advice ..........but my cam and pistion s are already brought .....the vavle springs are tested 115 on  seat and 310 @ .550 lift ....i have stainless vavles in the heads ....as for the fuel pump ....this is a roller block .....the rebuild kit i ordered came with a roller cam that does not have a pump lobe on it .....that y im running electric maybe 95-115gpm .......the carb i got off ebay ...will go with a 600 or 650 and try to get rid of the 750
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Offline 1980c10

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Re: bottom end question
« Reply #8 on: April 19, 2011, 06:08:01 PM »
I would still consider upgrading the pistons if your budget allows, it's easy power and would make a noticable difference.

Offline Captkaos

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Re: bottom end question
« Reply #9 on: April 21, 2011, 11:02:55 AM »
4 bolts are weak, for a street motor that will rarely see constant about 2bolts are plenty strong.  Altogether my buddies broke more 4bolts than 2 bolts.  I never ran a 4 bolt.  If you are going to drag race, get the 2bolt machined for splayed caps.

your cam is barely over stock and doesn't need that much stall and that carb is to big for the motor, it needs no more than 600cfm unless you plan to overrev it past 5000rpms.

Offline 305chevy c-10

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Re: bottom end question
« Reply #10 on: April 21, 2011, 03:25:50 PM »
well im looking into a summit 600 carb and i will have the specs on the cam tom ...when the kit comes in ...im hoping for atleast 350-375 hp/400tq ...i need to look at the old cam to cross reference the part # to see how much bigger is this cam
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Offline Da67goatman

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Re: bottom end question
« Reply #11 on: April 21, 2011, 06:00:14 PM »
How much abuse can a splayed 2 bolt handle?  Say 10k rpm?
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Offline VileZambonie

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Re: bottom end question
« Reply #12 on: April 21, 2011, 09:07:24 PM »
The weakness in the blocks webbing and caps aren't necessarily prone to destruction based on RPM. 10,000 rpm out of a small block isn't realistic or practical but it depends on how it is abused. If you're building a budget 400 HP small block and have a good seasoned block you're safe.
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Offline 305chevy c-10

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Re: bottom end question
« Reply #13 on: April 22, 2011, 09:36:52 PM »
got cam kit in my cam specs are 215 @ .050 ....268 advertised dur ...489 lift ...dont really know what kind or idle this will have though.
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Offline chevymanrob

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Re: bottom end question
« Reply #14 on: April 23, 2011, 07:27:06 AM »
sounds like you'll be in the 300-350 gross horsepower range. WELL within the safe 2 bolt range. i always hear that 2 bolt factory blocks are safe to 500 or so. unless you are planning on HUGE (300+) NOS you'll be fine.
and for what its worth my 2 bolt 400 ran 11s at 111-113 all day and never had an issue.
ex G-body drag fan. best was 11.86 on a 93 octane SBC street car.