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Old 09-24-2012, 05:57 PM
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info needed on splayed main caps for sbc

Ok i bought a 379010 4 bolt main 10/20 high nickel 350 block that im planning to build.
So this is the plan.get the machine work done for a 383
Scat balanced forged rotating assembly set at 10.1cc
Voodoo solid roller cam kit (have not decided which one yet)
Dart heads 200cc runner,64 cc,
Holley strip domminator intake

And some more but i got the internals that's is going to be used
now i am not going to be drag racing this motor on the strip its more a big toy with a lot of power but i will be beating on it from time to time so i want it to hold up to the abuse

Now i was thinking of putting splayed main cap for added strength but if i can get away with some a ARP stud bolts on the main caps i will .i plan to get around 450/500 up ..would like some info on splayed caps or just stud bolts on the main caps for my application
thanks Rob

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Old 09-24-2012, 06:06 PM
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You wont need to worry about the caps letting go.You can upgrade the bolts. New bolts are always a good idea,,, 500 hp is moderate,,
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Old 09-24-2012, 06:10 PM
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Four bolt factory blocks are usually not candidates for splayed caps. The outer bolt holes have to be filled and re-drilled. Cheaper to do on two bolt blocks. Stronger too.

Expensive way to go for a moderate engine. Much machine work and cost. Caps have to be trimmed and fitted to block. Block drilled and tapped, then line bored/honed.

Just put ARP style studs in the four bolt and go.

Oops! didn't mean to step on your post.. Slow typer ^^^^^^
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Old 09-24-2012, 06:19 PM
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Yea i thought it would be a lil over kill on a 500+ up motor just wanted it to hold up to the abuse lol .so stud the mains and run it.
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Old 09-24-2012, 06:48 PM
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I put on a lot of splayed caps and billet 4 bolt replacement caps because over the years I have seen to many stock grey cast broken or have seen a alot of fretting on the bottom of the caps. Splayed caps do tie the pan rails with the main webbing for more added strenth over a stock 4 bolt caps.

The only 4 bolt caps GM used for years in there performance builds was the 2482 center caps.

Start adding stroke and HP and stock caps don't like that much.

Before spending money on machining a block its a good idea to have the block sonic tested for cylinder wall thickness also by the time you spend money on machining a stock block with all the bells and whistles you might no be far off from a Dart SHP block.

Here is a quote I did on some other forums a few weeks ago.
Quote:
Originally Posted by CNC BLOCKS View Post
I have been asked about the installation of splayed caps many times over the years. Plus the reason for using 10 degree outter bolt VS 15,22 degree outter bolts First of all this proceedure can be done in a Bridgeport, knee mill, CNC machine ETC. Any machine shop should be able to accomplish this machining operation without any problem

I use flat bottom caps with 10 degree angle outer bolts because with the 10 degree outter bolts you should not get into the water jackets. I have had many calls about outter bolt holes getting into the water jackets only to find out its because of the 18 or 22 degree outter bolt holes.

Alot of classes out there are restricted to run OEM blocks and most racers like the weight savings of the OEM block and 383's we are now seeing over 500 plus HP and with the added stroke its best to go to a splayed center cap, Its always best to sonic test the cylinders for thickness before spending time and money on cap work.

Caps I prefer are caps from CIPCO Industries, LLC. or American Made - American Proud: Pro-Gram Engineering Corp - Manufacturer of Race Engine Parts - Home Price on cipco caps are right at 160.00 a set Programs are right at 210.00 a set.

First process is to cut the register either with an end mill or I use a 2.5 shell mill on 2 bolt blocks the register has to be only cut appox. .120 deep measure of the pan and on 4 bolt blocks the register have to be cut appox. .140 deep. I like to see a .003 press fit. Both companies use a 10 degree outter angle.



Next step is using a 1/2 in end mill at a 10 degree angle is to mill a flat spot.



Next is to center drill



Next drill holes using a the letter U drill appox. .800 deep



Next would be taping with a spiral tap seems to work best.



Line boring can be done with a line boring machine or I use the PLB-100 which seems to very fast and accurate, I cut the housing bores close to size.



Once line boring is complete the caps are taken off and cut appox. .0025 to .003 off the bottom then then reinstalled and aligned honed to the last .001 caps are loosened retorqued to check for size and hone to size.



Finish product


Note: On the Cipco caps they are OEM height and you can use an ARP bolt kit and on the Porgram caps they are appox. .200 taller and would require a stud kit.

Hope this thread answers most questions about cap installation.
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Old 09-24-2012, 07:10 PM
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Not trying to hijack the thread but what would the approx. cost be to align hone a block and bore the cam tunnels for a full roller cam? I know this depends on the area and the machine shop but looking for a ballpark figure.
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Old 09-24-2012, 07:31 PM
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That is some very nice work CNC i did notice that you used a 2 bolt main block for the splayed caps and mine being a 4 bolt main block would take a lot of work to do a splayed cap like the poster above said.i will be inline honing the mains when i have the block work done also.so if i did just stud the mains will i need them before i have it inline honed.
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Old 09-24-2012, 07:45 PM
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Wow i just looked at a DART SHP block and they start at 1500 bucks lol that's a lil rich for my blood
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Old 09-25-2012, 08:12 AM
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It's a bad idea to install "splayed bolt" caps on a previously-drilled 4-bolt block. The "straight" bolts go directly into the main bulkheads. This does "weaken" the block (350) SOME. We insist, if the customer really wants "splayed" caps, they start with a 2-bolt block. There's no real "effective" way to restore the lost strength in the orginal outboard holes, so why bother...

We've built hundreds of 500-plus HP 355s, 358s, 383s and 389s using the factory 4-bolt arrangement. No issues AT ALL regarding the caps. I HAVE seen a couple later blocks (passenger side dipstick) burn up a main and the cap come off in two pieces. NOT the cap's "fault". The earlier 350 blocks seem to be pretty tough, no matter what you throw at them.

All that said, using splayed caps DOES increase the strength overall, AND improves main bearing "life". The splayed caps tend to maintain "round" better than the conventional caps. Virtually ALL modern race blocks without "skirted mains" use splayed caps.

For those wanting a strong block and a 4 1/8" bore, pretty hard to argue with the Dart "SHP". I see a complaint about $1,500. Go price some others... It's a SCREAMIN' deal! Probably not necessary for a sub-600 HP 350-based build, buit for the 400SB, excellent.

Jim
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Old 09-25-2012, 09:08 AM
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Quote:
Originally Posted by S10 Racer View Post
Not trying to hijack the thread but what would the approx. cost be to align hone a block and bore the cam tunnels for a full roller cam? I know this depends on the area and the machine shop but looking for a ballpark figure.
Line honing should run around 175.00, Roller cam bearings in a 010 block your only going to get a 48MM which takes a stock journal cam core other then blue printing the cam tunnel there really is no gain.

Your better off to cut the can tunnel to BBC and go to a babbit cam bearing as there is more power to be gained on babbit bearings over roller cam bearings.

Its a crap shoot to get a 50MM roller in a OEM block when machining the oilgrooves there is a good chance of getting into water.
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Old 09-25-2012, 09:11 AM
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Quote:
Originally Posted by 350chevyrob View Post
That is some very nice work CNC i did notice that you used a 2 bolt main block for the splayed caps and mine being a 4 bolt main block would take a lot of work to do a splayed cap like the poster above said.i will be inline honing the mains when i have the block work done also.so if i did just stud the mains will i need them before i have it inline honed.
It would not take any more work to splaywd caps on a 4 bolt block. I have put more splayed caps on 4 bolt blocks then 2 bolt blocks.

I would at least go to a billet 4 bolt replacement center caps if you are going to use a 3.750 stroke or more.
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Old 09-25-2012, 09:26 AM
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Quote:
Originally Posted by Mr. P-Body View Post
It's a bad idea to install "splayed bolt" caps on a previously-drilled 4-bolt block. The "straight" bolts go directly into the main bulkheads. This does "weaken" the block (350) SOME. We insist, if the customer really wants "splayed" caps, they start with a 2-bolt block. There's no real "effective" way to restore the lost strength in the orginal outboard holes, so why bother...

We've built hundreds of 500-plus HP 355s, 358s, 383s and 389s using the factory 4-bolt arrangement. No issues AT ALL regarding the caps. I HAVE seen a couple later blocks (passenger side dipstick) burn up a main and the cap come off in two pieces. NOT the cap's "fault". The earlier 350 blocks seem to be pretty tough, no matter what you throw at them.

All that said, using splayed caps DOES increase the strength overall, AND improves main bearing "life". The splayed caps tend to maintain "round" better than the conventional caps. Virtually ALL modern race blocks without "skirted mains" use splayed caps.

For those wanting a strong block and a 4 1/8" bore, pretty hard to argue with the Dart "SHP". I see a complaint about $1,500. Go price some others... It's a SCREAMIN' deal! Probably not necessary for a sub-600 HP 350-based build, buit for the 400SB, excellent.

Jim
Jim

When shoud I start having problems with putting splayed caps on 4 bolt blocks as I have done hundreds of blocks this way and there has never been an issues that I know of.

The caps I use are 7.500 wide and go right over the outer bolt holes.

You can buy an SHP block all machined that's line honed to at least the middle of the spec or to the high side, decked to any demension, bored to any size plate honed, lifter bores checked, oil galleys holes taped deeper, main housing bores, freeze plug and cam plug holes chamfered, lifter bores checked for sizing for under 1850.00

By the time you spend money on a used 350 block machine work to get the caps on, cost of the caps, hardware, line bore and line hone the main line deck the block, Rough bore the cylinders and plate hone check for worn lifter bores and if worn install bushings now the SHP block is a better deal.
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Old 09-26-2012, 07:50 AM
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Having experience in most engine families, not "tied" to small blocks, but having built MANY, we apply what we learn from one to another. I didn't say you WERE going to have problems. I suggest the potential exists. There are other engines out there with similar issues. The Pontiac, for one, has many blocks "drilled" for 4-bolt caps, with 2-bolt caps installed. Not really "apples to apples" due to the much larger "parts" in the Pontiac, but still a good illustration.

The worst small block for this is 400, obviously. The wider "spread" between the caps without more "meat" in the bulkheads is one of the prime reasons 400 needs so much "prep" to make big power. We've seen far more main bearing issues with 4-bolt 400s than 2-bolts, at power levels up to 600-plus. Except for pickups and mild street performance, we insist a customer use a 2-bolt, at least "for starters". Adding the splayed caps to those make them just about as strong as they CAN be.

Thanks for adding up the numbers to show how the SHP blocks aren't really as expensive as the price tag "sounds". Folks forget just how much labor they pay for when building an engine. We've used a few of those, mostly for boats. Good blocks.

Jim
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Old 09-26-2012, 08:04 AM
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Well all the info iv read on 4 bolt splayed caps and the UP rating im shooting for plus the fact that it will be expensive to do i will probably just stud the main caps.now with doing the machine work to make a 350 to a 383 and inline hone the mains new freeze plugs,cam bearings, should be around 600 to do or will it be more can you guys give me a round about number that it will cost for a 383 machine work
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Old 09-26-2012, 09:50 AM
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dont forget when you prep your block to deck and square it.you can get the machine shop to clearance for the crank also.
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