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SmokinLowriderSS
03-21-2006, 03:00 AM
A co-worker loaned me a Chevy High Performance magazine due to an article in it on a conversion process to convert the stock Chevrolet 2-bolt main block/caps to a 4-bolt configuration.
chevyhiperformance.com The article is titled "Rat Motor Upgrade" Four-Bolt Mains Under $300 by Steve Magnante, April 2006 issue
I can't put the pix on here and the article is not YET available online (I looked) but the text & instructions are as follows. Hope it may be of use to somebody.
4-Bolt Mains under $300
26 April 2006 Chevy High Performance Magazine
chevyhiperformance.com
Most owners of '65-'90 Mk-IV 396-454 Rat motors with 2-bolt mains don't
know that a simple machining operation is all that stands between them and
the added strength and reliability of 4-bolt main caps. But, It's true. Virtually
every Mk-IV block was cast with enough bearing bulkhead material to accept
either 2-bolt or 4-bolt main caps on the assembly line.
Armed with this knowledge, the people at Johnson Machine Service (JMS)
devised a novel method of literally tapping into this unused potential, but with a budget minded twist that retains the stock 2-bolt caps. That's right, instead of spending upwards of $800 for billet 4-bolt main caps, the stock JMS reconfigures 2-bolt caps to accept a second row of 7/16" fasteners.
Though the add-on 7/16" outboard fasteners are smaller than the
factory-specified 1/2" bolts used on OE 4-bolt blocks, there's no denying the
extra fasteners are better even if they are a bit smaller. Proving the point, the JMS crew has several customers with converted Chevys putting out as
much as 840HP without problems. Follow3 along as Don Johnson shows
how to transform a 2-bolt bottom end to super-sexy 4-bolt status for dimes
on the dollar.
Unfortunately, I have no way to put the pictures on here.
Step 1, a 4-bolt Chevy rear main cap is required to set up the Bridgeport mill for the 3.060" distance for the outboard row from the crankshaft centerline. It also is required to properly locate the x/y axis locations for the staggered outboard bolt locations for the 2-bolt rear main cap modification. Install the block properly leveled & squared on the Bridgeport.
Step 2, Install and tighten down the 2-bolt caps so they cannot move. Install the 4-bolt #5 main cap with the 2 stock bolts.
Step 3, use 3/4" end-mill to spot face caps 1-4 3.060" outboard from
crankshaft centerline. Due to variances in the caps designs, the depth of cut
will vary. The finished spot does not need to be perfectly circular. To do that
that could unnecessarily reduce the cap thickness on certain low-mass caps.
It is only necessary to remove enough material to leave a nearly circular pad
capable of fully supporting the bottom of the 0.650" diameter Allen-bolt head.
Step 4 Drilling depth is set to make 1.0" holes into the block.
Step 5 To insure perfect alignment, pilot drill the caps & block in 1 operation. A U-drill bit was used to make the pilot holes .012" smaller than the 7/16" holes needed for the bolts. This extra material is the root diameter for the threads after tapping.
Step 6 Use care in taking the cap holes out to 7/16" final size so as to not remove any block material
Step 7 The block tapping begins by using a 3/8" drive ratchet and a #5 tap socket. The 7/16" holes in the caps perfectly center the standard tap as it cuts threads in the block. Follow the standard tap with a bottoming tap to insure full thread depth & engagement. Use compressed air to remove chips between tapping operations.
Step 8 Install the Grade 8, 1 1/4" X 7/16" NS Allen bolts that'll help prevent cap-walk and extend bearing life. Don says reduced-head hex head bolts can also be used but he prefers Allen bolts because they are easier to install and just as strong.
Step 9 Torque specs fro the outer row of fasteners, 65 foot-pounds on 30wt motor oil on threads and under the heads to prevent galling & false readings.
Step 10 Unlike the rest of the caps, #5 has staggered bolt holes offset 0.343"
Failure to match this will cause you to drill through the back of the block and into the crankcase resulting in a persistent oil leak between engine &
transmission. This is why it is critical to use the stock 4-bolt cap or an
identical aftermarket cap during set up to use as a centering fixture and
show you where to put the holes.
Step 11 Spot face & drill the #5 cap the same procedure used on #1-4 but take care to not enter the block just yet.
Step 12 With the cap removed, the same x/y co-ordinates to drill the cap are duplicated on the mills digital readout. Then, drill with the u-drill exactly 1" deep into the block. Breaking through the block will not destroy the block but is guaranteed to foster customer complaints about excessive oil leakage. Don as not lost one yet.
Step 13, Reinstall the cap centered atop 2 3/16" spacers and drill the final 7/16" holes in the cap only for the new bolts.
Step 14 Reinstall the cap fully and tap the holes using the same procedure as the #1-4 holes were.
Step 15 The upgraded bottom end looks impressive. Don says that if this procedure is done on a good-running engine, there is no need to align-hone the main caps after the 4-bolt conversion. Still, JMS usually align-hones the blocks just to be certain. JMS charges $250 for the conversion process
(including fasteners) and $150 if align-honing is done.

holorinhal
01-13-2007, 11:21 AM
SmokinlowriderSS,I was startin My 454stroker489 build and was building for a pleasure performance boatbefore I got struck with the need for speed bug.
At any rate I changed the focus of my performance and HP goals,but was tsuck with a two bolt block.I had allredy sunk too much money into my block ,what with purchase of the motor and all machening expenses,to justify switching to a 4 bolt block.
I was'nt happy with the HP numbers that I was told the 2 bolt block would be limmited to.My machinest told me that He had been toying with the Idea of converting a two bolt to a 4bolt and if I wanted to be the ginne pig ,He would try it.Itold Him that I would think about it,and lo and behold A bout a month later,that article came out.
I about fell out when I saw it ,here was a sep by step istruction guide to what I was thinking of doing.
I imediately purchased the Mag and went staight to the machine shop.
After dennis read the article He said He didnt see any problem with performing the upgrade,and it should be good to atleast 850 HP.He told Me He would do the work for what the article said it costs, as a test.
To make a long story short,I had that upgrade done,and now my HP goal is limmited only by My finances!
Before I thought i would be lucky to get to 550 Hp,now I can build To atleast 850HP.It will be a slow build,as I can only buy parts as I can afford them,But thats My goal.May be too much motor for My Kona But we will see.
The upgrade turned out great,and for only 300 bucks! Now I just have to get My Mag back from My Machineist....Hal

UBFJ #454
01-13-2007, 04:15 PM
Your conversion similar to this one?
http://www.dvorakmachine.com/4boltconversion.shtml

Moneypitt
01-13-2007, 10:00 PM
This is exactly what Art Anderson, (gofastracer), was saying a week or so ago. He has been running one for awhile w/o any problems. I have a question about required machine, (mill) size. Will a standard shop size Bridgeport type mill do this job? Does a 36-40" table have enough travel in X? And are the valley ends square enough, or are shims required to square it up? Hold downs T'd to bottom of cylinders for anchoring down?........I seriously intend to try this and have a busted block to practice on if I have access to a big enough mill..........MP

Fiat48
01-14-2007, 06:29 AM
I want to enter this food for thought.
What do 4 bolts do for the main cap? Do they keep the main cap from walking? No. Maybe they help if splayed but they dont help with straight.
Using main studs does not stop the main caps from walking either.
Since I never saw a bbc main cap actually break....I have to wonder what converting to 4 bolt caps really does for me? Is it possible this is more cosmetic than structural?
I understand the resale value of a 2 bolt engine vs a 4 bolt. And for that reason alone would not consider sinking a bunch of money in a 2 bolt motor.
But if the main caps are walking around....transferring metal from one surface to another and changing the dimensions of my critical line hone....I have to ask myself what am I solving (except for etticut) by going to 4 bolt caps?
Would it not be better to dowel pin the caps? How about a girdle?
These are questions in my mind and have been for many many years. What I have seen is the more hp....the more the caps walk regardless. Perhaps shortly I will have a little more data. My current engine runs high rpm and is splayed cap (but it is a Dart). Now that it has run 3 seasons it will come apart
and be inspected.
Also a 427 was fitted with a girdle and it has been run hard all season and it will come apart also for inspection. Maybe some data there.

GofastRacer
01-14-2007, 09:09 AM
This is exactly what Art Anderson, (gofastracer), was saying a week or so ago. He has been running one for awhile w/o any problems. I have a question about required machine, (mill) size. Will a standard shop size Bridgeport type mill do this job? Does a 36-40" table have enough travel in X? And are the valley ends square enough, or are shims required to square it up? Hold downs T'd to bottom of cylinders for anchoring down?........I seriously intend to try this and have a busted block to practice on if I have access to a big enough mill..........MP
Yes it will do the job but you will need a spacer to raise the head!..

Moneypitt
01-14-2007, 10:53 AM
Yes it will do the job but you will need a spacer to raise the head!..
Is this an accessory for the mill, or a homemade deal? Pics?.........Ray

GofastRacer
01-14-2007, 03:42 PM
Is this an accessory for the mill, or a homemade deal? Pics?.........Ray
It is an accessory and pricey, I don't have a pic because I don't have one on mine, used to do it on a friend's mill now I have to get it done!..

Blueoval
01-15-2007, 06:52 AM
Hey Gofastracer!!
I was looking over your photo's on your web page?? (Parker ski race) I noticed you have a few pictures of a Ford engine Twin turbo>>>
Do you have any info on the engine, builder, owner??
Thanks!!!

Kurtis500
01-15-2007, 08:44 AM
How about a girdle?
Thats exactly what I intend to do with the 496 now.

GofastRacer
01-15-2007, 07:22 PM
Hey Gofastracer!!
I was looking over your photo's on your web page?? (Parker ski race) I noticed you have a few pictures of a Ford engine Twin turbo>>>
Do you have any info on the engine, builder, owner??
Thanks!!!
Sorry, don't know anything about it other than it's one clean piece and it ran great!..

obnoxious001
01-16-2007, 10:13 AM
Hey Gofastracer!!
I was looking over your photo's on your web page?? (Parker ski race) I noticed you have a few pictures of a Ford engine Twin turbo>>>
Do you have any info on the engine, builder, owner??
Thanks!!!
My guess, without seeing the photo you mentioned, is that it would be Billy Mason's boat. Does it have stacked intercoolers? If that is the one (probably boat #275) he does his own engine building.

Blueoval
01-16-2007, 11:01 AM
My guess, without seeing the photo you mentioned, is that it would be Billy Mason's boat. Does it have stacked intercoolers? If that is the one (probably boat #275) he does his own engine building.
Yes that's the engine!!! Looks as if it's a jet boat!!! I'd like to find a Ford builder on the west coast that really knows what he is doing!! I like John Kasse but he is East coast. Thanks for the help

smokinflatties
04-23-2007, 06:56 PM
somthing to think about

BrendellaJet
04-24-2007, 09:58 AM
This isn't a new operation. My jetboat motor that was rebuilt in the early 90's had this done to it...

v-drive
04-26-2007, 05:00 AM
Is this an accessory for the mill, or a homemade deal? Pics?.........Ray
Worked in a friends machine shop part time and didn't realize why it was such a long reach to loosen the collet until I stood back and looked.
It's pretty basic and if you had a lathe big enough you could build one.
I have also seen them on e bay from time to time...v-drive

DaveA
04-27-2007, 09:06 PM
Fiat,
Have you found out anything interesting about the Dart and the 427 w/the girdle once you cracked them open??
Just wondered.
DaveA
I want to enter this food for thought.
What do 4 bolts do for the main cap? Do they keep the main cap from walking? No. Maybe they help if splayed but they dont help with straight.
Using main studs does not stop the main caps from walking either.
Since I never saw a bbc main cap actually break....I have to wonder what converting to 4 bolt caps really does for me? Is it possible this is more cosmetic than structural?
I understand the resale value of a 2 bolt engine vs a 4 bolt. And for that reason alone would not consider sinking a bunch of money in a 2 bolt motor.
But if the main caps are walking around....transferring metal from one surface to another and changing the dimensions of my critical line hone....I have to ask myself what am I solving (except for etticut) by going to 4 bolt caps?
Would it not be better to dowel pin the caps? How about a girdle?
These are questions in my mind and have been for many many years. What I have seen is the more hp....the more the caps walk regardless. Perhaps shortly I will have a little more data. My current engine runs high rpm and is splayed cap (but it is a Dart). Now that it has run 3 seasons it will come apart
and be inspected.
Also a 427 was fitted with a girdle and it has been run hard all season and it will come apart also for inspection. Maybe some data there.

Fiat48
04-28-2007, 12:38 PM
Fiat,
Have you found out anything interesting about the Dart and the 427 w/the girdle once you cracked them open??
Just wondered.
DaveA
Yes sir I have.
Morg's motor....the 427 N/a alcohol deal.....no sign of cap walk and all the bearings were perfect. I attribute this to the girdle since before the girdle there was cap walk plus the fact the motor since the girdle makes more Hp and turns at least 500 more rpm than it did before.
My Dart I have not got to work on yet. BUT:
A 541 N/A Dart motor I built about 3 years ago has come back for a blower upgrade. This thing runs about 7500 rpm in a flat.
That motor is apart now and no sign of cap walk and all bearings are perfect on that one. It's a splayed cap deal (not billet caps and using original Dart supplied main cap bolts) Scat 4.250 stroke crank, eagle steel rod and 14.8 compression.
Also just completed a 521 Ford 2 bolt deal and did a girdle for that. But I prolly won't see that one back for a couple years.
Also you might want to read this thread:
http://www.***boat.com/forums/showthread.php?t=148270

Fiat48
04-28-2007, 12:47 PM
If someone's entertaining the conversion (worth it or not) make sure the machine shop knows what they are doing. I had it done by REX Racing Engines in Sacramento and they ended up raiseing my crank .020 closer to the cam. Chains dont come in .020 so you need a gear drive with smaller idlers. It was a big surprise when my new motor blew in short order, I tore it down and found a sloppy IWIS chain...
Prolly because they could not find a set of caps close to your originals. Caps are not bored nor created equal. This is one of the reason I shy away from converting to 4 bolt caps. With better aftermarket blocks out there and what it costs to build a motor today....I say go aftermarket block. There are just too many advantages than to mess with 30 year old plus BBC's not to.

GofastRacer
04-28-2007, 08:15 PM
Heck, I remember picking thru 10 sets of caps to find some that were decent so it wouldn't take a massive line bore make them work!..

thatguy
05-01-2007, 11:38 AM
Originally Posted by Fiat48 View Post
I want to enter this food for thought.
What do 4 bolts do for the main cap? Do they keep the main cap from walking? No. Maybe they help if splayed but they dont help with straight.
Using main studs does not stop the main caps from walking either.
Since I never saw a bbc main cap actually break....I have to wonder what converting to 4 bolt caps really does for me? Is it possible this is more cosmetic than structural?
I understand the resale value of a 2 bolt engine vs a 4 bolt. And for that reason alone would not consider sinking a bunch of money in a 2 bolt motor.
But if the main caps are walking around....transferring metal from one surface to another and changing the dimensions of my critical line hone....I have to ask myself what am I solving (except for etticut) by going to 4 bolt caps?
Would it not be better to dowel pin the caps? How about a girdle?
These are questions in my mind and have been for many many years. What I have seen is the more hp....the more the caps walk regardless. Perhaps shortly I will have a little more data. My current engine runs high rpm and is splayed cap (but it is a Dart). Now that it has run 3 seasons it will come apart
and be inspected.
Also a 427 was fitted with a girdle and it has been run hard all season and it will come apart also for inspection. Maybe some data there.
__________________________________________________ ___________
We were doing 4-bolt conversions 25 years ago. To help answer Fiat's questions here is what I have learned, having done hundreds of line-hones on the CK10. Main caps stretch first, then start moving around due to lack of "squeeze" from the lips in the side of the block mating surface. It is readily visible when you grind the caps for line-hone.Just like big end egging on connecting rods.
Some blocks actually get weaker from drilling the outer holes in the web area.
Short of buying after market, quality blocks, I liked using good aftermarket steel caps, splayed outer bolts that were smaller dia. then the inner long ones. That left more material in the block. Then dowel the inner holes. Course I had access to bridgeports and Sunnen machines so labor never factored in. I could take as long as I needed fitting them as close as possible and matching before actually honing it.
Its all to try to reduce cap stretch. That leads to all the walking and moving.
I also would not consider doing it and using straight Chevy caps. Not worth in IMHO.
The biggest improvement doing this is on 400 small blocks. The 4-bolt 400 has almost no material in the saddle area. A 2-bolt 400 block w/ splayed steel 4-bolt cap conversion was always in better shape after races.
If your assembly isn't correctly balanced by some one who knows right from almost right, none of it matters anyway. That is where to spend the money.
I have no proof other than my own experiences and certainly don't claim to be the guru on this. Just my .02

78Eliminator
05-02-2007, 09:00 AM
If someone's entertaining the conversion (worth it or not) make sure the machine shop knows what they are doing. I had it done by REX Racing Engines in Sacramento and they ended up raiseing my crank .020 closer to the cam. Chains dont come in .020 so you need a gear drive with smaller idlers. It was a big surprise when my new motor blew in short order, I tore it down and found a sloppy IWIS chain...
Good god, what a nightmare.

Fiat48
05-29-2007, 03:00 PM
Fiat,
Have you found out anything interesting about the Dart and the 427 w/the girdle once you cracked them open??
Just wondered.
DaveA
Finally able to inspect my own motor. Here's the Dart:
http://www.***boat.com/image_center/data/500/SUC50213.JPG
http://www.***boat.com/image_center/data/500/SUC50211.JPG
http://www.***boat.com/image_center/data/500/SUC50212.JPG
I can't tell you how many times this thing has seen 8500 + rpm. So I am pleased at how it looks.