350 4 bolt main caps swap - Third Generation F-Body Message Boards

101btp · 10-16-2009, 09:04 PM

ok, just bought a decent stock 350 block for $125.00 not bad for including some stock setup to re-sell but my big question for now is I seen the 4 bolt main caps they look prety good but im gunna be running a 400 crank and not a stock one that is for the 350 to 383 conversion forged crank, prety much all forged for my block and I was going through my mail-order-jegs, summit, all other side mags and I had seen the eagle 4-bolt maine billte steel caps I know it's for the center 3 caps, and I just wanted to know if their was any difference in strength from stock to the bilet steel?
here is the caps @ http://www.jegs.com/p/Eagle/Eagle-4-...57799/10002/-1
let me know if you think it would be a good investment for a lengthened block life?

and I do know that they are for the conversion just wanted to get as much strength as possible and they will probably be used with a main griddle for even more strength, I do plan on running some high numbers out of this block 700HP at minimum
I had also seen on the add that the 350 and 400 caps are running the same 18 deg. angle their any difference in reliability?

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kens86 · 10-16-2009, 09:31 PM

If you plan on making that kind of power i would not waste your time and money with a stock block. By the time you put on billet caps, girdle and machining you can buy a Dart SHP block and feel safe with that power level.

BADMAN · 10-16-2009, 09:36 PM

If your block is already a 4-bolt main the caps are not splayed,but straight bolt design. Therefore you should not use the splayed caps because two of the bolt holes are drilled at an angle and will not work on a stock 4-bolt main block. If your block is currently a 2-bolt design,then you can have a machine shop drill the 2 extra holes for the splayed caps. I have seen and used stock 4-bolt main blocks,provided that the block is blueprinted(bored,honed,decked,line-honed), be quite stable up to the HP you desire. The shortblock needs to be balanced and all clearances set correctly if you are running a lot of HP. Proper prep is everything when building a 500hp+ engine. Or you can take the above advice. The Dart block is a very fine piece.

101btp · 10-17-2009, 02:11 PM

I was on a little later and still did see billet caps that were not splayed but had a straight up and down design like stock, but will this be any stronger than stock wasent sure the steel that was used to make the stock caps?

jaykar · 10-17-2009, 04:57 PM

Having run a few stock 2/4 bolt blocks converted to splayed design not a
problem.
You fill the outer holes with studs and redrill for the angle studs.

These were 372 & 378 motors turning 7500-7800 with all the good
internals & externals for our late model cars.
making in excess of 650 at that RPM. No problems other than blowing
across top of inner bore area, even when O-ringed. Only when pushing timming though.

Granted 400 4 bolt blocks but applies to the smaller blocks also.
Can do this with 2 or 4 bolts.

Good machining the key in any instance.
That was then though and this is now.
I'd go with the aftermarket blocks today and not have to worry about
machining and doing it rite.

Later

radical82 · 10-17-2009, 05:35 PM

Along with the price of the caps, you'll have to add in the price of having the old block align bored and honed---mandatory when changing main caps. Then, going to need to get it magnafluxed along with all the other general machine work for a build.... By the time you add it all up, plus the time used up while it's in the shop and running back and forth to the shop, you'll be real close to the price of a new Dart block, the SHP can be had for a bit under $1500.--if you're serious about 700 horse then you'd be better to step up a couple price ranges on the block!!!!!

700horse is a nice sounding number, and a good hp level if you're going to be racing only....but on the street it would be a royal pain in the butt to put up with... Takes a very strong drivetrain to live behind that power level, the stock stuff just won't cut it... If you run an automatic, it's expensive to build the transmission, and will require a torque converter with a lot of stall speed--which builds a lot of heat and makes cooling a challenge.......

Unless you are going to go to an all out competition type suspension along with a narrowed rear end, frame ties, and a lot of other incidentals you'll never hook up that kind of power on street tires..... An engine that builds reasonable torque numbers, say in the 400 to 425 ft. lbs. range is all you'll ever need on the street....

101btp · 10-17-2009, 06:15 PM

ya 1,500 is def not bad for what I am looking for and ya I mean this is an over time project not like needs done next week, but ya i do understand some of the work that will need done but It all good, ya driving to the shop no big deal!!!!!
and I would never go with stock for any parts in this engine other than this not being an aftermarket block, ya an all forged setup, allong with the trans it's gunna be a 6 speed, hope to get ratchet shift but not sure if that's good for maunal I know it's good for speeding through automatic gears
And ya it will also have GOOD setup on the suspension
This vehicle is not meant to have "NORMAL STREET TIRES" gonna go with hooser dot. approved street/strip drags

and by the way this is a good speed shop im gonna go to so their will be just as much of a chance as them screwing up the ballance in youres as aftermarket blocks as their will be with mine being machined with problems, and as is with you, hopefully .001 to none