(2ND try) Any "real" benifit from spayed main caps on an LT1?
I am starting my winter upgrades to the bottom end to support much higher boost levels. After consulting a few race shops that I respect I was interested to hear that they really do not see much need for splayed caps on the LT1 due to the webbing and block strength.
SO post up your opinions. Has anyone really found the limit of the 4 bolt caps on the LT1? Please don't just speculate, we all know what the splayed caps are supposed to do.
Is there really a way to tell if you've maxed out your main caps?? I had a nitrous accident last year and I spun 3 mains and cracked the forged crank in 4 places.
I think the consnesus is that if you do a partial block fill and have 4 bolt caps (splayed or not) then you should be fine.
I didn't go splayed due to the fact that I didn't wanna drill 6 new holes in my main webs. I did however put Pro-gram engineering staight billet caps in the center 3. I figured with the boost I plan on running Id hate to wipe a main bearing due to deflection.
Truth be told I have never seen a main cap failure in a sbc. ever. Ive seen a crank throw (with it's 2 rods connected) pease-out thru the side of the case, but it was a cast crank under a big roots blower and a missed shift.
The only thing that concerns me is how thin the webbing is in the front behind the timing chain. but all sbc's are like that other than after market.
IMO you'll be fine with your factory main caps, they're ductile iron and will match the block's expansion better than 1010. for street use.
Being a brother of the boost (turbo boost that is) your engine stress differs from similar output nitrous/na/blower motors in that the cylpressure rise is less like an impact load, and net stress at a specific output is less.
But make no mistake, at high boost all your innards are just a wigglin' around, just below the yield point hopefully. A very hard, stiff crankshaft can do worlds for helpin the block out by reducing deflection in the crank and therefore in the block.
save the 500 in caps and machine work and put it twards a freaking awesome crankshaft.
Is there really a way to tell if you've maxed out your main caps?? I had a nitrous accident last year and I spun 3 mains and cracked the forged crank in 4 places.
I think the consnesus is that if you do a partial block fill and have 4 bolt caps (splayed or not) then you should be fine.
what kind of accident? lean? if so we gotta ask ourselves "would any crank/cap hold up to severe nitrous detonation?"
Makes me wonder If I should have recorded the free length of the main studs, too.
On the killer street or drag engines I build. I use a 2 bolt LT1 F body block as a foundation. I then install a set of Pro-Gram Engineering splayed center caps. If the use of NOS is anticipated I then add billet front and rear caps to the recipie as well. It maybe overkill but I feel its better safe than sorry later. Especially with an expensive rotating assembly.
I have yet to have a failure. On one particular solid roller engine which is drag race only, all 5 locations are billet caps and the block has a partial fill. It spends all season making 7500 RPM shifts in a 10 sec 3rd gen F body, and the bearings look like new during a recent tear down.
IN retospect I shoulda spent the extra 2 bennies on the front and rear. I have a little more than partial fill (oops) right up the the bottom of the water pump. hence the use of piston oil spray to keep things cool and happy down stairs. Extensive use of swaintech coatings as well. I want to push past 30 psi. with my UTV-94. I think it will hold together, though alot of people don't share my opinion.
That callies crank is very nice! an excellent example of the right parts to use
I just used a 97 pontiac block and dumped the 2 bolt main and went to spladed main caps ,cola crank and sprayed the pistons and everything else I could.
At that point you are just running the LTx block and all the rest is a standard small block old style chevy.
Starter and flywheel is standard chevy.Just the cooling system is diff.
I would go with a Sheroff engine with a 2 year warranty.
When you are done none of the motor inside is neew school just old school parts.
swap the center 3 caps for replacement straight 4 bolt billet caps, get a main cap girdle to help minimize deflection, and a set of ARP studs to hold it all together. that will hold about all you want on a motor, add a 1/4 fill to help out some more with deflection if you want, and make sure your oil passeges are thoroughly cleaned and a hot tank and steam bath is used in block preperation. use a quality oil pump and make sure your engine builder knows what plastigauge is when doing the final measurements on the assembly. with the new caps you will need to register them to the block and have the mains line bored and honed, all this should be done with heads bolted on and the same gasket you will be using and everything torqued properly. this will give the best end result.
I started with a 2 bolt block with splayed center caps because of the fact I knew I wanted to spray. I think it is definatly over kill for under 600 HP but then again I always try to error on the side of caution.
I had my stock block, no fill, stock caps, arp bolts pushing 641hp at the wheels with 3-5psi of boost and 250 shots of juice. But now i'm concerned because i have cog system and it allready went 20psi +/- 610rwhp. I'm going to tear down the engine and i was thinking of filling the block. But my problem is that i have to sent it the US.
Well to give you the background, I made 649RWHP/651RWTQ SAE corrected on 15PSI on my 6" rod 383 w/ single turbo. After the dyno session I have some blowby and it ran rough. I I suspected rings or ringlands and pulled the motor to diagnose and rebuild properly. I found the #3 top ringland cracked and showing blowby. I had been making due with this motor for a few years while I concentrated on working the single system.
There were many "bandaids" as I call them that amaze me that they did not go up in a loud boom with parts flying lol. The motor was using Eagle I-beam SIR rods (well past there recomended useage), JE SPR -16cc forged pistons(non designed for FI), SCAT crank (not sure what model, but was part of a budget kit so I am sure not terrribly good), adn the cu-de-gra(sp)...I lowered CR to 9.1-1 using a Cometic MSL HG that was .074 thick. LOL I would like to say that I talked to the Cometic engineer about this and he swore it would hold, and it did. I believe the huge quench was causing some other problems but that is for another discussion.
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(2ND try) Any "real" benifit from spayed main caps on an LT1?
your engine stress differs from similar output nitrous/na/blower motors in that the cylpressure rise is less like an impact load, and net stress at a specific output is less.
