Factory 4 bolt block limit

[blown383ta]

So I'm neck deep into the complete rebuild of my blower setup, 383 with forged eagle crank and H-beams, and 2618 Mahle 26cc piston. Cam is xfi lobes 230/236 on 114. Factory vette block with studs. Vortech S trim being upgraded to an experimental Ti trim modified fit an aftermarket scroll large enough to accommodate the impeller. Guesses are in the 1300 cfm range.

Now, the engine builder, very respected and accomplished for high power LS builds these days, as us lt1 guys are becoming relics of the past and all but forgotten, is warning me that my setup going be capable of 7-800 flywheel with the canfield 220 heads (300 cfm, 9:1CR) I was going to use, and that the bottom end, mainly the block, isn't going to hold that for long.

Now I hoping for 600+ to wheels, and would be happy to restrict it to that is need be for longevity, but what are your thoughts here? I've seen many lt1 in the 600 rwhp range, but for how long, and probably with better quality cranks and rods and splayed mains.

I'm not interested in the "you should have done this or that" at this point. Engine is together besides the heads, and he's telling me leave the ported stockers (260cfm, 9.5CR) and the upgraded blower still going to put me in the danger zone power wise. Car is fitted with 31x12x3.5 FMIC and meth this time around.

On another note, I believe if I were to use the S trim on this 383, with either head combination, that blower may actually be too small, especially the canfield heads, and become a restriction. Maybe not so much with ported stockers, but I never saw more than 10psi with those heads and cc305 cam for whatever reason, maybe belt slip with 2.7 pulley, and that was only 350 ci.

Engine builder suggesting the same thing everyone else says "should have went LS". Had I known where I'd end up today, I might have built a dart block, but I'm not really interested in starting over at this point either way. I'd rather throttle back the hp and maybe start another build when this one is done due to current situation with warehouse. Need to get the car done and go with smaller, more affordable place or a house and decent garage and no home owner commandos association, and that's tough in Florida.

[SSlowBoat]

So I'm neck deep into the complete rebuild of my blower setup, 383 with forged eagle crank and H-beams, and 2618 Mahle 26cc piston. Cam is xfi lobes 230/236 on 114. Factory vette block with studs. Vortech S trim being upgraded to an experimental Ti trim modified fit an aftermarket scroll large enough to accommodate the impeller. Guesses are in the 1300 cfm range.

Now, the engine builder, very respected and accomplished for high power LS builds these days, as us lt1 guys are becoming relics of the past and all but forgotten, is warning me that my setup going be capable of 7-800 flywheel with the canfield 220 heads (300 cfm, 9:1CR) I was going to use, and that the bottom end, mainly the block, isn't going to hold that for long.

Now I hoping for 600+ to wheels, and would be happy to restrict it to that is need be for longevity, but what are your thoughts here? I've seen many lt1 in the 600 rwhp range, but for how long, and probably with better quality cranks and rods and splayed mains.

I'm not interested in the "you should have done this or that" at this point. Engine is together besides the heads, and he's telling me leave the ported stockers (260cfm, 9.5CR) and the upgraded blower still going to put me in the danger zone power wise. Car is fitted with 31x12x3.5 FMIC and meth this time around.

On another note, I believe if I were to use the S trim on this 383, with either head combination, that blower may actually be too small, especially the canfield heads, and become a restriction. Maybe not so much with ported stockers, but I never saw more than 10psi with those heads and cc305 cam for whatever reason, maybe belt slip with 2.7 pulley, and that was only 350 ci.

Engine builder suggesting the same thing everyone else says "should have went LS". Had I known where I'd end up today, I might have built a dart block, but I'm not really interested in starting over at this point either way. I'd rather throttle back the hp and maybe start another build when this one is done due to current situation with warehouse. Need to get the car done and go with smaller, more affordable place or a house and decent garage and no home owner commandos association, and that's tough in Florida.

It will handle that....what the hell is he talking about? More than one person on factory blocks handling that and some more. If you're scared, do a half fill and some billet main caps.

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[Catmaigne]

Assuming the rods are 4340 and the pistons aren't heavy as hell (unlikely with current mahles), I wouldn't worry about it. The biggest drawback is the factory main caps because they are brittle iron, but the 4-bolts are generally thicker near the bearing and your studs should prevent them from walking within the rpm range of your cam. If you were spinning high with a larger cam, I could see the caps becoming an issue. Don't think there are any limitations other than that, there have been guys with 4 digit fwhp #s using a factory 4 bolt block with steel caps.

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[blown383ta]

Assuming the rods are 4340 and the pistons aren't heavy as hell (unlikely with current mahles), I wouldn't worry about it. The biggest drawback is the factory main caps because they are brittle iron, but the 4-bolts are generally thicker near the bearing and your studs should prevent them from walking within the rpm range of your cam. If you were spinning high with a larger cam, I could see the caps becoming an issue. Don't think there are any limitations other than that, there have been guys with 4 digit fwhp #s using a factory 4 bolt block with steel caps.

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Yeah, good point on the rpm range. I forgot to mention I dont plan on spinning this past 6500 the way its set up. Cam is 114
+4 and I was planning on going bigger crank pulley to avoid belt slip and attempt to max the blower rpm by 6300 shift points. I have a few pulleys so I could spin it slower if necessary to bring the hp down, but I think my goals are modest and fairly on point with other builds results.

[firebird_1995]

I made 625 to the tires on a factory 4 bolt main block with no steel caps. It was on my 383 d1sc setup. Man I miss the procharger....

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[Injuneer]

2001 George Baxter made 1,125 flywheel HP on a 383ci, Vortech S/C, stock straight 4-bolt mains, not sure but I think Pro-Gram caps, and I know no fill. Routinely exceeded 7,000 RPM (MoTeC engine management system, with Opti as cam position sensor). Callies Stealth crank, Oliver billet rods, (I think) BME 2618-T16 pistons, Canfield heads, LT1 intake. Close to 4,000# 97 Camaro convertible ran 9.04 @ 155.3.

When he decided to go go bigger and run in the NMRA Vortech Xtreme Street series, he pulled the LT1 block. It was in excellent condition, and was sold to someone who wanted to build a high HP nitrous motor. Second Street claimed the LT1 block had many of the strength features of the Bowtie block, and claimed since the LT1 block was designed for the straight bolts, that's where the meat was. Not sure why they followed my instructions for a splayed setup if that was the case.

[blown383ta]

Thanks for the input guys, but the real question, which I understand is a best guess upon many factors involved, is, what is a safe limit? I think 500 like the builder is saying is just to cover his butt. Of course none of us will disagree 500 is completely safe and daily driveable. This is not a daily driver, its my toy. That being said, I drive it hard every time I get in it. Probably equivalent of 1/4 mile runs cause thats where I playon the street. I dont do much highway long pulls to 150+ mph. I do however dog my vehicle on a regular basis from 0-100 or better, in mexico of course. I really wanted the added deck thickness of the canfields, and I guess I could stick with the S trim, but Im afraid at 1000cfm its going to be somewhat of a restriction, and if Im not making 15 psi i really dont need 9:1 CR either. Or, I do the upgraded blower with the stock ported heads at 9.5:1 and limit the boost to 12? Either way, I feel my goal of 600 whp might be pushing it for long term durability, but I dont know how long is long as hard as i drive it. Honestly if i get 30k miles out of it Id be happy

[SSlowBoat]

Thanks for the input guys, but the real question, which I understand is a best guess upon many factors involved, is, what is a safe limit? I think 500 like the builder is saying is just to cover his butt. Of course none of us will disagree 500 is completely safe and daily driveable. This is not a daily driver, its my toy. That being said, I drive it hard every time I get in it. Probably equivalent of 1/4 mile runs cause thats where I playon the street. I dont do much highway long pulls to 150+ mph. I do however dog my vehicle on a regular basis from 0-100 or better, in mexico of course. I really wanted the added deck thickness of the canfields, and I guess I could stick with the S trim, but Im afraid at 1000cfm its going to be somewhat of a restriction, and if Im not making 15 psi i really dont need 9:1 CR either. Or, I do the upgraded blower with the stock ported heads at 9.5:1 and limit the boost to 12? Either way, I feel my goal of 600 whp might be pushing it for long term durability, but I dont know how long is long as hard as i drive it. Honestly if i get 30k miles out of it Id be happy

If you build it right, it will survive. That's why ellwein built @Ltconvert boost built forged 383. Stock ported heads. Upgrading to trickflow 21 degree ported. Car is 100% a street car, built for burnouts and quick pulls. It's a splayed 4 bolt block, used cola crank, callies rod and wiseco pistons. but no reason yours shouldn't survive if its built right. I've never heard of canfield heads, what's the advantage to them?

At 30k miles expect to change valve springs and some small other things, consider it maintenance work.

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[firebird_1995]

Couple things I'll add...
If all you're looking for is 600 to the tires, the ported stock heads will be fine. On my current setup (355, 88mm turbo) I run a set of edelbrock performer heads that don't flow much better than unported stock heads and make around 700 to the tire (estimated by mph in the 1/4 mile) at around 16# of boost. When you are pushing the air in, the only thing a lesser flowing head will do is make the turbo/blower work harder to make power. Eventually you will get out of the efficiency range that the compressor is capable of and that's where you'll see guys that pick up more power at the same boost level, or same power with less boost when going to better heads. I'm not familiar with what that vortech unit is capable of so I can't give you an apples to apples comparison but on my d1sc I was running a 7.5" crank pulley and a 2.75" blower pulley. That setup made 625 at the tire with a 383.
If it were me and I had the Canfield heads, I would run them and the upgraded blower, turn the boost down and have fun. After that gets old, turn it up. It's much easier to turn down the power on an over capable setup vs trying to squeeze everything out of an less than optimal setup.

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[Catmaigne]

The S-trim should get you to 600 at the tire reliably but you will have no headroom beyond that. It is similar in power capability to a P1SC and will be maxed out pretty quickly on a 383 with monster heads. If your blower was any larger and your cam was any bigger then I'd be concerned, but the current setup sounds fine for the studded stock 4-bolt mains. I wouldn't worry about it. The only reason you don't hear more about guys using stock 4-bolt caps is because a stock vette block is a rarity. Your builder doesn't sound too familiar with the platform and I don't blame him for wanting to be conservative.

There was a guy over on LS1tech who made just shy of 800whp on a stock 2-bolt shortblock (down to the main/rod bolts). He was at 5k+ feet so the correction factor was huge, but it still made a true 660hp on the rollers. The secret was to keep the revs low, high power + rpm is killer with a heavy rotating assembly.