RonBrooksGA

I apologize if this is a newbie question and the answer is a resounding, "NO!" I have a 94 LT1 engine transplanted into a '95 968 Porsche. It sounds great and the car has enough output but I want it to rev higher safely. I would like the car to be able to red line at 7000. If a new engine is balanced will that be safe? Most crate engines I find are 383 strokers. That's fine but I really do not need more than 350hp I'm more interested in higher rpms. I would appreciate any info you may have to help me accomplish this.

Thanks,
Ron B.

hemivett

To get those kinda rpm's safely, you need serious upgrades. IMO. Forged steel crank, Maybe even something with a shorter stroke, if you are planning on running it at that rpm for any length of time. H beam rods, and forged pistons, 11:1. AFR heads, and a complete roller top end. Finding a cam that likes those r's, and will still be streetable is gonna be your biggest challenge. Somebody else will chime in with an answer Im sure. As far as staying around 350hp. That wont happen.

If you want to have your cake and eat it too. You may want to consider selling the LT1, and buying an LS motor. h

cv67

2 valves dont wanna run up high like a 4valve motor willl without supporting mods like the last poster said

The stock bottom end wont handle 7k without puking
Id look into a solid roller myself..dont need anything too huge to hit 7k parts arent cheap and will have to check lash 1-2x a yr depending on how often you drive it. You want a motor that will rev tha will do it.


I see you spending at least 10k easy from start to finish.
Is it really worth it if youre not after power and just want to watch the tach swing?

RonBrooksGA

An LS would definitely be better for what I'm looking to do but that's an entirely different installation and wiring kit. The LT1 is what I have to work with. The engine just sounds so great I wanted to get that higher rpm roar. Spending over $10k would just be crazy. My intention is to have a new engine built for a later installation. From what you guys are saying my money is better spent doing a balanced and blueprinted engine to get things smoother and leave well enough alone. The car is fantastic with the stock output. It's my daily driver and never ceases to put a smile on my face. Thank you for the advice!

5abivt

Just do it ! fill the pan with 8 litres itll keep it full.. just put a huge cam in it and it will rev forever !

Snake.Oiler

If 350hp is all you need, then drop worrying about revving to 7K. Absolutely no need for it. Even if you wanted 400hp, still no need to go to 7000rpm. Drop the idea now before you end up spending more money than you care to. Just my opinion.

Churchkey

Nice ride! Always wanted to drop American muscle in either of the 944's I had.

Suggest exhaust work to get the sound your after. The only way to get the Indy car sound with a V8 is with 180* headers.

Good luck.

STL94LT1

I do short burst to 6500 rpms in my LT1 stock short block nearly everytime I get the car out. But, for a sustained 7000 rpm engine that will hold up, it could be an expensive build.

T. Wayne Nelson

I have a 406, 4340 bottom and rods. I normally shift at around 65/6700 rpm. My rev limiter is set at 6700. I suspect it would rev to 7,000 with cam I have, but I don't go there, ie rev limiter....

leesvet

so, you're looking to spin 7000 just for the sound?

Tom400CFI

This is strange criteria to me...not a build that *I* would pursue, but if this WAS my criteria, I would accomplish it by using a short stroke crank to lower loads on the reciprocating assy. Since you don't need the power, you simply don't need the displacement.
*I'd get a cheap/stock 3" crank (which would give you a 302 CID) -or an even smaller one if available,
*I'd use stock rods, ARP bolts, and cast or hyper pistons for a 3" crank
*I'd throw enough cam at it to get it to go to 7k with what ever heads you have. The better the heads, the less cam you need to reach you 7k goal.
I'd expect it to pull to 7k w/o issues in a street driving environment, BUT if it did take a dump, I wouldn't be too upset, given the budget nature of that build.

OP never said that it had to sustain high RPM. It's a DD...not a race car.

Tom400CFI

True^. Get a SOUNDRACERV8 and save a lot of hassle!

383vett

Horsepower is a function of rpm. It's hard to not go much over 300hp with a motor that revs over 7000. The pushrod smsllblock does not have the inherent rev capabilities of the overhead cam. As stated, maybe play with the exhaust configuration. Supertrapps (if you can get them) have a unique sound. Otherwise a smallblock will always sound like a smallblock.

aboatguy

7K is easy with the right valvetrain here's a shot of my daily driven 355 at a hair over 7100 in my 95. (only the 16 bit data will show rpm over 6375)


I agree with the OP my LT1 sounds sweet at 7K.... stock crank.... 6.0" rods mahle power packs..... and the rotating assembly was balanced.

Top end is spec'd by AI.

BrianCunningham

Not that I build mine for RPM, the bottom end could handle that.

Fully forged 383 with splayed caps.

I'd have to change the valve springs to rev higher.

But that's what the blower is for

93Rubie

The beauty of a SBC is that you do not need HIGH RPMS for HP. 350 is nothing. 450 out of a stock bottom end LT1 is not hard at all, and easily at less than 7K more like 6500 if that.

If you want the sound you need to get a LT5 or go back to a Porsche engine.

That or drop in a 67-69 DZ 302 out of a Camaro. However, you'll be making a LOT more than 350hp.

I question the pursuit of this in the name of noise. Just enjoy it for the SBC it is.

I have the book, How to Build Max-Performance Chevy LT1/LT4 Engines by Myron Cottrell and Eric McClellan, there is builds in the back. Only 3 of the 13 builds go above 7K. Most are from 5700 to 6500 or so. Those 3 builds make 602Hp, 559hp, and 566hp, respectively.

I personally like the 355 w/super charger that makes 580 on 8psi @5800. Same engine with 14psi makes 645@ 5800. ZR-what???
FYI, stock GM block, crank, and heads, properly prepared.

aboatguy

Wow great line "...If you want the sound you need to get a LT5 or go back to a Porsche engine..." Too bad its wrong. Its easy to get the shortblock to stand up to 7K or higher, and a top end to handle revs is not all that exotic either.

Seem like you prefer torque monsters and for the vette I prefer engines that love to rev. I don't know what I'd do with any more torque, my current 355 will smoke/shred the tires at will so I'm lucky to be able to have a wider rpm range in each gear. The good news is we can each enjoy the type of LT1 we want.
Mike

leesvet

I was thinking a cassette or CD whichever the car has....

gerardvg

I have been there and done that, take my advise there is no need for a high rpm in a road car.

I had a AMC Hornet with 351 ford cleveland nascar spec engine that would rev to 8,500 rpm... then a few months later had to repair a dropped valve.
The valve collets wear heaps at those rpm with big valves needed replacement every 3 months, then you have the maximum piston speed issue. You will wear the bores heaps past 7,000 rpm. (in Australia the AMC Hornets only came in 6cycl there were kits available to fit the ford engines)

Now years later i have a Corvette with roughly the same horsepower at way lower rpm, i ran 8 psi boost thru the original 350 chev for more than 6 years, just recently installed a 383 chevy with forged steel crank, rods and forged pistons. This is so it can handle more boost no need for high rpm. I have a mountain of torque from idle onwards no hard start lag no misbehaving engine, your mother could drive a blown vette just depends on how much you press the accelerator as to how much of a shock she will get. Never need to do more than just touch the accelerator to blow away any competition.
If you are game enough she will safely spin high rpm, but with a linear h/p increase with boost/rpm. You will loose traction well before reaching the rpm you are talking about.

Leave the high rpm to Nascar, and build a torque monster that will be ready for anything at any time without lag hard starting or misbehaving on the street.

vetteoz

But it had a solid flat-tappet cam with 254/254 duration that didn't come in until 4K ; great for a DD
It revved like hell but was a pig of a road car given it was only built so GM could go road racing

In practical application, the crossram intake system added notable power in the upper rpm ranges,
which was exactly what was needed on the race track. However, with its huge common plenum design,
the crossram intake made the 302's already-lacking low-end torque situation even worse.
Not a problem on the track where the engines seldom saw the low side of 5000 rpm, but definitely not ideal for street use.

Even in stock form, the 302's lack of low-end torque often made for somewhat labored street manners under
less spirited driving conditions. A wide-ratio 4-speed transmission was a welcome addition behind many 302's,
as were rear end gears well into the 4-series range and beyond.
Excellent for racing, not-so-hot for daily commuting. Road trips?
Only for the bravest of the brave. In the simplest of terms, a 302 needed to rev to do its thing.