65 fi

I have a 1970 LT1 engine. I would like to stay with an original LT1 cam and Holley 750 carb. Can I bring this engine' horsepower up 475-500 without changing the carb and cam?

John S 1961

not without changing everything! why are you so in love with the cam? the carb ought to do it.

65 fi

Alright, how about keeping the carb?

dugsgms74

I think the carb is up to the challenge, not so sure about the cam and heads.

65tripleblack

The carb is good for 500 HP, and so is the intake, but the intake must be ported to get more than about 450 HP.

Must use headers into very low restriction mufflers.

The heads are good for about 440 HP if you port them fully. I ported mine to 183cc and got about 440 out of my 327. But I had .610 lift.

The cam doesn't have enough lift. If you port the heads as I did, then you can install 1.6:1 rocker arms which will probably get you to around 420 with that cam. If you want "old school" then the 30-30 cam will get you slightly less torque but more power.

If you want 475-500 HP, from 350 cubic inches then it is essential for you to use a high lift roller cam.

65 fi

This is really good information. Maybe the thing to do is lower my expectations and just use the LT1 cam. I would like the sound to be similar to the original but would like to see additional power.

Crunch527

I'd look at an aluminum AFR head and cam combo...I don't think it's worth the effort to fool with porting the LT1 heads and then still not hardly get there...can you get an RPM manifold under the hood? That would help as well.

Cheers,

Frank

Kerrmudgeon

You should be paying more attention to things like reliability and servicing instead of playing with numbers. If you want that much out of a small block you will have to tinker with it all the time. And be ready for other stuff to start breaking with that much power. The stock LT1 will give you all the 'seat of the pants' excitement you can handle, and even it requires solid lifter adjustments regularly.
You could put a roller cam and rockers in those heads. Port and polish the heads, add some full length headers, and have reliability AND LOTS of excitement (power) when you mash that pedal.

65 fi

Yeah, probably a little over regarding expectations. Thank you all for shining the light of reason.

MidShark

Also, what are you going to run for a tranny and rear end gears? I had a '71 LT-1 that was rebuilt with the stock flat top pistons for that year, a little mild head porting, stock LT-1 cam, and it dynoed at 385 hp (cant remember the torque). I had a close ratio M-21 and the original owner had opted for the 3.55 economy gears . The car was a little bit of a dog until I changed it out to 4.11s. Then it was a really fun car. Night and day difference.

uxojerry

I would contact Mark Jones at vortecpro to find out what can be had out of your LT1 and what it would cost. My guess would be 450ish hp with headers.

Much would depend on your budget and there are probably cheaper routes to more hp. Ive found myself more interested in nostalgia rebuilds.

I mention Mark Jones because he recently did a nostalgia sbc 327 and got low 400hp using stock parts. He ports a lot of steel where most are into aluminum, lol.

MikeM

Jack the heads, intake and carb up and run a 400 SB/short block under them. Recurve the distributor, richen the carb up a little. You'll get quite a boost and keep reliability.

Best bang for the buck.

65tripleblack

Explain your concept of "power". It is probable that it's not the same as mine, or the same as that of any other mechanical engineer. Power production of an engine is mainly limited by the flow restriction in the heads. More cubic inches will mean more low speed torque, but your engine's power production will not change.

With 1,000,000,000 cubic inches, your engine will produce earth tilting torque at low speeds. It will still produce equivalent power to a 350 cu-in engine at higher speeds. Power is directly proportional to the ability of the engine's throughput of intake/exhaust gases, which directly correlates to maximum developed cylinder pressure.

The cheap and easy way to get more torque (ie: low/midrange acceleration) is to increase engine displacement. The more expensive way to more engine power (high speed acceleration force) is to increase engine throughput.

jimgessner

Look at the ''Kerrmudgeon'' avatar. Would you modify this? I don't think so. Some times it is best to leave it alone.

Go find a race car and build it anyway you want.

SEE BELOW. Kerrmudgeon, you be the man !!

65 fi

Explain my concept of power? Really?
Okay, improved low end torque and exhilarating acceleration up to somewhere around 90mph to 120mph.
I know the 1970 LT1 was a very strong engine but as it compares to the new LS and LT engines it gets left behind.
As Jim Gessner has pointed out, with appropriate referencing, I should just leave it alone and enjoy it for what it is.

SI67

Not according to Edelbrock's notes: Will not fit under stock Corvette hood.

Maybe with a big-block hood?

Steve

Crunch527

Yeah...for some reason I locked on to the LT1 aspect and was thinking about the LT1 hood style...I have used the RPM Air Gap under a stinger hood with no issues.

Cheers,

Frank