I'm doing a rebuild on mt '72 LT-1 engine. I have one incorrect head (which I am going to find a replacement), but am thinking of getting a bit more punch. I will keep the stock heads on the shelf and putting on Dart Pro aluminum heads with a roller cam. Anyone here ever done the same? I plan to keep the same intake and Holley carb so that it looks much the same externally.

 

IMHO, I would shift the discussion to a completely fresh build and leave your entire LT-1 on the stand. If you're going to start beating on it, you sure as heck don't want to scrap the numbers-matching block...

 

I started down that road a few years ago. I took my 72 LT1 and installed headers on it. Then a different cam. Then AFR heads. Then a new intake and carb. Now it is a solid roller cammed 385 ci forged bottom end with new AFR 210 heads and fuel injection. It is a long expensive road. HP is a drug and there is never enough of it.

Yes a cam and heads will really wake up the LT1. I hope headers and good exhaust are part of it, they need to breathe. The stock manifolds and exhaust don't flow enough.

 

My name is Gordon and I'm a power-aholic

HI, GORDON!

My name is Bill, and I'm a power-aholic

HI, BILL!

This little trouble is what got me into aircraft ;-)

 

It has headers and side pipes. Since the engine has been gone through before, it is not perfectly stock. It has pop-ups and one head with the wrong casting number. I am working on getting the right head, but figured to take my time hitting swap meets and put it on the shelf. Everything could be brought back stock if someone wanted to do so. No body mods or such. But I want more power while still having it look basically stock if you pop the hood. Just my thing.

 

I love stock looking engines that are "sleepers" - I'm just encouraging you to consider that if the block goes, so does a significant portion of the value of your car. Blocks are cheap, and even decent shortblocks are relatively cheap...

'nuff said.

With a 350, I'd tend towards a 180cc or max 195cc head. If you really want a stock look, consider going with a set of Dart/World Products iron heads and spending a little porting money on them. Matched with a roller cam, that'll get you in the ballpark. Note that roller rockers aren't going to fit under the stock valve covers, so you'll be looking at getting a set of aftermarket knock-offs, cutting the drippers and putting on a spacer.

The LT-1 intake is a pretty decent high-rise dual-plane; I still have one of them on the shelf myself. But it is a significant limiting factor on the heads, especially something like an AFR.

 

I like what you said except for 2 parts, I ran 12.60@113MPH in my 72 LT-1 Vette with a factory intake and ported 65FI exhaust manifolds. Admittedly this motor had a roller cam but, the factory intake is a decent piece and can get the car down the track pretty well. The Edelbrock Performer RPM sowed less than a 6HP gain over my factory intake in dyno testing and I like stock appearing motors so I went with the GM hi-rise in my final combination.

I fit roller rockers under LT-1 aluminum valve covers all the time, I have to crush the oil baffles to clear rocker bodies (just a slight amount of crush.) The rollers will fit if you measure rocker heigths and cut down the polylock nuts about 0.200-0.250" and also make sure the set screws are the proper length after shortening the nuts. The covers will clear on most cams under 0.600" lift. You will have to find a set of 1969 covers without the drippers or cut them off to clear the roller rockers (can be done with a Dremel tool and cut-off wheel at home.)

When I put a set of Hooker Super Comp headers on the same motor with 4.56 gears, the same GM intake went 12.28@117MPH but, no longer looked like a sleeper (HP gain from headers alone, around 25HP, torque gain WAY MORE through the entire range, about 35ft/lbs at it's peak just from headers.) That carb on both motors was a re-worked "swap meet special" Holley #4777 650DP with a milled off choke horn and casting polishing by Dremel tool, many would say it was too small but, in track testing against a 750DP the 60ft time went off while the MPH went up 1.5MPH but, because the Vette is mainly an autocross car, I went with the throttle response of the 650DP.

Yes it takes some work but when someone freeks out at the fast Vette at the drags and you say, "I think it's pretty stock inside, it's just one of the better running ones they made" that right there is PRICELESS!

 

There is nothing 'special' about the LT-1 block except the 4-bolt mains. If you go to build it up for power, most the other components in the engine will be replaced and you will then be wearing out a decent LT-1 block.

Do the sensible thing: save the LT-1 engine and, thereby, maintain the intrinsic value of your car. You can buy a crate engine or build one with another block [with 4-bolt mains] for a little more money and not risk the integrity of your 'original' engine. Then you can have a ball with the new power and sleep better at night that you didn't do something "dumb".

 

I don't take my Vette on the track. I do enjoy getting on it every so often, though. Most of my miles are long runs with the club. It's just that my '63 looks much less like a performer, but would have blown the doors off my '72. I don't want a "no go showboat." I had though about dropping in a crate, but having an LT-1 without an LT-1 is not for me. Yeah, I know that things like a roller cam make it technically not an LT-1 anymore, but at least it's the same block.

 

I kind of did the same thing about 12 years ago. My 71 LT-1 was worn out. I had the Crane 238/248 solid lifter powermax cam installed with a nice balance job and forged pistons. I'm using better flowing heads and 1.6 roller tipped rockers, hedman headers with 2.5 duals. aluminum flywheel 3.55 rear gears. It's probably a true 400 or so hp and really runs sweet. I used to put on about 10K miles a year

 

Thanks for the info. Lt1er, what heads are you using?

 

This was 12 years ago. I went with 200cc world products with 2.055 intake Manley race flow valves. I would go with the more modern Darts and aluminum if you have the money.

http://www.dartheads.com/products/ai...itfile_id/113/

 

No pushback on the manifold in general; I noted that it was 'pretty decent' and I agree - but it appears that you were running stock heads (?) and as I noted the limitations don't really show up until you get a better set of heads.

My thoughts on the covers was based on the thought that he wouldn't want to cut up a set of factory original covers.

 

These castings here are like the heads I had on my 72 LT-1 but, these belong to my wife and are going on her 70 LT-1. Heads are 492 castings, 2.05int/1.6ehx Manley "severe duty" Sstl valves, pretty good porting job, proper chamber work (flow is around 235CFM@28" intake, 195CFM exhaust based on data from my previous efforts in "improving" factory castings)

While they cost more than a new set of RHS or Dart heads (if you can't do the work yourself), they look right on a "stock" LT-1. The heads will have stock valve covers hiding all the good hardware below: Comp Cams Pro Magnum roller rockers, 7/16 studes, Beehive springs, tool steel retainers, ect.

Intake runner size is around 175cc of volume with full porting job, they could be made bigger but the Chevy hi-rise intake flange is pretty thin above the intake runners and going to a #1205 Fel Pro intake gasket size won't really help the flow, it will just kill port velocity (whats he talking about?) and increase the chances of getting a gasket leak.

I think any cylinder head runner over about 180cc on the intake side is getting too big for a street driven 350cu/in Chevy but, what do I know about building motors

 

Here is the shortblock the 492 heads on top of, like other poster says "nothing special about an LT-1" this motor has Manley 5.85 rods (why longer, because I bought them used for $250 thats why), stock LT-1 1182 crank (it's Tuftridded by GM only LT-1 and HD truck 350's had these cranks, nothing special), Mahle 383 forged pistons (again another "sale item" and they have right compression heigth for my 5.85 rod 355 motor), Melling "M select" oil pump (std volume high pressure spring installed, pump housing deburred and ported because I like to do that kind of thing in my spare time), Cloyes true roller chain, Billet timing gears, Ultradyne flat tappet cam, AC Delco "585" edge orifice lifters in grooved lifter bores (my stock on these is getting low!) New harmonic balancer, and a lot of EFFING grinding/detailing of engine block/oil passages by yours trully (let's just say, I'm not a "crate motor" type of guy.)

Anyone want to run their sub $3500"crate motor" against my sub $3500 355 Chebbie? I'll even let you bring out your 383 motors

 

Eric,

You THE MAN!!!!

Regards from Down Under

aussiejohn

 

Okay, here's what I'm thinking:
Original block with flat tops
Dart Pro 1 heads
Edelbrock Rollin Thunder roller cam kit
Summit roller rockers

I figure I should get about 10:1 and a power range of 1500-6500

I know it's not cheap, but I don't plan on doing this again.
Am I nuts?

 

One thing to think about when building motors is the $$ per hp. It's very easy to get over $1000 in the cam, lifters, pushrods, timing set, and a roller button or some special timing cover and with only 355 ci lets say that going from a solid to a roller nets you 20 hp in a sub 7000 rpm motor.

Lets call it $50 per one measly hp. The same $1000 can buy you a great set of headers and dual free flowing exhaust or .............

 

Got headers and sidepipes. i know sidepipes are not as efficient as Flowmasters and such, but they look and sound great.

With the oil we have now, a roller cam is insurance as well. I also got different opinions on horsepower increase, much higher.

 

DO NOT! I repeat DO NOT! buy any cams from Edelbrock, they are just repackaged Melling camshafts maked up double.

Do buy cams from Comp, Bullet (my favorite brand), Lunati, Isky, Crower, Crane or one that your local automotive machinist reccomends (that same machinist can look up the specs on a Edelbrock cam, order it from Melling and sell it to you at about 1/2 the cost you'll pay to Vic for his fancy packaging if you really want 10-20 year old lobe designs in your motor.)

PM me if you need help picking out a cam for your LT-1. Sounds simular to what I built for my wife's 70 Vette.