Thread: Easy HP for my 454 vette

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I have a 74 corvette with a 270 HP 454 right now. I want to get a little more power out of it without pulling the motor. The guy I bought it from just put a new cam in it and I hate to tear into it now. I just wanted some ideas on how to get more outta this motor. It's stock now,and I think the cam the guy put in is a mild one,maybe stock also.He was a stickler for not modifying anything at all because he felt it would effect the value of the car. What can I do ? Intake? Carb? Heads? Can I get 400 with bolt on parts?Any advice would be appreciated. I have ideas but some of you guys do a lot more of these than I ever will! Thanks, Mike...

The biggest deficiency those 70's vettes had was the compression ratio. The only way to raise the compression ratio without pulling the motor would be new heads. Look for some closed chamber heads or some similar aftermarket pieces, try to get your ratio up around 9.5:1. That could get you in the 400+ hp range if coupled with the right cam. Of course, you will have to change the manifold and intake to match the heads and cam. That Qjet flows 750+ cfm, but a lot of people prefer to go with the Holley or Carter. They may make a little more hp with better throttle response, but who cares about that with gas prices as they are.

I kinda like the idea of the mild cam coupled with the higher compression ratio, so if I leave the cam alone and just replace the heads ,intake and carb.That should boost the power and still not spoil the driveability? I want it to run smooth, not that big cam shaking and popping . This is not a race car but the power, or lack there of, is rediculas right now. I would pull the motor if absolutely necc. but I was hoping I could get away without it ,at least for now. Are those heads readily available? I think the intake and carb will be "no problem". The other thing, this car has tons of torque which is nice, a real stump puller ya know.I'm just torn about which to do??? Thanks... Mike

just get a mild cam, not somthing with a huge lope to it. Heads are available aftermarket for around 1,500 a set depending on what you get. Trick flow has a nice set that is 1,995.95 assembled that would be good for what you want, there summit part number tfs-41300001 if you wanted to look.

Im not sure what pistons went in the corvette engines, but I'll bet they were flat tops, and even if you bought a good set of heads, they are still pretty large in chamber volume....changing the heads alone would be your biggest power adder, but without boosting your compression ratio, it's kinda wasted money. Try to find out what pistons are in there, and if they are flat top, you can look for a set of GM heads, closed chamber from late sixty's engines...97 to 101 cc's would give you somewhere around 9 to 1 with flat top pistons. That would give you a pretty big increase, and let you use a better cam...bigger cam with low C/R isnt going to work. If you do decide to go with aluminum heads (new), look at Canfield from Competition Products in Wisconsin...they are selling for 1399.00 a pair, assembled, not bare. Go with a mild hydraulic cam, around 224/230 duration at .050, with maybe 112 or 114 LSA, it will idle smoother. Get a Performer intake and use your carb, or get a 750 Holley or Edelbrock vacuum secondary carb, and you'll be there.Dont forget about headers too...

I know you dont want to pull the engine, but it would be much easier that way, plus you can always change pistons that way and know exactly what you have!! (making more work for you!) John

well heck. I was hoping I would hear better news, I really was not in the mood to pull that motor but I will. Just may as well do it right the fisrt time. If i'm gonna do cam and pistons them oh well. The thing is , this motor is guttless now. Absolutely guttless. I gotta do something soon. Mike

Yep, Im sure it's from super low compression. You might as well do it right....but you wont believe the difference!! It will be worth it.

Johnny, have you been studying on your big blocks? Heh sounds like it, your helping people out left and right these days. Looks like you are knowing more about these big blocks! I wish I knew that much on them, like I don't know how to change compression by changing the heads, etc and know what heads will change the compression to 9:1, etc. Your one smart guy that's all I gotta say. But anyways, if you don't pull that engine you will have problems with working on it and wish you did pull it in the end. It may seem like a pain in the ass or something but if you don't do it then wait until you can't get to something and you spend 30 minutes figuring out what to use to get to that bolt or nut or whatever it is. Also you will know what the pistons are and then learn more too while your at it. Now if your a big hot rodder and like to learn more then that's the way to go IMO.
Good luck man!

Using the requested "bolt on" as the base could I suggest a 125hp shot of NO2?

Around $500 gets you a basic kit and 395HP if your 270HP baseline is close. I've gotta believe a low compression big block would accept this without too much protest.

Moving a rung or two up the ladder - Vortech, Paxton, or Powerdyne centrifugal superchargers are still a bolt-on and would work well with the low compression 454. Downside is now we're in the $2,500-$3,000 range for the basics.

With both of these approaches you can unbolt the horsepower when you sell the car - just transfer it to the next one. Just make sure the engine is still is good basic mechanical order.

Regards, Mark

I was thinking of a Pro-Charger for my older 454, stock compression...Only because you dont see many in a Chevelle...most guys go for the normally aspirated route (nothing wrong with that either) but all the plumbing that goes with the supercharger looks so cool! It's just the cost that held me back. It didnt look too bad at first, but by the time I added up all the brackets and add-ons that I needed, I was up over 3K....yes, you can take it with you, but I just didnt have it to spend. Still a good idea though if I hit the lottery.

Hey Shawn, what's up man?? How's ur projects coming? My 496 is history for this year, both blocks I brought him were NG for what I wanted to do, and now Im just gonna build a 468 (stock stroke, .060 over) and use the parts I have....still not bad. Im just a little dissapointed. J

I am pretty good. Bought me a 66 Ford truck for my everyday driver and working on that for now. I am going to lower it soon, fix the engine up a bit, paint it, and a few other small maintanance stuff and then start putting the rest of my money into the 48. So basically the 48 is on hold for another 3 months now. Maybe 2 but it all depends. Anyways, sorry to hear about your engine. But think of it this way, it's better than nothing AND better than what I have. I am still looking for a plain block. Everyone is trying to sell me complete engines for liek 3 grand and I don't have that much money for some plain boring 454. I wan't a block and maybe heads to go with it or something like that. I am not sure anymore on this now. Money is hard for me since I will be going to college soon. I am going to just save a few thousand bucks this summer and then put half away and the other half into the 48 and just keep doing that. It will take me WAY longer to get this thing done then expected. Maybe another year and a half to two years.

I am still deciding what to do but all the ideas sure help. I think I will just pull the motor and see what exactly I have. I found the sheet on this motor and it has 8.25:1 compression ratio.It has tons of torque , like 395 but will hardly spin the tires ,(even when it's wet). I just won't be happy till I have at least 400 HP, more if practical. Still fun to drive tho. Well I'll write down the numbers you gave me Johnny and go from there. The super charger is a neat idea also .Thanks again. see ya. Mike P.S. I'll keep ya posted on how it's going for fun.

with that much torque you should be able to roast the tires from even a 20mph role.... I would do a compression test.... I'll bet the motor is a little tired.... Or is in dire need of a good tune to make it work...

Here is a recipe straight out of the Engine Masters spring 2005 book....

454 big block with forged internals 8.6:1 comp rated 425hp
472 actual hp 500

Edelbrock RPM intake

Test #1 cam XE268H Peak hp 483 @ 5300
Peak tq. 541 @ 3900
Average TQ. 506 3000-5600
Idle vac 15.7 cranking comp 165

this is with 118cc rectangle port heads

test #2 XE274H Peak TQ 538 @ 4000
Peak HP 508 @ 5600
peaks are up +5 and idle vac drops to 12.4"

these were done with a 850 demon carb.....

Low compression like that will be good for a supercharger if you go that path. That right there will add heaps. Throw a good exhaust system on it, air filter, cam, supercharger and some head work and you will telll a HUUUUUUGE difference.

Yeah dude,

I am nowhere near the expertise of others on here BUT, as I read your threads you kept talking about no power and thats not right. Before you go tearing down your motor you need to tune what you got cause your motor right now isnt running worth a shit.

I had an old 77 GMC C1500 pickup with a stock 454 low compression smog engine and even though the HP was low, the torque was great and I would roast those tires all day long with a Quadrajet that only opened the primaries and a burt valve in one of the heads. If you want something smooth and very driveable I would get that carb changed and or rebuilt, check your HEI ...maybe full HEI rebuild with new wires and plugs as well. Get a decent timing light and make sure its timed correctly. After all that I cant imagine the motor not smoking the hell out of those tires even with a 3.08 rear end.Do all that and if none works then my guess is real weak cam or maybe installed incorrectly. My guess right now is that carb is in a bad way right now and your HEI is dying for a complete rebuild ( my last small block I couldnt figure out why was so sluggish, turned out the springs in the HEI were rusted and not letting dist adbvance) If that stock motor is fresh, a decent manifold, well tuned carb and adding some headers you should be having traction problems with that car. My .02