KNOT-HEAD

I have a matching number 77, L82. I removed the engine and replaced it with a beefed up 350 ci engine but I need help trying to figure out how much more horse power it will have over the original engine without having it put on a Dynamometer. Can anyone give me a rough idea based on the parts installed in the engine? Please read the attached parts list.

73racevette

Not really anyway to answer this with the info you gave. Without knowing the compression ratio and the specific cam info (could look this up) it could be just about anything. With that said, assuming a decent build, I would guess around 1hp/CI is a pretty normal amount these days. That would put your 350 engine at something in the neighborhood of 350-380 HP. That would put your new engine somewhere in the 150 hp more than stock range.

All of this is a complete SWAG though with no more info than what you have given.

jim2527

Probably real close.... http://www.compcams.com/Company/CC/c...?csid=108&sb=2
Lift .489 .476
Dur @ 50 235 249
DCR should be decent with that 67 abdc intake closing

KNOT-HEAD

Thank you for your help. I asked around the office after giving them the Comp Mother Thump-er cam specs and they seemed to think it would be in the neighborhood of 420 hp. That falls in line with your evaluation. I'm confused about the statement you made concerning the original 350 L82 engine. The specs on the car list the L82 as 220 hp not in a range of 350-380 as you quoted. I know the new engine has a great deal more power. You can tell the difference just standing behind the car and feeling the amount of pressure that comes out of the exhaust... it's nice!!!! The Mother Thump-er can us more of a "show" cam compared to the "Thump-er". I will dig up the cam and any other specs i have on file and post them. Maybe that will help with the rating.

Thanks again
ddhebert

73racevette

I quoted around "150 hp more than stock". That 150 + 220 is in the neighborhood of the 350-380 I posted for your new engine.

KNOT-HEAD

Thank you again. I miss understood the way you totaled the horsepower. I was hoping the 420 hp guess was going to be what I had. 350-380 is MUCH better than the original 220.

mobird

I'd be VERY surprised if your motor is making much more than 300 with those heads. Stock, those heads barely flow 200 CFM, so they would take some pretty significant porting to even get up to Vortec-level flow. Heads and cam is where the power is made, you have a decent cam, but those heads are choking the motor (assuming they haven't had SIGNIFICANT port work to open them up)

lars

[QUOTE=ddhebert;1597791395]they seemed to think it would be in the neighborhood of 420 hp. /QUOTE]

Not a chance. With those heads and cam, you're maybe in the 320 - 350 range on a good day. I've dyno'd engines with the ****** Thumper cams, and that cam design gives up a a lot of potential power for the benefit of the sound. Combined with the low flow on those heads, getting power over the 300 mark would be pushing it.

Lars

Edit: I just saw mobird's post, and I think he's closer to the truth...

KNOT-HEAD

Thanks. I have documentation of the head work. I will post it once I find the information. Do you think it would be better to take the L82 heads off my old engine and put them on the new one?

derekderek

No. Vortec or better. AFR, Brodix, Patriot (whatever they are called these days.)

Vette5311

Very hard to beat the Vortec with the guides cut down for a bigger cam, especially for the price. When cutting the guides put the new springs on at the same time and your ready to go.

Sigforty

It is real hard to give you a good figure. I didn't see part numbers on that list. Part numbers could help with a better guess, but it still will only be a guess. Who did the head work? If the person knew what they were doing it could be an improvement. If they didn't know what they were doing the heads could be worse than before the work. I see you are in Sorrento, LA. There are quite a few chassis dynometers in the BR area. I would suggest waiting for a dyno day where you can put it on one and get 3 pulls for $50 range.

cagotzmann

Take it to your local drag strip, have fun and post your times. Your fastest MPH after a 1/4 mile will show how it compares to stock. Much cheaper than a dyno and you can have a little fun at the same time.

MotorHead

300hp

mobird

What's your budget?

Vortec heads can be had for around $500, they should be a decent improvement.

If you are going to go for aluminum heads, my vote is for the Jegs re-branded Profilers. They are $999 for the pair at Jegs, and they flow nearly the same as AFR heads of similar runner size. Those heads would be capable of getting you over the 400hp mark, though I would reccomend a different camshaft "while you're at it".

KNOT-HEAD

Thanks guys. It seems, all bets are off concerning the beefed up engine I just bought. I finally found a mechanic shop that is knowledgeable about vintage cars. They are basically reworking everything that has previously been done to the car by the four so called mechanics I have had work on it. The last and worst thing is the new beefed up engine I bought from a private individual off of Craigslist was was poorly put together. I paid the person I bought it from to install it and that was an even worse mistake. Bottom line is the new crank shaft drifts about 1/4" after the engine has warmed up. The heads were supposed to have been reworked but when we pulled them we found they had not, also, the rocker arm mounting studs threads have been stripped so a stud puller may not work on removing them so they can be replaced. There are large gouges in one of the cylinder walls. It seem as though some metal fragments were left in the cylinder before the heads were installed or possibly a part of the valve or stripped off fragments from the rocker arm mounting studs fell in to the cylinder. Either way we have to start over from scratch. I brought my original matching number L82 engine to the shop with the intentions of swapping the high performance parts (approximately $1,800.00 worth) that were installed in the "junk" engine into it. Hopefully that engine is still strong enough to take the new Mother Thumper cam and matching valve springs. I also found a used 700r4 transmission to install in the car and had it re-worked bu a professional transmission shop. Hopefully that will not be a mistake too.

mobird

What are these supposed "High performance parts" that were on that junk motor? Sounds like that motor wasn't worth much more than the scrap metal weight.

pauldana

What I was going to say... ^^^^^^this^^^^ 300

zmanabba

It's your car but something that has been said but for some reason you haven't acknowledged. YOU NEED TO DITCH YOUR ****** THUMPER CAM. You are leaving power on the table. Those cams are designed to impress posers that value sound over real power. I get that money is tight and this is an unexpected expense. We have all been there. It's entirely possible to reach your 420 horsepower goal, with the right head/cam combo. Not with what you have. Good luck with whatever you decide

KNOT-HEAD

So far it looks like I've been taken for a long ride on a short bridge. I was given some documentation on the parts that were supposed to have been installed. I guess we will see once the engine has been dismantled.
ddhebert