Engine performance problems

[Tepot]

He's not just having dyno porblerms , there are other issues ...
I think the 400 block is a fine solution - apart from the go fast bolt on stuff - he has 50+ cubes extra and will get a lot more low end grunt...
My advice is to use a new cam and lifters in that set up , 400 hp and a huge bump in torque is easy...

I was thinking maybe I should go with the comp cam 270 since everyone said there was no problem with Vaccum. I don't want to go too big and then starting to have break booster problems and problems with light not being able to go up anymore.

 

[Tepot]

Sounds like an extreme solution for what could be a minor problem. Did you look at your ignition? The first generation Pertronix pos are famous for erratic ignition (right before they die and leave you stranded)

I know it sounds extreme with that solution, but you know what. Since I've had the car, I've been dumping a bit of money every year to get that extra power. and It seems that everything I do is not helping at all. By now I should be closer to 400HP at the crank. But instead I'm going down.

So I'm so tired to put money into this engine and never see results that I'm thinking. The hell with this, let's build a 406 and use my existing new parts so I don't loose my money and then get what I've always deserved. A well working beast with lots of power.

 

[glen242]

Tepot:

How do you like these numbers?

Stock '74 L-48 = 195 HP (Net engine)

Stock RWHP allowing for 15% drive train loss = 165

You have 225 RWHP on the dyno = 60 RWHP over stock. This seems about right.

I had similar numbers on my 350 using about the same parts as you.

I now have a 383 in my '76. No dyno numbers yet as I am working on the suspension and steering. Dyno run next year for sure!

BTW, you cannot get 225 RWHP from a stock L-48, so your base line was not correct.

 

[Evolution1980]

Your response to Mikey about the ignition...

I know it sounds extreme with that solution, but you know what. Since I've had the car, I've been dumping a bit of money every year to get that extra power. and It seems that everything I do is not helping at all. By now I should be closer to 400HP at the crank. But instead I'm going down.
So I'm so tired to put money into this engine and never see results that I'm thinking. The hell with this, let's build a 406 and use my existing new parts so I don't loose my money and then get what I've always deserved.

It would somewhat seem that you are missing Mikey's point. If you have a shoddy ignition system and "move all your existing new parts" to the new engine, you might be carrying over the problem. You should really make sure that you eliminate the ignition as a problem otherwise you're possibly going to continue to waste more time and more money. You'll have a newer engine and still be scratching your head while everyone except you is getting paid for their time and services.

This is somewhat a rhetorical question, but you do realize what the ignition/distributor does for the engine...?

In other news...you're essentially learning what most people learn when they decide to build up an older OEM engine: "It's cheaper and less hassle in the long run to just buy a crate engine and be done with it." If it wasn't, crate engines wouldn't be as popular as they are.

 

[Vettehead Mikey]

The new engine they're building might be capable of 400hp, but I'd be surprised. In any event, that would be gross HP at the crank. What are they telling you to expect as rear wheel HP?

 

[Tepot]

Tepot:

How do you like these numbers?

Stock '74 L-48 = 195 HP (Net engine)

Stock RWHP allowing for 15% drive train loss = 165

You have 225 RWHP on the dyno = 60 RWHP over stock. This seems about right.

I had similar numbers on my 350 using about the same parts as you.

I now have a 383 in my '76. No dyno numbers yet as I am working on the suspension and steering. Dyno run next year for sure!

BTW, you cannot get 225 RWHP from a stock L-48, so your base line was not correct.

The base line I gave you was without the heads, But I already had the cam shaft, intake, carb, headers, etc... so my baseline was 225 RWHP before i've swapped the heads. So the heads should've made a difference.

I know I started with 195 HP but that was before the cam shaft, headers, carb, intake etc. The 225 RWHP was the results of all these mods with the stock heads of the L-48. That's why i'm wondering how come the new heads didn't bring the number up.

 

[Tepot]

Your response to Mikey about the ignition...It would somewhat seem that you are missing Mikey's point. If you have a shoddy ignition system and "move all your existing new parts" to the new engine, you might be carrying over the problem. You should really make sure that you eliminate the ignition as a problem otherwise you're possibly going to continue to waste more time and more money. You'll have a newer engine and still be scratching your head while everyone except you is getting paid for their time and services.

This is somewhat a rhetorical question, but you do realize what the ignition/distributor does for the engine...?

In other news...you're essentially learning what most people learn when they decide to build up an older OEM engine: "It's cheaper and less hassle in the long run to just buy a crate engine and be done with it." If it wasn't, crate engines wouldn't be as popular as they are.

Well don't worry, if I build another engine using my parts. There is a new MSD distributor and ingnition box going on that one for sure

 

[Tepot]

The new engine they're building might be capable of 400hp, but I'd be surprised. In any event, that would be gross HP at the crank. What are they telling you to expect as rear wheel HP?

yes you are right, The engine they are building me will be close to 400HP but this would be at the crank. If I'm getting anything close to 300 RWHP , I think I'll be happy with that. Also the torque this engine is supposely capable of creating is alot better than a 350 could give me. So both way I'm winning.