4.9L Cadillac Information (Page 7/11)
Johns 4.9 AUG 18, 11:40 AM
I like the Allante lower manifold. I have used it for my supercharger build as well as my fuel injection set up. This engine has the big valve heads and 180 degree headers with duals.
Cheers
Reborn756 AUG 18, 11:52 AM
Howdy John! I've been on your website a time or two. How much power do you estimate that critter is putting out?

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- Darryl

Johns 4.9 AUG 18, 12:43 PM
Hey Darryl,
Thank you for visiting my website. Estimating horsepower is a touchy subject. I hate throwing numbers out there. But my engines are built for road racing and autocross. I am more in to great handling and braking then I am about quarter mile speeds. So the square bore and stroke, 3.62, of these engines is never going to see high horsepower and high revs over 6200. The 4.9 engines is a good choice for a sports car but really not much of a dragster engine. So if your concerns are quick quarter mile speeds, you are better off with a different engine. But for handling and spirited driving, I like the torque and light weight of the 4.9 engine.
Cheers,
John
Reborn756 AUG 18, 01:06 PM
That's exactly what I'm looking for John, and also why I was looking towards the 4.9L as my first choice. I keep asking about power because, as someone from a drag racing family, power's always been my main metric. Let me specify a little more so i sound more reasonable: I'm only hoping for between 300-400hp max. I assume 300 is doable, only 100 more than the stock rating.

Thanks for the info so far!

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- Darryl

Johns 4.9 AUG 18, 01:16 PM
I think 300 hp is the top power possible being normally aspirated. You 400 hp goals would have to be a boosted engine. But I'm working on that also with a boosted 4.5 engine. The 4.5 has a shorter stroke and lighter crankshaft then the 4.9 and has the potential for more revs than the 4.9 engine.
John
Reborn756 AUG 18, 02:47 PM
That's good to know! I wouldn't mind a turbo, providing the engine could handle the boost without sending the rods into orbit, but on the same side of the coin the added weight of a proper turbo setup is something I'd like to avoid. Keep the car light and it ought to corner better.

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- Darryl

Raydar AUG 18, 03:18 PM

quote
Originally posted by Reborn756:
...

the added weight of a proper turbo setup is something I'd like to avoid. Keep the car light and it ought to corner better.



Keep in mind that the 4.9 weight is within shouting distance of the stock 2.8.
Some people say it's about the difference of the weight of an A/C compressor. Others don't even go that far.
Reborn756 AUG 18, 03:39 PM
Another big reason I'm specifically looking at the 4.9L over the other obvious V8 options: the weight of the engine. I think I read that the 4.9L is a whopping 5 pounds heavier than the factory V6

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- Darryl

FieroWannaBe AUG 18, 06:32 PM

quote
Originally posted by Johns 4.9:

I think 300 hp is the top power possible being normally aspirated. You 400 hp goals would have to be a boosted engine. But I'm working on that also with a boosted 4.5 engine. The 4.5 has a shorter stroke and lighter crankshaft then the 4.9 and has the potential for more revs than the 4.9 engine.
John



Stroke has very little to do with the ability of street engines to "REV" its has everything to do with airflow and camshaft timing, Neither of which this platform is designed for. What will happen, is with an identical top end, the lower displacement engine will achieve peak power and torque at a higher RPM. This has been proven time and time again the dyno.

Wear and tear is a factor, but it's affect on power production, as far as street engines are concerned, is effectively nil.

My point is, there is rarely ever a reason to not go with the maximum displacement possible. it makes reaching the desired power goal much easier, since engine speeds can be lower to achieve the needed airflow for a certain power level, provided you have the top end airflow (read: mass-flow) needed to reach that power level.

[This message has been edited by FieroWannaBe (edited 08-18-2020).]

pmbrunelle AUG 18, 07:54 PM

quote
Originally posted by Reborn756:
Let me specify a little more so i sound more reasonable: I'm only hoping for between 300-400hp max. I assume 300 is doable, only 100 more than the stock rating.



Well if you're throwing out the stock heads and using custom-made billet heads, then the flow limitations of stock 4.9 (or stock-based) heads no longer apply to you. The sky is the limit.


quote
Originally posted by Reborn756:
the added weight of a proper turbo setup is something I'd like to avoid. Keep the car light and it ought to corner better.



Using my personal Fiero as an anecdote...

I'd guess that bolting on a turbo increased my car's overall weight about 1.5% (maybe less), but power may have increased 50%. In my mind, the choice wasn't hard...

I think the biggest downside of a turbo is slow throttle response.