Horsepower increase ?
 

I'm considering replacing my 463" with a 495" short block.
I have about 580 rear wheel HP now.
Any guess how much I might gain.
Thanks, OGR

Definitely a TQ increase, thus HP increase with a 495 vs 463, regardless of carb, cam, heads and manifolds. :) - Cpt Oblivion

Depends on cam and topend but possibly peak hp gain of zero, just a good gain in average power.

When we switched the Grocery Getter from 455 to 540, but kept the same e-heads and cam, it was hard to measure any gain in ET but the added torque was terrific for burnouts! Changing to Tiger heads really woke up the horsepower.

Eric

If you keep the same top end parts you will see no HP increase, or nothing much to write home about anyway!
Right now if you where making 580 flywheel hp your using 280 cfm out of whatever the peak air flow number is that your heads flow and or intake can pass on to the heads.

What will happen with the 7% cid increase is that your rpm of peak torque and Hp will take place 7 % sooner in rpm, and as posted above you will see a torque increase due to the added cid.

If at this point you want a noticeable Hp increase you can go for more valve lift to access more flow if your heads have such left, and this can be done by means of a cam change or higher ratio rockers if you want to keep the head porting as it is now.

If you want to pull the heads and mill them for a full 1 point of compression increase you would pick up 1.5% more hp using flywheel numbers, or like 9 more hp at best.

Why is it that your using rear wheel Hp numbers anyway, are you just going by your ET/ mph?

I punched the number into a program for my High Port heads on my current 461. Then punched them in with the same heads on a 540.
HP was the same but the RPM range dropped for the 540.

I went from 461 to 499 ci with the same cam and heads and gained 0.12 in ET and about 1 mph.

I gotta say that I learned a lot from this Thread question. Explains to me why some folks were in the 10's with 400s about 40-30 years ago, while i was doing 12s and "Headed" into the lowest 11s (pun intended).

The other detail here to having a performance gain while hp does not really change is if the percentage of torque increase is greater then the percentage of internal friction increase of the larger motor.

If there’s still a net torque gain left over then the new motor will gain rpm faster then the old one until the rpm of peak torque is reached.
This faster gain in rpm after shifts is what will make for a increase in ET, but with little change in mph.

As always this all hinges on applying this new found extra torque down to the track.

Other details that can take place with a increase in ET which of course produces a increase in G force on the car during a pass and especially at the green light can be finding out the limit of what you fuel pressure can over come in terms of G forces.

At 2 Gs which is like a car that can run in 9s in the 1/4, a fuel system will drop .3 psi per ft of run that it makes getting up to the carb inlet.

Why is it that your using rear wheel Hp numbers anyway, are you just going by your ET/ mph?

I used the Wallace calculator. 9.88 @ 133. 3150 #

My guess is you will gain about a tenth and half in et.

Remember by using the same top end he will be gaining compression with the extra cubes
under the same chambers

My experience was the opposite way. I broke the 4.5” M/T crank in my 495 and put the same cam, heads and intake/carb on a 4.25” stroke 467” engine and went the sameET within a tenth of a second. Heads were 320cfm Edelbrocks with a .440 lobe Butler roller cam and Victor/ Dominator intake and carb.

( This Thread reminds me that ) The Bore increase is worth more HP than the Stroke increase.

4.351" Bore seems like a practical parameter-goal. Hey Olds 403s in T/As. 403s still lack a strong block right?

Did you run both engines with the same rear end gear?

Stan

Sounds like the HP/ET gain is not worth the $$$$/Labor.
Thanks for your replies gentleman.
OGR

was your gain in the 0-60' and 300+' mark sections?
did you notice any more traction related issues?
did you make carb change?

i'm looking to gain more in the mid/top end, don't want any more low end traction issues, or harder hitting torque resulting in parts breakage (well, to the best i can)

i've been leaning towards a headswap, but.... i could only image the fun factor of more low end torque (on the street for such easy burn outs, but tires getting VERY expensive, hence the higher end range desire)

I didn't have any gain in 60', I would have to check timeslips for a 330' change. No traction change since the 60' stayed the same. Used the same carb and complete top end with the same SCR of 11.2:1 so all Hp and torque gain was the result of extra cubic inches.

I gained over a tenth just from a converter change and the converter I replaced was a high end converter.
I replaced a trick TCI converter with a PTC converter that was less expensive but gained ET in the middle of the track.
Same 60 foots and MPH but over a tenth quicker.
Lane from PTC spec,ed it for me.