377 Build cam advice

[wyrmrider]

right
I should have spelled out the formula- we all should
but it's moot
go for the heads
"without a larger cam"
and spinning it faster

[CamKing]

Going from 350ci w/13:1 to 377ci w/12.5:1 will only add about 20hp.
Going from the old heads that were choking the engine at 6,500, to the profilers that will allow the same cam(with a higher rocker ratio) to pull past 7,200, will add another 70hp.

[cgarb]

Yes I've calculated my 355 from 500 to roughly 550hp depending on if you calculate et or mph. The motor is a beast to the 1/8th mile it makes good torque. Runs 6.6-6.7 at 100 in the 1/8th. It just cruises along after its in high gear. So your saying i need 700 plus hp to go 10.20? What math is supporting that? Most calculators I've used online say I need more along the lines of 600-650 for a half second increase I'm looking for. I think that is attainable with what I'm doing. Chad Spiers has a pump gas 383 build that made 580hp with the same heads. I belive you guys are ovethinking this way too much. Agian I'm not going to be upset if it runs 10.40's vs 10.20's as long as it runs the number and is reliable. Ive been racing the same stuff for a while and I'm ready for a change. I like knowing my car and equipment well, in my mind makes a better racer. Its hard to be competitive bracket racing with a new motor every 2 weeks.

[CamKing]

Yes I've calculated my 355 from 500 to roughly 550hp depending on if you calculate et or mph. The motor is a beast to the 1/8th mile it makes good torque. Runs 6.6-6.7 at 100 in the 1/8th. It just cruises along after its in high gear. So your saying i need 700 plus hp to go 10.20? What math is supporting that? Most calculators I've used online say I need more along the lines of 600-650 for a half second increase I'm looking for. I think that is attainable with what I'm doing. Chad Spiers has a pump gas 383 build that made 580hp with the same heads. I belive you guys are ovethinking this way too much. Agian I'm not going to be upset if it runs 10.40's vs 10.20's as long as it runs the number and is reliable. Ive been racing the same stuff for a while and I'm ready for a change. I like knowing my car and equipment well, in my mind makes a better racer. Its hard to be competitive bracket racing with a new motor every 2 weeks.

Run the same cam, increase the rocker ratio, and shift it around 7,000-7,400.
You'll be fine.

[randy331]

A 1 hp gain or loss is not remotely realistic for 500+ horsepower engine. 25-35+ hp per 1 comp point is in reality for a 500 hp engine

1 HP is a lot more realistic than 25-35+. 7% per point of compression isn't even close.

If 7% was realistic cgarb should just raise his comp to 15/1 on his 355 and walla, 70 HP and low 10s.

Power just doesn't come that easy.

rfoll is way more on target. Point 7% (7/10 of 1%)

And he's right on what the OP stated. He wanted to run a 377 not a 406.

If it's factory 400 block I'd stay 3.5" stroke too, just to help the block survive.

Randy

[CamKing]

If everything was optimized, the difference between 12.5:1 and 13:1 would be a maximum of18hp at 6,500rpm.

[user-612937456]

A 1 hp gain or loss is not remotely realistic for 500+ horsepower engine. 25-35+ hp per 1 comp point is in reality for a 500 hp engine

1 HP is a lot more realistic than 25-35+. 7% per point of compression isn't even close.

If 7% was realistic cgarb should just raise his comp to 15/1 on his 355 and walla, 70 HP and low 10s.

Power just doesn't come that easy.

rfoll is way more on target. Point 7% (7/10 of 1%)

And he's right on what the OP stated. He wanted to run a 377 not a 406.

If it's factory 400 block I'd stay 3.5" stroke too, just to help the block survive.

Randy

Randy .7% huh? Well if cam king is right lets say this is a 500 hp engine. Lets do the math mike says in idea situation going from 12.5:1 to 13.0:1 compression there is a potential of 18 Hp to be gained this is .5 compression point difference right? ok now for the math 18 hp (Gain) divided by 500 Hp (estimated Hp) My calculator cays .036 or 3.6% lets do a self check on the math to see if the equation is correct 500Hp times 3.6% = 18Hp. Ok some more math the increase in compression ratio .5+.5=1.0 does this mean 18Hp+18Hp=36Hp or does 3.6%+3.6%=7.2%? Is there an increase of about 7% in Hp per 1 point rise in static compression ratio?

Here is where I admit my fault I am basing the 7% value only for this example of the 500-600 horsepower range, cgarb's cam, and 12:1 to 13:1 rise in comp. I should have represented this calculation as a variable, influenced by the compression ratio range, as well as horsepower, cam overlap, ICL, and rpm range applied to NA engines. In most real world engines this can range from 5% up to 9% depending on starting compression and other variables. Also I am not entirely sure if the 7% is for average or a peak Hp numbers.

So yes Randy I think it is roughly 7% per 1 point increase not .7% for this application or 3.5% for 12.5:1 to 13.0:1

[rfoll]

It wouldn't be much of a slice on the heads and or deck to get to 13:1

[Old Viking]

Going from 350ci w/13:1 to 377ci w/12.5:1 will only add about 20hp.
Going from the old heads that were choking the engine at 6,500, to the profilers that will allow the same cam(with a higher rocker ratio) to pull past 7,200, will add another 70hp.

Use one thought, wouldn't spinning a larger engine higher benefit of a lager carb than the 750 he has now?

[cgarb]

Just say no to the bigger carb...lol. Maybe, I have an 850 i can sent to rupert, but I'm gonna see how it runs first. We have a 750 on a friend of ours 418 SBF and we swapped an 830 on it and it didn't make one bit of difference. On the track at least, maybe on the dyno you might have found a 1 or 2hp gain, but real world it ran almost identical.

The block is at the shop now it will have .008" of deck clearance and I plan on running a .027" cometic gasket should put the quench at .035". When I calculate that out on a 72cc head I got around 11.9-12.2-1 depending on what calculator I use online. I want to have the heads trimmed down some to maybe 68 or 69cc should get me up to 12.5 or a little higher. If I don't run into intake alignment issues I would go more.

[Old Viking]

Well changing carb is something that you can try later on when you are at the track. One old dragracer told me many years ago: Dragracing is about making as many hp as possible at the shift recovering point, not hp at peak rpm.

[cgarb]

I think that statement is a pretty good rule of thumb but I would say thats where you would want your peak torque to be not HP. If your shifting 500-1000rpm past peak HP I would think your car would nose over and you would be giving up ET.

[randy331]

So yes Randy I think it is roughly 7% per 1 point increase not .7% for this application or 3.5% for 12.5:1 to 13.0:1

I think that 7% is way out to of reality. I think you and camking are wrong.

There is no way to make some blanket statement like ( If everything is optimized it's worth 18 HP )
How that compression is gained would be a big factor in how much a .5 compression would gain/loose power.
And yes, if you added .5 point of compression by milling the heads on a 23* SBC you are just as likely to loose power as gain.

Randy

[cgarb]

I agree too. Static compression is a good figure on paper but dynamic compression is what the motor see's when its running. I could change the installed CL on the cam and change the cranking compression without loosening a head bolt. Thats how they make low compession motors run well. I know you cant take an 8-1 dish motor and make it perform like a 13-1 motor but camshaft plays a big part in that. Half a point on compression in my mind isn't worth fussing over.

[Old Viking]

X2 I know that Mark Jones in some thread wrote that milling CBB PP heads would make them.flow less. I also know I read it after i milled mine...