Effect of compression on horse power

[Windingout]

I am pondering what pistons to use in my single notch 409 truck engine. I have 690 heads with a miild port job. They have been spray welded and resurfaced to repair pitting. My target HP would be about 450. The question is what compression do I have to run to get to 450. The car will be used for street with the odd trip to the strip. I am thinking of a Ross of 11:1 to end up with a theroetical 10.5:1 allowing a drop of .5 for the notch. Can I go lower? Based on the original 425 HP that had 11.25:1 I am concerned that I will not reach my HP target. I am using a 881 manifold with 2 AFBs .Other than headers and cam ( yet to be determined) every thing else is the same as a 63 engine except, compression ratio, cam and headers.
What flat tappet hydraulic cam should I use. What is the max I can go for the street. The car is a 63 ss with a m20. The gear will be 3.73.

 

[MRHP]

10.5 would be great for our poor fuel.

 

[Ishiftem]

Yeah, 10.5 would work and be plenty to get to 450 hp with a roller cam. Flat tappet cams are soo 20th century.

 

[pvs409]

I would not use 11 to 1 - as said above, 10:5 on a truck block is fine.
Too much chance of not running on normally available pump gas without pinging. That's what I learned before I started to build my 409 truck motor. I do run premium unleaded but only one station in town carries it. It will run fine on regular unleaded.

I had a rebuilt stock 409/380 HP 11:1 0.30 over Ross pistons stock intake and stock large carter AFB . I had to use racing gas to not ping.

I have 530 HP /590 torque on a out of car dyno - with 454 Eagle stroker cranksfhaft (originally from C & H Enterprises via Phil Reed , 454 big block rods (C & H), 65 409 truck block -also from Phil Reed , 0:30 over Ross 10:5 to 1 pistons, 2 -4's edelbrock 1406's on
2-4 stock intake, single point 409 distributor w/petronics , with Edelbrock heads with a mild street porting on the heads and Jardine 2" big tube headers.
The first cam I used was a .615 lift solid lifter. I then went went to hydraulic roller and comp cam roller rockers, ported heads and got increased HP. I have more torque and HP at 5400 RPM with the ported heads and the hydraulic roller cam-- .526 intake lift /510 exhaust lift - duration @ .50 234 intake/ 249 exhaust - lobe separation 107.
I was going to use ported 690's but found out they were cracked and had to switch to the edelbrocks ---after waiting one year for my motor to be done.
On the street its very fast compared to my 62 409/380 HP solid lifter motor. I think from the 1/4 mile times I ran with the .615 lift solid lifter and non ported heads & no slicks, that I will be around 12.90 and 107 miles per hour in the 1/4 with the new heads and roller cam.

Phil do you remember what you told me about stroker motors....???

I do not have a 9" ford rear end nor do I intend to install one. I have Aubrey Bruneau girdles on my stock posi rear end with dual upper control arms. I do not have better axles -probably should have better ones but I have not had a problem with my stock axles -lots of experience over the years drag racing without ever breaking stock axles. to date...

I have another 62 truck block and 690's for it that I will port like the edelbrocks (carefully) if I built a race motor.....

Paul

 

[Don Jacks]

If you must have a hydraulic flat tappet cam,a really good choice would be to have Lunati apply the grind for pn#10110704 [233 intake,241 exhaust @.050,.554 in.,.574 ex.,110 lobe separation,106 intake centerline].A hyd.roller ,which would be better for several reasons,would be also a Lunati grind,part number 20110712[231 in.,239 ex.@.050,.600 lift on both intake and exhaust,the same 110-106 set up as the flat tappet].Either of these cams would be custom[sort of] in that they would apply these to the approiate W cam blank.Howards Cams lists a couple of cams as off the shelf grinds,but their roller cam stuff is of the 4-7 swap varity ,which effects your header choices.Probally the best header choice for all around performance would be the Dougs tri-y 1 3/4 tube on this "little" engine,but they will not perform as well with the 4-7 swap,so I can't recommend going there.Either of these cams on a 10-10.5 compression engine with iron big port[690's or 583's]heads that have been bowl-blended will be streetable comfortably on 91-93 octane fuel,and will exceed your 450 hp.goal using the intake[881] and carbs that you're planning.As to your original question,figure anywhere from 15-19 hp change per point of compression IF ALL else remains the same.

 

[yellow wagon]

Roller cams are nice for sure. But my little stock stroke, solid flat tappet cam'd, truck headed motor seems to run ok

 

[skipxt4]

Just a FYI. I've been told by Summit and Jeg's, Motive Gear has purchased Richmond. All 3.73 gears from Richmond, will now be 37-10 (3.70) Ratio. Will no longer sell 41-11 (3.73) Gears. That's 1955-1964 Full Size Chevy's. That Sucks.

 

[Don Jacks]

Not necessarily Skip.From the factory,the gear was 3.70,not 3.73 anyway.The extra .03,you'll never feel,or measure at the track.

 

[models916]

Makes the pinion thicker, right? Maybe problems with the old version.

 

[skipxt4]

I know the original R & P were 3.70, Don. Richmond came out with the 3.73 41-11 gears, in the nineties. They were more Street friendly. They also, could fit in Series 3 and 4 Posi Units. I put a set, in my 64 in 2008. They are Much more Quite, than the original 3.70's. I installed them, in a Series 3 Posi Unit, and had to use a Spacer. The New 3.70's, do have a Larger Pinion, Mike. Who would have thought, Motive would Buy Richmond. Usually, the Big Fish, eats the little fish.