Best Compression for KRE D-Port Heads
 

I'm going with KRE D-Ports on my 462 motor. What's optimum with a 236/245 HRoller cam in a 69 GTO with 3200 stall converter and 3.07 12 bolt? Not settled on intake/carb yet. Torker 2 or even reworked original Qjet manifold intake/carb.

I was thinking about 10.5:1.

14-1 will work better

:)

Yeh, might want to confirm you want a pump gas motor. Similar motor to Cliffs and he runs 11:1 and states he runs 87 octane. If you are a sharp tuner, go for it.

You said 10.5 and Jack said 14 so the difference is 3.5 points of compression.

It is a known fact that every point of compression will get you 3% more power.
("HO Racing rule" but verified by me at work as a valid "back of envelope" number.)

So Jack's engine would make 17.5 more HP assuming a 500 HP engine) vs your 10.5 compression ratio engine.

Tom V.

11.0 to 1 vs 10.5 to 1 might get you a better transient drive but the HP difference could be small on some applications.

I usually shoot for 10.7:1

I think it depends on the fuel avil in your area and just how much you want to push the envelope on staying on top of the tune.For our 91 piss gas in so cal I chose 10.25 for much the same build.Tom

I ran 11.1 to 1 with those heads, bigger solid roller. Shell 92 unleaded and dynoed at over 600 hp. Ran great on and off the track. Aluminum and that chamber are very friendly to pump gas.

Gas here is lousy but the hot temps in South Florida don't help either.

8.5 then add some boost.

I'm running two engines with KRE D-ports at 10.5-1 and 91 octane, 32 degrees tt, and same cam as you listed in one and runs great. 560 h/p 580 torque.

Unless of course, (you posted in race section!)

Charles

for best drivability/vacuum, I'd go with 11:1

I'm pretty sure cliff mixes in some higher gas when he runs at the track, don't think he runs straight 87 when racing it, I could be wrong tho.
My last motor I ran 10.7 with the road paver, no issues at all, I ran the old faithful before that, same comp. new combo will be 11.1, but with a true solid roller 265/270, and still pump gas. Just be on top of your tune and it will run fine and get great mileage!

My math says 52.5 HP more...?

The rule of thumb is 1 to 1.25 points higher with aluminum cylinders heads verses iron heads. If you're running a 9.5:1 c /r, you can safely run a 10.5-10.75:1 c/r assuming all other factors are the same.

FYI here in Central Florida I have several Sunoco stations that sell 100 octane gas. It is not cheap $8.99 a gallon but you could mix it with 93 octane they sell.

I run it straight in my 2 stroke KTM dirt bike that has had some head work. Smells great and definitely helped. Our races are a mix between 2 hour hare scrambles and some MX races. Conditions can range from 90+ degrees with over 70% humidity to 30 degrees with less than 50% humidity!

MarkC

Dude, I haven't seen a post from you in a while, how have you been, and Happy Holidays!:cool:

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Dude, I haven't seen a post from you in a while, how have you been, and Happy Holidays!

Hey Slick! Been well. Happy Holidays to you as well. I have been lurking around in the street section for a while now. Always looking for good advise from the experts here. I just purchased the 74 GTO that was for sale on this site. Will be pulling the Butler built aluminum 496ci motor and putting it in the '71 Bird in my signature. Trying to decide if I want to make a few changes to it before the swap. Possibly a little more head cfm or solid roller lifters on the Hyd roller cam. Got some 1 7/8" Hedman headers coming for it and a Northwind intake.

That was a good deal.

For sure a great deal. The car is in my shop, but will likely be a couple weeks until I can get home to see it! I am going to try and sell the car rolling first. If need to, I will put my current 462 in it and try to sell it that way. Any leads on persons interested in this car would be appreciated. Car has a ton of nice parts on it.
My apologies to the OP for getting off subject. On that subject, I think compression between 10.5 and 11.0 would work well.

500 HP going from 10.5:1 to 14:1 CR.

Can you please explain your math?

Stan