# KRE D ports idea



## Duff (Jan 12, 2020)

Awhile back, I talked with Pontiac Jim about having a Butler or KRE pump gas stroker engine built, he had some really good suggestions, but I don't have all the cash to pull the trigger. Well, my next thought is putting a top end on my factory short block, which is a 1968 400 HO bird, all stock, #16 heads, long branches etc... runs well, no issues. I was thinking a set of 74cc KRE D ports, stock intake and Q jet, recurve my original distributor. I'm guessing even with new heads, I'd still have to run a race fuel mix for the street, my goal is to have 390 - 400 HP. Is this a way to go or should I continue to save for a stroker?


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## armyadarkness (Dec 7, 2020)

There are so many schools oif thought on the topic. I have never subscribed to the "no replacement for displacement theory", simply for the fact the GM's most potent engines were always lesser displacement than some of their brethren. 302, 327, 389, 400, 350, 396 are all examples of engines in stock form, which out-performed their larger companions.

Lately we've had heavy discussions about cam degreeing and timing curves, and when you hear "what should be done" and compare it to what most are doing, you can immediately see how some racers have gone down in history.

I think that having an engine where the cam was degreed, the timing curve was set, and the carb was properly jetted, would be much better than simply having a big engine, without those things. So if more performance is your goal, have you already verified that youre getting the most from your current setup?

When I was young I had a 91 RS Camaro, throttle bodied 305. I was very envious of the Tuned Port Z28 and Iroc guys, but I just didn't have their wallets. So, I did 1.6 ratio rockers, Bosch platinum plugs, accel super coil, K&N filter, and 3.73 gears, and I whizzed all over them for about $500.

Doesn't a 68 400 HO engine make 360hp in stock form? If so, hitting the 400hp mark should be a breeze.


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## armyadarkness (Dec 7, 2020)

bare in mind this is all theoretical. In actuality, i have no idea what Im talking about.


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## BearGFR (Aug 25, 2008)

In the infamous words of A.J. Foyt: "Speed costs money. _How fast do you want to go_?"

It's a trade off between a little fun now, or (maybe) a lot of fun "someday", and no one can, or should, make that decision for you. 

But... let's do some quick checking. Stock 400, for which expediency's sake I'll assume is stock bore, stock stroke, pistons the "usual" .011 "down", standard 0.042 compressed head gaskets, flat top stock pistons with 6 cc's in the valve pockets, KRE 74cc aluminum heads.

Putting that in my spreadsheet I get a static compression ratio of just a taste under 9.9:1 If anything, that's a little bit _low_ for aluminum heads. My opinion is that it'd be happy on just about anything that comes out of any pump. No race fuel needed. Even if it's bored +0.030 that only puts it at 9.97:1 which still ought to be fine with aluminum heads.

I would, however strongly recommend switching to some good forged rods at the same time. You can get a set for not much more than reconditioning a set of stock rods will cost you, and they're WAY stronger. Cheap insurance.

Bear


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## Duff (Jan 12, 2020)

I had to fix some other issues with the car and haven't tuned it yet, but now am close to that and getting it on the road. The 16 heads on my car are suppose to be 72cc making the advertised compression 10:75:1, is this not accurate?


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## BearGFR (Aug 25, 2008)

No, it's not accurate. Here's how that worked "back in the day": the factory would publish the 'official' dimensions and specs for engines, but what they published was almost always different from what was rolling of the line.

Go to a web site that has a cr calculator, and put in these dimensions: 72 cc chamber, 4.120 bore, 3.75 stroke, 6 CC's in the valve pockets, 0.042 head gasket thickness, 4.300 head gasket bore size, 0.011 deck clearance, and see what you get. It won't be 10.75:1. 

Back to our story. Ever heard of "blueprinting" an engine? Know what it really means? It means re-machining the engine to match the published factory blueprint specs. This is how manufacturers were able to put cars on the street that were reasonably drivable and durable, yet still provide a way for racers to remain legal for NHRA Stock competition and be competitive. The racers could legitimately claim their engines were 100% factory spec. The well kept secret was that the engine in your brand new GTO wasn't. 

Bear


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## Duff (Jan 12, 2020)

At 9.97:1 you pretty much answered my questions. Thanks!


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## PontiacJim (Dec 29, 2012)

Duff said:


> Awhile back, I talked with Pontiac Jim about having a Butler or KRE pump gas stroker engine built, he had some really good suggestions, but I don't have all the cash to pull the trigger. Well, my next thought is putting a top end on my factory short block, which is a 1968 400 HO bird, all stock, #16 heads, long branches etc... runs well, no issues. I was thinking a set of 74cc KRE D ports, stock intake and Q jet, recurve my original distributor. I'm guessing even with new heads, I'd still have to run a race fuel mix for the street, my goal is to have 390 - 400 HP. Is this a way to go or should I continue to save for a stroker?


You will be throwing your money away and be disappointed. What has not been covered is CFM flow and port velocity. My opinion - KRE heads on the stock engine will be a dog on the bottom end and you better be able to spin 6,500 RPM's on the top end to take advantage of them.

Also, the heads may flow well, but the stock intake won't. As I have said in the past, you want to match all your parts. The KRE heads are a poor match on a stock engine.


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## Baaad65 (Aug 29, 2019)

....but if you want to pick some KRE heads up I'll trade you my ported 7K3 heads, I take an 85cc regular 😀


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## PontiacJim (Dec 29, 2012)

Baaad65 said:


> ....but if you want to pick some KRE heads up I'll trade you my ported 7K3 heads, I take an 85cc regular 😀


Wow, that's some biggins'. I go for 42DD firm, and I'll keep my 7K3 heads.


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