[Mike S]

I will rebuilding my engine in the street car. I am thinking of going with KRE D-ports. The 290 and 310 are the same price. Right now I have a set 0f 6x heads on it. Home ported and milled to 90cc. The car ran a best of 11.8/113 at 3900lbs.

Cam is a ram air 4 grind. Performer rpm with 750 holley. ATI tree master 10" converter stalls about 3200. 3.73 gears with 28" drag radials. Car weighs 3900lbs.
I shift at 5500 rpms.

I was reading that too big of a port will kill the bottom end. Do yo think 310 cfm would be to much? I would like to try and get it to 11.50's if possible.


Thanks Mike

[shaker455]

What CR Mike?
I'm pretty sure you'll be fine.
Jeff

[77 TRASHCAN]

Have you read about T/A man's exploits here (in the street section?) with his T/A?

[ta man]

I think the OP 's times with his current setup is more impressive than my exploits. I'm sure you won't lose any torque. Push the compression ratio to the 10.75/11 to 1 range ,your a good tuner so should be no issues on pump gas.

[steve25]

The question you need to ask KRE is what is the minimum port area difference between both heads, after you get that info then there is very accurate math formula you can use to find out where rpm wise your motor will make peak HP .

Since I have ported more then a few of there D port heads I will venture a educated guess that you have no need to go with a 310 cfm head if your only looking to pick up 3/10 ths in the 1/4'mile.

The other thing that is certain also with either head is that you will need to shift some 400 to 500 rpm higher then you are now to pick up that added et.

You have a very great opportunity here to do a Apples to Apples test here!

[Cliff R]

My Ventura went 11.52 with the stock 260cfm versions sitting on my last 455. We used a 230/242/112 HR cam from Comp with XFI lobes, it dyno'd right at 514hp, race weight with driver 3640lbs.

Pretty much a "wash" comparing 290cfm to 310. We have a set of KRE 310 cfm heads on a pretty "basic" 455 engine that pushes a 1981 FB to 10.80's, so I think you'll meet your goals with either version without much effort.......Cliff

[HWYSTR455]

When you say 'rebuilding', as in, replace pistons, bore, machine crank & rods? Is this a 400 or 455?

You probably see where this is going...and in that case, no, 310 is fine...

.

[i82much]

i always use guns and roses as my philosophical guide to these sort of questions. “i used to do a little but a little wasn’t doin’ so a little got more and more ...”

[stickboy]

310's at 11:1 comp maybe an 850.
You got the smarts on the chassis so you should pick up a lot

[Lee]

^ agree, got 310. Any "lowend" you lose will be below your converter's stall speed, so you'll never notice it.

[torqhead]

Since there's no difference in cost and no material impact in performance I would recommend going with the 310. I went this route as well as we all know as we continue to play with our cars a lot of us continue to see how much more we can wring out of it. In this case as you progress you'll have the heads another step forward so to speak if you want to go there.

[Mike S]

After 25 years it's time to retire the TRW pistons and stock rods. I am building another short block with some ex race car parts. Ross pistons and eagle rods and a spare cast crank I have. Compression will go to 10.5 to keep it safe. It is 9.5 with the steel heads.

Still up in the air if I want to retire the flat tappet cam and go with a roller.


I do have a 850 Holley laying around since I went to a 1050 on the race car.


The car was perfect for 12.00 index but of course they changed to 11.50. So that is the goal. Trying to talk the wife into running 11.50 while I run 10.00.

[Steve C.]

For interest, SD Performance dyno tested combo...

474ci engine running a set of 290cfm CNC ported KRE D-port heads with 10.2 to 1 compression on 91 octane fuel with a 236/245 duration hyd. roller cam. Cast iron intake with the CNC machined plenum copied from Cliff's personal intake. With some minor tuning it ended up with 527hp @ 5300rpm and 579 lb ft @ 4100rpm. A Performer RPM intake would up the anti.

.

[Skip Fix]

Mike I have 320 cfm round port E heads on my 78s 455 and it has gobs of bottom end. It has gone 10.90s in good air and light wheels. 11.50s with the spare back in it and heavy snowflakes and street tires in the Texas heat.Did I miss what CI?

Now a single plane and big heads on a 400 would be a whole different deal.

[ponjohn]

Every car I have seen with KRE 310 port has performed very well.

[64speed]

The 310s are what I ordered for my build after exhaustive research and talking to a lot of people on here

[Steve C.]

Two more combos....

.030-over 445, KRE 300/305 cfm heads, Torker II intake w/HP950 carb, 246 degree hyd roller with solid roller lifters, 1.52 rocker ratio.

589 hp at 5,800 rpm. Peak torque at 4,700 rpm with 531 ft.lbs.

440 cid 4-inch stroke, 310 cfm KRE heads, Northwind intake w/850 cfm 4150 carb, 248 degree solid roller cam w/1.6 rockers and headers.

575 hp at 6100 rpm. Peak torque at 4700 rpm with 541 ft.lbs.


.

[Cliff R]

We sent a Q-jet and HEI to a customer who built a pretty "basic" 455, .030 over with 290cfm KRE's from Dave at SD and his Old Faithful cam. He also had Dave port the RPM intake to match the heads. It made 552hp/604tq on the dyno. That's enough power to put a 4000' car DEEP into the 11's without much effort.......Cliff

[PunchT37]

Originally Posted by Mike S

I will rebuilding my engine in the street car. I am thinking of going with KRE D-ports. The 290 and 310 are the same price. Right now I have a set 0f 6x heads on it. Home ported and milled to 90cc. The car ran a best of 11.8/113 at 3900lbs.

Cam is a ram air 4 grind. Performer rpm with 750 holley. ATI tree master 10" converter stalls about 3200. 3.73 gears with 28" drag radials. Car weighs 3900lbs.
I shift at 5500 rpms.

I was reading that too big of a port will kill the bottom end. Do yo think 310 cfm would be to much? I would like to try and get it to 11.50's if possible.


Thanks Mike

Easy. 310`s. IF it "loses" bottom end, tune for it.

[Steve C.]

"We decided to do some intake manifold comparison testing on a 474ci engine running a set of our 290 cfm CNC ported KRE D-port heads with 10.2 to 1 compression on 91 octane fuel with a 236/245 duration hyd. roller cam. "

Dave Bisschop

http://www.sdperformance.com/newsStory.php?newsID=44



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