TheSamba.com :: View topic - Please check my DCR number and will this run on pump gas?

Thu Jul 10, 2014 11:10 am

Planning a 88 x 74 1800.
5.325 rods
50 cc chambers
0.04 deck
9.0/1 CR static
Web 86a (cam card says Intake close @ 54 after BDC @ 0.050 lift)

The calculator at uempistons gives a 6.9 DCR
The one from RB Racing gives a 7.7 DCR.
The one from PCEngines gives a 6.69. (using duration and lobe angle)

Which one is it, and will this run on pump gas?

Thanks for the help
Andrew

Thu Jul 10, 2014 11:16 am

Should be ok on pump gas IMO.

The ported big valve heads will move the torque peak and whole VE curve UP to higher rpms on the smallish CC engine, so you can run a bit more compression than if it had stock heads.

Thu Jul 10, 2014 11:25 am

I got 9 static and 7 DCR. When you need to start checking and paying attention to dynamic ratios imo is at 10 and up.... You can run 89 octane on your engine, but I recommend 92 cause statiscally you get better mileage per price difference and better cooling ( not an issue in your build).

Edited originally I put in .050 instead of .040. I used United engines calculator also. .040 Deck... thats cutting it pretty close. Get the rotational components balanced. Even my own personal motor, im at .048 DH.

Thu Jul 10, 2014 11:38 am

Jfat has the right idea. When you get Into the realm of 10:1 that's when you need to start worrying about it. 7.7 is quite high and I would say something isn't right with that calculator.

I dig your using Porsche length rod. Good choice.

To give you an idea of what works. My old motor had 7.55 dynamic. Ran 10.5 static. 91 octane and i couldnt make it ping at all when i tried. Uphill 4th gear pulling parking brake and flooring gas pedal. But that was with a very large and efficent set of heads which helps running such high compression

Thu Jul 10, 2014 12:17 pm

Considering ANC 40x35 L5,
DRD L5,
Tims Stage 1 China or Stage 1 043 Heads

Thought about including MOFOCO on the list, but with all the noise/tone in the step/no step thread, just decided to stay away.

Not sure which way to go with these.

1.5" merged exhaust.
40mm Dual Dells
Start with a SDVA and use to work into crank fire in the future.

Mission is a strong DD, with a torque peak about 5000-5500.

Ready to spend the money I don't have...

Andrew

Thu Jul 10, 2014 12:25 pm

Tell me about it, I had my car stolen, would cost me 15-20k to replace all the work and parts I had done on the car. The 2332 I mentioned in earlier post with 10.5:1 was apart of that car.

Im in the process of building my 55 I had in storage for years, so I can have a vw again... and being me.. I have to have correct tail lights $500+, currently lookin for correct front fenders $500+...... damn early car stuff. All my money went Into my 68, hard to get i to such an early car project.

Your on the right path with your motor though. I would stay 9:1, keep it on the higher side of mild, you'll be happy

Thu Jul 10, 2014 12:30 pm

Any thoughts on the heads kielbasa?

Thu Jul 10, 2014 12:58 pm

Im not really up to date with current production heads. I've always used hand ported heads from the good ole jeff denham. But I'm sure any of those would work. I'd stick with a 40x35 valve. As long as the port is good, and chamber shape is efficient enough... can't really go wrong. I'd look up reviews on the heads your looking at and pick the one that fit your budget

Thu Jul 10, 2014 1:16 pm

Both of those heads mentioned are quality heads. Darren has a great cnc program and Tims do hand port work that is quality. It'll be a stumper to decide, but i think the stage 1s are better for torque and the L5s are a better high rpm peak head. Irregardless, both heads are hotsh-t.

Thu Jul 10, 2014 1:59 pm

Using this:

http://www.race-cars.net/calculators/compression_calculator.html

i get a compression ratio of 9.02.

Using this:

http://www.wallaceracing.com/dynamic-cr.php

Web cam shows an advertized duration of 290* subtract the 252* and you get 38* divided by 2 for the opening and closing and you get 19* that you need to add to the 54* closing point.

using a closing point of 73* i get a dynamic of 6.70 at sea level

It drops to 6.5 at 1000' etc.

My rule of thumb is anything under 7.0 is good for 91 octane provided there is a good tight deck.

Hope this helps!!

Thu Jul 10, 2014 3:09 pm

ap_sand wrote: Considering ANC 40x35 L5,
DRD L5,
Tims Stage 1 China or Stage 1 043 Heads

Thought about including MOFOCO on the list, but with all the noise/tone in the step/no step thread, just decided to stay away.

Not sure which way to go with these.

1.5" merged exhaust.
40mm Dual Dells
Start with a SDVA and use to work into crank fire in the future.

Mission is a strong DD, with a torque peak about 5000-5500.

Ready to spend the money I don't have...

Andrew

yeah, you've got to stay away from those steps. They get icy, slippery and you can break an ankle.... :roll:

Thu Jul 10, 2014 7:05 pm

[email protected] wrote: ap_sand wrote: Considering ANC 40x35 L5,
DRD L5,
Tims Stage 1 China or Stage 1 043 Heads

Thought about including MOFOCO on the list, but with all the noise/tone in the step/no step thread, just decided to stay away.

Not sure which way to go with these.

1.5" merged exhaust.
40mm Dual Dells
Start with a SDVA and use to work into crank fire in the future.

Mission is a strong DD, with a torque peak about 5000-5500.

Ready to spend the money I don't have...

Andrew

yeah, you've got to stay away from those steps. They get icy, slippery and you can break an ankle.... :roll:

That's a good one Roy! I know what you mean, I have 4 2387's all with steps in the heads and I can't drive any of them because I keep falling down :lol:

Thu Jul 10, 2014 7:29 pm

I called DRD last week and ordered a set of heads. Darren talked with me for about 45 minutes and asked me questions about my build and intended use and actually sold me a less expensive set of heads than I was planning on buying. He was more than happy to answer all of my questions and explain things to me on my level.
Nothing slippery there!!!
Good Luck
Kenric

Thu Jul 10, 2014 8:27 pm

quit distracting roy!! he is suppose to be building my heads not posting on here :lol:

Fri Jul 11, 2014 7:46 am

woodsbuggy wrote: I called DRD last week and ordered a set of heads. Darren talked with me for about 45 minutes and asked me questions about my build and intended use and actually sold me a less expensive set of heads than I was planning on buying. He was more than happy to answer all of my questions and explain things to me on my level.
Nothing slippery there!!!
Good Luck
Kenric
So who is porting heads for Darren then while he's on the phone? ha ha