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| Cam and compression check https://slantsix.org/forum/viewtopic.php?t=61872 |
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| Author: | Eltonsd100 [ Fri Jan 26, 2018 3:35 pm ] |
| Post subject: | Cam and compression check |
Looking for power from 2000-2600ish Piston to deck .170 58cc chamber Felpro gasket Oregon cam 203 210@50 252-260 .401-.417 110 lobe seperation Is .100 off the head what I'm looking for still ? Pump gas 87-89 Any advice on advancing the cam etc |
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| Author: | DadTruck [ Fri Jan 26, 2018 4:10 pm ] |
| Post subject: | Re: Cam and compression check |
Would be best for you to put your numbers into an online compression calculator, but I am thinking that .100 off the head will get you above 8.5 static and that is about where you want to be running regular gas. On the build for the 83 D150, I had .010 taken off the block to clean it up and .047 off the head. Hit 8.49 on the compression calculator. Since you have the numbers, put it in a calculator, every cc you remove from the head is about .0067 machined away. .038 to .040 is a good thickness to use on the Felpro gasket |
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| Author: | Eltonsd100 [ Fri Jan 26, 2018 4:44 pm ] |
| Post subject: | Re: Cam and compression check |
If I go to 45cc chamber I get to 9.06 -1 .. Do you know what dynamic I should shoot for ? |
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| Author: | DusterIdiot [ Fri Jan 26, 2018 5:02 pm ] |
| Post subject: | Re: Cam and compression check |
Assuming it's a 225 with standard bore, it's about 8.43:1 SCR... advancing the cam to a 104 intake centerline will be at 7.44:1 DCR... so it will run regular and peak torque at 3000 rpm... you could almost get away with 100 centerline at a 7.59 DCR and have best torque between 2500-and 3000, with a slow taper off above that... but the heavy vehicle may not like that much advance and ping a bit depending on fuel grade and timing... 8.0 DCR is best... but it will depend on vehicle, gearing, etc... at 104 that will make best peak torque at 3000 with the 45cc chamber and puts DCR at 7.94:1.. but its only splitting hairs at a couple lb/ft between it and the 8.43 SCR... you will have to watch it if it's a late head (post-74), the cuts down to 46- cc on chamber volume tend to really limit volume quickly as you are cutting into the wedge/shelf at that point which can increase compression quickly, putting you out of your target range... |
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| Author: | Eltonsd100 [ Fri Jan 26, 2018 5:20 pm ] |
| Post subject: | Re: Cam and compression check |
It is a standard bore 225 ( knew I forgot something) It weighs 3600lbs on the certified scales at work .. it's a d100 short box but add 1,500 towing max (specific trailer and motorcycles ) , Gears are 3.55 with 26 inch tires and the 833 od. Which is why I'm aiming for such low rpm performance. Just want to cruise down the road. I believe it's a 1970 head mechanical cam converting to hydraulic cam .. I'd have to recheck numbers are starting to run together |
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| Author: | Eltonsd100 [ Fri Jan 26, 2018 6:00 pm ] |
| Post subject: | Re: Cam and compression check |
I reread the post ? Is milling worth it then ? If I understand right your saying where it's at now vs a 45cc chamber is splitting hairs ? The engine was in running condition. |
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| Author: | DusterIdiot [ Fri Jan 26, 2018 6:21 pm ] |
| Post subject: | Re: Cam and compression check |
Quote: If I understand right your saying where it's at now vs a 45cc chamber is splitting hairs ?
The difference between 8.43 (milling .100) and 9.01 (a whole lot more) would be splitting hairs...especially with a 1 barrel...The cam you suggest looks like a typo and should be the 2103, which per your last post would be a late hydro cam block going to a mechanical cam setup. |
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| Author: | Eltonsd100 [ Fri Jan 26, 2018 8:27 pm ] |
| Post subject: | Re: Cam and compression check |
He said the specs pretty quick as i wrote them down but I thought I had it. Repeated it even , he described it as a street/tourqe cam. It's a hydraulic cam going into a mechanical block , forged crank, drool tube , revised chamber. It came out of a 70car. Rocker shaft and hydraulic parts are coming from another motor. I am planning on a motorcraft 2100 1.21 350cfm that was rebuilt and given to me. I'm going to edit my previous post .. I was attempting to communicate performance in overdrive is what I'm after. Whether that be 1 or two barrel carb. I'm planning on a split manifold and dual exhaust if it will yield good gains. If .100 thousands off is where the easy gains are ; not fighting ping all the time .I'll do that. I will double check cam specs before degreeing etc .. it hasn't actually arrived yet. |
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| Author: | DusterIdiot [ Sat Jan 27, 2018 9:32 am ] |
| Post subject: | Re: Cam and compression check |
Quote: He said the specs pretty quick as i wrote them down but I thought I had it. Repeated it even , he described it as a street/tourqe cam.
Oregon cam203@50 210@50 252/260 @20 .401I.417E lift at 1.5 110 lobe separation It looks like your cam is the 640 grind... |
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| Author: | Eltonsd100 [ Sat Jan 27, 2018 11:21 am ] |
| Post subject: | Re: Cam and compression check |
So am I okay on the 104 centerline And more importantly the .100ths off ? I'm getting ready to go to the machinist Would I be better off with less off in trade for more cam advance ? |
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| Author: | DusterIdiot [ Sat Jan 27, 2018 12:12 pm ] |
| Post subject: | Re: Cam and compression check |
Quote: So am I okay on the 104 centerline
And more importantly the .100ths off ? I'm getting ready to go to the machinist Would I be better off with less off in trade for more cam advance ? I am rerunning this since you changed to a hydro cam and it wasn't the 2103 mech cam... .100 is going to clobber 15 cc out of the 58 cc chamber... that makes a 43cc-42cc chamber...which will bump the compression to 9.2:1+ and bring the DCR up 8.13... I think with that mild of a cam, I would be more prone to wanting to cut .080 out and split the difference to be safer (leaves you at a safe 7.68 DCR)... which brings up another question: Is the machinist going to check to see if the seats, springs and guides are in good order? If he has to regrind the seats that may change the valve head position in the chamber and then change what the cut needs to be to get your target CC (he will have to make the repairs first, then install and remeasure the current chamber volume). |
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| Author: | Dart270 [ Sat Jan 27, 2018 1:21 pm ] |
| Post subject: | Re: Cam and compression check |
I would say go for 0.080" off the head. That will have nearly the same effect at 0.100" and will be on the safe side. Lou |
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| Author: | DadTruck [ Sat Jan 27, 2018 3:35 pm ] |
| Post subject: | Re: Cam and compression check |
Quote: Pump gas 87-89 and I was attempting to communicate performance in overdrive is what I'm after
the guy inquiring is wanting to run low octane in a heavy vehicle, he has also mentioned towingI am thinking he will want to cut much less than 80 thou, probably in the 60/s a good target for static compression would be 8.5, to be able to run any kind of ignition advance in a 3600 lb brick of a vehicle, while motoring on the highways, up hills, pulling a trailer with motorcycles in OD ,,,, |
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| Author: | DusterIdiot [ Sat Jan 27, 2018 5:59 pm ] |
| Post subject: | Re: Cam and compression check |
Quote: up hills, pulling a trailer with motorcycles in OD
He's most likely going to be in 3rd during these parts... he may get into OD towing on the flats, but uphill and towing I'd give the tranny (and engine) a helping hand and go to 3.91's in the rear... |
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| Author: | Killer6 [ Sat Jan 27, 2018 7:09 pm ] |
| Post subject: | Re: Cam and compression check |
Quote: So am I okay on the 104 centerline
One word of caution, with a switch to Hydraulics, You are going to be over-preloading the lifters by that .080-.100". And stock preload is usually more than desired performance-wise, You may want toAnd more importantly the .100ths off ? I'm getting ready to go to the machinist Would I be better off with less off in trade for more cam advance ? check the actual preload & get custom pushrods, just a thought............................... |
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