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| Cam and compression check https://slantsix.org/forum/viewtopic.php?t=61872 |
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| Author: | Eltonsd100 [ Sat Jan 27, 2018 7:23 pm ] |
| Post subject: | Re: Cam and compression check |
The head is in good shape ,I don't see it cc much different .just a light lapping and new valve seals . It was a running low mile engine. Lower gears was my next step if I'm unhappy with the power still. I thing the gains per $ are much better beyond the basic stuff. Or I can slow down.. I've never seen great gains from pushing a tow vehicle 10mph faster .. time is lost in fuel stops. Or mechanical problems. The towing is one trip a year really .. use the truck to get us across the boredom of Kansas and then ditch it and ride the bikes across Colorado. |
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| Author: | DadTruck [ Sat Jan 27, 2018 8:05 pm ] |
| Post subject: | Re: Cam and compression check |
there is an eight page post in this forum that I started on this subject back in 2011 titled Hydraulic Cam for low RPM torque and HP http://www.slantsix.org/forum/viewtopic ... RPM+torque I have ran the cam that was developed in that post in the 83 D150 for 5+ years and over 25,000 miles in a slant powered 83 D150, A833 OD, short bed, probably pretty similar to Eldonsd100. The 83 D150 is my summer time daily driver and I tow the 68 Barracuda on a twin axel trailer with it. With a 3.73 gear set in the 8.25 rear axel I can tow fine on the highway in OD. I set the cruse control on 65 to 70 MPH and motor down the road. Only on the steepest hills I will shift down to third. The cam that I have is very similar to what is what is being considered here, the biggest difference is I have a 105 LSA. The cam spec that leads this post off has a 110 LSA. I believe that a tighter LSA is directionally the right way to go for low end torque. The engine basics are: .030 over pistons 8.49 static compression I did the dynamic compression calculations, but I don't have the computer that info is on handy OS valves Holly 2280 Dual Dutras HEI runs regular gas, no knocking or pre ignition issues ever. nothing real fancy, and it pulls fine In one of the recent posts there is a comment concerning hydraulic lifter preload. I watched that closely, I disassembled a slant hydraulic lifter and found it had approximately .090 of preload travel. On the engine prior to disassembly the pushrod was .040 into the lifter. After the rebuild the preload ended up with in .005 of where it was originally. The reground cam with the smaller base circle off set the stock removal from the block and head. |
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| Author: | Eltonsd100 [ Sun Jan 28, 2018 4:35 am ] |
| Post subject: | Re: Cam and compression check |
Dadtruck ... your build and a few others were the reading materials for the direction I'm heading. I have a carter bbd two barrel , but the motorcraft was free and figured with it already overhauled it couldn't hurt. Another build i was trying to research was "aggressive teds " I've seen his build referenced a lot but when I go looking his old posts are blank. What I'm wanting to do is very similar to your build.. you're trailer probably weighs as much as I'm wanting to haul. I have stock valves with a blend job and standard bore. I almost went with a stock cam based on another thread I read regarding power at low rpm .. but I kinda leaned on oregon cars experience in selection. I figured if they were off a little it wasn't by much. Something I thought last night is premiuim fuel would be cheap while hauling if nessecary ,but I daily the rest of the time .... also I didn't want to worry about availability in some of these podunk towns we go through, |
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| Author: | DadTruck [ Sun Jan 28, 2018 9:40 am ] |
| Post subject: | Re: Cam and compression check |
torque is a product of the cylinders compression ratio and ignition spark advance. I intentionally went conservative on the compression knowing that I would be able to run a more aggressive ignition curve. Once the engine is built, the ignition curve is a major tuning avenue to maximize performance. I run a lot of initial advance, a 9R regulator in the distributor and an adjustable advance can as well as a dash mounted manifold vacuum gauge. I have plotted out distributor vacuum advance and mechanical curves so with the dash gauge and tach I always have a good idea of what distributor advance is doing. I built with the idea of using regular gas and have always been able to do so. Concerning the static and dynamic compression that you end up with in your engine. I am a believer in folks doing their own calculations. Going through the process gives one a feel for the interplay of the variables and demonstrates the importance of having accurate input data. RB Racing has a good compression calculator, there is also a dynamic compression calculator and several MC calculators at that site https://www.rbracing-rsr.com/compstaticcalc.html you have had a lot of great questions and there is always great info available at .org You may see differences in some of the responses, that is because the folks on this site build the slant six motors that they want to. So figure out what you want to do and build it and keep posting. and I don't know what happened to Aggressive Ted, he has not posted here in a while. He and I used to talk a bit off line. Ted had a lot of ideas on: ignition curves, cool air to the carb and controlling under hood temps... |
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| Author: | Eltonsd100 [ Sun Jan 28, 2018 2:40 pm ] |
| Post subject: | Re: Cam and compression check |
I appreciate the response and help. I can do the math that's easy. Knowing how it's going to impact everyday running I'm not to sure of. It looks like .100 off is out and it's a question between .60 and .80 off.. with stock valves I should end up with less tourqe i.e. ( cylinder pressures) than your build? Also will my lobe seperation bleed more off than yours? That was what I kinda thought you were implying with your cam. It's these little questions were the setup you're building is close to something else but not exactly the same that are kinda annoying .... great if your racing and experimenting... not so great at finishing projects lol. Also there are a lot of speculative threads on power and the effects of modifications... with very little dyno evidence to plot curves , a lot of talk about peak hp/tq but a graph can be more useful to see how an engine might behave in the real world |
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| Author: | Eltonsd100 [ Mon Jan 29, 2018 6:07 pm ] |
| Post subject: | Re: Cam and compression check |
Am I gonna have problems with .070 off I've run the numbers a lot ( my head is killing me from flu) They're all a ways off of 8.0dcr and my numbers are coming in .2-.3 less than what has been posted here? |
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| Author: | DadTruck [ Mon Jan 29, 2018 6:20 pm ] |
| Post subject: | Re: Cam and compression check |
what are you getting for static compresion |
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| Author: | Eltonsd100 [ Tue Jan 30, 2018 5:06 am ] |
| Post subject: | Re: Cam and compression check |
Okay static is figured three ways right now 50cc chamber 8x.0066=.0528 off head Bore 3.4 Stroke 4.125 Deck.170 Piston top =0 .040 headgasket 8.55 static 49cc chamber 9x.0066= .0594 off Ditto 8.64 static 47cc at .070ish off 8.84 static Intake close figured by . 2/252 =126+110=236-180=56 52 is 4 advanced Intake close at 56 at 8.55 static Is 7.28 dcr Intake close at 52 at 8.55 static 7.44 In 49cc head 8.64 static At 56 7.35dcr At52 7.52dcr 47cc head 8.84 static At 56 7.52dcr At 52 7.61dcr |
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| Author: | Dart270 [ Tue Jan 30, 2018 8:43 am ] |
| Post subject: | Re: Cam and compression check |
Based on those numbers and your desired usage, I'd take 0.060" off. Lou |
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| Author: | DadTruck [ Tue Jan 30, 2018 6:53 pm ] |
| Post subject: | Re: Cam and compression check |
Quote: I'd take 0.060" off.
and I agree with that.are you taking the head completely down for the mill? or will the valves be left in place? if taking the head down completely machine shops will normally hot tank the head and wash it in an automatic washer,,, that process typically gets all the chips from the machining washed out of the water jacket and ports. if you are getting the head machined with the valves left in place, the machine shop may do a hand flush of the water jackets and vacuum the ports, there may still be some machining chips in the water jacket and ports ,, notice I said 'may'. This will vary widely from shop to shop,, just something to watch for. to verify the water jacket is clear of chips, inspect with a magnet on a probe, flush the water jackets with pressurized water,,,blow dry with compressed air. |
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| Author: | Charrlie_S [ Wed Jan 31, 2018 4:34 am ] |
| Post subject: | Re: Cam and compression check |
Trick I learned, when installing a head that might have some trash in the water jacket, is to put shaving cream in the holes. Then nothing can fall out into the cylinders, or onto the deck. As soon as water hits the cream, it desolves. |
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| Author: | Dart270 [ Wed Jan 31, 2018 5:30 am ] |
| Post subject: | Re: Cam and compression check |
Cool trick! Thanks, Charlie. Lou |
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| Author: | Eltonsd100 [ Wed Jan 31, 2018 7:08 am ] |
| Post subject: | Re: Cam and compression check |
Thanks guys! I went with .060 off Pulled the valves and he's gonna hot tank it before hand.. idk what he's gonna do after he machines it. Shaving cream .. great idea . I've been pulling casting wires and stuff Will see how it runs I guess .I've been bouncing back and forth ,but I think I'm looking for modest gains and between , shorter tires , two barrel carb , exhaust, cam , compression,recurve .. it should be close enough and after that I think gears are the cheapest gains. I'm pretty happy with it already just 4th gear is lacking some. The current motor is tired too. Machine shops are getting thin around here. The two good ones I know of the main guys have cancer. My machinist is gonna jump right on this but he was just rediagnosed with a brain tumor ... hopefully all turns out well. He helped my dad put his blown hemi together so he has probably forgotten more than most people know.lol |
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| Author: | DadTruck [ Wed Jan 31, 2018 5:42 pm ] |
| Post subject: | Re: Cam and compression check |
Great, let us know how it runs,,, |
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