1981 c10 truck

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larry
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Joined: Fri Jul 16, 2010 7:14 am

1981 c10 truck

Post by larry » Sun Jul 25, 2010 5:14 am

Have just fitted some Edelbrock E street heads (70cc ) looking for a bit more compression. Went for a drive and there doesn't appear to be much difference over the stock heads. This engine is stock, other than a Weiand intake manifold. I suppose these heads might like a change in camshaft. Any suggestions? I discovered that the vac advance diaphram has blown so I have made an adjustable one. I had an old Pro comp adjustable one, also blown, and ground the rim off it, separating the two halves. I then machined a short piece of tube to 2" id, and welded the adjustment half of the old can to the tube. In the open end, I cut a circlip groove. I then made a piston,to take a 2" o-ring, and welded a rod to connect to the pickup stator. A retainer washer,held in by the circlip, keeps the piston and spring in the bore. The plate attaching the can to the distributor is welded to the retainer washer. I used the Pro comp spring plus another smaller spring inside it,as the vac advance was starting to early, I felt. (5'' hg). I can now adjust it to begin at about 11"hg. When cruising at 60 mph,on flat ground, the engineis pulling about 13" vacuum. I still need to mess around with the mech. advance. It's all in by 2200 rpm,but not very linear. Anyhow,its running ok. It's my everyday transport,so will have to use it, regardless. My next job is to build a distributor machine, so will sort out the advance then.


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Steptoe
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Re: 1981 c10 truck

Post by Steptoe » Sun Jul 25, 2010 4:54 pm

I discovered that the vac advance diaphram has blown so I have made an adjustable one
With a good VA that works near enough withing the deg and vac range reqd, these can be adjusted by adding stop tags to the activation arm.
Adjustables come in Vac several ranges, there is 1 model that has 6 basic Vac ranges that can be changed by pushing the adjusting screw hard in the turning...the scew then changes the starting piont but not the finish point of the vac range, doing so also reduces the range of vac and degs.
Using tags to restrict the movement of the actuating arm can also be used to change ranges and starting /finsh pionts.

You need the cent set up..both the all in and the idle before establishing what you need in the VA..and require a vac gauge in car to establish what vac the engine has at different loads, speeds, Diff cruise speeds etc.
I suppose these heads might like a change in camshaft. Any suggestions?
The secret to engine design is have ALL the go components (cam, header, heads, compression, inlet, carbs, drive train ratios etc) to work in the rpm range that is required. .. mis match parts and one is just banging ones head against a wall.
So you need to establish what the vechice is for 99% of the time, what rpm range its working at 99% of the time.
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storm
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Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: 1981 c10 truck

Post by storm » Mon Jul 26, 2010 4:18 am

Steptoe wrote:The secret to engine design is have ALL the go components (cam, header, heads, compression, inlet, carbs, drive train ratios etc) to work in the rpm range that is required. .. mis match parts and one is just banging ones head against a wall.
So you need to establish what the vechice is for 99% of the time, what rpm range its working at 99% of the time.
I couldn't have said it better myself. There seems to be phases when people want high stall/high revving etc yet want to be able to drive at 100kmh (60mph or so) at 2000 rpm. Match your parts combination well and you will enjoy your car alot more than a high powered beast that you can't use for 99% of what you want it for.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

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Steptoe
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Re: 1981 c10 truck

Post by Steptoe » Mon Jul 26, 2010 4:18 pm

enjoy your car alot more than a high powered beast that you can't use for 99% of what you want it for.
I have a bottom end cam..more bottom than a stock...1200 stall, duel plane, truck rams horns, carb(mixer) about 450 cfm the gives bottom end reponse, a 255 diff/350 turbo )30 mpg=1000 rpms
She tows well, runs sweet around city streets, cruises quietly out on the highway, any passing manuver is very quck...(a truck and trailer hit 100+ mph level with the truck cab) If I want to show off, she lights up real easy..too damn easy if pulling into a gap in heavey traffic...and its damn sight quicker on the strip than the factory stock equivient...(quck change of torque convertor into high 13s.)
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storm
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Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: 1981 c10 truck

Post by storm » Mon Jul 26, 2010 5:07 pm

My old T/A was like that. 25mpg at 100kmh with a 400ci Pontiac engine running a slightly modified Quadrajet (LPG wasn't readily available when I had her unfortunately).

Sorry about the off-topic :oops:
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

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Steptoe
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Re: 1981 c10 truck

Post by Steptoe » Mon Jul 26, 2010 5:47 pm

Forgot to mention...at current petrol/lpg prices a fast trip 75/85 mph....cost lpg converted back to mpg petrol 32/33 mph.
If I was running petrol would be lucky to hit 20 mpg.

Yep its all about having all the go stuff doing the same thing in the same rpm range.
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