73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Performance => Topic started by: IOVMatrix on December 28, 2008, 03:58:53 pm
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So I have the stock 454 in the '86 Chevy. I have been reading many many articles and I am still stumped on what a good set up would be for this engine. It will mainly be towing heavy loads. I do have a new TH400 and 1500 stall converter going in it. I do have a 750cfm Double pumper on it right now with a set of no name headers(came with the truck).
I would like to have that low idle cam lope as well. Any help would be appreciated.
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Will this truck have to pass emissions?
What is your budget for this buildup?
Edelbrock has some nice power packages for this motor. You can start off getting a performer cam/intake/ and 750 CFM carb (my choice over the Holley). You can add the aluminum heads now or later when you have the cash.
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I don't think a stall convertor is a good idea for towing
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First off get rid of that dbbl pumper and get a vac secondary carb. You can pick up a set of alum heads, air gap intake and a decent cam to work with the gears and TC you have.
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You don't need aluminum heads. What are the casting #'s on the heads you have? Definitely bring the compression ratio way up. The big blocks can handle much higher compression ratio's better. The edelbrock performer is a decent cam as is their intake. Headers, at least 2.5" ehaust, the TH400 is a good trans however no overdrive. 3.42 or 3.55 rear will be good too.
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You don't need aluminum heads
The heads on those later 80s big blocks have really small intake ports (much smaller than oval). If nothing else get some earlier casting heads, those small port heads suck.
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For pulling the smaller heads are better, just don't expect good breathing over 5500rpms.
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The truck barely sees over 5000 rpms now anyways. Why should I get rid of the Double Pumper?? The 454 did not come from the factory it replaced the 350 that was in it. It does have 4.11 gears in it now. This truck does not have to be emissions tested at all. I dont have an exact budget set but I would like to keep costs down.
Vile, where could I find the casting numbers. This engine does have an egr/emissions setup on it already. Are you suggesting I have the heads milled or ported??
Also, I was looking at the thumpr cams from comp cams. Is this a good buy or should I just stick with the edelbrock??
Thanks for all you help so far, Im mainly a Motorcycle/ATV Mechanic this is the best spot for info on these vehicles I have found so far.
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The double pumper is a mechanical secondary carb and is mainly for vehicles that doesn't see a varied load like a truck does. Vacuum secondaries can deal with say going up a hill, pulling your trailer, or just cruising down the highway better than a double pumper.
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I would agree with a vacuum secondary carb. I had a dominator I was constantly playing with and traded it and a few other goodies for this carb click here (http://store.summitracing.com/partdetail.asp?autofilter=1&part=EDL%2D18134&N=700+400065+4294919007+305249+115&autoview=sku) and was able to dial it in very easily with literally no frustrations. I'm leaving it there for now. If I had a race track within a reasonable distance and was running it frequently I would have stuck with the dominator.
The casting #'s can be found by removing the valve cover. Many of the factory heads can be modified to perform excellent. Porting is something that takes a LOT of time and is tedious but the results speak for themselves. I wouldn't spend hours and hours doing it if the results weren't noticeable. There are lots of technical articles you can read about proper techniques but, tight radius', port alignment, multi valve angles, all = HP or you can whip out your wallet and pay someone to do it for you. Another option is an aftermarket head but they aren't cheap.
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I think Isky makes a towing cam for the 454. I remember I was looking into it when I first bought my dually. I ran it through the DD on a stock 454 and it picked up a good bit of torque in the lower rpms. You may want to check that out.
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If towing is your main concern, the peanut port heads are your best choice (which sounds like warping of the brain tissue coming from a performance enthuisiast), but it's true. Small ports make for excellent cylinder filling at low rpm's, just like your heavy hauler needs. Compression ratio was kept around 7.8:1 with the dished pistons, which yours likely has and that is because the 454 from the mid 70's up was mainly used for heavy duty purposes. Heavy loads and low octane fuel spell detonation on an engine with too much compression. The cam is an area that could use improvement as the original for the engine has 193-204 deg's duration @.050 and a lift at valve of .398-.430. Be careful about how much duration a cam has, it is probably the biggest deciding factor on an engines attitude. More duration moves the engines rpm range up the scale where it will make peak torque. For a good towing motor, look for dur@.050 to be around 205 in. and 215 ex. with a lift at valve around .480-.500. This size cam would still work well with peanut port heads and an rpm range of idle to 5000. I reccomend mathcing valve springs for your cam pick as the stock GM springs are quite spongy and will contribute to a very early valve float. If you are currently useing an Edelbrock performer manifold, that will be your best choice as it is a match for peanut port heads. The same rule with head port size applies to carb size, smaller area equalls better low rpm velocities. A switch to a 600-650 cfm carb would provide more low rpm power and would still not run out of carb at 5000 rpm, which your motor probably never see's anyway. Go with vaccum secondaries if you make the switch, mechanical secondaries are best not used for your truck or any other heavy vechicle. I built a 454 for my dually several years ago (check out my video's on youtube A169KL)and carefully chose all my parts to work together. When parts are chosen for power in the useable rpm range and application, you cant go wrong! Good luck with your project. JW.
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You can definitely up the compression ratio on a big block. I wouldn't purposely set out looking for smog heads and limit yourself. the torque will be there with a big block. If you want it to make torque at lower RPM's you can easily pick a cam to do so however a better breathing engine will make more torque and hp. Find out what you have for heads already on there.
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Improved breathing, port size and shape is in direct relation with rpm useage, so a large oval port head such as the 781's or 049's isn't going to improve the engines power output at speeds below 4000 rpm. and torque within this rpm range will be lower with the large ovals. Shift points in this truck are probably occuring at 2500 - 3000 rpm on the average with a TH400 and 4.10 rear. As for compression ratio, I would not push it beyond 8.5:1 in a towing motor. When you get into pulling that long hill and cylinder temperatures hit the roof, detonation will set in. After a few episodes like that, you will be speaking about the motor in the past tense. Of course improvements could be made to the existing heads such as pocket porting, widening the short turn radius, cleaning the rough casting in the ports, port matching intake, gasket and head, and a quality 3 angle valve job. One important aspect in regards to proper quench, upping the compression ratio a little and helping to control detonation is the fact that with a factory engine useing a composition head gasket, the pistons have a negative deck height of .020. Combined with a composition head gasket of say .040, that puts quench at .060. That's far beyond the desired .038 that engine was originally intended to have. One easy solution is to substitute the composition gasket for the steel shim gasket which the engine was designed to use, and get the quench were it needs to be.
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Howdy.
You aren't trying to bring the engine to high rpm. 600 or smaller carb. Intake Edelbock Performer Air Gap, not the Rpm.
crane cam customer service is tops with giving you a great cam with your specs that you tell them and of what you want what you have to do.
Porting the heads is always a great choice in my opinion. If nothing else, having the valves done up, back cuts,etc, smooth porting, will improve your engine. Aluminum is lighter, but more of a cost issue.
Stall convertor is a bad idea. You don't want a heavy load on the truck and have the weight slap your gears. Increase your electric current ability for better performance with a good performance plug, well insulated large core wires, and make sure your exhaust can breath. Tri Y headers, H pipe or X pipe, 2 1/2 or 3 inch dual exhaust.
If you can, change to an electric fan. keep the oil clean, and make sure the oil is capable of lubricating the bearings. a 5w30 is not going to do the job. 10w40 might do the job, all depending on the oil and your engine, and a 20w50 will more so do the job, all being that the weather is capable or that the oil is capable of the temperature. I myself run Redline 15w50 in my super mouse. 30 below zero on the cold and the heat is about the best I am going to get with the 50 weight. I also use a quart of Lucas synthetic for added protection. Make sure your fluids are good, especially the rear axle.
Best I can tell you. As well that I believe the engine can handle 8.5:1 compression without batting an eye and that using aluminum heads will allow the 9.5:1 compression.
Oh and forgot to mention, changing your rockers and lifters over to rollers is a very great choice and will bring great improvements. Less friction equals more horse and more torque.
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budget will tell you
but get a nice truck cam, you can gain rediculous amounts of torque with a truck cam, and have a little idle lump, comp sells a 4x4 cam, thats the way to go