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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: Spoonbill on August 21, 2017, 06:33:39 pm
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I have an 87 c10 305 tbi 700r4. The question I have is that when you look up cams on jegs or summit it will show some cams for my truck they have ones that you would normally see like 234 / 238 and then they have a bunch have numbers like 296/304. I thought numbers that high was only for race cars. These weren't unknown cams. This is companies like edelbrock and comp cams so you know the numbers are real. I had an 82 a few years ago and checking them out in jegs and summit. The high numbers back then were like 240's & 250's. How are they so high now. Would roller setups have anything to do with it??
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The lower #'s are at .50 lift on the cam and the higher with 0 lift. Go by the #'s at .50. Anything higher for a small block than 224 int/ 230 exhaust especially on a 305 makes for an unruly street machine...imho......ie less vacuum for power brake booster, need for a higher rpm torque converter, rough to a lopey idle etc. The higher the CI of the engine the less "unruly" IE the above cam in a 350 or 400 would be tamer......overlap makes a big difference also. 107 degrees = lopey idle, 110 to 112 rough idle. 114 and up pretty much unnoticeable. You're passing gas from the intake and out the exhaust the lower the overlap until the rpms get up then you're getting more combustible gas to air mixture and that= more power......but less mpg. Depends on what you want and what you're willing to put up with
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These numbers are 0.50, I have found one that is probably ok, it is 234/238 @.050. Let me ask you this. Truck is all original 87 305tbi 700r4, it only has 66,000 original documented miles. We have had it since we picked it up from the dealership. I don't like this efi crap. I know exactly nothing about it don't want know, grew up with carbs I want to take all of the efi off and get heads, cam, intake and carb. When you look up my truck on anyone's website it will tell you that it has vortec heads but they aren't. They are swirl port heads. So since I am changing it over to carb at that point would I maybe just put in that it is an 86 model or is the block just machined for that type of swirl port head??
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Some one else may want to chime in but I think the only difference in the early model (pre 87 ) and the 87 heads is the angle of the four bolts in the middle of the manifold. Most aftermarket mfg have manifolds that can fit either with the use of provided spacers. I have a pre 86 305 carbed engine with the "old style heads" and an 87 350 TBI engine with the heads drilled to the different angle for the 4 interior bolts. The 2 manifolds I have will fit either........the 85 w/o spacers, the 87 with. I think the intake to head mounting holes changed from 86 to 87 along with the small block going to a single rear main seal instead of the 2 piece. Should be an easy swap going from a tbi to carb
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234/238@0.050 is still pretty big for an otherwise stock 305. You will want a high-stall converter (2500 for sure, maybe 3000), and you ~should~ raise the compression significantly. If the lift is over 0.480", you will need to machine the heads for more clearance. That cam should ~start~ making power around 2500 or higher on a 305.
I would encourage staying around 218° or smaller. a 218° will still have a noticeable idle, but a lot less "snowball" effect of changes that you need to do to make that cam work.
There are EFI cams that you can put in, that will make considerably more power and still be able to keep the TBI, which is hands down better than carb for driveability and economy. I know carbs very well, I know EFI really well.
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I think I might just stay with efi then. That way I won't have to change everything. Since you lined me out with numbers what about I think it is the runners number. I see everything from 170 to 225 what do I need on those numbers to work good with the 0.50 you gave me??
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I don't know what you mean by "runners number." Can you elaborate?
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Intake runner volume
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Is this intake runner in the manifold or in the head itself?
If you're looking at buying aftermarket heads, look for 305-specific heads. The combustion chambers are very small so that you can have good compression. 60cc or less, likely. I think Edelbrock among others have a 58cc head. Once you pick your combustion chamber size, then see what intake volume they offer in that size. Smaller volumes keep the port velocity high which benefits torque - desireable on the street, and in a truck.
BIG cams will want BIG volumes, but BIG requires a whole fleet of other mods to make work - usually at the cost of low speed torque. Err on the side of small, and you will be a lot happier.
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Thanks a lot for the help guys. Answered all questions about that whole part of the engine
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When looking at heads you see numbers like 180, 190, 195. I think it is maybe the volume number but not sure. Maid up my mind and I am going to stay with the tbi but I still want to get heads, cam, intake and Holley has a new tbi system that has more than the stock tbi so I will replace the factory one and keep of course. Anything I do to this truck will be bolt on and I will keep all the original parts. By doing it this way it won't take anything away from the originality. So with all that in mind what heads should I look for. Already got me figured out on what cam do I just need some help now on what heads I should be looking at
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Which cam have you decided to install? Be specific. Same question regarding the Holley injection system.
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The Holley injection is just a tbi replacement. It has 670 cfm which has to be bigger than stock because if you went with a carb and did the numbers deal it comes out to 516 cfm so I figure the stock tbi has to be close to that 516 number. As far as the cam that I have in mind is an edelbrock 22046 rolling thunder hydraulic cam & hydraulic lifter kit which is a complete roller setup for 87 and later sbc chevy 283-400. I want a 1500-6500 setup and I figure this will all get me to that. Not only is this setup all 1500-6500 but the Holley efi intake is that range too. I'm just sure on what heads will work good with this setup. Any ideas??
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That's a big cam.
Unless you're also going to upgrade the rods and rod bolts and valve springs, you will never see 6500. More than once. Not sure how long the pistons will last at that rpm either. You WILL have to modify stock heads to run that much lift.
Don't do this.
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Cam with the same specs (prolly the same cam, less pushrods and such):
https://www.youtube.com/watch?v=8HKlFOJZ0sk
S-n-o-t-t-y.
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I am going to just do a edelbrock total power top end kit so that way it is all designed to work together and just not go over 5000 rpm until I am ready to do the lower end. I think that is the most simple and cost effective way to go at this point. What do ya think?
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You're going to pay $650 for something you're not going to be happy with........just send the $650 to me....at least one of us will be happy.
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I am just going to go with an edelbrock top end package so that I will know that it all works together
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Sorry, didn't notice there were 2 pages on this. If you think going with the edelbrock would be a bad choice what you say to with?
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What this topic actually boils down to is the suitability of your modifications to the specific use you envision for your truck. How will the truck be used? Work truck? Daily driver? Weekend cruiser? Towing? Stop light terror? Race track? Will it be used in mostly flat or hilly terrain? Realistically, what are the typical speed constraints for that environment ...0-40 MPH ...70 MPH ...unlimited?
Trucks are heavy and boxy on relatively tall tires. It takes considerable torque to get them moving and keep them moving. The modifications that work for a lightweight, aerodynamic car that rides close to the ground don't fair as well, or at least fair differently than expected, when applied to trucks. The benefit to cost is lower for trucks. Hence, trucks require a different mindset and approach in the planning stage to attain a suitable outcome. So, my advice is to begin your project by being totally honest about the vehicle's primary environment and its intended "normal" use.
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It will be a daily driver and miles will be 25-70 mph. I want more power cause it is definitely a turd from the factory. I am buying a bass boat so I want more hp & torque for that but it will also be used for shows and cruise nights. I am just so confused about how to go with this. Whether to stay with tbi or change to carb. I just really need help on what to do because what I think looks like the way to go I am being told that that isn't the way to go. The reason I was looking at the edelbrock package is because all the parts in the package are made to work together. I really want an rpm air gap intake but that means going carb. Could someone please find me a top end package that will work. I don't even know what direction to start at. Also with an air gap intake it is 1500-6500 rpm range. I just don't know. Please help
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You need to concentrate on torque. Realistically, how much are you willing to spend? How much of the work will you do versus paying someone else?
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If you're looking for more power
Swapping in a 350 would be a good increase in power
Probably 50 HP and 50 Ft Lbs
The efi stuff is all the same except the 2 injectors
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What do you think about going with an msd atomic efi system. I'm liking what I am seeing and msd is one of the all time great performance companies. I'm really excited about this one. Please let me know. Thanks
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Sorry, I didn't answer all of your questions. I will be doing all the work myself unless I get majorly stuck
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I would recommend staying with TBI, and I would recommend a torque-friendly cam that the TBI can work with, without re-programming. Any stand-alone computer (like the Atomic EFI) will still need some careful tuning to get the most out of it. You could by a chip burner and learn how to program your own TBI for less than the cost of ANY aftermarket fuel system, and still have any-parts-store-component-replacement happiness.
Once your cam starts getting away from stock, you will also need a high-stall torque converter, which, when I bought mine, comes with a stern "no towing whatsoever." I still tow garbage to the dump or recylcling, but I'm not hauling another car, or a big boat, and I am very mindful of what gear I am in so as not to overheat the tranny fluid with the heat from the loose converter. You will also want to be cruising on the highway at about 3000rpm for that cam you had picked - if you have a 700R4, the truck won't likely be happy in overdrive.
If you buy 305-friendly heads, they will likely be useless for a later 350 - it's good to buy parts that can swap around if and when you change motors.
An air-gap intake will be a bit more of a challenge in winter, as there is no heat to help vapourize fuel from the TBI or carb. It will likely run poorly and burn more fuel until it's fully warmed up. You ~can~ put TBI on an air gap (they sell TBI-to-carb-intake adapters).
If you pick a cam that's a whole lot milder/streetable/trailer-friendly, your costs go way down. With a reasonable and mild cam, you don't really ~need~ killer heads. Stepping up in cam is a big snowball effect.
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Ideal situation if the $$$ were available is 2 trucks....... one a low end torque beast for your haulin and toodling around town needs ......and a high end high HP, gas burning, tire smokin screamer for the "Friday/Saturday" night adventures. The unfortunate thing is you can't have both with the same vehicle.........dadgum the physics of it all.
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So I can still get the air gap intake with tbi? That would be awesome. I don't want to crack the tranny open so no go on a new torque converter. What cam would you suggest and what heads?
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What do you think about the fitech unit? Looks pretty cool.
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I can't find a single bad review on it anywhere. I don't even think I have seen one below a 5. If this fitech really does what it promises then that is a heck of a price
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I would encourage staying around 218° or smaller. a 218° will still have a noticeable idle, but a lot less "snowball" effect of changes that you need to do to make that cam work.
If you're looking at buying aftermarket heads, look for 305-specific heads. The combustion chambers are very small so that you can have good compression. 60cc or less, likely. I think Edelbrock among others have a 58cc head. Once you pick your combustion chamber size, then see what intake volume they offer in that size. Smaller volumes keep the port velocity high which benefits torque - desireable on the street, and in a truck.
An air-gap intake will be a bit more of a challenge in winter, as there is no heat to help vapourize fuel from the TBI or carb. It will likely run poorly and burn more fuel until it's fully warmed up. You ~can~ put TBI on an air gap (they sell TBI-to-carb-intake adapters).
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Thanks for all the help guys. She threw me for a loop yesterday. I go to do some errands, started the truck and you have to let it full warm up or it will die but this time it was much worse but I finally got it warmed up. I put it in reverse and it almost died so I throw it back to park so I can get gathered up. As soon as it got to were it would idle I shifted it into drive and same thing and this time it did die but it started right up. I went to do my errands and every time I got to where I was going same thing every time. Today, same thing. I just don't get it
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Hey skinny, what top end would you go with if you were me??
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I would leave the engine completely stock, except find a GOOD "torque" cam that the TBI computer and stock torque converter can still work with, then enjoy decent power and decent mileage.
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What cam would you suggest
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Hey guys, say you are building a top end like I am and you know intake you want so you are building your kit around it can you put in a intake that has an rpm range of 1500-6500, even though you won't take it that high can you put in a cam & heads that have an rpm range of idle-5500???
Does anyone know if this will work?
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You hear all kinds of stories about how there are a bunch of parts on a 350 that can go on a 305 and give it more performance than a 305 a part that is made for a 305. I had a conversation yesterday with a guy that told me you can put a performance 350 cam in a 305 and it will make it scream as well as a lot of other parts. I find this very hard to believe. Is there any truth to any of it?
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With the exception of the roller cam generation he's is correct. A cam from a 1956 265 cu in SB will work just fine in an 86 350 and vice versa. You gotta remember the laws of physics though. A radical 350 cam put in a 305 will become even more radical. HP will peak higher in the rev range but low end torque will suffer. You also have to watch the lift. Higher the lift the more fuel to theoretically pass into the comb chamber but at a certain point w/o the right combination of pistons, heads and springs............BANG pistons hitting valves........again you can't have a low end stump puller and a high end screamer in the same vehicle
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Gotcha. Thank you
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So I'm doing the top end and know what intake I want and it has an rpm range of 1500-6500. I'm not finding any cams or heads with that range. If I put in a cam and heads with an rpm range of idle-5500 would those work with the intake or does it all have to have the same range???
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Why are you dead set on an intake that makes power up to 6500 RPM ? Are you EVER going to hit 6500 rpm ? Without the pistons. rods, crank, cam, valve springs to support 6500 rpms you're whizzin in the wind and that intake manifold will make your motor perform worse instead of better. Decide what you're going to do with the truck and go from there. People are trying to help you but you're not listening
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A common misconception is that with RPM increase comes power increase which is false. They are not linear, just look at any dyno results. Once you've hit your peak power output your gains drop off. Think of it in a simple manner and while not technical seems to help people grasp the concept, torque helps give you the push you need to get that big lump of steel moving. Power is the ability to continue pushing. Engines have a happy place where torque reaches it's peak operating range and where in your initial launch will get the most pull. The whole concept of the CVT transmission is to optimize this. Read up on them to better help understand how the whole package is what you need to think of when designing your power plant.
A cam, intake and head combo should make sense for the vehicle it's in and the powertrain it is equipped with. In most cases people go right to the wrong system first. The biggest performance gains in these trucks actually start with optimizing final drive ratio, upgrading from the old 3 speed transmissions and so on. Building a top end performance engine behind a loofy powertrain and numerically low final drive will yield negative results. So unless you've already done these things you shouldn't be aiming for 6500 RPM operating range.
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What do you think about the fitech unit? Looks pretty cool.
Fitech is a really good set up. Just as good as the "larger" brands at a lower cost. I know a few guys that run them and all of them say they would never go any other way again.
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