84 K10 is still gutless after cam heads intake

[CentipedePerformance]

So I bought an '84 k10 as a daily a while back. It had a GM Goodwrench 350 put in it 4 years ago, and was otherwise stock. I rebuilt the 700r4 with the better pump, planetaries, a shift kit and mild converter. I then put port matched TBI heads on, an Edelbrock Performer intake, Edelbrock 650 cfm carb, with a Melling MTC-1 cam, Tri-Y headers, 2.5" mandrel bent y pipe to 3" single in/out Flowmaster. Distributor has an Accel ICU, Accel coil, timing at 37* with full advance coming in at around 3000 rpm. Vacuum advance is hooked up to manifold vacuum. There is no longer any emissions junk on the truck. No smog pump, no cat, no egr, and it has the hard parts for a solid running motor. It has way more just off idle than it used to, but is still gutless. I am hard pressed to feel a difference between 1/2 and full throttle. What could I be missing? Gears maybe? Its got a 4" lift with 33's and what I would guess are stock gears.

[chebyshortbox65]

Advance should be hooked to ported source not manifold that could be your problem the timing is advanced all the time
Posted via Mobile Device

[CentipedePerformance]

hooked up to manifold only advances the timing at high levels of vacuum such as cruising. As the throttle blade opens further, manifold vacuum decreases, and pulls the vacuum advance out. Ignition timing is set at 37* with just the mechanical advance, if you could put a timing light on it running down the road, timing at cruise is probably 45*. When cruising, the mixture is very lean, which takes longer to burn, so you need to advance the timing more. Difference between ported and manifold, is that the ported vacuum has nothing at idle. Advancing the timing at idle makes for a smoother idle, and decreases exhaust temperatures, as well as coolant temperature at idle. The reason OEMs went from manifold to ported, was because they needed to meet the new emissions requirements. Higher egts along with the air pump system allowed for the excess hydrocarbons to be completely burned further downstream by the Catalytic converter.

[CentipedePerformance]

Oh, and I should add, the timing mark on the balancer is correct.

[ont_guy_38]

If you have 3:08 gears and 33" tires that would kill alot of your power . i have 29" inch tires on my 2wd and went from 3:08 gears to 4:10 and it's like I put a whole new drivetrain in. I would see what you got for gears . With 33 I would think you would want atleast 4:10

[CentipedePerformance]

The fender tag says "Axle Ratio-Standard" so I can only assume 3.08? which would explain the lack of power.

[INSIDIOUS '86]

Originally Posted by CentipedePerformance

hooked up to manifold only advances the timing at high levels of vacuum such as cruising. As the throttle blade opens further, manifold vacuum decreases, and pulls the vacuum advance out. Ignition timing is set at 37* with just the mechanical advance, if you could put a timing light on it running down the road, timing at cruise is probably 45*. When cruising, the mixture is very lean, which takes longer to burn, so you need to advance the timing more. Difference between ported and manifold, is that the ported vacuum has nothing at idle. Advancing the timing at idle makes for a smoother idle, and decreases exhaust temperatures, as well as coolant temperature at idle. The reason OEMs went from manifold to ported, was because they needed to meet the new emissions requirements. Higher egts along with the air pump system allowed for the excess hydrocarbons to be completely burned further downstream by the Catalytic converter.

If he's running a 650 it still may be pulling vacuume at higher rpm.

Also the exhaust is still undersized and 33 tires and 308s would kill any stout motor.
Posted via Mobile Device

[CentipedePerformance]

The heads don't flow a whole lot of air, and the cam is relatively mild. I built it more for torque than for top end. High port velocity vs. lazy huge ports, that's why I chose the 650. If there is any manifold vacuum, it's not going to be a whole lot, I guess I could put a vacuum gauge on it and find out. Point being, with the low compression I have, even if it adds a few degrees past 37*, I don't think it would be as lazy as it feels. And what would you suggest for exhaust? Dual 2.5"? When I was under there, it didn't look like there was much real estate on the passenger side to run exhaust between the t-case, and the support bar for the t-case, Which is why I ran the y-pipe. I built a very similar motor for a 2wd, the only difference being that truck had true duals, half a point more compression, and a slightly larger cam, and it ran really strong. I think it really comes down to the gears. First gear pulls OK, but anything after that is lazy. I think I will just save my pennies for 1-ton axles instead of re-gearing these 10 bolts.

[INSIDIOUS '86]

Get all your timing at 2500 rpm and if your running a single pipe run a Better flow muffler as well. Your first gear is low and will feel strong with a 700r4. Also please boost valve and sonnax servo your trans.

If your doing a lot of off road better axles and gear are a good idea. If not the ten bolts are almost as strong as car 12 bolts.
Posted via Mobile Device

[mopar346]

Gears definitely play a huge role in feel, but what has me a little puzzled is you say it is fine on take-off, if anything a 3.08 would be lazy from a stop and run out the big end hard. The exception is if it is combining with the convertor to hold your RPMs down.

I initial reaction from the first post is that I have always heard TBI heads are junk and really cant make them work. I have never tired or never seen any flow numbers on them so I cant say personally, but people I trust a great deal in this area have repeated it over and over. That don't make it true but it is something to consider.

[INSIDIOUS '86]

Originally Posted by mopar346

Gears definitely play a huge role in feel, but what has me a little puzzled is you say it is fine on take-off, if anything a 3.08 would be lazy from a stop and run out the big end hard. The exception is if it is combining with the convertor to hold your RPMs down.

I initial reaction from the first post is that I have always heard TBI heads are junk and really cant make them work. I have never tired or never seen any flow numbers on them so I cant say personally, but people I trust a great deal in this area have repeated it over and over. That don't make it true but it is something to consider.

700r4 has almost a granny low first. So take off will be good till 2nd
Posted via Mobile Device

[CentipedePerformance]

Originally Posted by INSIDIOUS '86

Get all your timing at 2500 rpm and if your running a single pipe run a Better flow muffler as well. Your first gear is low and will feel strong with a 700r4. Also please boost valve and sonnax servo your trans.

If your doing a lot of off road better axles and gear are a good idea. If not the ten bolts are almost as strong as car 12 bolts.
Posted via Mobile Device

The 3" tail and Flowmaster were already on the truck when I bought it. I'm not a huge fan of the Flowmaster sound anyway, so I was looking at going to a Magnaflow before too long. I plan on doing a decent amount of off-roading, and would like to go larger on the tires. I have heard that anything larger than a 33" and the 10 bolts will start to break stuff if wheeled with any skinny pedal. I didn't personally build the 700r4, I gave it to my tranny guy and said build it so it won't break lol. I'm sure he took care of anything that needed to be done. He built my buddies 4l80e which is behind a twin turbo LS3 in a Silverado so he knows what he is doing.

Originally Posted by mopar346

Gears definitely play a huge role in feel, but what has me a little puzzled is you say it is fine on take-off, if anything a 3.08 would be lazy from a stop and run out the big end hard. The exception is if it is combining with the convertor to hold your RPMs down.

I initial reaction from the first post is that I have always heard TBI heads are junk and really cant make them work. I have never tired or never seen any flow numbers on them so I cant say personally, but people I trust a great deal in this area have repeated it over and over. That don't make it true but it is something to consider.

If I just mash on it off idle it will chirp the tires (it has the gov-lock in the rear) and carry pretty strong through first. The TBI heads are no good for making a high horsepower drag mill. That you are correct on. But they are decent for a towing/offroad motor. They can be had for basically dirt, and they are swirl port, with plugs closer to the center than conventional sbc heads. They produce good torque, and better mileage than equivalent iron heads. I would like to upgrade to some better aluminum heads at some point, but for now, these should be fine.

[Firebirdjones]

Might be a low compression issue as part of the performance missing.

Those goodwrench 350's were only rated at 8.5:1 but I believe several magazines have torn them down for buildups and cc'd everything only to find it really only has about 7.8:1 with those large 76cc heads they come with, and the fact that the engine even has a dished piston in it last time I saw one apart.

It would help, and probably perform much better all around, if you went with a set of vortec heads and their smaller 64cc chamber, not to mention they flow decent for a stock head, and 170cc intake runners make great torque, better combustion chamber design to promote better burn, etc.... That would have been my first choice for a cheap engine type of build.

If those TBI heads also have a large 76cc combustion chamber,,,and you installed those heads with your typical .038-.041 compressed head gasket rather than the thin .015 steel gasket GM had on there, then the compression is going to be much lower than 7.8:1 that I've seen these engines reported to have.
When you couple that with a larger camshaft with more overlap that bleeds off cylinder pressure and kills your dynamic compression ratio, it really makes a lazy engine that feels down on power.

I'm just spit balling here because without all the specs and variables it's anybodies guess. Just some thoughts that crossed my mind.

[CentipedePerformance]

Its true, the compression on these motors is pretty wheezy. I'm not looking for a tire roasting 1/4 mile burner, just an old truck that can pull itself around pretty decent. The only problem with Vortec heads is by the time you machine the spring pockets and valve guides, it runs the cost up. This was done on a budget, and not meant to be a screamer. The more I think about it, I think the gears are the issue. I'm trying to be realistic with my expectations of this motor. Only problem is, my old truck was a 1st gen Dodge Cummins, that I p-pumped, worked over pump, had big injectors, bigger turbo, and put down 398/1011 on a dyno in Phoenix, so pretty much everything feels gutless compared to that thing. It just broke stuff all the time and was really expensive to maintain. I think with gears it will be much closer to what I am looking for. I appreciate all the help, I guess I was hoping for an easy fix or something simple I may have overlooked lol.

[Firebirdjones]

Originally Posted by CentipedePerformance

Its true, the compression on these motors is pretty wheezy. I'm not looking for a tire roasting 1/4 mile burner, just an old truck that can pull itself around pretty decent. The only problem with Vortec heads is by the time you machine the spring pockets and valve guides, it runs the cost up.

You can buy them brand new with the valve spring/guide work already done from Scoggin-Dickey for $600 or in that neighborhood last time I checked. That's dirt cheap. Cost more than that to refresh an old set of heads.

[Firebirdjones]

Eh,,,just checked, appears prices have went up on these since last time I've played with them.

http://sdparts.com/details/scoggin-d...enter/sd8060a2

At this point may as well do a good quality aftermarket aluminum head for a few hundred more and call it done,,just my opinion.

[CentipedePerformance]

Mine were $200 on craigslist, already freshened up and machined for positive valve seals, with a new set of Comp Cams springs. I got the intake with them for another $50, and bought a gasket set, cam and lifters, and carb for another $500. After hoses, belts, fluids and a 100 amp alternator, I have about $900 into redoing the top end. Yes I could have bought new heads for a bit more money but I have an 81 c10 that I am building up and putting all my money into, big block, 4l80e yada yada. I was just freshening this one up to give it a bit more oomph for regular duties. This is just the towing/hunting and camping rig. Nothing special.

[INSIDIOUS '86]

^ with him on this. Your almost better with any other head other than 305 heads. Some l98 heads would still make low end and raise your compression with 58cc chambers ( these are zz4 heads as well) They are a factory head and can be had cheap. Untill you go above 195cc runners on engines with higher overlap cams low end torque isn't at risk.

Change your gears and be carefull with that gov bomb locker
Posted via Mobile Device

[mopar346]

Originally Posted by INSIDIOUS '86

700r4 has almost a granny low first. So take off will be good till 2nd
Posted via Mobile Device

Isn't it basicly a 350 with and O/D meaning the same gear ratios 1st through 3rd?

[CentipedePerformance]

305? I was under the impression 305 heads were super small combustion chambers and valves. Or are they the same for 305 and 350 TBI? Mine have the 193 casting numbers and come with the 1.94" intake valves, and IIRC 64cc combustion chambers, where I thought the 305s had 1.84"? Either way, the engine is back together, and I am not willing to change the heads again any time soon. I don't think I will mess with the stock half ton axles. The gov-lock is prone to failure, and by the time I bought gearsets and install kits, along with a better locker for the rear, I could practically have a set of 1 Tons.

[Firebirdjones]

It all depends on what you want out of it. If this is just transportation and it's getting the gas mileage you want, dependable etc.. I'd leave well enough alone.

It sounds like it's all going to steam roll into a big money pit if you keep going

[mopar346]

I don't believe TBI heads are known to give good MPGs either.

[CentipedePerformance]

I have heard that they are better than conventional SBC heads due to the swirl port design. I don't claim to be an expert, but I did a bit of research before I bought them. And the money I spent on complete heads with the right valvesprings and retainers, would have only probably covered machine work to get a set of Vortecs or my stockers re-done. I think we can all agree that the 3.08 ratio axles and 33" tires are my biggest problem at the moment. The motor is not getting opened up again for a long time even if I have to deal with it as is. Its not terrible, just not as good as I had hoped. And money pits are what I seem to love lol. My old Dodge was a huge money pit, my '81 is a money pit, this thing is a money pit, but hey, that's what we all like doing right? Modifying our vehicles to suit our particular needs or wants.

[mrhino]

Im with Centipede on those TBI heads. I been planning the engine build for my crew cab and actually went looking for those heads. iv done quite a bit of research on them. heres what iv found. There junk they dont flow for **** and that big hunk of cast right in the middle of the runner just flat ****s up the flow. at the upper rpm range, most guys throw them away. now that iv said that. these heads work great for low end torque. the swirl port actually works at low rpm about 3500 and under . and if you clean up the exhuast port it flow pretty good to. The set i have have been surfaced and mild pocket port done there are a small 58cc. and yes i will be running a dished piston. Im hoping for some awesome torque numbers and great fuel mileage. I guess we'll see how it goes.

Dont give up on that head just yet. I cant wait to get started on my engine. So keep us up to date on what you find.

Oh its just my opinion but I wouldn't run a edelbrock on anything. plus it might be to big. Im willing to bet if you got a smaller carb it would run better and accelerate better to. good luck to you

[Firebirdjones]

3.08's and 33's aren't a horrible combination, definately not the end of the world. You won't be setting stop lights on fire, but still very driveable.

I had an 84 blazer with 3.08's and the 700R4, and actually had a bone stock goodwrench 350 in it. Drove that for years, wasn't all that bad with the 3.06 first gear. Was just a driver though and was never interested in changing much else on it.

My current 72 blazer had factory 3.07 gears, I threw 33's on it. 350 turbo only had a 2.52 first gear, and the 355 was mild, forged flat tops, small RV type cam, performer rpm intake and 750 holley. It actually would get up and go decent considering. I modified the trans governor to hold the part throttle shifts longer for around town driving which helped alot with stop and go. Still knocked down 13 mpg city and 16 mpg highway.

Switched to a 6.0 LS engine and 4L60E, left everything else alone for a while. The 3.06 first gear and 1.62 second pepped things up, and it would actually lay some rubber with the 33's.

After a year of that I swapped in a set of 3.73's so I could enjoy more of that 6.0 and I think the setup now as a whole is about perfect.

Gears are funny like that though, you could put 4.88's in a 6 banger and feel like it would rotate the earth I have a couple other cars here with 4.56 and 4.88 gears, heck of alot of fun.