Pulled the engine in my 87, suggestions on rebuild please

[weider1717]

Hi all,

I have a near mint 1987 that has 68k original miles and just due to age the valve seals needed done and I have a core plug leaking. I know it was extreme but I just pulled it I have it on the stand soon to go to a trusted builder that does builds on the side.

Any suggestions? It’s an 87 350 and rated at approx 210hp? I don’t want the block decked which would lose my stamp pad numbers etc.

Since it’s a v10/k10 4x4 I think I am even a bit against putting a big lopey cam in it (maybe if it was a c10..)

I also plan to tell him only overbore just the amount needed to get rid of the ever so slight “lip” at the top of the cylinders.

I also don’t want to swap heads, or intake manifolds, I want it original.

I know all that limits me extremely! But are there ant go to cams that would be better than the stock grind and I’d be silly to pass on? Any particular timing gear sets I should suggest and pay up for, run a thinner head gasket for a little more compression, just any suggestions are all even a specific brand piston to request? I had planned to just tell him same as stock with the overbore amount.

I am engine savvy but just don’t know the details, only rebuilt and put back top ends so any suggestions on what you would make sure to do would be appreciated.

I already have a nice felpro gasket set one piece for the oil pan etc I’ll just have him use that unless he suggestions otherwise

Thanks guys
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[57NAPCO]

Still running the original TBI system? Not many options if you are....just my opinion.

[LT7A]

You can do a cam swap, but you will need a new chip. Literally. Your TBI is run by an OBD1 computer. And that computer is severely limited in its ability to understand modifications. What has worked really well for my 93 TBI is a performance cat back exhaust system. A metal matrix catalytic converter, because the stock ones are very restrictive. Next, opening it up on the intake side. There is an aftermarket salad bowl that lifts your air cleaner up above the injectors and allows a better path for the air. I also run an open element air cleaner which nets an immediate gain, however does not look stock. Search ultimate TBI mods. And check the web page TBIchips.com. the guy who runs that page can probably burn you a chip if you do swap your cam, but it seems to be a drawn out process. However, he has many good tips on how to do minor power tweaks. With just the exhaust and intake changes my truck pulls much better than it did when new and it's got 230,000 mi on it. I also run an MSD 6A and high quality distributor cap, rotor, plug wires. Stock AC Delco plugs work best, just need to be changed with relative frequency.

[THI]

Consider replacing the heads, the factory TBI heads are about the worst flowing heads GM ever put on a 350. For about what it cost to rebuild the factory heads you can buy a set of Dart Iron Eagle SS heads for a 1987-1995 350 with 67cc fast burn chambers - more efficient than the factory chambers.

As for a cam, look for one with an intake duration around 205* (at .050" lift) and a wider lobe separation (like 114*). The factory cam used in the CrossFire Injection and early TPI Corvettes would be a good one, it was also used in the 305 HO cars of the 1980's. Howards makes a duplicate of that cam https://www.summitracing.com/parts/hrs-112001-14

[kwmech]

I second the motion on a different cyl head. AND if your block (and it should be) is roller cam ready, I would look in that direction also.

[jayoldschool]

Reseal it, more up to date cam if you really want (and do a timing chain same time), roller rockers, new (better) springs. Vortec heads if you want to get deeper.

[kipps]

The flat tappet cams were an Achilles heel on these 1987 TBI engines. They would wipe cam lobes, and then completely defy any attempt to get them running correctly.

I suspected and/or knew about three problems with my '87 TBI before I ditched it. Wiped cam lobes, plugged catalytic converter, and corroded electrical splices in the engine wiring harness. Resolve or rule out those three issues, and you should be good to go.

[Tom]

Since nobody listened to you wanting to keep the stock big stuff:

-The block should be a roller cam block with a flat tappet inside. Buy oem vortec cam, roller lifters, and hold down tray and use that instead.

-You are already buying pistons, so get ones with a skirt coating and a bit more compression. I'd go with 9:1 if you want to use 87 octane still. Get whatever head gasket that will get you close to .040 quench.

Otherwise, pretty much everything on that old TBI system will require a new chip being burned to tune and you don't sound like you want that.

[Nick_R_23]

Here’s my $0.02 on the things I’ve learned from messing around with hundreds of TBI engines: Leave them alone.

Luckily, it sounds like you want to do that for the most part. It’s an extremely basic speed density system, and changes tend to compound other changes, and most any modification puts you out of the parameters of a stock chip. Can you have success having a custom chip burned? Absolutely, but once you’re through with the changes, you’ll realize a newer EFI/generation swap would have been the way to go.

If there’s one recommendation I would do, echoing Tom above, convert to a roller cam if your block has the provisions for it. Do not use a 96-00 Vortec cam, use a factory TBI Caprice roller cam. It is the closest to your OE flat tappet cam and will play nice with the factory chip.

Higher flowing exhaust does help a bit, but it may also give you an EGR code depending on the style of EGR installed on the truck, and your driving habits. This is because some TBI EGR systems are calibrated to the factory exhaust, and use the slight pressure in the system to assist in valve operation, which can be lost with a less restrictive exhaust system. A non or partially functioning EGR may throw a CEL, or may cause pinging due to less recirculated exhaust gasses helping to cool the combustion chamber. This can be magnified during towing, although may not always happen due to driving style.

Flat top pistons that raise the compression may yield a gain on paper, but GM’s reasoning for the dished pistons was to help control detonation, especially during higher load times such as towing. This may also require the use of a higher grade fuel, and may also still cause pinging or detonation, in which the knock sensor will retard the timing and counter any gains seen from a slight bump in compression.

Other popular modifications, such as Vortec cams or Vortec heads, bored throttle bodies, oversized exhausts, aftermarket intakes, do provide a large increase in flow, but increase the air flow SO much, that a custom chip will be required. The factory fuel system WILL NOT keep up with the additional fuel demand to correct the now-offset air/fuel ratio. This tends to also lead to higher rated fuel pumps, aftermarket regulators, and oversized injectors, which there is no baseline and is essentially an experiment. Open element air cleaners are actually a detriment on these trucks due to eliminating the factory cold air intake system, and replacing it with a filter exposed to the hot engine bay temps, coupled with the disruption in air flow caused by the engine fan.

If the performance and drivability of the engine have never disappointed you and satisfied your needs, keep the engine as it was. I’ve gone the modification route multiple times, and now perform stock specification rebuilds with the only update being the addition of a roller cam. You can also find a machinist with newer equipment that will allow decking of the block without disturbing the factory stamping pad.

[LT7A]

Well weider, I don't know if you're going to come back and look at your thread, haha, but you've gotten a surprising number of responses. Nice to see that nobody is simply saying don't waste your time. A lot of people seem to think that way about the TBI motors. Everything I listed is on my daily driver. No problem with my exhaust and my research shows people have had similar results. Not sure how common the feedback EGR system is. Many like myself, have found that the cold air stock system is restrictive. I run a K&N filter with a K&N open lid *beware, controversial* but I bought that before the filter tests had come out that show that K&N lets more dirt through than some others. My truck was just a few years old when I put that filter on and so I would say that the 230,000 miles indicates that it's not letting too much extra dirt in, haha. No need to spring for that, but per my experience and others, you will feel the seat of the pants improvement if you swap in the open element air cleaner. If you've opened up the exhaust, then it'll want to breathe. The volume of air available with an open element more than offsets the warmer underhood temperature it's drawing from. Cool air is a plus, but the open element is far better than breathing through the factory snorkel. Pre ignition or pinging has never been a problem for my truck - in fact it's common to advance the timing up to 6°. I run 4° advanced, have towed a 33-ft travel trailer that way, on 87 octane with no pinging. I like the roller cam idea for durability and since you're going to be into the motor. Just don't expect much in the way of power gains. I do agree that you can't change the cam profile without a chip telling the ECU how to deal with it. The reduced friction of a roller cam will net a small gain. I have had no problem with my flat tappet cam, but depending on how you take care of it they are susceptible to wear with today's common oils. I like to run amsoil that takes my flat tappet cam into account but if I was doing a rebuild would probably go roller. Big question is, do you need to go into your motor at all, and if so, why? Sounds like your heads need minor attention, but is there a problem in the motor itself?
In real world driving, my truck is far more responsive than when it was new. Weighs 5,000 lb and has a 3.73 rear axle. Would not break the 265 75 16s loose when new, but makes the 285 75 16 BFG ATs howl now from a standing start, despite the age and mileage.

[68post]

The cyl heads were not the problem with TBI engines, the tiny cam and restrictive exhaust were/are.
My $.02 ; a very VERY small cam (single pattern)that's above the original 187*intake duration @ .050 factory cam, K&N filter, and preferably headers with an H-pipe and free flow exhaust. The factory cold-air intake system isn't a problem - but the restrictive paper filter is.
Headers can actually add an approx 25 to 45 ft lbs of torque in the mid-range, (long tube ONLY).

EDIT : reset ignition timing to a custom curve to suit your driving/load/octane.

May not be big gains but you've limited yourself in choices !

[SunSoaked]

Bag it and put it in the corner of your garage. With all the $ you're gonna save buy a decent modern crate motor with all the costs up front. When you're old and lost interest in the truck, sell it with the original engine as a "numbers matching, unrestored, original" vehicle.

Your inching up on the proverbial Rabbit Hole.

[57NAPCO]

By the way Welder, I just did the very thing you posted about in your first post. 1987 V10 short Stepside fully loaded Silverado. I pulled the 5.7 engine and had it rebuilt, put all new A/C Delco parts everywhere I could. I left it 100% original and promptly drove it 2500 miles.

[weider1717]

Thank you for all the replies I told the builder gl back stock and only note what is needed to clean it up 👍🏻👍🏻👌🏻
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[Nick_R_23]

Good choice! It should be a good runner for you for a long time.

[weider1717]

Guys, here is the update on the engine build, need suggestions on this.

So, as mentioned I told the builder let’s
Go back stock and clean up the bore only what’s needed.

He is onboard but suggest not getting into a custom size piston if it only needs a .005 clean up etc and I’m onboard with that go .020 etc I just didn’t want to jump to .030 unless it needed it. He is being nice and just trying to save me money from a non typical piston size I’m ok with that..

He also suggested that I go with flattop pistons instead of the 4 eye brow one and said it should bump the compression up enough for 25-30hp it will still be a cast piston and we plan to still go with a stock cam.

Thoughts on the flat top pistons???

Thanks
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[THI]

I agree with the .020" over, I have done many engines that way. Considering GM recommends .040" over max on those blocks I would leave as much as possible.

Your heads are already 64cc chambers and you actual compression is over 9:1, a flat-top piston would put you in the 10:1 area - that is too high for the iron heads with the small stock cam. I would consider a "D" dish piston to improve quench verses the round dish of the stock piston.

[LT7A]

I think 25 to 30 horsepower on the compression increase is quite optimistic. I don't mean to call your engine builders knowledge into question, but I think that would be optimistic even with good high performance heads and cam. My research would indicate to expect a single digit performance in gain with a bump in compression, I think 10 plus percent would be hoping for too much.

[weider1717]

Thanks for the info guys I will be talking with him this week on this.

The H580p30 piston but “looks” seems like it’s fished out more than my 4 eye brow stock pistons are you sure that would bump me up a little in compression over stock?

Could you please suggest again the piston of your preference it may be that only one that you think would be better than the stock option and also what cam.

He asked me for my vin number if we got back with the stock cam but if you have any suggestions that will play well with the tbi and may be a notch better like to research it and the piston you suggest.

I think for sure were in agreement the flat tops would be too much and I’m sure he wouldn’t have concluded that once he really studied what he had he just mentioned that when I dropped it off.

Thanks again guys, learning..
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[Nick_R_23]

Your best bet is to stock with OE replacements for pistons, unless you feel like running premium fuel.

The camshaft should stay stock as well. The ECU does not like camshafts outside of OE parameters. The general exception is if your block has provisions for a roller cam, a good upgrade would be the TBI Caprice cam. Not a performance gain, but it removes the possibility of wiping out a flat tappet cam on break-in, and having to worry about oil additives.