Thread: Engine rebuild tips and help

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I’ve got a 78 Firebird that I’ve had a Chevy 350 in for a couple years now. The engine is pretty near stock. I’ve been looking at upping the performance with a new cam and heads for a while now. Been doing tons of research too. I’d just like to hear from some people with more experience with these engines before attempting this myself. I have a lot of experience working on cars, but this’ll be the first time I’ve ever taken an engine apart.

It’s been about 8 years since the engine was built, the car was hardly driven in that time because I was away in college for 4 of them so it’s a bit hard to remember what how exactly it was built, but I do know the block has been bored out slightly.

I’m looking for a new cam with optimal performance around 5500 rpm with not much over 500ths lift and a set of matching, better breathing, aluminum heads and hydraulic lifters. Something with high light, low duration.

I would like to know what people’s preference on suppliers & manufacturers are and what their experiences have been. Ideally, I’d love a kit, or just one supplier that I can get everything I’m going to need from. When looking at parts, I just find myself getting lost in all the slight variances. I’d like to be able to confirm that whatever heads I end up getting will match my block. I’ve got the casting number. I just need to know what I’m looking for on the part of the heads so I can see everything is gunna match up nicely. Or are these engines really that universal where all it needs to say is “small block Chevy” and it’ll line up?

I’ve also been researching how to actually do all the work required myself, and I’ve seen a lot about degreeing a camshaft. Do suppliers make make camshafts that can be installed out of box, or is degreeing a procedure that’s specific to each engine?

Any tips or things to look out for or extra things I should consider are greatly appreciated.

Welcome to CHR!
The 350 Chevy in a Firebird has been a very popular swap and not to get too far ahead of myself, yes, most parts for small block Chevys (SBC) are literally swappable and do just bolt right up – with very few exceptions.

A couple questions before we jump right into the “how to build it” sessions:
1. What is your budget?
2. What casting number(s) do you have?
3. Is this an automatic or a stick? What transmission?
4. What is your rear end ratio?
5. What do you want to do with this car? You want optimal performance at 5500RPM but how often will the car really see 5500RPM? If you’re going to use this for a daily driver it will be different that say a boulevard bruiser or a drag car.

I would strongly recommend a total engine build rather that just heads and cam. To do this right, you should pull the engine and have the block prepped by a competent machine shop. There’s a whole list of other things we can discuss here and I would caution you not to select a cam (consider only a hydraulic roller) and heads without knowing for certain what pistons are in place and if the block is square. Along that line, you can do some of the work yourself if you have the proper tools (some of which are expensive) and it may make sense for you to have a machine shop do the heavy work and you can perform the final assembly.

I would also encourage you to consider a 383 stroker approach as this really brings the SBC alive and has a lot of potential as both a streetable ride and one that can allow you to see God when you shift into second gear when it’s built correctly. This approach does require custom machine shop work on the block as well as a stroker kit with crank, rods, and pistons.

Let us know what your thoughts are and we can jump in with some proven build recipes.

Regards,
Glenn

Thanks for getting back to me Glenn!

To start, there really isn’t a budget. I’m not really constrained here, but I obviously don’t want to shell out 10’s of thousands of dollars for a little small block. Ideally I’d like to just find a few options at different price ranges and see what I think is worth the money, or if you or anyone else has recommendations, I’m all ears! If I have to pick a number though, I feel like around 2k is enough. Just from what I’ve seen online at least. Heck it may even be overkill, I’m not sure to be honest.

Second, the casting number is 3932388. From what I’ve seen online, I believe that makes it a ‘69 model year.

The transmission is a turbo 350 automatic. I just had it rebuilt with a higher stall converter and a shift kit so it can handle a bigger cam.

I believe the read end ratio is a 2.7:1 or somewhere around there. That’s just from me rotating the tire and counting the driveshaft rotations, so I’m probably a little off.

I want to keep it streetable for sure, ultimately I’m just looking to go fast. I should also clarify, I should have said “peak” performance at around 5500 rpm. It probably won’t see it that often honesty. What I should have said is I would like a good power band from 1k - 4 or 5k. This will remain a street car, but obviously I’m here for as much power as I can reliably get. This car is strictly a weekend toy as well. I mostly drive it to shows and meets, but I’d love to start drag racing at my local track just for the fun of it.

As I mentioned before as well, the engine was completely rebuilt about 8 years ago, that’s when I got the car and put the 350 in it. Beforehand a friend of a friend had it in his truck. Once I got it, it was sent off to a machine shop, that’s where it was bored out a bit and got brand new pistons, rings, and rods. Unfortunately, it was 8 years ago and I was just learning about cars at the time and I don’t recall what size pistons are in it. I figured that it might make a difference for picking the right head though.

Ultimately I would rather not have to send the engine off to a builder, if at all possible at least. If that’s really the only smart way to do it, then so be it. I’d love to put in the time and effort to learn how to build these, and I’m ready to spend a pretty penny.

Thanks again for getting back to me, Glenn. I really appreciate your help so far.

-Vinny

I'll toss in some thoughts / opinions as well. Like a lot of guys, my thoughts ramble and I type what I am thinking in the moment, but I'll try and keep it all "straight". I would think you'd be better served ( after reading the above) to remove and disassemble the motor first. Inspect the interior components and evaluate the needs before the wants. It may simply need a freshening!

The one thing I would do is replace the rear differential gears. 2.7 is a good highway ratio, but if you want to do street and strip you need to have something that starts with a 3.0 to 4.0 ratio, I would also advise you to watch for the "combination" because the cam has to work with the Cylinder Heads and the Torque Converter as well, and even the tire size / O.D. and rear axle ratio come into play. If you want serious power, and want to do racing - then consider aluminum heads, if you want to use a ceiling of 4 to 5 thousand rpm, then the advantage of high flowing heads will be wasted. Same goes for the camshaft you choose. It sounds to me that you'd be better served with a "torque" cam, like they grind for RV's and trucks. You are wanting the most power at a lower rpm.

Like I said, just some thoughts, hope it helps and gives you some things to think about. It is good to see you here, welcome aboard!

Originally Posted by 34_40

I'll toss in some thoughts / opinions as well. Like a lot of guys, my thoughts ramble and I type what I am thinking in the moment, but I'll try and keep it all "straight". I would think you'd be better served ( after reading the above) to remove and disassemble the motor first. Inspect the interior components and evaluate the needs before the wants. It may simply need a freshening!

The one thing I would do is replace the rear differential gears. 2.7 is a good highway ratio, but if you want to do street and strip you need to have something that starts with a 3.0 to 4.0 ratio, I would also advise you to watch for the "combination" because the cam has to work with the Cylinder Heads and the Torque Converter as well, and even the tire size / O.D. and rear axle ratio come into play. If you want serious power, and want to do racing - then consider aluminum heads, if you want to use a ceiling of 4 to 5 thousand rpm, then the advantage of high flowing heads will be wasted. Same goes for the camshaft you choose. It sounds to me that you'd be better served with a "torque" cam, like they grind for RV's and trucks. You are wanting the most power at a lower rpm.

Like I said, just some thoughts, hope it helps and gives you some things to think about. It is good to see you here, welcome aboard!

It’s not that I feel it’s gotten slower or just old. It’s always been slow ever since I had it rebuilt 8 years ago. I’m here for more than a refreshening and I’d like to do it right.

I’ve thought about changing the rear end as well. I’d like to still be able to drive on the highway though and ultimately I’m chasing more power, this is what I would like to do. However I am considering a rear end swap to something around a 3.2:1 in the future.

I understand how the torque converter, cam, and heads should match which is precisely why I’m here. I’ve had a higher stall torque converter swapped into my transmission so I’m able to handle a bigger cam. These stock heads just stifle and struggle to breathe right and I’m after more air flow. I would love a set of aluminum heads. This won’t be the last time I touch this engine and I want to continue to add power, but this seemed like the right step first. I know aluminum heads are friendly to high power and they cool better. I figured if I’m getting new heads, may as well swap out the stock cam and try and match the heads and torque converter.

If you think this would be a waste to keep it at/below 4 - 5k rpm then let’s go higher. I only say that because I know these aren’t rev happy engines and I’d like to keep mine somewhat reliable. I’m here for whatever advice. I’m definitely still learning. Appreciate your feedback. Thank you!

-Vinny

Figured I should go a head and mention some more modifications I’d like to do to the engine in the future too far after I get new heads and a cam. I currently run an Edilbrock 4 barrel. It’s been good to me, but I’ve had my eye on those Holly Sniper EFI conversions. Holley also makes an ignition system that integrates perfectly with it. I want a good dual plane intake manifold as well. I’m running a close to stock performance, Edilbrock manifold and I know many companies out there make manifolds than can match your desired rpm range. I have a nice radiator right now, but I’d like to switch to a set of electric fans at some point. Like I mentioned in my last response, I’ve also been considering a new rear end dif. These aren’t mods I plan on doing super soon, but I’d like to get to some of them before the year is up.

In this day and age----------I'd suggest that you look for a late model LS aluminum engine, fuel injected, roller cammed, accessory drive,probably maybe even the transmission---------------better performance, milage etc etc etc

Originally Posted by jerry clayton

In this day and age----------I'd suggest that you look for a late model LS aluminum engine, fuel injected, roller cammed, accessory drive,probably maybe even the transmission---------------better performance, milage etc etc etc

Is that really going to be cost effective though? I’m not looking for a junkyard engine or something used that has problems. Between a new engine, transmission, and wiring harness, plus a myriad of other fitment issues, to me it just doesn’t make sense right now.

Are you suggesting small block Chevys aren’t even worth building if LS engines are out there?

Unless you're a bit nostalgic, go with the LS. Even in a mildly warmed over state they can make 5 to 600 HP Easily.

I've said it before too, my favorite rear axle ratios are 3.25 / 3.50 and 3.73 toss in a overdrive trans and you have the best of both worlds, good highway rpms and good fuel economy.

That would be nice. I just don’t have 10+ grand to throw at a new engine and transmission right now. I’d rather just spend the 1500-2000 dollars on a new set of heads and cam because this engine is what I’ve got.

The latest improment on the engineering/performance of the so called small block chev hasn't had any improments since 1992--------LT1 & 4
If you might even want to KEEP it PONTIAC-look for a 1999 Firebird WS6 and get engine, trans, fuel system, accessories and wiring harness----------

If you want to stick with a package for your 350-------Edelbrock has everything in a package plus also add some higher compression pistons to get around 11 to 1 CR

Okay Vinny – here’s a few thoughts/ideas:

If your rear end is stock, it’s probably a 2.56 as there were a gazillion of them installed in corporate GM 10” rear ends in this era. It’s a fine ratio for the intended purpose (family fun car of the late 70’s) but it will never be what you want in terms of snap off the line unless you throw 600 horses at it (which will blow it to smithereens). You need to get to numerically higher ratio – unfortunately it may require a rear end swap. I would go with a 3.73 and since you’re spending money there, go with a good aftermarket posi-traction. Have this work done at a competent axle shop and be prepared to spend $800-1200.

You said you have a higher stall converter – do you know what RPM it is? (Stock would have been 1800 so anything in the 2000 range would be higher). Depending on final head/cam selection you may want mid 2,000’s.

It sounds like you do not want to disassemble your engine – that’s okay but you will need to check a few things prior to selecting heads.

1. Accurately measure the bore. Stock is 4.000” and if the block has been bored, cylinders will probably measure 4.030”
2. Measure the distance down in the cylinder that the piston stops its upward travel. A stock 350 block leaves the factory at 9.025” and the stock stroke on a 350 is 3.48. Most aftermarket pistons have an extra .020" of deck clearance built in; on top of the usual .025" that is present in a stock (9.025) block. As such, you may have as much as.045" at TDC. This is an important measurement and it should be done at all four corners (#’s 1, 2, 7, and 8). While nowhere near as accurate as measuring the block outside the car, it does give an indication if the block is square.

If the four corners are all within .002 than you’re probably okay to just bolt up a pair of cast iron Vortec heads. I’d opt for L31 Vortecs, casting number 12558062 or 10239906. They were used on '96-'99 Chevy trucks with the L31 5700 Vortec engine and are readily available in wrecking yards and on Craigslist / eBay (if you buy them on-line, make sure they’re genuine GM heads – not knock offs!). These heads use rail rockers, so get the rockers with them if you can. These are some of the best flowing production heads that Chevy ever made. Have your machine shop pin the studs, install new seals, and perform a 5-angle valve job. You can buy valve springs and retainers that complement your cam and you have a great set of heads.

You could also buy new Vortecs (GM Part # 12558060) from Speedway, Summit or JEGS for about $440 each with free shipping - which may be a better deal than reworking bone yard heads.

So with rear end work and heads we’re past $2K and we have not even talked about a cam yet. A new cam needs to be a roller and your 1969 block was made for a flat tappet cam. The good news is that there are some great kits (like Comp Cams K11-600-8) that include the cam, lifters, valve springs, new push rods (different length than flat tappet), roller cam button (to prevent the cam from moving), timing gears and double roller chain, and even a new pushrod for the fuel pump. The bad news is that you’ll have another $1000 tied up here.

Buy some Hooker 1 5/8" long tube, equal length headers that fit the car and route through Flowmaster 40 series mufflers – I really like ceramic coated for looks, longevity and heat dissipation. Add another $750.

Stay with the stock fan setup and shroud – resist the temptation to use an electric fan. They do not save horsepower nor do they cool anywhere near as well as the stock GM fan.

The reality is that $2K will not get you where you want to be. A turn-key 383 crate engine that produces 430 HP is about $5200 and its real tough to beat price with a home build. I've built a lot of SBC engines and it always costs more than you want it to and remember that big HP almost always equals big $$'s.

So another option would be to drive what you’ve got and bank some money to get either all the pieces or a complete replacement engine.

As mentioned above, late model LS engines and transmission combos are available at bone yards at reasonable prices as well.

Others will continue to chime in so you'll get a lot more advice!

Regards,
Glenn

https://www.jegs.com/s/tech-articles...ne-builds.html

very good artical about availbilities of the LS series engines and what to look for-------

Originally Posted by glennsexton

Okay Vinny – here’s a few thoughts/ideas:

If your rear end is stock, it’s probably a 2.56 as there were a gazillion of them installed in corporate GM 10” rear ends in this era. It’s a fine ratio for the intended purpose (family fun car of the late 70’s) but it will never be what you want in terms of snap off the line unless you throw 600 horses at it (which will blow it to smithereens). You need to get to numerically higher ratio – unfortunately it may require a rear end swap. I would go with a 3.73 and since you’re spending money there, go with a good aftermarket posi-traction. Have this work done at a competent axle shop and be prepared to spend $800-1200.

You said you have a higher stall converter – do you know what RPM it is? (Stock would have been 1800 so anything in the 2000 range would be higher). Depending on final head/cam selection you may want mid 2,000’s.

It sounds like you do not want to disassemble your engine – that’s okay but you will need to check a few things prior to selecting heads.

1. Accurately measure the bore. Stock is 4.000” and if the block has been bored, cylinders will probably measure 4.030”
2. Measure the distance down in the cylinder that the piston stops its upward travel. A stock 350 block leaves the factory at 9.025” and the stock stroke on a 350 is 3.48. Most aftermarket pistons have an extra .020" of deck clearance built in; on top of the usual .025" that is present in a stock (9.025) block. As such, you may have as much as.045" at TDC. This is an important measurement and it should be done at all four corners (#’s 1, 2, 7, and 8). While nowhere near as accurate as measuring the block outside the car, it does give an indication if the block is square.

If the four corners are all within .002 than you’re probably okay to just bolt up a pair of cast iron Vortec heads. I’d opt for L31 Vortecs, casting number 12558062 or 10239906. They were used on '96-'99 Chevy trucks with the L31 5700 Vortec engine and are readily available in wrecking yards and on Craigslist / eBay (if you buy them on-line, make sure they’re genuine GM heads – not knock offs!). These heads use rail rockers, so get the rockers with them if you can. These are some of the best flowing production heads that Chevy ever made. Have your machine shop pin the studs, install new seals, and perform a 5-angle valve job. You can buy valve springs and retainers that complement your cam and you have a great set of heads.

You could also buy new Vortecs (GM Part # 12558060) from Speedway, Summit or JEGS for about $440 each with free shipping - which may be a better deal than reworking bone yard heads.

So with rear end work and heads we’re past $2K and we have not even talked about a cam yet. A new cam needs to be a roller and your 1969 block was made for a flat tappet cam. The good news is that there are some great kits (like Comp Cams K11-600-8) that include the cam, lifters, valve springs, new push rods (different length than flat tappet), roller cam button (to prevent the cam from moving), timing gears and double roller chain, and even a new pushrod for the fuel pump. The bad news is that you’ll have another $1000 tied up here.

Buy some Hooker 1 5/8" long tube, equal length headers that fit the car and route through Flowmaster 40 series mufflers – I really like ceramic coated for looks, longevity and heat dissipation. Add another $750.

Stay with the stock fan setup and shroud – resist the temptation to use an electric fan. They do not save horsepower nor do they cool anywhere near as well as the stock GM fan.

The reality is that $2K will not get you where you want to be. A turn-key 383 crate engine that produces 430 HP is about $5200 and its real tough to beat price with a home build. I've built a lot of SBC engines and it always costs more than you want it to and remember that big HP almost always equals big $$'s.

So another option would be to drive what you’ve got and bank some money to get either all the pieces or a complete replacement engine.

As mentioned above, late model LS engines and transmission combos are available at bone yards at reasonable prices as well.

Others will continue to chime in so you'll get a lot more advice!

Regards,
Glenn

Thanks for the info!

To start, the rear end is stock, so 2.56 sounds right. It’s something I’ve been meaning to change for a while. Regardless of an engine swap or just a top end rebuild, I’ll be swapping that out in the future.

Torque converter is 2500rpm stall.

I’ll look into measuring my block like you describe. Doesn’t sound too bad and probably something I should do.

Now for head selection, for every guy I find that says to use a set of vortec heads, I find another that says don’t waste your time with them. Ultimately I’d like to just buy some kind of aftermarket head that’ll just bolt right on. I don’t have the ability or means to machine something like that myself, and it gets costly quick having someone else do it. I’ll keep in the back of my mind for sure though.

I don’t really have a preference toward flat tappet or roller cams, but you mentioned this my block was made specifically for a flat tappet cam. Are they not interchangeable? Assuming you change the lifters too of course.

Headers are something I’m on the lookout for, but I figured those can wait a bit.

Now someone mentioned an Edelbrock rebuild kit. I didn’t know these existed, but do you have any opinion on them?
Here’s the one I was looking at:
https://www.edelbrock.com/performer-...hevy-2098.html

Personally I feel like it’s not really fair to include the price of headers and the rebuilt rear end in the price estimates since both of those would have to happen regardless of if I kept my 350 or swapped it for something else. If that’s the case, that would bring your estimate down right about to 2k wouldn’t it?

Again thanks for your help. I really do appreciate your time.

Originally Posted by jerry clayton

https://www.jegs.com/s/tech-articles...ne-builds.html

very good artical about availbilities of the LS series engines and what to look for-------

I will definitely keep for the future, I just would rather keep what I’ve got for now. I know it works and I don’t have to deal with junkyard engines. I’m aware it’s a potentially cheeped option, but I’m afraid I just don’t know enough to not get screwed over. Dealing with a complete engine swap with a new wiring harness from a car or truck that was salvaged for unknown reason is just too big a task for me right now, but I honestly appreciate the input, however.
I’m here for options, and at least if I can’t find an avenue I want to take, I can find the ones I don’t want to.