flat top pistons

[justinburnett]

So I have to rebuild my engine. 1973 350. If I put flat top pistons in but leave everything else stock, would that be safe? Would it help? I'm not really sure what it would accomplish but they're the same price so i was just wondering if anyone had experience. If I can get a little more power out of it without being enough to start hurting things, i think I'll go for it.

[3r!c84]

need to give us alittle more info on the motor. what year and such and such. but thats going to bump up your compression

[justinburnett]

Being as I have no idea what the stock compression is... probably just leave it stock. It didn't have much power before tho so I assume it was fairly low, but their could have been all sort of things wrong with it to )egun with I guess. I'll just replace them with whatever is already in there when I pull it to look. If I knew. What cc the heads are it might help. Where are the numbers located on the heads?
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[3r!c84]

Originally Posted by justinburnett

Where are the numbers located on the heads?
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pull the valve covers off and look inside.

[spudz]

yes.... it will be fine.

[xrcr]

My free advice is no more that 10:1 for pump gas. The cc # for your heads will affect that so you kinda need to figure that first.Like 3r!c84 said pull the valve cover and it should be stamped somewhere between the studs, or that general area. I'm running a 358 with 10.125:1 KB's with 76cc heads and have no issues. But I am by far an engine guru.

[justinburnett]

I am by far not. With all the work I've been doing lately I'll get there someday. Sure have been enjoying myself even though it's been one frustrating problem after another. never knew working on vehicles would be so much fun. I'll get into it as soon as i can and let you know about the heads. It is in a friend of mine's garage right now and he locked it up and I can't get ahold of him, which is irritating, but hopefully he'll call me back. It was his idea to put it in there, so maybe I can get a key from him while it's there or something.

Thanks for everyone who has helped me with any of my questions and i'll get back to this one soon.

[allengator]

Yes it is safe, and yes it is a good step.
BUT... I would really recommend finding out what heads you have on the motor, consider your goals and budget... THEN see if your goals can be met with your current heads, flat top pistons, and a carefully chosen cam... or you if need to change the heads to reach your goal. Obviously buying different heads will significantly increast the cost of the rebuild...

But when it comes to cam selection, research well... talk to the cam companies... they will help you!
Dont just throw money at parts recommended by a bunch a "bench racers" that may have never built an engine before!

[justinburnett]

Well for now I'm not trying to build a race engine or anything, just trying to get the old truck back on the road. I have some dreams for the future but they'll run into a lot of money I don't have right now. I was just thinking since the rebuild kit I'm buying has pistons, but there are flat top hyperacutetic (sp) for not much more, maybe it would be a good idea. Someday id like to build one with a roller cam/rockers and vortec heads but that's far off in the future.
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[allengator]

get us the head casting numbers and maybe we can give you a place to start!

You maybe able to select your pistons and cam now... that would respond well to a VORTEC head upgrade later!

[ont_guy_38]

You will be fine with flat tops

[justinburnett]

Okay. Got valve covers off and the head numbers are 333882. I leave it to you more knowledgable types to figure out what that means. Thanks in advance.
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[3r!c84]

70-80year 1.94/1.50 valve 76CC chambers

[justinburnett]

So with a 76 cc chamber how would I figure out the compression?
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[allengator]

those are "OK" heads... not really known for performance... but not too horrible! Very common head...
I have a set on one of my engines....

With a 76cc chamber, flat tops would help bump up the compression!
Call COMP CAMS and ask for a recommendation for a mild engine with good lowend torque...

I bet they recommend flat tops with a 262 or 268 cam... a "performer" manifold (not RPM) and about a 600-650 carb... should be good from idle-5500 ish...

A nice strong yet reliable street engine

[3r!c84]

says your right at 8:5:1 stock. flat tops would bump you up to 9:1 or maybe 9:5:1 you would be fine on pump gas

read this. VVVV
http://www.hotrodders.com/forum/comp...-a-163016.html

[justinburnett]

awesome. I don't want to get anywhere where I can't use normal fuel. The pistons have .030 stamped on them so I imagine that means they're .030 over standard bore right? I didn't see anything on the main or rod bearings but I don't know where i should be looking. Would it be on the backside? Thanks.

[Tx Firefighter]

76cc heads and flat top (w/ 4 valve reliefs) pistons will net you a nice streetable engine. That gets you right at 9:1 compression ratio. I've built a whole bunch of engines over the years for my various trucks and I have run flat top pistons on every one of them. They cost the same as dished pistons and give you a bit more power and snappier throttle response.

You bearings will have size stamped on their backsides. Look for STD, 010, 020 etc.

[Altec]

Lord, did you steal my 350? haha. I have a 010 block that has flat tops, and 882 heads. But, my heads were cracked... Which, from everyone I've talked to said that is a common problem for the 882 heads. I ended up swapping them for 487 heads.

Allengator hit the nail on the head for the combo I plan to run. A 262 with a Air Gap.

[RWilliamsGa]

I had 2 engines this way with flat tops A 400 30 over and a 350 30 over with mild camshafts both engines had 76 cc smog heads and both needed super unleaded and still had trouble with spark knock matter of fact I had to pull 350 back apart and put dish pistons in it my advice don't what you may gain in performance is not worth a 1/2 point of compression and is not worth the headaches that go along with it if you have similar problems keep in mind I am no novice at this as I have built numerous circle track / street engines in my day just my opinion.

[justinburnett]

Funny how so many people have different results out of the same thing. It'd be worth it for me not to have any problems if it could cause some. 9:1 compression doesn't seem like it should pre-ignite with street fuel. Wiki says there were a engines built with higher compression from the factory but I guess you can't argue with personal experience, it's just that it varies so much. What I might do is put flats in, and if I have trouble pull them out and put the originals back because they look like they're in decent shape. I don't know. Need to order parts tomorrow as soon as I figure out if the bearings are under. Any advice for re-assembly? Tips to keep it from leaking oil longer or anything like that? Thanks.

Another thing I was going to ask is has anyone used moly rings? Last longer, or totally unnecessary... Just curious. Willing to spend a little extra for a big increase in reliability but not just for the sake of fueling the economy at this point. Thanks.

[ChevyC102007]

When I built the 406 that was in my 71, the machinist ordered a set of SpeedPro Hyperutectic Flat Top pistons with 4cc valve reliefs. Ran 89 octane fuel in it (which here in Nebraska is 10% ethanol) with 76cc truck heads not sure of the part number with no detonation.

I ordered a Melling RV Torque cam with a Double Roller Chain and SpeedPro Lifters from Northern Auto. Worked well, plenty of low end torque and throttle response (Nice lope at idle too )

As far as reassembly............Take your time, dont get in a hurry. Plenty of assembly lube on your bearings, cam, pistons and rockers make the initial start up alot easier. Priming the motor also helps. Change the oil after 500 miles, recheck the torque of the headbolts and readjust the valves (0 lash plus 1/4 turn) should be all you need to do for a fresh rebuild. Just my .02

[justinburnett]

Do you mean 0 lash plus a quarter tighter, or back off a quarter to give some room for expansion?
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[Altec]

Originally Posted by justinburnett

Do you mean 0 lash plus a quarter tighter, or back off a quarter to give some room for expansion?
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The first one. This is how I was always told how to do it.

[ChevyC102007]

Originally Posted by Altec

The first one. This is how I was always told how to do it.

Yup 1/4 turn tighter after 0 Lash. If ya have a manual it will give you the proper sequence to adjust them in. Always seems to be a "right way" and a wrong way with these SB Chevy motors but done right they run like a dream .