flat top pistons - The 1947 - Present Chevrolet & GMC Truck Message Board Network

justinburnett · 03-10-2011, 12:57 AM

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 · 03-10-2011, 01:54 AM

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 · 03-10-2011, 11:34 AM

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 · 03-10-2011, 02:04 PM

Quote:

Originally Posted by justinburnett

Where are the numbers located on the heads?
Posted via Mobile Device

pull the valve covers off and look inside.

xrcr · 03-10-2011, 02:15 PM

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 · 03-10-2011, 02:28 PM

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.

spudz · 03-10-2011, 02:08 PM

yes.... it will be fine.

allengator · 03-10-2011, 02:36 PM

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 · 03-10-2011, 03:44 PM

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 · 03-10-2011, 04:33 PM

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 · 03-10-2011, 05:38 PM

You will be fine with flat tops

justinburnett · 03-11-2011, 02:12 PM

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 · 03-11-2011, 02:42 PM

70-80year 1.94/1.50 valve 76CC chambers

justinburnett · 03-11-2011, 02:54 PM

So with a 76 cc chamber how would I figure out the compression?
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allengator · 03-11-2011, 02:59 PM

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 · 03-11-2011, 03:00 PM

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 · 03-11-2011, 04:25 PM

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 · 03-11-2011, 09:45 PM

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 · 03-11-2011, 11:10 PM

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 · 03-11-2011, 11:26 PM

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 · 03-11-2011, 11:34 PM

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 · 03-12-2011, 03:07 AM

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 · 03-12-2011, 04:22 AM

Do you mean 0 lash plus a quarter tighter, or back off a quarter to give some room for expansion?
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ont_guy_38 · 03-13-2011, 07:04 PM

Without a pressure washer what you are doing is the only way and yes it sucks . Trying to blast grease is just a waste of time , it has to be cleaned first but once you get that done blast away if you want

rayfinseats · 03-13-2011, 09:57 PM

I wouldnt run Hyperutectic pistons. If you're gonna go there just get forged. HYpers are hard but brittle so when they let go they let go hard. I don't feel hypers are much better than cast pistons. The lighter the better. And make sure you adjust the lifter correctly or you'll ruin the cam.

03-10-2011, 12:57 AM	#1
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	flat top pistons 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.

03-10-2011, 01:54 AM	#2
3r!c84 Badass Join Date: Jan 2009 Location: lox. fl Posts: 4,586	Re: flat top pistons need to give us alittle more info on the motor. what year and such and such. but thats going to bump up your compression __________________ Think outside the box? -84c10 (1stcar)→My Build← -00 Saturn 5spd drop a gear and disappear! 1/4:13:90

03-10-2011, 11:34 AM	#3
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: flat top pistons 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? Posted via Mobile Device

03-10-2011, 02:15 PM	#5
xrcr Registered User Join Date: Dec 2008 Location: Foristell, MO Posts: 418	Re: flat top pistons 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.

03-10-2011, 02:28 PM	#6
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: flat top pistons 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.

03-10-2011, 02:08 PM	#7
spudz Registered User Join Date: Oct 2005 Location: Branchville SC Posts: 1,647	Re: flat top pistons yes.... it will be fine. __________________ 2004 z71, 96 z71 on 38s, 88 Chevy k5 blazer, 4in lift. 84 swb project, 82 SWB project , 84 chevy 4x4 lwb project, 88 Jimmy beater/highschool ride. 79 c30. 99 tahoe 4x4 project. and a bunch of parts trucks..

03-10-2011, 02:36 PM	#8
allengator Registered User Join Date: Dec 2010 Location: Burleson, Texas Posts: 596	Re: flat top pistons 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! __________________ Allengator Outta the Blue (my band - available for hire in the DFW area!) 1980 Chevy SWB Pickup (build thread) 1951 Chevy Sedan Delivery 2004 Chevy Tahoe Z71 2011 Harley Davidson Street Glide 2018 Silverado Z71 Crew Cab

03-10-2011, 03:44 PM	#9
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: flat top pistons 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. Posted via Mobile Device

03-10-2011, 04:33 PM	#10
allengator Registered User Join Date: Dec 2010 Location: Burleson, Texas Posts: 596	Re: flat top pistons 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! __________________ Allengator Outta the Blue (my band - available for hire in the DFW area!) 1980 Chevy SWB Pickup (build thread) 1951 Chevy Sedan Delivery 2004 Chevy Tahoe Z71 2011 Harley Davidson Street Glide 2018 Silverado Z71 Crew Cab Last edited by allengator; 03-10-2011 at 04:33 PM.

03-10-2011, 05:38 PM	#11
ont_guy_38 Registered User Join Date: Jul 2007 Location: Ontario Canada Posts: 1,006	Re: flat top pistons You will be fine with flat tops

03-11-2011, 02:12 PM	#12
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: flat top pistons 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. Posted via Mobile Device

03-11-2011, 02:42 PM	#13
3r!c84 Badass Join Date: Jan 2009 Location: lox. fl Posts: 4,586	Re: flat top pistons 70-80year 1.94/1.50 valve 76CC chambers __________________ Think outside the box? -84c10 (1stcar)→My Build← -00 Saturn 5spd drop a gear and disappear! 1/4:13:90

03-11-2011, 02:54 PM	#14
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: flat top pistons So with a 76 cc chamber how would I figure out the compression? Posted via Mobile Device

03-11-2011, 02:59 PM	#15
allengator Registered User Join Date: Dec 2010 Location: Burleson, Texas Posts: 596	Re: flat top pistons 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 __________________ Allengator Outta the Blue (my band - available for hire in the DFW area!) 1980 Chevy SWB Pickup (build thread) 1951 Chevy Sedan Delivery 2004 Chevy Tahoe Z71 2011 Harley Davidson Street Glide 2018 Silverado Z71 Crew Cab

03-11-2011, 03:00 PM	#16
3r!c84 Badass Join Date: Jan 2009 Location: lox. fl Posts: 4,586	Re: flat top pistons 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 __________________ Think outside the box? -84c10 (1stcar)→My Build← -00 Saturn 5spd drop a gear and disappear! 1/4:13:90



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03-11-2011, 04:25 PM	#17
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: flat top pistons 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.

03-11-2011, 09:45 PM	#18
Tx Firefighter Watch out for your cornhole ! Join Date: Jun 2003 Location: Azle, Texas Posts: 14,162	Re: flat top pistons 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. __________________ I'm on the Instagram- @Gearhead_Kevin

03-11-2011, 11:10 PM	#19
Altec Getcha Pull Join Date: Nov 2010 Location: MD Posts: 691	Re: flat top pistons 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. __________________ '81 K10 454/SM465 '86 S10 Blazer '95 H-D Softail '96 Integra

03-11-2011, 11:26 PM	#20
RWilliamsGa Registered User Join Date: Nov 2010 Location: Silver Creek Ga Posts: 12	Re: flat top pistons 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.

03-11-2011, 11:34 PM	#21
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: flat top pistons 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. Last edited by justinburnett; 03-11-2011 at 11:43 PM.

03-12-2011, 03:07 AM	#22
ChevyC102007 Registered User Join Date: Sep 2007 Location: Emporium,Pa Posts: 248	Re: flat top pistons 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 __________________ "When you were born, you cried and the world rejoiced. Live your life so that when you die, the world cries and you rejoice." [Cherokee saying] 2001 Dodge Ram Sport 1500 4x4. (old ride) 1987 GMC V1500 Sierra Classic ("new" ride)

03-12-2011, 04:22 AM	#23
justinburnett Registered User Join Date: Sep 2010 Location: The Dalles, OR Posts: 392	Re: flat top pistons Do you mean 0 lash plus a quarter tighter, or back off a quarter to give some room for expansion? Posted via Mobile Device

03-13-2011, 07:04 PM	#24
ont_guy_38 Registered User Join Date: Jul 2007 Location: Ontario Canada Posts: 1,006	Re: flat top pistons Without a pressure washer what you are doing is the only way and yes it sucks . Trying to blast grease is just a waste of time , it has to be cleaned first but once you get that done blast away if you want

03-13-2011, 09:57 PM	#25
rayfinseats Registered User Join Date: Dec 2010 Location: sioux city, iowa Posts: 619	Re: flat top pistons I wouldnt run Hyperutectic pistons. If you're gonna go there just get forged. HYpers are hard but brittle so when they let go they let go hard. I don't feel hypers are much better than cast pistons. The lighter the better. And make sure you adjust the lifter correctly or you'll ruin the cam.

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