flat top pistons

[justinburnett]

Speaking of valves now, I just got everything torn apart. Cylinder 6 was running pretty low compression, if I remember right, and here are the valves off that side. Looks burnt or something but I'm no expert, what do you think? Should I just put new ones in? Cost being kind of a big issue right now. Also, #2 had a broken ring. No wonder the danged thing was so off balance.

[ChevyC102007]

If my eyes arent playing tricks on me it looks like theres a small chunk missing on the upper left of the valve face. The intake valve looks pretty pitted too.

I would replace at least those two, if you have it machined the machinist might have a couple laying around that he/she could throw in.

Either way a good clean up in a "hot" tank will help with the gasket sealing too.

[justinburnett]

Yeah, that's what I thought is why I put that on here is there was a piece broken off. Didn't know if it would be significant enough to cause a pressure loss. I'll take it down to a guy that's done some work for me before and have him fix it. Just hate spending any more money on this right now.

Ended up getting a fairly short duration cam. Wanted to keep my power in the low range. I do a lot more pulling and hauling in this than racing around at high rpms, and I'm not one to care so much how it sounds as opposed to how it runs. Did get the flat top pistons, and a complete timing/gasket/ring kit with new lifters too. Just playing the "wait for UPS to show up" game now.

[ChevyC102007]

Hurry Up and Wait huh.

[justinburnett]

I figure while I'm waiting to re-assemble, I'll clean and paint some stuff. Starting that this morning as soon as its late enough to start running the pressure washer and sandblaster. Hopefully I can get it all purdy-like in addition to running right.

Truck is still gonna look like hell, but hey, it's what's on the inside that counts right...?

[ChevyC102007]

Thats for sure. Dont want one thats all show and no go. The rest will fall into place once the mechanicals are dealt with thats the way I figure it.

[justinburnett]

Speaking of cleaning stguff, does anyone have any amazing ideas for how to clean engine parts? I'm just using degreaser, soap, and a really stiff brush and its working, but its killing me. Been at it for hours and have the valve covers, oil pan, and mounts done is all. I'm dreading the intake manifold as its disgusting. Could I sandblast it with glass bead or would that tear into it too much? Any other ideas appreciated.

Also I was wondering if any of you guys Would know, being a GMC should the block be blue or orange. The engine was orange to start with but I've heard that some GMC trucks had blue and I want it to look stock. Thanks.

[ont_guy_38]

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

[BigRed76]

Originally Posted by justinburnett

Speaking of cleaning stguff, does anyone have any amazing ideas for how to clean engine parts? I'm just using degreaser, soap, and a really stiff brush and its working, but its killing me. Been at it for hours and have the valve covers, oil pan, and mounts done is all. I'm dreading the intake manifold as its disgusting. Could I sandblast it with glass bead or would that tear into it too much? Any other ideas appreciated.

Also I was wondering if any of you guys Would know, being a GMC should the block be blue or orange. The engine was orange to start with but I've heard that some GMC trucks had blue and I want it to look stock. Thanks.

I believe 76 was the last year they were painted orange, and 77 was the first year of the blue...

[rayfinseats]

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.

[wyattglock]

Originally Posted by justinburnett

Speaking of cleaning stguff, does anyone have any amazing ideas for how to clean engine parts? I'm just using degreaser, soap, and a really stiff brush and its working, but its killing me. Been at it for hours and have the valve covers, oil pan, and mounts done is all. I'm dreading the intake manifold as its disgusting. Could I sandblast it with glass bead or would that tear into it too much? Any other ideas appreciated.

Also I was wondering if any of you guys Would know, being a GMC should the block be blue or orange. The engine was orange to start with but I've heard that some GMC trucks had blue and I want it to look stock. Thanks.

Since I clean cast iron engine blocks all day, I actually have some input on this. As it was said before, wire brush and lots of elbow grease. Get some good penetrating oil to help break up the grease and grime. WD-40 works, Kano Labs Kroil works better. WD is a lot cheaper, but you will burn through a gallon pretty quick. Get a stiff brush for a drill and it will help your elbows out a lot. After it is good and broke up, use some simple green and the pressure washer and it should take it the rest of the way down to the metal. Blow it off really well and then be ready with the 30 weight motor oil to protect the surfaces or else you will be right back to square one.

[justinburnett]

If I only had a pressure washer. the kroil I can do tho. Good idea.

As far as the pistons go, I've already ordered those so It's kinda too late for that one. I'll probably only be driving about 5000 miles a year or so and I'm pretty easy on the gas so hopefully they'll last a while. What do you mean about adjusting the lifters though? Is there more than just adjusting valve lash or is that what you meant ay that? Just curious. Thanks.
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[justinburnett]

So. Good news guys. I'm a dumbass!

When I bought the truck the guy said it was a 350. I just assumed since he said he'd owned it for years that he knew what he was talking about, but apparently....

Took the heads in to get a valve job since there were two burnt exhaust valves and I didn't know what shape the rest were in so I figured I'd just have them all done. Guy was like "I thought you said on the phone you had a 350" and I was like "yeah" and he's like, "these are 400 heads" and I was like "wtf" and he was like "dude go measure your bore" and I was like "4.155..... Sh*t".

So... good news is I have a bigger engine, I guess. Called Northern Auto Parts and switched my order for a rebuild kit which ended up costing me an extra $160 for the 400 kit instead of the 350 which is gonna kick my ass. They still had my kit all ready to ship on the loading dock so they were able to catch it.

Now, the big $1600 question. I put a new flexplate on my engine when I got it. For a 350. With no weights. Did I kill it? Also, how do I balance it now that I know what it is?

[ChevyC102007]

400's are externally balanced so a good flexplate for the 400 and a harmonic balancer should do the trick.

[3r!c84]

400s shared heads with 350's just with steam holes. run the numbers on the block just to double check



ps. rear pass side of block

[justinburnett]

I'm going to get the block numbers in the morning just to be sure, but I know the block has the steam holes too, and the bore would have to be .155 over for it to be a 350 block with 400 pistons. Why would someone do that? As far as the flexsplate goes, are the weights symmetrical or does it have to be put on a certain way? Also will a 350 plate bolt onto a 400 engine? Finally if someone put the wrong flexplate on it would it shake itself to death? Thanks.
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[83burban]

You will have bad vibrations if it is out of balance, and it can certainly damage your motor.

I would ask the machine shop if they can drill the counterweights or add a couple Mallory slugs to the crank to make it internally balanced.

I don't know the whole process or what it costs, but I would seriously consider it just because I wouldn't want to risk a rebuild ruining itself if the balancer separates or something. Plus, it can't hurt to ask.

You only want to rebuild once...

[justinburnett]

I was wondering because I had my transmission rebuilt and they put an unweighted plate on and everything went to hell right quick after that.
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[rayfinseats]

400's kick ass. Don't let anyone tell you any different. TONS of torque. We raced em and I had one in a 73 caprice 4 door that would smoke the tires (and it had posi) Great engine

[jrcaprai]

Mine is 11.6 Compression on Pump Gas... all depends on your combination, Cam plays a big part in that, and having aluminum heads helps by one compression point

[jrcaprai]

Originally Posted by justinburnett

So. Good news guys. I'm a dumbass!

When I bought the truck the guy said it was a 350. I just assumed since he said he'd owned it for years that he knew what he was talking about, but apparently....

Took the heads in to get a valve job since there were two burnt exhaust valves and I didn't know what shape the rest were in so I figured I'd just have them all done. Guy was like "I thought you said on the phone you had a 350" and I was like "yeah" and he's like, "these are 400 heads" and I was like "wtf" and he was like "dude go measure your bore" and I was like "4.155..... Sh*t".

So... good news is I have a bigger engine, I guess. Called Northern Auto Parts and switched my order for a rebuild kit which ended up costing me an extra $160 for the 400 kit instead of the 350 which is gonna kick my ass. They still had my kit all ready to ship on the loading dock so they were able to catch it.

Now, the big $1600 question. I put a new flexplate on my engine when I got it. For a 350. With no weights. Did I kill it? Also, how do I balance it now that I know what it is?

Just because you have 400 heads does not mean you have a 400....
Check the Block # to be sure .... Duh, just saw that you measured the Bore to 4.155

[maynardtruckin]

OK if you put flat top pistons in a motor that had dished originally it would make it more like a 1970 truck motor and you would have a higher horse motor. Your motor is like 150 horse and a 70 motor is like 200 horse ruffly. The numbers are a guess but realy you get the idea. it is just a stock motor either way!

[jrcaprai]

1 point of compression is worth approx 4%.

Sooo, if you have a 300 HP motor at 10.0 to1 then bump to 11.0 to 1 you will get approx 312 HP

[justinburnett]

Well that's not really that much at all but ill take what I can get. Having the heads done right now. Offer 4 valves. Painting the block right now. Masking always takes so much more time than I think it will.
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[ChevyC102007]

Stock or modified a 400 is still a bad ass motor in my opinion. Wish I still had mine that I put in my '71