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Overheating on Hwy 350 SBC

4X4HIGH said:
9.78:1 is ALOT of compression with an iron head in a 6000lb. vehicle. If the heads were aluminum then you can get away with more compression but this isn't the case. Also, a 72cc head with a domed piston is going to net more than 9.78:1 compression. If he can give me specific numbers i can tell exactly what the compression ratio is. Highy doubtful though that he has all the required numbers to accurately figure it out.

Just checking with some easy numbers he's already looking at closer to 10.2:1 CR
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what to you need to know??? I will tell you, I can be absoutly wrong.:doah:
you know the heads, .030 over and pistons are federal or speed pro, I have one in the garage I could send you a pic email, part number I dont know, its not a large dome like in circle track I think it was the smallest dome they made.
 
I think I found it, .125 dome, which with 64cc heads are 10.68:1 CR, so with 72cc heads it is ?????
76cc heads are 9.34CR
Part number STL-H618CP30
 
In order to calculate exact compression ratio i need, heads chamber CC's (72cc), head gasket bore diameter (most SBC are 4.166"gasket bore diameter), compressed head gasket thickness, cylinder bore diameter (4.030" in this case), deck height clearance, and piston dome volume CC's. (I took a look today and the smallest one the Silvolite has is -5cc's). With this info i can tell you exactly what your compression ratio is.
 
Now you need gasket thickness, Fel-Pro stock blue gasket in an engine gasket kit, 5.7 rods too. I forgot that. The other stuff, out of luck, just got part numbers, but they should get close.
 
I just did a search on that piston number and it is a flat top piston with 4 valve reliefs. I don't have a federal mogul book in front of me but most of that style piston are 7cc valve pockets and if the block has never been decked GM SBC blocks are usually right between .020"-.025" deck height, the gasket will either be .039" or .041" compressed thickness so you're actually only looking at about 8.88:1 CR
 
4X4HIGH said:
I just did a search on that piston number and it is a flat top piston with 4 valve reliefs. I don't have a federal mogul book in front of me but most of that style piston are 7cc valve pockets and if the block has never been decked GM SBC blocks are usually right between .020"-.025" deck height, the gasket will either be .039" or .041" compressed thickness so you're actually only looking at about 8.88:1 CR
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Well I messed up then looking at old invoices, I know they are Federal Mogul and they have .125 dome on them, and they are .030over and they are float or press wrist pin because I questioned how short the pins where from the snap rings when I put it together.
 
It looks like you have 20 different things contributing to your problem.

There are so many conflicting statements it's pretty hard to know where to start looking for the root cause.

If I have been following along..
You took a bunch of go fast stuff and just bolted it all together not even bothering to check what the compression ratio or anything would be, or what you are bolting together and how it will function with the rest.

FWIW I built a .060 over 350 for my 69 and it came out to be 9.17:1 with Silvolite 2 eyebrow flattops. I have a cc kit. And a heat gun, ok two of em.
Gotta have one for home.

plain street/strip build engine using Edelbrock RPM components
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What does that mean??
 
If it is running lean could that increase cylinder temps enough to overheat? Also 210-215 I though was normal temp for a SBC. That is why we have a pressurized coolant system.

The way you contridict yourself in some of your posts makes me question your engine building abilities. You also cannot seem to get past your personal pride to accept the advice of several knowledgable people from this board.

Just my observations.

Dik
 
JPMSK5 said:
Well I messed up then looking at old invoices, I know they are Federal Mogul and they have .125 dome on them, and they are .030over and they are float or press wrist pin because I questioned how short the pins where from the snap rings when I put it together.
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Unless you can either come up with the CC's of the dome volume or a part number i can't help you calculate true compression ratio.
 
Ok, i found the piston info i need. With a 72cc head chamber volume, .041" compressed head gasket thickness, -3.5cc piston dome volume, assuming .020" deck height, with a bore of 4.030" you're looking at 9.89:1 compressio ratio. That is too much compression for an iron headed engine in a 6000lb truck. Also, unless you have a cam with alot of valve overlap that engine is going to ping badly on the upper RPM's probably anything over about 4500 or so. If you do have a cam with lots of overlap then it's the wrong cam to be using for a truck engine expecting to make torque down low.
 
If you replace a clutch fan, be sure to get one setup for your current gear ratio because it does have an effect on it. As for this guys problem, I'd say high compression creates too much heat, and it's pushing around a heavy K-5. Take that power plant and stick it in a sub-framed NOVA an go street racing
 
Did you ever check the lower radiator hose hold a high rpm and see if the lower hose colapse. May need to add a spring inside or hard line it.
 
Places I would check.

1)Make sure your running a correct rotation fan
2)Not sure but possibly same problem for water pump
3)Change out to a higher quality t-stat
4)Cant head gaskets give some trouble with coolant passages if install them backwards or the wrong ones?

I know my truck used to over heat because it would blow air the wrong way. the 88 and up trucks are opposite rotation of all the earlier trucks.
 
Wrong fan, or water pump would cause issues all the time. Head gaskets on SBC are symetrical and can go on either side up or flopped no difference 1955-1995.
 
4X4HIGH said:
Wrong fan, or water pump would cause issues all the time. Head gaskets on SBC are symetrical and can go on either side up or flopped no difference 1955-1995.
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Ok I was thinking along the lines of the 400 sbc problems with the extra steam holes and people not opening them up on the gasket. Just wondering if that could be a possible cause.
 
Since he isn't running a SBC 400 that's not an issue. Even those gaskets are symetrical and can go either way, the only difference in 400 gaskets are the bore diameter and the steam holes in the gasket.
 
4X4HIGH said:
Since he isn't running a SBC 400 that's not an issue. Even those gaskets are symetrical and can go either way, the only difference in 400 gaskets are the bore diameter and the steam holes in the gasket.
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Yeah I got ya now. Was just curious if something like that could occur in another application.
 
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