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Looking for a little advice..I've got a '79 350 on the stand from a Riviera (3A non-AIR heads), planning on dropping into an '85 Eldorado (did this years ago with a 403 and had a blast). Initial teardown looks promising, planning on dropping it off for hot tanking and magna-fluxing tomorrow. Cylinders look good, so I'll stick with the std pistons unless I hear different from the shop.
Stock ratings on this are 160HP/270 torque. If possible, I'd like to bump power up a little to 403 levels...185/320. I believe I'm locked into the factory intake due to hood height with FWD (correct me if I'm wrong there). I realize the smog heads aren't great, but do plan to port/polish to get rid of the EGR bumps, 3-angle valve grind and open up the exhaust on the vehicle side to a 2.5" single, and I'm not shooting for the moon here.
That leaves me with a couple options... a slightly more aggressive cam, and milling the heads to bump compression...9.1? Worthwhile? Recommendations?
Any advice/feedback appreciated. I've searched the archives but most results tend to focus on higher HP builds. Thanks!
Get the shop to crack check the heads. They are restrictive and crack prone. Early heads are a better starting point, especially on the exhaust side. You can go with W31 valves, 2"/1.625" valves and the bowls opened to start. Your heads have 1.875" intake and 1.5" exhaust valves. Don't be surprised if the block needs an overbore. There are a couple of hone to fit options in a 4.065" size, if your block is really good. CP makes a 1.3cc dish and Mahle has a 10cc in that size. Yes, the factory cam is super mild. The 204/214 cam is a cheap option, especially if leaving the 14cc factory pistons.
Get the shop to crack check the heads. They are restrictive and crack prone. Early heads are a better starting point, especially on the exhaust side. You can go with W31 valves, 2"/1.625" valves and the bowls opened to start. Your heads have 1.875" intake and 1.5" exhaust valves. Don't be surprised if the block needs an overbore. There are a couple of hone to fit options in a 4.065" size, if your block is really good. CP makes a 1.3cc dish and Mahle has a 10cc in that size. Yes, the factory cam is super mild. The 204/214 cam is a cheap option, especially if leaving the 14cc factory pistons.
I must admit you do have me thinking. The machine shops around here are so backed up I think I'll have a little time to see what's out there for earlier heads while they clean up the block.
If I do end up using the 3A's (I've got a couple sets), do you think I'd gain much milling them? I see the aftermarket headgaskets are roughly twice as thick as the originals, so I'm at a deficit right off the bat.
Yeah, it will, bump compression a bit and will depend on the pistons used. Honestly if they have to do anything to the block, even a hone to size, get them to 0 deck the block. Your pistons are probably .020" in the hole and Felpro are .042" thick compressed. Realize you may have to mill your intake manifold or the intake face of the head with any amount of head milling to fit even the Turkey tray gasket. Also CC the combustion chamber on the heads to see exactly where you are. What head gaskets were in the motor? Good luck.
I see the aftermarket headgaskets are roughly twice as thick as the originals
I thought I had read somewhere that the later engines used thick composition gaskets the factory? Is that not so, and they used the thin steel gaskets?
[QUOTE=olds 307 and 403;1399693]. Your pistons are probably .020" in the hole
I have heard this quite a bit. I have .30 over cast pistons on my 455 and they came up flush with the deck. I don't what brand because I bought the motor rebuilt and we just pulled the heads to see the condition of the motor. The pistons looked stock with a v-notch and shallow dish.
. Your pistons are probably .020" in the hole
I have heard this quite a bit. I have .30 over cast pistons on my 455 and they came up flush with the deck. I don't what brand because I bought the motor rebuilt and we just pulled the heads to see the condition of the motor. The pistons looked stock with a v-notch and shallow dish.
They decked the block probably twice that if cast. Factory Olds aren't bad, especially with shim head gaskets. The old Dodge 318 can be .080" in the hole factory. My 360 Magnum wasn't that much but even they are .040" in the hole.
I thought I had read somewhere that the later engines used thick composition gaskets the factory? Is that not so, and they used the thin steel gaskets?
Curiosity got the better of me and I grabbed a caliper to check 'em out. The gaskets on the heads off the '79 Riv 350 measured around ~0.028 thick. This motor appears to have never been apart. I did the same on the '79 Eldo 350 heads and those were in the ballpark of 0.040. Judging by the steel timing set and RTV on the oil pan, this one was serviced some time back in the day, though I can't confirm one way or the other that the heads were off. Whatever gaskets were used, the surface on the heads is a consistent light blue color, similar to string-line chalk.
Dropped the block off at the machine shop yesterday, so I should have some feedback in a couple weeks. Thanks for the replies so far!
Yeah, the 307 I pulled down, along with my 403 had the head gaskets replaced when I got them. A nylon timing set is also a dead giveaway for a stock motor. Both my 76 350's had them and shim head gaskets. The 73 350 had Felpro head gaskets and a minimal slack double roller, not stock for sure. It makes sense the head gaskets were slightly thinner. Supposedly the pistons are also less bwlow deck, in the .015" to .020" vs .025" to .030" for the earlier blocks. My 403 pistons were about .020" in the hole.
Yeah, it will, bump compression a bit and will depend on the pistons used. Honestly if they have to do anything to the block, even a hone to size, get them to 0 deck the block. Your pistons are probably .020" in the hole and Felpro are .042" thick compressed. Realize you may have to mill your intake manifold or the intake face of the head with any amount of head milling to fit even the Turkey tray gasket. Also CC the combustion chamber on the heads to see exactly where you are. What head gaskets were in the motor? Good luck.
I did a little research and I believe the previous owner said he used Mahle cast pistons when he rebuilt. They have the v-notch (68 to 70 455 replacement). The compression height on the Mahle is 1.72". The factory compression height is 1.74, so mine may be 0.02 in the hole, but factory dish depth is 0.15 for 10.25:1 and the Mahle depth is 0.12, so probably about the same volume or very close. The Felpro gaskets on the other hand definitely lower the compression.
Just wanted to give a quick update- machine shop came back and my 350 block is good to go with a 0.030 overbore, no cracks. I hesitated since a smooth running 403 popped up locally for cheap this weekend, but was snagged within an hour of posting (guy was LS-swapping). So back to the 350 it is. 1979, 3A heads.
Played around with the CR calculator and it looks like running the SP L2320F flat top pistons would get me just over 9:1 CR without decking the block and using the inexpensive FelPro head gaskets. Saves a little bit of money there, and no change to pushrod length or head milling. For a little punch above stock on a budget build in a FWD Eldo for daily-driver use, I'm thinking this should suffice.
Can you guys recommend any good ring packages for those flattops? Thanks- C
Are you committed to the 3A heads…? It’s just a lot of work instead of grabbing $200 cores of 3, 4, 5, 6, 7, 7A and installing big valves in them as well as having the head bolt holes drilled square (milled) to 17/32.
orherwise, yeah a set of 1.62/2.00” valves would go a long way. Even without touching the rest of the port.
Are you committed to the 3A heads…? It’s just a lot of work instead of grabbing $200 cores of 3, 4, 5, 6, 7, 7A and installing big valves in them as well as having the head bolt holes drilled square (milled) to 17/32.
orherwise, yeah a set of 1.62/2.00” valves would go a long way. Even without touching the rest of the port.
If he does that, get them to open the bowls with a cutter. Yeah, all the "A" heads have tiny exhaust valves and terrible ports.
Thanks on those rings!
Yeah, I've had my eye out for an early set of heads, been trolling the usual places. Seems like this stuff was everywhere when you didn't need it.... If nothing turns up in the next month or so I'll look into oversize valves. Appreciate the info!
