SBC 350 Compression question

[Gordon]

Hey guys I finally have everything i need to do my V8 swap in my 95.

I tested the compression of each cylinder and they read 170-175psi... isn't that a little high for a V8

I'm not sure if the engine was ever rebuilt or not but the truck i yanked it from had 230,000kms on it.

Gordon

[Smiliesafari]

Sounds good to me.

[Gordon]

Any idea if a set of 98' vortec heads will fit on this old 88' motor?

I remember something about the middle bolt holes being different


This old 88' motor runs great but the stock heads are crap and it has the stupid manifolds with "emissions" bungs... gotta plug those and weld up.

[Kabey's Van]

Sorry Gordon, your 98' v-heads will not fit an 88' block. There are many other chioces of head avaliable for your engine that will work better than what you have. If you have a sound block there are lots of head, piston and camshaft combinations you can match up and build a nice motor from.
Don't get you mind "set" on a Vortec, they are not the engine they were once claimed to be.
The compression readings you pulled are high for an engine with 230,000 k's on it. An engine of that vintage is more likely to be huffing out in the 135-150 psi range.
If you are pulling 170-175 psi, evenly, across all cylinders why would you mess with it?

Peter

[Smiliesafari]

Contrary to some misinformation in our world the vortech heads will fit on the earlier blocks. The difference being how the intake manifold bolts to the head. Non vortech manifolds use 12 bolts. Vortech manifolds use 8 bolts. There are manifolds available although they are a bit pricey. I've done a lot of research on this swap as this is exactly how I'm going to build my V8 conversion motor. 1988 Camaro 305 with Keith Black flat top pistons, 350 vortech heads, 6 inch rods, roller rockers. The rest will be pretty much stock. I'm staying with the center port fuel injection to keep it a bit more simple.
I do agree with Peter. Those numbers do sound a little high for an old motor. Not knowing the history leaves one to think that it may have been rebuilt or replaced with a new motor.

[Gordon]

Thank you for the information, i'm off to go "head hunting" lol

[Mr_Roboto]

I'd call that a "winner" personally. But that's just me. 170-175 is great! This can vary some depending on your camshaft among a lot of other things. I'd throw that in and run it as it's still nice and tight. You should look into the 305 Vortec heads smile. 58CC chambers and very similar flow to the 350 ones! not as good of chambers though. I am going to do 350 TBI heads on mine so I can turbocharge down the road and get a bit more CR drop.

[Gordon]

ok so let me get this straight... vortec heads from say a 98 truck (096 castings) will bolt onto any SBC or just certain years?

I can get set of vortec heads for $200 freshly pulled from a 99 vortec 350.

He also has the vortec carb intake with a holley 750 double pumper carb.

Should i go for this?

I will also change my cam out before the motor goes in.

[Smiliesafari]

That is correct. The vortech heads I'm going to use are from a 98 Suburban. That could be a good combination. It depends on what you expect from the finished setup. Have you decided what you want from this engine?

[Smiliesafari]

I'd call that a "winner" personally. But that's just me. 170-175 is great! This can vary some depending on your camshaft among a lot of other things. I'd throw that in and run it as it's still nice and tight. You should look into the 305 Vortec heads smile. 58CC chambers and very similar flow to the 350 ones! not as good of chambers though. I am going to do 350 TBI heads on mine so I can turbocharge down the road and get a bit more CR drop.

I haven't looked at the 305 heads. It's my understanding that they have smaller valves also. The 350 heads have 64 cc's. With the flat top pistons that should give close to 9.0 compression. This motor is going to be strictly a daily driver. I'm looking for good MPG. And I know I'll enjoy the extra torque. (Old hotrodder at heart). When Cherie and I travel, the van is loaded with around 1000 lbs of ballooning gear and other stuff. You know how women pack,LOL. I'd like to do a little more than 60 MPH and get better MPG. I have no complaints about this 4.3. It has served me well. It's over 200,000 now and still runs great. It's just that when you push the van past 60 MPH the MPG really starts to suffer.

[Mr_Roboto]

Yeah, I understand that but even a stock swill gas Vortec 305/350 or a TBI/TPI engine range from 9.3:1-9.5:1. You may be able to get away with more timing to make up for it though. Yeah the Vortec 305s have smaller valves but look around for some flow #s. They were well within 10% of the Vortecs and I think within 5% even with the 1.84 intakes. From my understanding they are stout enough to even make them work decently on a 350. Unless you shave the 350 heads you will probably drop into the high 8.X:1 range on a flat top equipped 305.

Either that or what heads do you have now? You may consider doing a bowl blend on them and back cutting the valves or installing new ones. You could probably do damn well on them especially if you're using a lower lift cam. Swirl ports are a fairly demonized head but honestly for lower lifts (where your cam spends its time anyways) they have very good #s believe it or not. It's mostly the smog cams that kill em. You can also use standard intake manifolds which is a huge boon IMO.

Vortec heads will bolt on to any gen I block and work fine. It's the intake that's the catch. You will also need self aligning rocker arms if you don't have em already (pulling a whole head is a good bet) center bolt valve covers and a special Vortec intake. That's all. Oh yeah, and an external EGR setup if you're smog compliance required. I'd grab the one off the truck in question if you yank em.

Is your engine roller or flat tappet? There's a chance it could be either. It may have the bosses for the roller cam or it may not, it may have em not drilled (my last 350 was not drilled but it had em) If you can consider upgrading to a roller cam. If you have a roller cam even the stock TPI cam is a HUGE upgrade for one of these. I got lucky and scored one off ebay for my 305 mk-II for $22 inc. shipping. Cam would be my priority LONG before heads would in this case. You can make more power with the heads but a cam would be easier and probably cheaper and make more power too.

[1Gary]

I think by the time you invest in a used set of Vortec's,you would be better off buying a new set steel heads from GMpartsdirect or a set from RHS which would be a little more money.The nice part of those heads is they have a dual bolt pattern where you can use the early 12 bolt intake or later intakes The eight bolt later Vortec's are said to have a tendency to leak at the intake manifold gasket and have ruined a number of engines.I posted a thread recently that spoke about the complaints about that.