I've finished slotting the 2 center bolt holes on my 88 TPI manifold (PITA...but a fairly clean job) and put it all back together on the old 882 head castings on my new 355. But a well respected machinist at a well respected machine shop says he guarantees it will cause a vacuum leak and subsequent damage down the road... What are peoples experiences with this mod...now that the intake is back together I don't think I can even see the center bolts any more...what is the final word? Do have to rip it down again?

 

The center bolts on sbc intakes are notorious for intake leaks as it is. It could very easily cause such a problem.

The real key to success is how it was done. If all you did was slot the holes so the bolts would line up and now the bolt heads aren't sitting flush the the intake surface then I can nearly guarantee that it will leak eventually.

If you spot faced the places where the heads seat so they make a nice flat positive contact, used a washer and filled the void with RTV; that's a different story. I've done two intakes like that and had no leakage problems. Ones got over 50,000 miles on it now, adn still no leaks.

 

I have had mine on for almost a year now, no problems what so ever. All we did was to slot the intake manifold so the bolt holes would line up perfectly. I had the vortec style bolts that were a little different angle than my old 86 head bolts were(92 with 86 heads). I work for a well known mechaninic and I am good friends with the well known mechanic and he helped me with it. Problem free. We did vaccum tests and the soapy water test, works fine.

 

Thaks for the input guys. I will grill my mechanic tonight to see how careful he was. What are the consequences of a leak?

 

Usually you get oil all over the center intake area and if there's a vaccum leak the engine will run poorly at and just off idle.

 

What made you choose #882s???

 

thread sealant is very important on those bolts stock. It's even more important now. Hopefully you put angle adapter washers under the bolt heads so they have a firm pressure against the intake. I don't see a vac. leak happening. Oil leak, yes. When there are proper (read: 85-86 and Vette) intake bases out there, I probaboy wouldn't modify an intake as you did.


Please don't call bolt patterns "Vortec" when they are not Vortec.

 

My Friend dremeled himself one of those to fit on his early style heads about 6 months ago.
I helped him put them on they seemed to hold well and have not leaked yet.

 

I know that they are not Vortec. I used that term because that is the term I have heard people use when reffering to the bolt angle style on the newer heads. Sorry about the misunderstanding.

 

Will it work if done right? yes.

But I don't care HOW GOOD you, or your mechanic is, it WILL seep oil eventually. Just a matter of time, and whether or not you even notice it if you change your oil regularly.


I've done probably 4 or 5 of these conversions. Using thread sealant on bolts, and cut to fit washers, it ran fine...but after about 2k daily driver miles, if you looked you could notice the slight stain around the bolts on the intake where the oil was seeping...not bad at all...but it still happens.


I agree with the post about finding the correct intake.

All alum head Vette TPI intakes will work since they had the pre '87 intake bolt angle. Only difference I'm aware of is the EGR valve location.

 

Sweets10v8 - I didn't choose them - I bought the whole engine (freshly built) from someone with those heads on. I would do things much different if I had to do it over - next time I blow it up I guess! They are supoosed to be good flowing heads for their time though - not as good as Vortecs but much better than stock. They've been mildly ported , good valve job, etc.

 

What type of pistons? dome/flat-top/dished??

If you have dished you have 7.5-8:1 compression
Flat tops would yeild about 8.5:1 compression

Stock L98(350) TPI cars come with 9.3:1 stock

Also what cam does it have? Not being picky, jsut concered you paid more than it was worthby being told it is a "performance" motor

 

Flat tops with a thinner gaket - he though the compression would be closer to 9:1. It came with an L79 cam but I yanked it and put in a comp cams xe262. And actually, I just read an article in an old Super Chevy last night that said that the XE series, because of an early closing intake, creates a lot of extra dynamic compression, and therefore wasn't recomended for anything above a 9.5:1 motor...so I felt better about my puny compression!

 

I would be thinking of replacing the heads at the first opertune moment. The 882's are a light weight casting with TWO EGR passages. This makes them extreemly prone to CRACKING!!!
I'm not trying to scare you, I myself have had this problem after porting & polishing the heads. I would invest in a book that covered indepth the different factory heads like "Chevy Small Block V-8 Interchancge Manual" by David Lewis. It has lots of info on the head selection as well as other components. This is just one that comes to mind, there are several others out there as well. I'm rebuilding my camino from the ground up, when I get to the engine I will be running a set of Edelbrock Performers or Trick Flows.

 

If you're looking for an aftermarket aluminum head I would seriously give AFR a look. They are a bit pricier than the Edelbrocks or Trick Flows, but they are better heads than either of them. AFR's head designs are light years ahead of either casting in terms of airflow and velocity. Look at the flow numbers they get with normal size valves. They're comprable to the numbers most heads get with 2.02/1.60 combos. When I get around to actually diving into my Camaro's motor I will be running AFRs.

 

I 2nd that! The thing i miss about my S-10 is sold(see sig) is the AFR heads I let go. If I have save for a year, and not do ANY mods to my car, AFRs are on my list.......again

 

I did one over 8 years ago, and it still doesnt leak.

The aftermarket manifolds (well, most of them) come machined for both patterns. I cant recall anyone complaining about it.

 

I had forgotten about them, Thanks. I'll have to take a look at them.

Bill

 

Forgot AFR

Thats like a sin against the car gods!!! lol j/k

 

Don't worry, after teaching all day I'd forget my head if it wasn't attached.

Bill