compatibility

[WH1 85]

I have a 109 block that I got out of an 87 cutlass. It was an n/a motor with air. The difference between this block and an 85 are glaring. It is definately a stouter unit.

Question is are any hot air guys using the 86'-87' 109 block?

If so did you have any problems. How about all of the bolt holes, will they match up? If not will I have to tap more, are there bosses on the 109 for any needed taps. Anyone with any experience with this please chime in.

The motor also has 8445 heads. Can I use these as well?

 

[FJM568]

Originally posted by WH1 85
I have a 109 block that I got out of an 87 cutlass. It was an n/a motor with air. The difference between this block and an 85 are glaring. It is definately a stouter unit.

Question is are any hot air guys using the 86'-87' 109 block?

If so did you have any problems. How about all of the bolt holes, will they match up? If not will I have to tap more, are there bosses on the 109 for any needed taps. Anyone with any experience with this please chime in.

The motor also has 8445 heads. Can I use these as well?

No problems at all using the 86/7 109 block...As you have noticed, the block is better...You will need to use head bolts for the 86/7 motor...They are a different length than the 84/5s...Otherwise, no other differences, all the other bolt holes/locations are the same...The other thing different about the 86/7 block is the deck height is a little lower, so you either have to use the 86/7 compostion head gasket or double stacked 84/5 steel shim head gaskets, unless you don't mind a very minor static compression increase of at the most .5 points...Use either the GM factory composition head gasket or the FelPro 9441s...You will be fine...

The 8445 "NA" heads are identical to the 8445 "turbo" heads...NO difference in them, either, other than the different valve spring required for the turbo application...Actually, a lot of people think there is a turbo specific block and head, but in reality, there isn't...They used the same blocks and heads on all the motors...

The only boss on the 109 block that would need to be drilled and tapped is the one on the front of the block for the turbo oil return ONLY IF you plan on converting over to the 86/7 setup with the turbo located in the front...Otherwise, there are no holes that need to be drilled and tapped anywhere to use in the 84/5 setup...

 

[WH1 85]

Cool that is just what I was wanting to hear.

My car will be staying a hot air. So I wont need to tap the boss for the oil return line.

I understand what you are saying about the 109 having a lower deck and there for making higher compression ratio. So if it goes up .5 that will give me a c/r of 8.5. How much extra power do you think this would be good for? Or how many cubic inches would I be losing? I think the tta's had a c/r of 9/1. But didn't they have different sized combustion chambers?

Do you think that I'd be running the risk of having more detonation at the higher c/r? Especially on a hot air. If so would running alchy compensate for this?

 

[FJM568]

Personally, IMO, the extra compression wouldn't be noticable other than you may detonate earlier...For example, if you were able to run 16# of boost on 93 oct pump gas on the stock 84/5 block, you may only be able to run 14-15# boost on 93 oct pump gas with the 86/7 109 block with one steel shim head gasket...Don't know if you would gain any power by doing it, might be equal in the end, cyl pressures may be about the same, so really no gain...

I would stick to the 86/7 composite head gaskets or the FP 9441s if you switch to the 109 block...

I really don't have any firsthand experience with running a single steel shim head gasket on the 109 block, but there are probably a few people that have tried...You may want to try posting the question on the general tech section of this board and ask what the pro's and con's would be on running 1 steel shim head gasket on a 109 block on the hotair motor...

Or start another thread here and ask for Lee Thompson to look at this thread for his opinion...He has done a lot of things running his car over the years...

 

[cool 84]

It really doesn't matter which headgasket you use. I've used composite on my hotair block and friends have used steel shims on their 109 blocks. Higher compression will make the turbo spool a little faster, better gas mileage and more power with the same amount of boost. That's why I bumped mine to 8.5 when I had my pistons made. There was no noticable difference in what level it detonated at but the above differences were there. I would definately run the steel shims if it were me.

Another thing is the 109 has never been proven stronger than the hotair block. It looks better and has recessed headbolt holes but in the main webbing area the meat looks the same.

The TTAs had the same compression as the TRs and you can't gain or lose displacement from altering the compression.

 

[WH1 85]

Yeah 8.5 c/r is about what I was looking to run. And sounds like I should be able to do so without worrying about excessive detonation. I'm only looking to be at 16 or 17 with the boost anyway.

How has that 4.1 worked out? I have thought about going that way with my firebird. it has the 2.8 in it now. So it is in dire need of some buick power.

 

[GnTooFast4u]

109

I'm running a 87 109 block in my 85 gn and I dont seem to run into any problems other than I dont have anymore money to make it faster for now. Just got my engine rebuilt and its nice. 30 over,custom je pistons,custom lunati cam,carillo rods,fordged crank,new 8445 heads cleaned up a little bit. Next parts are tm v2 intake or v3 intake, t-60 turbo,50lb injectors,and headers,3200stall and a bottle. In the near future about 2-3 months

Allan