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HT4100 4.1, 4.5, 4.9 Discussion, I'm going to try the 4.1->4.9 conversion in Cadillac Engine Technical Discussion; I recall a post from Bbob saying that there were minor differences between the 4.1, 4.5, and or 4.9 concerning ...
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    Re: I'm going to try the 4.1->4.9 conversion

    I recall a post from Bbob saying that there were minor differences between the 4.1, 4.5, and or 4.9 concerning either the gasket mating areas or the coolant passages. I cannot for the life of me remember what thread that was... I was browsing posts from ages ago deep into the 4.x section. I'll try to find it again...

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    Re: I'm going to try the 4.1->4.9 conversion

    Quote Originally Posted by ehall View Post
    I keep forgetting to look at the brake booster vacuum setup on the 4.9 DeVilles... where does the vacuum supply come from? They don't have a supplemental vacuum pump right? Any pics would be great. I'm thinking about simplifying some of the vacuum setup and may delete the vacuum pump or (more likely) put it on a pressure switch. In either case I will need to isolate the brake booster vacuum supply
    Vacuum supply comes straight from the TB, no assist from a pump.

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    Re: I'm going to try the 4.1->4.9 conversion

    Several years ago I bought 4.1 and 4.9 manifold gasket sets and compared the holes, but I don't remember all the details. What I do remember is thinking that I needed to use the 4.9 gasket set since the ports were larger, and it would ensure that the gasket was pinched between the intake and the head (if I tried to use the smaller gaskets it would suspend over the holes in the block). I haven't looked at a 4.5 gasket but I'm guessing that it's pretty much the same situation.

    My hope is that since the 4.9 and 4.5 PFI manifolds are the same part number that the later 4.5 TBI manifold will also be free flowing. There are multiple part numbers so hard to keep track of what is what.

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    Re: I'm going to try the 4.1->4.9 conversion

    On 05-06-08 06:59 PM, edahall wrote

    We changed over the 4.1 on my dads 1987 Deville. We used the whole 4.9 motor but used a 4.5 intake manifold and the original 4.1 TBI. The coolant passages on the 4.9 heads don't exactly match the 4.5 intake manifold so it was modified to mate up with some JB weld and some grinding. I don't have any pictures but pictures would not do any good because both engines look identical.
    On 03-31-04 11:38 AM, BeelzeBob wrote

    I am not sure that your original 4.1 manifold will bolt onto the 4.9. I tend to think it would although I know the coolant ports will not match at the coolant crossover at the front of the engine. The ports in the head (for the coolant) are different shaped than the ports in the manifold....I think that they will still seal up, though....with some liberal use of RTV/silicone. Just glue the manifold in that area with the RTV and let it set up for at least 24 hours before filling with coolant. If you take the intake gasket and line them up to the ports on the head and intake it would be obvious. Use the 4.1 intake gaskets as they would fit the best.
    There are several mentions of this general subject but some of them talk about head-to-block alignment and others are just guessing. There are only a few posts like the ones above that are definitive. Looking at the pictures in the 4.x Rebuilder scans, it doesn't seem like the intakes are that different. In any event modifications are doable.

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    Re: I'm going to try the 4.1->4.9 conversion

    I looked at the 4.9 and 4.5 gaskets some, it looks like the water channel on the 4.9 is slight taller and narrower (more square) but still the same basic shape. It doesn't look like it will be very hard to fill in the differences.

    I bought an intake and throttle body from an 89 4.5 out of a junkyard in upstate NY (good price on the pair), should have them in the middle of the week

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    Re: I'm going to try the 4.1->4.9 conversion

    After reading about other people's experience with the timing cover and thinking about the corrosion damage on mine I decided to just replace it so I bought one of those too. I hope I won't find damage on the inlet--it's getting damn expensive to buy clean-up parts.

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    Re: I'm going to try the 4.1->4.9 conversion

    Quote Originally Posted by ehall View Post
    After reading about other people's experience with the timing cover and thinking about the corrosion damage on mine I decided to just replace it so I bought one of those too. I hope I won't find damage on the inlet--it's getting damn expensive to buy clean-up parts.
    Yeah, the inlet is usually the most sensitive component of the assembly. Those fine threads for the 10mm bolts don't hold up well after 20 years, and are generally overtorqued by inattentive and/or novice mechanics replacing the water pump. This is the cause of many 4.X water pump leaks, especially the do-overs. When installed correctly, the 4.X water pump is relatively troublefree.

    The timing cover can be cleaned up with tap and a wirewheel as long as none of the studs pull out or loosen on disassembly. If the front crank seal was leaking, the new cover will come with a new seal pressed in.

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    Re: I'm going to try the 4.1->4.9 conversion

    Here's a pic of the front cover. You can see how the aluminum is pitted along the old gasket seam. This is why I bought another one... even if I could get a seal this time it would only be temporary.



    The back side of the cover looked fine. The inlet had some minor rust spots on the outside but the inside looked pretty good. I have cleaned and painted it anyway.

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    Re: I'm going to try the 4.1->4.9 conversion

    Somebody put pictures and diagrams of the 4.5 vacuum lines here which is very useful for planning purposes. I might just switch to the 4.5 vacuum lines, minus the AIR pump valving. The only real concern is that the 4.1 did not have a reservoir canister (it had the pump so it did not need a reservoir). I might install an old-school coffee can reservoir in the spot where the AIR pump inlet filter canister currently sits but I think I will also try to integrate the vacuum pump with some kind of switch since it's a more technically advanced setup. Interestingly, some of my google searches for vacuum switches have turned up articles about the brake light vacuum warning switch on the SeVille is supposed to act as a pressure switch for the vacuum pump too but I'm pretty sure my DeVille does not work that way--the booster check valve prevents low vacuum, and I never see the light again after startup, so it would not be useful as a double-duty switch. Maybe the Seville has another secondary switch somewhere.

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    Re: I'm going to try the 4.1->4.9 conversion

    I said earlier that I painted the water inlet but unfortunately I had a lot of problems with adhesion and the paint just wouldn't set up properly. There were also some small rust patches that I wasn't able to clean properly. The dealer wants $80 for the inlet so I took it to a local small-job machine shop and had them sandblast it for $20. It looks and feels like aluminum under the paint, but it's magnetic and it had some rust so it's some kind of steel. The pieces look to be held by copper brazing. Same part number for all of the 4.x engines btw.



    Wiped it down with mineral spirits and painted it with engine enamel (the same stuff I painted my brake calipers with a few years ago), and itt should stick pretty good this time



    The 4.5 TBI throttle body showed up from the junkyard but the intake manifold hasn't arrived yet. The large pipe sticking out the corner is for the brake booster vacuum.



    Here's a pic of the 4.9 PFI throttle body for comparison. Some of the vacuum lines are in the same place but the overall layout is just completely different--even the throttle cable hookup is completely different.



    I haven't checked everything for sure but I think the butterfly valves are the same. It will be interesting to compare the stock bore size of the 4.1 vs 4.5 vs 4.9. My bet is they are the same.

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    Re: I'm going to try the 4.1->4.9 conversion

    Quote Originally Posted by ehall View Post
    I haven't checked everything for sure but I think the butterfly valves are the same. It will be interesting to compare the stock bore size of the 4.1 vs 4.5 vs 4.9. My bet is they are the same.
    I remembered I had the 4.9 throttle body gasket, so I did some quick measurements. On the 4.9 throttle body there is about 1/16th of an inch lip before the gasket, but on the 4.5 throttle body there is about 1/8th of an inch lip. This is all metric and I was not able to line this stuff up perfectly, so my assumption is that there is a 1-2mm difference in the lip between the bore and the gasket edge, meaning 2-4 mm difference in overall bore diameter. GM clearly thought it would be worthwhile to have a larger throttle body so I will try to get the 4.1 or 4.5 units bored to match the gasket. I don't know the 4.1 size yet so I will do have to do that later.

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    Re: I'm going to try the 4.1->4.9 conversion

    If I remember correctly, those gaskets are completely different animals. I'm not sure about the bores themselves, but the TBI gaskets are a spacer type gasket with inserts in each bolt hole to control crush. The TBI gasket is a good 1/4" thick. The PFI gaskets are just a regular flat gasket. Might want to consider that in your decision.

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    Re: I'm going to try the 4.1->4.9 conversion

    I got the 4.5 TBI intake manifold today and spent some time studying on it. For reference, here are pics of the top and bottom, with the 4.5 intake on the left and the 4.9 on the right.





    The bore on the 4.5 throttle body and manifold both measure at 45mm, while the 4.9 throttle body and manifold measure at 47-48mm. The size of the intake ports for head are also larger on the 4.9 (pics below). I don't know if the runners inside the intake are larger, but the exterior casting looks the same. I could bore the 4.5 intake and throttle body to 4.9 sizes (or even larger I suppose) but all of the ports would need to be made bigger to get equal amounts of airflow. I suspect the intake port is the real limit, so there would probably be some gain from making the throttle body and intakee bores larger (maybe up to 49mm or thereabouts). On the other hand, the SBC 305 and 350 TBI engines used the same bore size as the 4.5 setup. I imagine that any benefit would show up at higher RPMs and would have no affect below 4000 RPMs. I might call a machine shop tomorrow and ask what they would charge to bore out the intake.

    Look inside the 4.5 intake and you can see little ridges in the chambers. My assumption is that these are to help direct fuel towards the ports and keep it from pooling up. The 4.9 is smooth inside and since it doesn't move fuel it probably helps airflow to have a smooth surface.

    The EGR tubes are rusty on the 4.5 intake. The hex-head button-head screws on the bottom provide access to the tubes but the tubes are crimped in from the top and bottom, and cannot be easily removed. This is another thing to talk about with the machine shop--perhaps they could press in some stainless tubing for me. Also note that the 4.9 only has one EGR supply port, and there is not a runner for the other port (which is blocked off inside with a dummy plate)--while the EGR supply ports on the 4.5 are both present.

    As mentioned above the 4.9 has larger ports going into the heads. As was also discussed earlier in the thread, the 4.5 has larger coolant ports. Here is a pictures showing the 4.9 intake gasket on the 4.5 intake manifold.



    As can be seen the 4.9 ports are significantly larger (and why the whole manifold would have to be shaped to match the overall airflow), while the coolant ports are somewhat smaller. In order to ensure that the gasket is sandwiched between the head and manifold, we will be using the 4.9 gasket, and then padding the inside edge of the intake manifold's coolant passage to guarantee a good seal.

    So the final decision is to use the 4.5 intake and throttle body with the 4.9 long block.

    I bought a TBI rebuild kit for the 4.5 throttle body and will be cleaning that up over the weekend. The only other part that we are waiting on is the front timing cover.

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    Re: I'm going to try the 4.1->4.9 conversion

    Some of the common SBC TBI mods look like they are easily doable with the 4.5 throttle body.

    Shave the lip, radius the inlet, and raise the pods

    http://www.cardomain.com/ride/598448...-camaro/page-4

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    Re: I'm going to try the 4.1->4.9 conversion

    I took the throttle body apart to replace the o-rings and gaskets and decided to go ahead and streamline it with my Dremel. I used a reinforced cutoff wheel to remove the raised lip (I left little sections by the edge to help center the intake collar), and then used a couple of grinding stones to shape a radius, and some polishing pads to smooth it all out. This is the way that most of the SBC TBI throttle bodies are shaped, and it's interesting that the 4.9 throttle body comes this way from the factory.



    I wanted to clean up the rust on the butterfly shaft, but the little screws all sheared off. I will get the machine shop to drill the tiny screw parts out of the shaft so I don't mess it up, then will detox and paint the thing after I get it back.

    I cleaned up the 4.5 intake manifold some as well. The Berryman's carb cleaner in a spray can is really good stuff, FYI

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