3800 NA block on a 2000 GTP

**weriven** · 02-17-2019

Ok, so my engine is knocking in my 2000 grand prix gtp and would have to be rebuilt. I have a 3800 na block from a 2003 impala that is in great shape. I was curious if the block from the impala could be used as the base for the engine and I can just take all the supercharger specific parts off the gtp engine and put onto the impala engine and put the whole thing in the car? I know there is differences in compression ratios but I don't know the specifics about anything related to that which is why this question is being asked. I also do plan to rebuild the block from the impala if i use it which I would prefer to do since it is in great shape I don't have to worry about any damage which I may find if I tear the GTP engine apart.

I hope my question makes sense, if not please ask and I'll clarify. Also my apologies if this has been asked before. I tried to go through everything as best I could to make sure a very similar questions had not already been answered. There are some resources that I can't even find that I know use to exist, such as the top swap thread.

In any event, Thank you

**Scottydoggs** · 02-17-2019

thats exactly what i did. blew up the l67, found a l36 swapped all parts over, heads, balancer idler stand, tensioner, all that jazz.

if your just running the stock pulley still there should be no tuning needed, but if your modded it will need some timing adjustments likely.

**weriven** · 02-17-2019

That is good to know, thank you. I don't have any modding on the car and don't intend to reduce the pulley size. I suppose at a later date if I do any modding then I will include this in whenever reprogramming the PCM.

**Scottydoggs** · 02-17-2019

you'll need to check your heads over good, they might have cracks between the valves, pretty common sadly. if you got high miles while the heads are off you can change the valve springs and seals too.

you will need new head bolts too, you can just use new tty bolts, run like 16 bucks, and you really should clean the head bolt treads in the block out with a thread chaser, or make your own out of a old bolt, cut 2 lines down the threads on opposite sides and run that bolt in and out of the holes. gets all the old thread locker out.

as long as the engines out, clean the piss out of it then take it apart.

get a lower conversion gasket kit, has all the gaskets for the block, front timing cover and seal, rear cover and seal oil pan oil filter housing and the pick up tube as well. as long as its out may as well make sure it dont leak right? kits like 35 bucks too, almost free at this point lol you also need new head gaskets, lim gaskets and upper plenum aka supercharger gaskets.

the oil pan bolts, put some thread sealant on the bolts on the sides, the threads can be the oil leak, you'll see how the threaded holes go into the block and oil can hit the bolt threads. i also ran a thin smear of rtv on the block and the pan to make sure it dont leak, smear = 1-2 mm thick.

**FordMan77** · 02-17-2019

"I also do plan to rebuild the block from the impala if i use it which I would prefer to do since it is in great shape "

Not sure what you mean here, but if you mean you want to touch ANYTHING in the bottom end/rotating assembly of the block- just don't. Leave it as-is and just swap the other parts. These motors are very touchy as far as the bottom end is concerned and require a lot of machine shop time to get right, and even then it's no guarantee you won't have a 500mi. motor.

**weriven** · 02-17-2019

Yeah, I meant the plan was to take it apart and replace the bearings, rings, etc, assuming it doesn't need machine work. So, that is a bad idea with these blocks and I should only worry about the seals to make sure it doesn't leak anywhere.

**FordMan77** · 02-17-2019

Yes, leave the shortblock alone. Just re-gasket everything like Scotty mentioned and go with that. If you take anything loose in the block you will need machine work guaranteed. There are guys running 3-400+ WHP on stock blocks so it's a non-issue.

Also, be sure to put a little thread sealer on the rear cover bolts as they like to loosen up and leak over time. Some have found they are finger tight when they check the factory ones.

**Scottydoggs** · 02-17-2019

the tq for the rear cover is less then snug, be sure to use some blue loctite. also front and rear covers, run some rtv 2 inches from the bottom up on both sides the gasket, thats a leak point on both covers. use a straight edge across the bottom of the block and the rear cover to make sure its sitting in place flush. theres small plastic spacers on each bolt, dont worry if some are broken. try not to break em tho lol the straight edge will align the cover for ya.

thread sealant goes on the 4 long water pump bolts and the all the lim bolts cause they all go into the coolant parts of the block.

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