The Stovebolt Site Forums The Shop Area The HiPo Shop Plastic LS3 mock engine

Does anyone know of someone offering an entire LS3 plastic long block? P-Ayr offers a partial one but with no bell housing bolt hole and no exhaust manifold bolt holes. We do our swaps with the vehicle on the drive on lift where both above and below areas can be observed for clearance/interference problems and mount patterns can be made in a comfortable standing up position. If lift is raised for cherry picker leg clearance it is then too high to swing engine/trans assembly in plus I hate cherry picker legs being in the way. With our plastic sbc and Windsor sbf plastic engines one can just set them in by hand. Have only used one 350 in the last two or three years so the LS is the one to have facilities for. Thank you.

I've searched for years for an alternative to the plastic blocks because they are fragile and I couldn't hang a starter from the SBC one I had. I used a P-Ayr plastic LS block for designing motor mounts. I wouldn't do it again. When compared to the parts I had laser cut off GM 3D computer drawing files I use I found the plastic blocks had way too much variance. I didn't have the problem with the SBC block from P-Ayr. I would highly suggest finding an aluminum block LS and gutting it. Once I did this everything fit properly with exceptionally good tolerance. I centered a Harbor Freight electric hoist directly over where I did test fitting of powertrains and this made it easy without the stupid cherry picker legs getting stuck under the frame.

As yellosub54 says: With your connections in the LS world, you should be able to find an unrepairable LS block. As you know, they are aluminum. Cut out the webs between the bores and maybe the journals. Create some adjustable end plates or adjustable motor mounts on it that just sit on the frame/clamp to frame. After hogging it out, it should be reasonably light. It will be exact and have threaded holes.
The lightened block can also be held "floating" on a wheeled, adjustable lift stand. It would then have all axis (X,Y, Z and pinion angle) adjustment from underneath.

On the other hand, the P-AYR are accurate and have many bolt holes. They have transmission mock ups also or an aluminum transmission core can be used and lifted up. Most of the time, the exhaust is not a feature used to locate a motor. the motor is located by more important factors. Then it's up to the swapper to find or build exhaust after motor is in or located. You will always have some extra work to do but fitting motor to firewall, it's X,Y,Z, pinion angle, fan clearance, motor mount locations and tranny clearance are the important issues, not exhaust. After you have solved these issues and cleared steering parts and suspension parts, you can't start moving the motor to accommodate exhaust. You can hand hold stock exhaust manifolds or headers in place to get an idea of what mods will need to be done for exhaust.

I know, you know all this already, just saying maybe sit back and decide what you can do and what you can leave as doable.

I disagree with the statement about the exhaust not being an important part of locating the engine. It is often necessary to locate the engine to the passenger side of the frame a small amount for exhaust/steering shaft clearance. How do you know how much is enough? answer: you don't without having ALL the components in place to check clearance.

Thanks everyone, yellowsub54 has finally got my butt tipped off center on putting a hoist rail above the drive on lift. Have been putting it off for a long time because the roof trusses run the wrong way for fastening a rail but a pair of cross beams will take care of that. I have a couple of iron LS blocks and with an electric hoist they will work fine for test fitting. Ceiling is 13' at the walls and 25' at center so if I back one on the lift there will be plenty of room for most any type of rail set up. Thanks again; Evan

I agree the exhaust is critical to engine location when building mounts. I install ALL accessories that will be used. This eliminates getting everything fitted and built only to find out that the exhaust would have fit IF the engine was sitting a quarter inch to the side. If you take precise measurements (I use 3D computer models from GM) you'll see that it is common that GM and most manufacturers offset a RWD engine to the passenger side for clearance even on late model vehicles.

My response was trying to answer the original question. You can't bolt heavy exhaust to a plastic or foam mockup. They won't hold it. That's why no holes.
So I gave alternate suggestions. Others continued to push the exhaust manifold which can not be done with the original request.

Now the OP has changed altogether and wants to use an iron block. I can not anticipate that an OP will not stick with his initial criteria. I got sucked in this time.

Yes, I did change after getting advice on an over the lift hoist which opened up a whole new scenario. If one won't accept change then there is a cave somewhere for them and a big club for getting a mate. I learn as much from being wrong (maybe more) as when being right. The last time I tried to walk on water I sunk. Chill out.

Play nice. Question was discussed and choices made. Let’s leave it at that.