FSV 1800 to 1600 compatibility questions

[Robert J. Alder]

To: ApexSpeed readers and knowers of all things important.

The '78 Lola T-620 FSV which I'm restoring actually had an 1800 in it and ran SCCA and RMVR as a FA in accordance with both club's rules. I was willing to just go thru the engine, refresh as needed and stick with the 1800. But long story short (and sad), the engine was pretty much crap, only being able to salvage the block and head, both of which still needed some attention. Arrrgh!

Anyway, I was willing to do that. But, I'd really rather put it back to the original 1600 for a proper original FSV configuration. And, it turns out I might even have a lead on a nice 1600 FSV engine out of a Ralt RT-5.

But before considering going back to 1600, and not knowledgeable at all about these power plants, I'm wondering about the dimensional (or other) differences between 1600 and 1800 engines besides displacement:

• Are motor mount bosses the same?
• Is the bolt pattern for the Hewland adapter to the block the same?
• Do both use the same Hewland adapter? The one on the 1800 was about 1" thick (I'm guessing from memory about it's thickness.)?
• Is the bolt pattern on the crank for the flywheel the same?
• Did they use basically the same flywheel and starter arrangement? (the starter on the 1800 mounted to the adapter.)
• Are there any other external dimensions that would create issues if reverting to a 1600 FSV engine?
• If the bolt pattern for the flywheel is the same, can both use the same flywheel.
• Are the intake and exhaust ports on the head the same?

In general, what are the issues of going back to the 1600 power plant which I need to consider.

Oh, if any of you have a good complete 1600 you'd be interested in selling, I might consider it providing answers to the above mean minimum of brain damage to revert back to a proper 1600.

Thanks for any input or advice.

Respond here or direct to r.alder@earthlink.net or 303-981-6364

[pooch776]

Yes to all of your questions. It is a direct replacement!

The other questions you may ask yourself is who you are goint to be running against. Are you going to race with a club that uses Monoposto rules?

Good luck, Joe

[Robert J. Alder]

Pooch,
Thanks. That's good news. Actually it's a project car that will be sold. So, I'd like to prepare it for maximum acceptance. That's another reason I was thinking that returning it to 1600 specs would make it more universally acceptable, even to Monoposto which does require the 1600.

[pooch776]

Putting a 1600 in it may increase you chances of selling the car overseas but you may want to go with the most cost effective engine if you plan to sell the car. You can easly have more money into one of these cars than you can sell it for. If you have a good 1800 head it can be used on a 1600 bottom end with some modifications.

Cheers, Joe

[revtom]

Just about all the 1800's you will find started life as 1600's. Block bored from 79.8mm to 82ish, and 1800 crank, and 144mm rods added, 1600 head retained. Three versions are usually found; 1800. 1825, and 1835, which had problems keeping head gaskets, as the tiny area between bores didn't offer much sealing area, even when O-ringed. Stick with 12.5/1 comp. or less, and it should be a happy engine. In the US, (at least Mid-West, and E. Coast) there are so few showing up at Vintage races, no one will much care if it's an 1800, 'tho Monoposto rules do say 1600. So many were converted to 1800 after Supervee's series ended, it's hard to find race prepped engines that stayed at 1600.

[Stan Clayton]

If you have a good 1800 head it can be used on a 1600 bottom end with some modifications.

The "some modifications" is a non-trivial exercise...

The 1800 head and block have an additional oil return hole (compared to the 1600), so to use the 1800 head on a 1600 block, one must fill in the secondary hole completely (or oil will literally drain out of the head onto the ground). Also, the 1800's primary oil return hole is generally welded up and then redrilled to match the smaller 1600's drain for best performance.