Datsun Roadster Forum-311s.org

will this work in a roadster? 2.5 sounds good, thats a stroker!!!!

just checking options...pistons and parts are the same price as the h20

thanks
steve

I have never actually seen one of these, but I talked to the local forklift store. They said that the engines will physically interchange, but very little will swap between them. The head on the H20 has TINY ports, so it is not a good thing for a car. I suspect that the H25 head is the same story. The reason that the H20 is doable is that the R head bolts to it. The head gaskets are different between the H20 and the H25 and the heads don't interchange, so the chance of making it work well in a car are pretty low.

IF you are bound and determined to use pushrods, take an H20, put U20 or VG30 pistons in it, bore it .060 over and port the heck out of a R series head. Run a big cam and have fun. Heck, I'd just go with a U20 and not worry about it.

Will

Will has a point, why waste so much gathering different parts to build a powerful motor, when you can just get a U20 and not have to waste as much trying to make it as powerful like a stroker.

Joaquin

I can answer that one. Cost. To properly rebuild a U20 is a pricey proposition. To build an H20 would be less than half the cost - maybe even closer to a third. When you are done, the car will still look stock, and will have herds of torque. Torque is what makes the car fun around town.

Have you priced the U20 specific parts lately?

All said and done, what will a H20 conversion will cost if the R16 head is reused? Does the R head need to be ported? Same carbs possible?

The H25 has a CR of 8.7:1 and a hp rating of the mid-60's. I imagine a good camshaft grind and larger ports and valves could do a lot to improve the performance of that engine. 8.7:1 is not that bad; our stock engines are 9:1 and my lowly J15 is 8.3:1 and rated at 78hp (SAE). Honestly, I think a lot could be done with an H25 to get good off-the line performance and keep the engine compartment looking pretty darn stock.

I have had the opportunity to drive a R16, Stroker and U20 cars. What I can say from my experience is the stroker is a stepping stone or a happy medium. I prefer the design of the R series for slimpicity and durability. Costs on a complete rebuild of a U series motor can run upto $4000. The stroker has great torque and enough HP increase over the R16 to let you know "it ain't stock".

Hell, ask Steve Allen. That guy was running circles around my S2000 with his stroker!

Alexi

About the only really expensive parts for a u20 are the timing gears and the rockers. You can get a cam reground to what ever you want for about $100. The rest arn't any worse than a R16 (the bearings, the chains, the rings, gaskets, ect.) To build a stroker, you will end up spending almost as much (to do it right.) U20 pistons are a bit $$ however one can swap a set of VG30 ones in for about the same as a set of R16s. The crank will be good, the rods are indistructactable. In the end when you factor in the cost of the U20 crank and rods, plus the machine work to the head and the crank, and the cost of the larger carbs, as well as a set of pushrods, just get a U20 and drop it in.
Beleve me machine work is not cheap.

Will

Will,

Been there and done that. When was the last time you looked at Ralleye's site to buy a timing set or solex carbs?

I guarantee you didn't completely rebuild your motor for $1100. You can't buy the timing components for that much.

Alexi

http://cgi.ebay.com/ebaymotors/ws/eBayI ... 67318&rd=1

Will, here are some more trick parts that you need.

Alexi

DELETED

Ouch! <rimshot!>

No I didn't replace the timing components, the guides had no wear, the gears had some, but as long as the chains stay tensioned, the arn't going to jump a tooth. I'd have my car up and running if I made more than $11000 per year.

Will

Hey Will,

Do yourself a favor and stop embarrassing yourself. We aren't here to discuss incomes. We all love the cars. Its just when you have the signature "and all the trick parts" and you state you had your whole motor rebuilt then you have a string of problems related to parts not being replaced, it just looks bad.

I understand everyone has different finanical obligations and for most the Datsun is down on the list every month.

Maybe its me but when you give advice and praise the U20 then all you end up with is a dead car it seems a little ironic.

Alexi