Engine size advice (RCM build 500 bhp)
 

Hi guys i am looking for advice, i am mid project to build a very fast reliable road car / toy with around 500bhp.

https://www.scoobynet.com/members-ga...rcm-style.html

The original plan was to build a 2.35 with the above spec ^. However due to the good condition of my block and to keep within my budget RCM have advised me to go with a 2.5l build. The car is not going to be used day to day just for fast road use and maybe a few track days, I really wanted something that can rev hard all the way. Maximum fun not necessarily the fastest option.

Can someone advice me of the pros and cons of the engine options so i have a little knowledge to go back to RCM with?


Thanks guys :thumb:

First of all I would trust the judgement of Matt and Olly, and merely be guided by what you may read here.

I would seriously consider a 2.5 build aimed at high 400hp level (ie 475+). With what you have planned for the 2.35, and equivalent (block aside) build would be very nice to drive and depending on how far you go with the heads, free revving. Based on my experience of standard 2.5 blocks, that is relatively safe power level to aim for and it has been done many times by a number of different tuners. Some go as high as 500hp and they are possibly okay if the mileage and usage are sympathetic to the engine.

However if you want to get near the levels of low down torque of the 2.5 but with a solid 550hp and reliability, then the 2.35 is really the only way to go. Given your 2.5 heads, 2.1 or 2.0 engines are really out of the question unless you purchase some new 2.0 N/A head castings to go with the smaller block.

Realistically, if you want to do this and you simply can't afford the 2.35, the 2.5 will still give you many smiles per mile, even if the piece of paper that goes with it has a slightly smaller number printed in the corner.

thanks for the advice paul, how do the two sizes drive. will the 2.35 rev higher and stronger, comming from a 2.5 wrx with lots of low down power but no real top end.
i think the plan was to use a sti block but re use some part of my wrx unit.

They are very close, and with the AVCS of your car, the 2.35 will spool nicely, probably the same as a 2.5 non AVCS car, but the 2.35 will always lack a tiny bit of off boost performance.

A fair few people still end up with 500+ on a 2.5 and go onto enjoy many miles of perfect reliability. If the money saved enables a proper overall package to be put together in one co-ordinated effort, it will be the best move in the long term.

I know nothing about engine building but Fiestaboy does check this out all his own work

https://www.scoobynet.com/scoobynet-...-the-dyno.html

Very good advise offered there by Paul.

Id agree and go with a 2.5l. For that power target it will be awesome. Matt and Olly are not likely to steer you wrong. :thumb:

Not quite all his own work!

might be a good idea if some one local to you can take you for a spin, ive got a 2.5 and to be honest couldnt ask for anymore for a fast road car. if your going to do a 2.35 you might aswel do head work slap a nice blower and the list wont stop. 2.5 will make a cracking road car.