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Carbs to EFI


Wattle

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Hi,

Can I please pick your brains?

I have a 1985 V8 110, and its engine is rather poorly, so I am in the process of building another 3.5 V8 engine to replace it with. The new engine is out of a 1985 Rangie and has a compression ratio of 9.35/1, I want to fit it with composite head gaskets, but I don't want to lower the compression ratio. Does anyone know how much I would need to skim the heads by to retain the higher ratio.

Also I will be converting it to EFI, and could do with a bit of advice regarding fuel pumps. It has a low pressure electric pump fitted to feed the carbs, I was wondering if I could replace it with an inline fuel injection pump from the scrappies. If so which vehicle?

Thankyou for any help.

Thanks Phil

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Composite gaskets will lower the compression by 0.6:1 (or there abouts… slightly different between 3.5 & 3.9)……….. probably not even noticeable. The compressed difference between the tin and composite gaskets is 20thou on the 3.5 and 28 thou on the 3.9.

The later heads that were designed for the composite gaskets have a smaller combustion chamber to make up for the loss of CR …………. IIRC I don’t think you can shave that much off the heads without running into problems.

When I rebuilt mine I fitted 9.75 pistons (on the V8 the compression ratio is also a function of the piston crown), had the block decked very slightly and had the heads shaved by about 10 thou………… my CR was very high at about 10.7:1 using tin gaskets …….. I soon was forced to change to composites due to timing/running issues and trying to keep tin gaskets in one piece ! :lol: . ….. runs really sweet now with a CR of roughly 10:1.

For EFI you can use many pumps ……… facet do a good unit if you are looking at new …….. I am using a pump from the old 4x4 sierra ………. Also the montego 2.0EFI works OK. Remember to mount the pump close to the tank ……. They are real good at pushing but not at sucking …… :rolleyes: .

Ian

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Not sure about this but think it might help

When I converted the 90 to EFI from carbs, the carb pump was fitted into the tank.

I removed it and compared it with a HP RR unit.

They were similar but different.

So, I used the top half of the LP 90 carb one, and mated it up with the bottom HP part of the RR pump.

Had a bit of fun in that I made sure the "new Unit" was the same overall length / depth as the LP one I had removed, then shoved the assembled unit back into the tank, and piped it up with a RR in line HP filter

Works for me !...simple and neat and easy

Nige

PS other option is a Rover 820 unit.

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Not sure about this but think it might help

When I converted the 90 to EFI from carbs, the carb pump was fitted into the tank.

I removed it and compared it with a HP RR unit.

They were similar but different.

So, I used the top half of the LP 90 carb one, and mated it up with the bottom HP part of the RR pump.

Had a bit of fun in that I made sure the "new Unit" was the same overall length / depth as the LP one I had removed, then shoved the assembled unit back into the tank, and piped it up with a RR in line HP filter

Works for me !...simple and neat and easy

Nige

PS other option is a Rover 820 unit.

Thats pritty much the same what I did to mine and never suffered any problems and it has been like that for 5-6 years now.

Caviler pumps are used alot by the racing boys as there very cheep and loads of scrappies have them I have not used them my self but they are man enough to run the efi on a V8.

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Golf GTi pumps have built-in swirl pot which is a bonus, Jag pumps work and are very similar to cavalier ones (they're all Bosch or Lucas or similar anyway). Look for engines with the same (or better) power output, not size, as the fuel requirement is a function of power not CC.

External EFi pumps do not like being used as lift pumps, they will work badly and die eventually, you need a normal lift pump to feed it.

I had a cavalier pump on the 3.9 for a while, it worked fine, although I have a jag one to replace it when the truck is back on the road.

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I'm doing the same (well, Megasquirt) conversion at the moment - now have everything I need bar the pump.

Is it reasonable then to use the standard in-tank low pressure pump to feed the high pressure, in line pump?

I like HFH's solution - anyone got a suitable in tank HP pump looking for a home?

Cheers,

Si

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