Setting up a V8

[morph]

I have just picked up a TR7 v8. It has a definite flat-spot at low revs, it then clears its throat and goes like ****!!!! It is the standard rover 3.5 with a Holley 4 barrell carb and Offenhauser manifolds. I fancy that it needs the carb setting up properly but I have no idea with this sort of carb. Does anyone have any wise words to help or know of a garage in Somerset that have the experience to set it up properly please.

 

Also the stereo is rubbish......who needs it with that V8 roar!! The bodywork is rough, lots to do but I love my V8 already!!!

 

Cheers

 

Morphgarth    

[Guest Chris Draper]

I never had any flat spots with my 3.5 running a Holley. Had it tuned at Interpro in Thornbury near Bristol, who definitely knew what they were doing, even if their standard fare is based around the Scooby / Evo end of the market; you don't get much change from 300 though & you've got to reckon on about half a day to get it done.

[Guest wakaday]

Morph.

I tore my hair out over a Holley. I tried everything but couldn't get it right.

In the end i bit the bullet and bought a Webber/edelweiss  carb and never looked back. It worked perfect straight out of the box and right through the rev range.............until one sad day last October when I decided to sell the car.  

[morph]

Thanks for the advice chaps, I will try Revington as they are only down the road from me, why I never thought of them I don't know.....doh!! Alec thanks for the offer of advice, may take you up on that, cheers.

 

Morph

[malcolm]

A wonderful thing the Holley carb.  When it is right you will know.  No flat spots on my track TR7V8, just power and torque everywhere.  It also seems to stay right once done and not require constant b*ggering about with.  Revingtons do more TR7/8 stuff than I'd realised until recently - be interested to know how you get on....

 

Malcolm.

[Guest hodgie]

Chris,

I plan to take my beast out to Interpro once i've sorted the gearbox :-(.

I have heard very good things from some chaps who do grass track racing.

Yours was a good and effective experience ?

[Guest Chris Draper]

Hodgie,

 

They know what they're at. I used them with my 3.5 + Holley when I fitted stage 2 heads a few years back & they were very thorough - toook a whole afternoon including a compression test on all cylinders before starting the job. Carburetion was spot on with no flat spots.

 

Used them again last year afte I fitted the 4.6 + Webber & they were equally good, including fitting bigger jets in the Webber. They do know their carbs, even if most of the kit you'll see there is of the more modern variety. They did comment that it's difficult to get the ignition curve right on a Rover V8, especially when you're running a very high compression ratio - I re-used my old stage 2 heads on the rebuilt engine & they'd been skimmed a few times so they reckoned it was well over 10:1 (made it bloody hard to get a seal on the intake manifold too, but that's another story...).

 

They also pointed out that you can get significantly more horses running on Optimax, so if you want to go that route make sure you've got a tank full of it when you take it in. In my case, I ended up with 235hp & 300lb/ft running on normal unleaded & they reckoned that it would probably make about another 30hp on Optimax.

 

Bottom line - yes they were good & they take the time to get it right, just get ready for the dent in the wallet...

[Cinnobar]

General consensus from those that know is that the Weber is closer out of the box & much quicker (AKA Cheaper) to tune than the Holley. Simon formerly of Rovercraft hated Holleys with a passion & reckoned the power was similar for a similar spec. Comments echoed by RPI & others seemingly.

 

Jim

[martynharrison]

I've got a 390 with no flat spots anywhere, S&S set it up so I guess it was done right. As for the Weber / Holley debate, I think either is good when set up properly.

 

:laugh:

 

I'd start off checking the timing as that's easy and it does go off. Also, the vacuum advance. Can't hurt to use carb/injector cleaner too in case that's the cause of it.

[tr8coupe]

weber all the way more power and no flat spots and edelbrock performer straight way more power than offenhauser  

 

happy

 

tr8ing

[Guest Chris Draper]

Just a couple of comments on Holley vs Webber:

 

My 3.5 ran perfectly on a Holley 390 in original form & with Stage 2 heads (after a tune by Interpro). The current 4.6 equally runs perfectly with a Webber 500.

 

From what I recall, RPI preferred the Webber primarily because of better part-throttle performance & efficiency, while one of the specialists over here in Brisbane says he doesn't like them because of heat soak; there is some evidence of the latter when dropping to low speeds after prolonged high speed, but not enough to be a problem. One thing I do notice is that I have to use the choke with the Webber - never bothered on the Holley, which probably supports RPI's comments.

 

I would note that the Webber, which was supplied by RPI along with the 4.6 short engine, was supposed to be ready to go out of the box, but when Interpro tuned it they had to increase the jet sizes to optimise performance.

 

As far as fuel economy is concerned, I'm getting low to mid 20's (depending on the weight of my right foot), which isn't bad for a 4.6 & is pretty similar to the figure I got from the 3.5 + Holley.

 

Frankly I reckon they're both good carbs & you wont go far wrong with either one when they're set up properly.

[Cinnobar]

I don't think anyone says the Weber will be perfect out of the box but is more likely to be nearer the mark.  Mine was brought s/h so could be set up for anything but isn't bad.

Mine is a mildly tuned 3.5.

I don't run a choke with mine and never had. Too tight to spend £ 30 on a choke setup I suppose.

Main thing I hear about the Holley is it needs extra money spent on it for jet plate etc. and also it's more prone tofuel leaks because of the vertically split float chambers.

Interesting that althought the Weber is well loved here the sceptics don't seem so keen over their, is that because of more knowledge of he Holley?

 

Jim

[Mike at Boost]

It's just not set up right. Either the vac spring is to soft or the primary main jets aren't big enough.  When a holley is properly set up you shouldn't fee the transition onto the secondary chokes.

 

Boosted.

[chris turner]

Mike hows the Chevvy installation coming along is it finished yet?

[Guest Larry J-C]

Just noticed this post - flat spots on Holleys are normally caused by the vacuum secondaries not opening at the right time.  It is dead easy to cure and does not need a rolling road.  You need a little conversion kit for the holley which allows the top of the vacuum chamber to be removed and the springs replaced as well as a selection of springs. Last time I did this Real Steal sold me the lot for about £35 and it took about 45 mins to convert the carb.  You then head off down the road and try different springs until the flat spot dissappears - sounds rather heath robinson but I've done it twice on two cars and it was very effective.

[dibbs]

I used to work at Rovercraft and the standing joke was that all Holleys should come with a free fire extenguisher!!

[samco]

Had an interesting chat with RPI a few days ago about mallory distributors. There was one on ebay for a v8 but it had no vacuum advance. Ho told me the racers use those because it gives a few extra horses at high revs but gives a wicked flat spot low down. An earlier quote about the advance curve was correct and the dissys for each different type of vehicle have different curves. I know he would tell me this because he wants me to buy bits from him but he swares you can gain substantial horsepower but using the correct mallory dissy with (£70) magnecor leads

[SteveP]

<font color='#000000'>I have just picked up a TR7 v8. It has a definite flat-spot at low revs, it then clears its throat and goes like ****!!!! It is the standard rover 3.5 with a Holley 4 barrell carb and Offenhauser manifolds. I fancy that it needs the carb setting up properly but I have no idea with this sort of carb. Does anyone have any wise words to help or know of a garage in Somerset that have the experience to set it up properly please.

 

Also the stereo is rubbish......who needs it with that V8 roar!! The bodywork is rough, lots to do but I love my V8 already!!!

 

Cheers

 

Morphgarth    </font>

 

It's also about the manifold, not just the carb ... I run a 390 Holley on a Rover V8 3500cc 10.5:1CR and although it ran very well I've just changed the manifold for an Edelbrock DUAL-PLANE, has given the car much more torque and pull from 1500RPM right through the rev range. I've seen numerous manifolds on these engines/carbs and it seems some are more open (i.e. single plane/chamber) for higher throughput or revvy engines.